Nuts & Seeds · Nut
Hazelnuts
Corylus avellana · also called Filbert, hazelnut, avellana (Spanish)
The hazelnut, also called filbert, is the kernel inside the hard shell of a nut. It is mostly fat, mainly the unsaturated kind, and is a food source of vitamin E, manganese and copper. Pooled trials found a small fall in LDL cholesterol and no weight gain, but heart-disease claims rest mostly on studies of nuts in general. The main cautions are tree nut allergy (including itchy mouth with birch pollen allergy), choking in children under 5 and mould toxins in old or damp nuts.
General information, not medical advice. Last substantive update · Not medically reviewed. A named clinician has not signed off on this page. How this page is made
About Hazelnuts
The hazelnut is a nutritious, high-fat tree nut. It is a food, not a proven remedy: the best evidence is a small fall in LDL cholesterol and no weight gain, and the most important caution is tree nut allergy.
What it is
The hazelnut (Corylus avellana) is the nut of a shrub or small tree in the birch family. People eat the kernel raw, roasted or ground into spreads and baking flour.
USDA data for raw hazelnuts: 628 kcal per 100 g. One ounce (28.35 g, about 21 kernels) has about 178 kcal, 17.2 g fat (mostly monounsaturated), 4.3 g protein, 2.8 g fibre, 4.3 mg vitamin E, 1.75 mg manganese and 0.49 mg copper. These are our scaling of the USDA per-100 g values. Values vary with variety and storage.
What the research shows
The firmest finding is a small fall in LDL cholesterol. Pooling 3 randomised hazelnut studies gave about 0.15 mmol/L lower LDL, and a larger review of 61 tree nut trials found a similar small fall that did not differ by nut type.
Reviews of nut trials found no weight gain. Lower rates of heart disease and early death in nut eaters come from observational studies of all nuts, and cannot show that nuts caused the difference. The PREDIMED trial tested a whole Mediterranean diet with mixed nuts, so it does not isolate hazelnuts.
Blood pressure, blood sugar and inflammation results are weak. Hazelnut oil, skin extracts and supplements were not studied in the trials read.
The whole nut versus oil and extracts
The trials used whole hazelnut kernels, with or without the skin. No trial of hazelnut oil, skin extract, flour or supplements was read here, so these results do not carry over to those products. Many nut studies pool several kinds of nut.
Amounts
This page gives no amounts to eat. Ask a doctor, dietitian or pharmacist what is right for you, especially if you take medicine or have a food allergy.
At a glance
Traditional uses history, not proof
- Eaten as a food, raw, roasted or ground into spreads and baking flour
- Long use as a food is not proof that hazelnuts treat any condition
Studied for research
- LDL cholesterol, low certainty (3 pooled hazelnut trials; all tree nuts show a similar small fall)
- Heart disease and stroke, low certainty (observational studies of all nuts; one diet trial with mixed nuts)
- Body weight, moderate certainty that no weight gain occurs
- Vitamin E, manganese and copper, high certainty as a food fact
- Blood pressure, blood sugar and inflammation, insufficient evidence
Main compounds
- Oleic acid (monounsaturated fat)
- Vitamin E (alpha-tocopherol)
- Beta-sitosterol (plant sterol)
- Manganese and copper (minerals)
Common forms
- Whole raw kernels as food (used in the trials)
- Kernels with or without the brown skin (child trials)
- Roasted kernels, ground nuts and spreads (not tested here)
- Hazelnut oil and extracts (no trial read)
Research links: Meta-analysis: hazelnuts, blood lipids and body weight (2016) · Meta-analysis: tree nuts and blood lipids, 61 trials (2015) · NHS: Food allergy · Research Library · Genes & Biomarkers Library
What it is and its history
- Accepted scientific name
- Corylus avellana
- Naming authority
- L. (GBIF accepted; usageKey 2875979)
- Common names
- Hazelnut (English); Filbert (English); Common hazel (English); Avellana (Spanish)
- Family or group
- Betulaceae (the birch family), as given by GBIF.
- Classification
- Plantae > Tracheophyta > Magnoliopsida > Fagales > Betulaceae > Corylus > Corylus avellana
- Native range
- Not verified from a source read.
- Habitat
- Not verified from a source read.
- What it looks like
- Roots: Not verified.; Stems: The existing nutrient summary calls it a shrub or small tree; not verified from a source read.; Leaves: Not verified.; Flowers: Not verified.; Fruit: The kernel inside the hard shell of the nut is the food. USDA gives a household portion of 1 ounce as 28.35 g (21 whole kernels), 10 nuts as 14 g and 1 cup of whole kernels as 135 g.
- Cultivation
- Not verified from a source read.
- Harvest and processing
- Eaten raw, roasted or ground into spreads and baking flour (existing nutrient summary). Processing effects on nutrients were not read from a source; a 2025 review says processing can reduce but not eliminate allergen exposure.
- Look-alikes and adulterants
- Name: Witch hazel (a different plant, Hamamelis); Note: Not related to the hazelnut and not a nut. It has its own page. Named here only because the common names look alike (general knowledge, not a source read).; Name: Other tree nuts such as almond, walnut or macadamia; Note: Different foods with their own nutrient values. Tree nut studies pool several of them.
- Sustainability and conservation
- Not assessed.
Photographs
Traditional use and history history, not clinical proof
| Tradition or era | Documented use | Source |
|---|---|---|
| Culinary use | Hazelnuts are eaten raw, roasted or ground (existing nutrient summary; no historical source was read). | Not verified |
Traditional use shows how it was used. It does not show that it works or is safe today.
What is inside, and how it may work
What it contains and how those compounds act in cells and animals. Laboratory and animal mechanisms are not proven effects in people.
Main compounds
| Compound | Family | Where it is concentrated | Activity studied | Level of evidence |
|---|---|---|---|---|
| Oleic acid (monounsaturated fat) PubChem 445639 | fatty acid | Kernel USDA: MUFA 18:1 about 45.4 g per 100 g raw hazelnuts (total monounsaturated fat 45.7 g) | The main fat in hazelnuts. Researchers describe hazelnuts as rich in monounsaturated fat; a causal link to the LDL results was not tested in the reviews read. 23 24 13 | Human data |
| Alpha-tocopherol (vitamin E) PubChem 14985 | vitamin | Kernel USDA: 15.0 mg per 100 g (about 4.3 mg in one ounce, our scaling) | Essential nutrient. MedlinePlus names hazelnuts/filberts as a vitamin E food. 21 24 17 | Human data |
| Beta-sitosterol (plant sterol) PubChem 222284 | phytosterol | Kernel USDA: 102 mg per 100 g (stigmasterol 1.0 mg, campesterol 7.0 mg) | A plant sterol found in nuts. Its role in hazelnut cholesterol studies was not tested in the sources read. 22 24 | Unknown |
Mechanisms, receptors and pathways
| Target or pathway | Gene or receptor | What was found | Level |
|---|---|---|---|
| Cholesterol lowering by nuts | Not specified | The 2015 review of 61 tree nut trials found that the main driver of cholesterol lowering appeared to be nut dose rather than nut type. No mechanism for hazelnuts was tested in the reviews read. 4 | Human data |
| Cross-reaction with birch pollen | Cor a 1 (hazelnut) and Bet v 1 (birch) | IgE antibodies and T cells from patients with birch pollen and hazelnut allergy reacted to both the birch protein Bet v 1 and the hazelnut protein Cor a 1. 10 | Human data |
| Cross-reaction with macadamia | Oleosin | Hazelnut extract blocked IgE binding to a macadamia oleosin in samples from 7 people allergic to macadamia. 9 | Human data |
Absorption, metabolism and elimination
- Absorption
- Not studied for hazelnuts.
- Distribution
- Not found.
- Metabolism
- Not found.
- Elimination
- Not found.
- Bioavailability
- Not established for hazelnuts.
Isolated compounds versus whole extracts
The hazelnut trials gave whole kernels, with or without the brown skin in the child trials. No trial of hazelnut oil, skin extract, flour or a supplement was read, so results here do not apply to those products. The all-nut reviews pool several nuts.
Nutritional composition
Nutrition from USDA FoodData Central (Nuts, hazelnuts or filberts, raw, FDC 170581, SR Legacy, last updated 4/1/2019, read 2026-10-26). Per 100 g: 628 kcal, 15.0 g protein, 60.8 g fat (4.46 g saturated, 45.7 g monounsaturated, 7.92 g polyunsaturated), 16.7 g carbohydrate, 9.7 g fibre, 4.34 g sugars, 114 mg calcium, 4.7 mg iron, 163 mg magnesium, 290 mg phosphorus, 680 mg potassium, 0 mg sodium, 2.45 mg zinc, 1.72 mg copper, 6.18 mg manganese, 15.0 mg vitamin E (alpha-tocopherol), 0.643 mg thiamin, 0.563 mg vitamin B6, 113 micrograms folate, 14.2 micrograms vitamin K. One ounce (28.35 g, about 21 kernels), calculated by us from the per-100 g values: about 178 kcal, 4.3 g protein, 17.2 g fat (1.3 g saturated, 13.0 g monounsaturated), 4.7 g carbohydrate, 2.8 g fibre, 32 mg calcium, 1.3 mg iron, 46 mg magnesium, 193 mg potassium, 0.5 mg copper, 1.75 mg manganese, 4.3 mg vitamin E, 0.18 mg thiamin, 32 micrograms folate, 4 micrograms vitamin K. USDA lists no omega-3 (ALA) of note: 18:3 is 0.087 g per 100 g. Figures vary with variety, growing place, roasting and storage; roasted hazelnuts were not read.
1 high certainty1 moderate certainty4 low certainty1 very low certainty1 not enough evidence
What was looked at
The 8 benefits and uses checked for Hazelnuts, each with how strong the evidence is. Tap one to open it.
- LDL ("bad") cholesterol (eating hazelnuts)Low certainty
- Heart disease and stroke (observational studies of nut eaters)Low certainty
- Heart events: Mediterranean diet with mixed nuts (PREDIMED trial)Low certainty
- Body weight and BMI (no gain found)Moderate certainty
- Source of vitamin E, manganese and copper (nutrition fact)High certainty
- Blood pressure, blood sugar and inflammationNot enough evidence
- DNA damage in blood cells in children with high blood fatsVery low certainty
- Death from any cause and total cancer (observational studies of nut eaters)Low certainty
Lab markers tracked in the studies
LDL cholesterolHDL cholesterol and triglyceridesBody mass index (BMI)DNA damage in blood cells (lab marker)
What is Hazelnuts good for?
The main studied uses and how strong the human evidence is for each. Many results come from studies of all nuts together, and from blood tests rather than illness.
Benefits, one by one
Each card is a research question, not a promise. Tap a goal to filter. Open a card to see the studies, doses and limits.
LDL ("bad") cholesterol (eating hazelnuts)
Low certaintyPooling three randomised hazelnut studies, LDL cholesterol was a little lower on a hazelnut diet than on a control diet. Reviews of all tree nuts together show a similar small fall. These are blood tests, not heart attacks.
3 studiesWhole hazelnut kernels eaten as part of the diet in the hazelnut tria…
Studies, doses and limits
What the trials found
A 2016 Bayesian meta-analysis pooled 3 randomised studies of hazelnut-enriched diets (29 to 69 g a day for 28 to 84 days) and found LDL 0.150 mmol/L lower (95% HPD -0.308 to -0.003). A 2015 meta-analysis of 61 tree nut trials (2,582 people, hazelnuts included) found LDL 4.8 mg/dL lower per serving a day, with no significant difference between nut types. In a small 2018 trial of 66 children and adolescents with high blood fats, LDL changed over time in all groups, including the control group, and the abstract reports no significant difference between hazelnut and control groups.
Results
A small LDL fall in pooled hazelnut trials and in all-nut trials. The one child trial did not show a clear difference from control.
Effect sizes as reported
Hazelnut diet: LDL -0.150 mmol/L (about -5.8 mg/dL). All tree nuts: LDL -4.8 mg/dL per serving a day (95% CI -5.5 to -4.2).
Why this rating
Only 3 randomised hazelnut studies could be pooled and the interval almost touches zero. The all-nut result is larger and tighter, and the authors found no difference by nut type, but it is not hazelnut-only. Trials were short. Blood tests are not heart attacks.
Form and dose studied
Whole hazelnut kernels eaten as part of the diet in the hazelnut trials. No trial of hazelnut oil, skin extract or powder is described here.
Who was studied
Adults in the pooled hazelnut studies; children with primary high blood fats in the child trial; adults without heart disease in the all-nut review.
Limits
Short trials; small numbers; nut-industry funding of individual trials is not stated in the abstracts. Lipids are a stand-in for heart risk.
Why researchers looked
Hazelnuts are rich in unsaturated fat, so researchers ask whether eating them changes blood fats.
Traditional use
Hazelnuts have long been eaten as a food. Long use as a food is not proof that they treat any condition.
Proposed mechanism Unknown
Hazelnuts are mostly fat, and most of it is monounsaturated (USDA: about 46 g per 100 g, mainly oleic acid). They also hold fibre and plant sterols (USDA: beta-sitosterol about 102 mg per 100 g). The reviews do not prove which part of the nut lowers cholesterol.
A proposed mechanism does not show that the effect happens in people.
Tree nut allergy is a real risk for some people. See the Safety tab.
Heart disease and stroke (observational studies of nut eaters)
Low certaintyIn large follow-up studies, people who ate more nuts had lower rates of coronary heart disease and cardiovascular disease. Stroke was not clearly lower. These studies mix all nuts and cannot prove cause.
1 studiesNuts of all kinds as usually eaten; the unit is 28 g a day (study uni…
Studies, doses and limits
What the trials found
A 2016 meta-analysis of 20 prospective studies found, per 28 g a day higher nut intake, a relative risk of 0.71 (95% CI 0.63 to 0.80) for coronary heart disease, 0.79 (0.70 to 0.88) for cardiovascular disease and 0.93 (0.83 to 1.05) for stroke. The authors say results were similar for tree nuts and peanuts. Hazelnuts were not analysed alone.
Results
Lower coronary heart disease and cardiovascular disease with more nut intake; no clear stroke difference.
Effect sizes as reported
Per 28 g a day: CHD RR 0.71; CVD RR 0.79; stroke RR 0.93 (not significant).
Why this rating
Observational studies cannot show cause: nut eaters may eat and live differently. Heterogeneity was moderate to high (I2 47% to 60%). Hazelnut-specific data were not given.
Form and dose studied
Nuts of all kinds as usually eaten; the unit is 28 g a day (study unit, not advice).
Who was studied
Adults in cohort studies.
Limits
Association only. All nuts and peanuts pooled.
Why researchers looked
Nut eaters were seen to have fewer heart problems in cohort studies, so researchers pooled them.
Traditional use
Hazelnuts have long been eaten as a food. Long use as a food is not proof that they treat any condition.
Proposed mechanism Unknown
No mechanism is proved. The authors of nut studies point to fats, fibre and other plant substances, but the review read here does not test this.
A proposed mechanism does not show that the effect happens in people.
None specific beyond allergy.
Heart events: Mediterranean diet with mixed nuts (PREDIMED trial)
Low certaintyIn a large Spanish trial, people at high heart risk who followed a Mediterranean diet with free mixed nuts had fewer major heart events than people told to cut fat. It tests a whole diet with mixed nuts, so it cannot be credited to hazelnuts alone.
1 studiesMixed nuts provided free as part of a Mediterranean diet. The abstrac…
Studies, doses and limits
What the trials found
The trial assigned 7,447 people aged 55 to 80 at high heart risk to a Mediterranean diet with extra-virgin olive oil, a Mediterranean diet with mixed nuts, or a control diet (advice to reduce fat). After a median 4.8 years, major events happened in 3.4% of the nuts group and 4.4% of the control group. The hazard ratio was 0.72 (95% CI 0.54 to 0.95). The 2013 report was withdrawn after some people were found not to have been randomised, and this 2018 version re-analysed the data.
Results
Fewer major cardiovascular events with a Mediterranean diet plus mixed nuts than with a reduced-fat diet.
Effect sizes as reported
HR 0.72 (0.54 to 0.95). Events: 83 of the nuts group (3.4%) vs 109 of the control group (4.4%).
Why this rating
The result is a randomised trial, but the first report was withdrawn over randomisation problems, the nuts were mixed and part of a whole diet, and people knew their diet.
Form and dose studied
Mixed nuts provided free as part of a Mediterranean diet. The abstract does not list the nut types or amounts.
Who was studied
Adults aged 55 to 80 at high cardiovascular risk, Spain.
Limits
Not hazelnuts alone. Revised analysis. One country.
Why researchers looked
Nuts were part of a trial of the Mediterranean diet for heart disease prevention.
Traditional use
Hazelnuts have long been eaten as a food. Long use as a food is not proof that they treat any condition.
Proposed mechanism Unknown
The trial changed a whole diet pattern, so no single food can be named as the cause.
A proposed mechanism does not show that the effect happens in people.
Anyone with a nut allergy should not use this trial as a guide.
Body weight and BMI (no gain found)
Moderate certaintyHazelnuts are rich in energy, but pooled trials of hazelnuts and of nuts in general did not find weight gain. This is not evidence that hazelnuts cause weight loss.
3 studiesWhole nut kernels or nut-based snacks eaten as food.
Studies, doses and limits
What the trials found
The 2016 hazelnut meta-analysis found BMI changed by +0.062 kg/m2 (95% HPD -0.293 to 0.469). The 2022 hazelnut review of 22 intervention studies said including hazelnuts did not adversely affect body weight and composition. A 2021 meta-analysis of 55 nut-feeding trials found no change in body weight, BMI or waist circumference, with or without swapping instructions; body fat percentage fell slightly only with swapping instructions.
Results
No weight gain found. No clear weight loss either.
Effect sizes as reported
Hazelnut diet BMI +0.062 kg/m2 (-0.293 to 0.469). All nuts, body weight SMD 0.01 (-0.07 to 0.08).
Why this rating
Three reviews agree that weight did not change, but trials were short (weeks to a few months) and the largest review is for all nuts, not hazelnuts alone.
Form and dose studied
Whole nut kernels or nut-based snacks eaten as food.
Who was studied
Adults in trials.
Limits
Short follow-up; study methods varied; nut-industry funding not stated in the abstracts.
Why researchers looked
Nuts are high in calories, so people ask whether eating them adds weight.
Traditional use
Hazelnuts have long been eaten as a food. Long use as a food is not proof that they treat any condition.
Proposed mechanism Unknown
Not established. The reviews do not explain why weight stayed steady.
A proposed mechanism does not show that the effect happens in people.
USDA lists about 178 kcal in one ounce, so energy still counts.
Source of vitamin E, manganese and copper (nutrition fact)
High certaintyHazelnuts are a food source of vitamin E, manganese and copper. This is about what the food contains, not a trial that hazelnuts treat a deficiency.
2 studiesRaw hazelnut kernel (USDA record).
Studies, doses and limits
What the trials found
USDA FoodData Central lists, per 28.35 g (one ounce), about 4.3 mg vitamin E, 1.75 mg manganese and 0.49 mg copper (our scaling of the per-100 g values). MedlinePlus names hazelnuts/filberts among foods that supply vitamin E and says eating vitamin E in foods is not risky.
Results
A real food-composition fact. No trial of hazelnuts for any shortage was found.
Effect sizes as reported
Per 100 g: vitamin E 15.0 mg; manganese 6.18 mg; copper 1.72 mg (USDA).
Why this rating
High for the nutrient content (a measured food analysis). It says nothing about disease outcomes, and values vary with variety and storage.
Form and dose studied
Raw hazelnut kernel (USDA record).
Limits
Composition data only. The USDA record is from 2019.
Why researchers looked
Hazelnuts are named as a vitamin E food by MedlinePlus.
Traditional use
Hazelnuts have long been eaten as a food. Long use as a food is not proof that they treat any condition.
Proposed mechanism Authoritative guidance
Vitamin E, manganese and copper are nutrients the body needs. USDA lists raw hazelnuts at 15.0 mg vitamin E (alpha-tocopherol), 6.18 mg manganese and 1.72 mg copper per 100 g.
A proposed mechanism does not show that the effect happens in people.
MedlinePlus warns about high-dose vitamin E supplements, which are not the same as food.
Blood pressure, blood sugar and inflammation
Not enough evidenceA review of hazelnut studies saw some improvements in these markers but said weak study designs make the results hard to read. A review of all tree nuts found no significant effect on blood pressure or C-reactive protein.
2 studiesWhole hazelnuts in hazelnut studies.
Studies, doses and limits
What the trials found
The 2022 systematic review of 22 hazelnut intervention studies reports some improvements in cardiometabolic risk factors but says limitations in study design make interpretation problematic. The 2015 review of 61 tree nut trials found no statistically significant effects on outcomes other than the cholesterol and blood fat measures, a list that included blood pressure and C-reactive protein.
Results
Not shown. Mixed and weak.
Effect sizes as reported
No pooled figures given for hazelnuts alone.
Why this rating
The hazelnut review is qualitative and calls its own results hard to interpret. The larger review is for all nuts.
Form and dose studied
Whole hazelnuts in hazelnut studies.
Who was studied
Mixed adult and child groups.
Limits
Weak designs, small studies. Details by outcome were not in the abstracts.
Why researchers looked
Nuts contain fats, fibre and plant substances that might affect these markers.
Traditional use
Hazelnuts have long been eaten as a food. Long use as a food is not proof that they treat any condition.
Proposed mechanism Unknown
No mechanism was established in the reviews read.
A proposed mechanism does not show that the effect happens in people.
None specific.
DNA damage in blood cells in children with high blood fats
Very low certaintyIn one small trial of 60 children and adolescents with high blood fats, 8 weeks of hazelnuts lowered a lab marker of DNA damage in blood cells. Oxidised LDL did not change. It is one trial, and a lab marker, not an illness.
1 studiesWhole hazelnuts with or without skin.
Studies, doses and limits
What the trials found
In a single-blind trial of 60 children and adolescents (15 to 30 g of hazelnuts a day for 8 weeks), endogenous DNA damage fell 18.9% with hazelnuts with skin and 23.1% without skin. Oxidatively induced DNA strand breaks fell 16.0% with skin. Oxidised LDL did not change.
Results
A lab marker fell. No illness outcome was measured.
Effect sizes as reported
DNA damage -18.9% (p=0.002) and -23.1% (p=0.007); strand breaks -16.0% (p=0.02).
Why this rating
One small trial, 8 weeks, a special group of children, a lab marker.
Form and dose studied
Whole hazelnuts with or without skin.
Who was studied
Children and adolescents with primary hyperlipidaemia.
Limits
Single trial. Not reproduced in adults in the sources read.
Why researchers looked
Children with this fat disorder are prone to early artery disease, and researchers looked at oxidative stress markers.
Traditional use
Hazelnuts have long been eaten as a food. Long use as a food is not proof that they treat any condition.
Proposed mechanism Unknown
The authors link the result to bioactive substances in nuts. This is their interpretation and was not tested directly.
A proposed mechanism does not show that the effect happens in people.
Children under 5 should not be given whole nuts (NHS). See the Safety tab.
Death from any cause and total cancer (observational studies of nut eaters)
Low certaintyIn follow-up studies, people who ate more nuts had lower rates of cancer and of death from any cause. These studies mix all nuts and cannot show cause.
1 studiesNuts of all kinds as usually eaten.
Studies, doses and limits
What the trials found
The 2016 meta-analysis of 20 prospective studies found, per 28 g a day higher nut intake, a relative risk of 0.85 (95% CI 0.76 to 0.94) for total cancer and 0.78 (0.72 to 0.84) for death from any cause. It also reported lower relative risks for death from respiratory disease, diabetes and infections. The authors say results were similar for tree nuts and peanuts.
Results
Lower rates with more nuts in observational data. Hazelnuts were not analysed alone.
Effect sizes as reported
Per 28 g a day: total cancer RR 0.85; all-cause death RR 0.78.
Why this rating
Observational. Healthy habits, income and other things can differ between nut eaters and others. Heterogeneity was moderate to high.
Form and dose studied
Nuts of all kinds as usually eaten.
Who was studied
Adults in cohort studies.
Limits
Association only; all nuts and peanuts pooled.
Why researchers looked
Researchers pooled nut studies to see whether nut eaters live longer.
Traditional use
Hazelnuts have long been eaten as a food. Long use as a food is not proof that they treat any condition.
Proposed mechanism Unknown
No mechanism was tested in the review.
A proposed mechanism does not show that the effect happens in people.
None specific.
Connections to the rest of health
How Hazelnuts connects to the rest of our health knowledge graph. Every link says what kind of connection it is. A safety link (for example to the liver) is a warning, not a benefit. A study that merely mentions a topic never creates a benefit link.
Explore every connection: goals, body systems, organs, symptoms, genes
B. Body systems
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Cardiovascular System | Biological association | Low certainty | Studied for: LDL ("bad") cholesterol (eating hazelnuts) Studied for: Heart disease and stroke (observational studies of nut eaters) | 13 4 5 1 6 2 7 |
| Metabolism Weight | Biological association | Moderate certainty | Studied for: Body weight and BMI (no gain found) Studied for: Source of vitamin E, manganese and copper (nutrition fact) | 13 2 8 24 17 4 |
| Immune System | Biological association | Low certainty | Studied for: Death from any cause and total cancer (observational studies of nut eaters) | 1 |
E. Health conditions
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Food allergy | Adverse effect or risk | Documented risk | Hazelnut is a tree nut allergen. Reactions can be severe. Preparation or compound: Hazelnut kernel (tree nut allergen) |
18 15 11 |
| Birch pollen food allergy | Adverse effect or risk | Documented risk | Hazelnut protein Cor a 1 cross-reacts with the main birch pollen protein. Preparation or compound: Raw hazelnut (Cor a 1 protein) |
10 11 |
I. Biomarkers
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| LDL cholesterol | Small change | Pooled hazelnut trials found a small LDL fall. Preparation or compound: Whole hazelnut kernels |
13 4 | |
| LDL cholesterol | Biological association | Low certainty | Measured in trials: lowered. A lab change is not the same as a health benefit. | 13 4 |
| HDL cholesterol and triglycerides | Biological association | Low certainty | Measured in trials: no change. A lab change is not the same as a health benefit. | 13 4 |
| Body mass index (BMI) | Biological association | Moderate certainty | Measured in trials: no change. A lab change is not the same as a health benefit. | 13 8 |
| DNA damage in blood cells (lab marker) | Biological association | Very low certainty | Measured in trials: lowered. A lab change is not the same as a health benefit. | 7 |
K. Biological pathways
L. Active compounds
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Oleic acid (monounsaturated fat) | Biological association | Human | The main fat in hazelnuts. Researchers describe hazelnuts as rich in monounsaturated fat; a causal link to the LDL results was not tested in the reviews read. Preparation or compound: Kernel |
23 24 13 |
| Alpha-tocopherol (vitamin E) | Biological association | Human | Essential nutrient. MedlinePlus names hazelnuts/filberts as a vitamin E food. Preparation or compound: Kernel |
21 24 17 |
| Beta-sitosterol (plant sterol) | Biological association | Unknown | A plant sterol found in nuts. Its role in hazelnut cholesterol studies was not tested in the sources read. Preparation or compound: Kernel |
22 24 |
Each connection is stored with the ingredient, the connected record, the kind of connection, the evidence status, the supporting studies, the preparation or compound involved, and a review date (last reviewed October 26, 2026).
The evidence
The research centre for Hazelnuts. Every record here was checked against PubMed or the publisher's page; we never list a study we have not verified.
Evidence by outcome
Bars show how many studies we found for each outcome, not how well it works. People are added up across trials only (reviews are not added, to avoid double counting).
How we rate evidence
High certainty
Several well-run trials or reviews agree; further research is unlikely to change the picture much.
Moderate certainty
Good trials point the same way, but some doubt remains.
Low certainty
Small, short or inconsistent trials. The finding could change with better research.
Very low certainty
Very little or very weak human data. Treat as a possibility only.
Mixed findings
Trials or reviews disagree with each other.
Not enough evidence
Not enough human research to say either way.
Evidence against
Good research found no benefit, or found harm.
We take the reviewers' own risk-of-bias and GRADE statements where they exist, and otherwise judge from study size, design, consistency, directness and whether a product matches what is sold. Many publications do not make evidence high. Method note: We started from our existing hazelnut summary, re-checked nutrition at USDA FoodData Central, and re-read the abstracts of the cited reviews and trials at PubMed. We also read the NHS, FDA, WHO and MedlinePlus pages named. Only abstracts were read for studies. Items we could not verify are flagged in the research gaps.
Study library: every study we checked 25
| Study | Design | People | Product, dose, length | Result |
|---|---|---|---|---|
| Aune 2016 Nut consumption and risk of cardiovascular disease, total cancer, all-cause and cause-specific mortality: a systematic review and dose-response meta-analysis of prospective studies BMC Med · PMID 27916000 · DOI |
Meta-analysis |
Adults in 20 prospective cohort studies (29 publications) | Nut intake of all kinds (tree nuts and peanuts) Kernel Per 28 g a day higher intake (study unit, not advice) Follow-up varied by study · vs Lower nut intake |
Higher nut intake went with lower coronary heart disease, cardiovascular disease, total cancer and all-cause death. Stroke was not clearly lower. The authors say results were similar for tree nuts and peanuts. Per 28 g a day: coronary heart disease RR 0.71; stroke RR 0.93; cardiovascular disease RR 0.79; total cancer RR 0.85; all-cause death RR 0.78 (CHD 0.63 to 0.80; stroke 0.83 to 1.05; CVD 0.70 to 0.88; cancer 0.76 to 0.94; all-cause 0.72 to 0.84) Methods, limits and fundingOutcomes: Coronary heart disease, stroke, cardiovascular disease, total cancer, death from any cause and other causes of death Limitations: Observational: people who eat nuts may differ in other ways, so this cannot show that nuts cause the lower risk. Not hazelnuts alone. Funding and conflicts: Not stated in the abstract. Read: abstract |
| Brown 2022 Effects of Hazelnut Consumption on Cardiometabolic Risk Factors and Acceptance: A Systematic Review Int J Environ Res Public Health · PMID 35270573 · DOI |
Systematic review |
Adults and children in 22 hazelnut intervention studies (25 publications) | Whole hazelnuts as part of the diet Kernel · vs Control or usual diet |
The review found some improvements in heart and metabolic risk markers, but the authors say study design limits make interpretation problematic. Hazelnuts did not adversely affect body weight or body composition. People kept accepting hazelnuts over time. Qualitative review, no pooled numbers in the abstract (Not given) Methods, limits and fundingOutcomes: Lipids, apolipoproteins, weight and body composition, blood pressure, glycaemia, antioxidant status, inflammation, endothelial function, acceptance Limitations: Qualitative review only. The authors call for stronger designs in more kinds of people. Funding and conflicts: The authors declare no conflict of interest. Read: abstract |
| Camus-Ela 2025 Update on hazelnut allergy: Allergen characterization, epidemiology, food processing technique and detecting strategy Compr Rev Food Sci Food Saf · PMID 39898897 · DOI |
Narrative review |
Review of hazelnut allergy research | Not applicable Protein |
The review says eating hazelnuts may be quite dangerous for allergic people. It says food processing can reduce but not eliminate exposure to hazelnut allergens, and that foods containing hazelnut must be labelled. Narrative review, no pooled numbers in the abstract (Not applicable) Methods, limits and fundingOutcomes: Allergens, processing, labelling and detection Limitations: Narrative review. The abstract gives no numbers. Funding and conflicts: The authors state that they have no conflicts of interest. Read: abstract |
| Del Gobbo 2015 Effects of tree nuts on blood lipids, apolipoproteins, and blood pressure: systematic review, meta-analysis, and dose-response of 61 controlled intervention trials Am J Clin Nutr · PMID 26561616 · DOI |
Meta-analysis |
2582 Adults without cardiovascular disease in 61 trials of tree nuts (walnuts, pistachios, macadamias, pecans, cashews, almonds, hazelnuts, Brazil nuts) |
Tree nuts, all types pooled Kernel Results scaled to one 28.4 g serving a day (trial detail, not advice) 3 to 26 weeks · vs Control diets |
Each serving a day lowered LDL cholesterol by 4.8 mg/dL, total cholesterol by 4.7 mg/dL, ApoB by 3.7 mg/dL and triglycerides by 2.2 mg/dL. No significant effect on the other outcomes, which included blood pressure and C-reactive protein. The authors found no significant difference between nut types. Effects were stronger at 60 g or more a day. LDL -4.8 mg/dL per serving a day (LDL 95% CI -5.5 to -4.2 mg/dL) Methods, limits and fundingOutcomes: Total, LDL and HDL cholesterol, triglycerides, apolipoproteins, blood pressure, C-reactive protein Limitations: All nuts pooled, not hazelnuts alone. Trials of 3 to 26 weeks; blood tests, not heart attacks. Funding and conflicts: The record lists U.S. National Institutes of Health extramural research support. Industry funding of individual trials is not stated in the abstract. Read: abstract |
| Deon 2018 Effect of hazelnut on serum lipid profile and fatty acid composition of erythrocyte phospholipids in children and adolescents with primary hyperlipidemia: A randomized controlled trial Clin Nutr · PMID 28606702 · DOI |
Controlled trial |
66 Children and adolescents with primary hyperlipidaemia (high blood fats), Italy |
Hazelnuts with skin, or hazelnuts without skin, plus dietary advice Kernel 15 to 30 g a day by body weight (trial detail, not advice) 8 weeks · vs Dietary advice for hyperlipidaemia only |
LDL cholesterol, non-HDL cholesterol and the HDL/LDL ratio changed over time in all three groups, but the abstract reports no significant difference between groups for those measures. Hazelnuts did raise monounsaturated fats and the monounsaturated-to-saturated ratio in red blood cell membranes compared with the control group. MUFA increase p=0.008; MUFA/SFA ratio p=0.002 versus control (Not given in the abstract) Methods, limits and fundingOutcomes: Serum lipids, body measurements, fatty acids in red blood cell membranes Limitations: Small, single-blind, 8 weeks, in children with a genetic-type fat disorder. Lipid change did not clearly differ from the control group. Funding and conflicts: Not stated in the abstract. Registered ISRCTN12261900. Read: abstract |
| Estruch 2018 Primary Prevention of Cardiovascular Disease with a Mediterranean Diet Supplemented with Extra-Virgin Olive Oil or Nuts N Engl J Med · PMID 29897866 · DOI |
Controlled trial |
7447 Adults aged 55 to 80 at high heart risk without cardiovascular disease, Spain |
Mediterranean diet supplemented with mixed nuts (or with extra-virgin olive oil), versus advice to reduce dietary fat Mixed nuts (the abstract does not list the nut types) Provided free; amounts not stated in the abstract Median 4.8 years · vs Control diet (advice to reduce dietary fat) |
The first report from 2013 was withdrawn after protocol deviations, including some people who were not randomised. The 2018 re-analysis found fewer major events with the nut diet than with the control diet. Results were similar after leaving out 1588 people whose group assignment was known or suspected to have departed from the protocol. Nuts group 3.4% (83 events) vs control 4.4% (109 events); hazard ratio 0.72 (HR 95% CI 0.54 to 0.95) Methods, limits and fundingOutcomes: Major cardiovascular event: heart attack, stroke or death from cardiovascular causes Limitations: A whole diet pattern with mixed nuts, so the effect cannot be given to hazelnuts alone. Revised analysis after randomisation problems. People knew their diet. Funding and conflicts: Funded by Instituto de Salud Carlos III, the Spanish Ministry of Health and others (abstract). Read: abstract |
| Guaraldi 2018 Effect of short-term hazelnut consumption on DNA damage and oxidized LDL in children and adolescents with primary hyperlipidemia: a randomized controlled trial J Nutr Biochem · PMID 29753234 · DOI |
Controlled trial |
60 Children and adolescents with primary hyperlipidaemia, Italy |
Hazelnuts with skin, or hazelnuts without skin, plus dietary guidelines Kernel 15 to 30 g a day by body weight (trial detail, not advice) 8 weeks · vs Dietary recommendations only (no nuts) |
Endogenous DNA damage fell by 18.9% with hazelnuts with skin and 23.1% without skin. Oxidatively induced DNA strand breaks fell by 16.0% with skin. Oxidised LDL did not change. DNA damage -18.9% (p=0.002) with skin; -23.1% (p=0.007) without skin; strand breaks -16.0% (p=0.02); oxidised LDL no change (Not given as intervals in the abstract) Methods, limits and fundingOutcomes: Oxidised LDL; oxidative DNA damage in blood cells Limitations: Small single-blind trial in a special group of children. Lab markers, not illness. Funding and conflicts: Not stated in the abstract. Registered ISRCTN12261900. Read: abstract |
| Guarneiri 2021 Intake of Nuts or Nut Products Does Not Lead to Weight Gain, Independent of Dietary Substitution Instructions: A Systematic Review and Meta-Analysis of Randomized Trials Adv Nutr · PMID 32945861 · DOI |
Meta-analysis |
Adults in 55 nut-feeding trials lasting over 3 weeks | Nuts or nut-based snacks and meals, all types Kernel More than 3 weeks · vs Control diets |
No change in body weight, BMI or waist circumference with or without instructions to swap nuts for other foods. A small fall in body fat percentage was seen only in studies that gave swapping instructions. Body weight SMD 0.01 kg (no instructions); -0.01 kg (with instructions); body fat -0.32% with instructions (Body weight 95% CI -0.07 to 0.08 (no instructions); body fat -0.61 to -0.03 (with instructions)) Methods, limits and fundingOutcomes: Body weight, BMI, waist circumference, body fat percentage Limitations: All nuts pooled, not hazelnuts alone. Methods varied between trials. Funding and conflicts: The record lists non-U.S. government research support. Industry funding is not stated in the abstract. Read: abstract |
| Gutiérrez-Díaz 2024 Identification of New Allergens in Macadamia Nut and Cross-Reactivity with Other Tree Nuts in a Spanish Cohort Nutrients · PMID 38612981 · DOI |
Lab human samples human-samples |
7 Seven people in Spain allergic to macadamia nut |
Blood IgE binding tests with macadamia, hazelnut and walnut extracts Protein |
Hazelnut extract, but not walnut extract, blocked IgE binding to a macadamia oleosin protein, which suggests cross-reaction between macadamia and hazelnut. Hazelnut extract inhibited macadamia oleosin IgE binding (Not applicable) Methods, limits and fundingOutcomes: Cross-reaction between macadamia and other tree nuts Limitations: Seven patients, laboratory tests. Not a measure of how common cross-allergy is. Funding and conflicts: The authors declare no conflicts of interest and say the funders had no role. Read: abstract |
| Hofmann 2013 Cor a 1-reactive T cells and IgE are predominantly cross-reactive to Bet v 1 in patients with birch pollen-associated food allergy to hazelnut J Allergy Clin Immunol · PMID 23246018 · DOI |
Lab human samples human-samples |
People with birch pollen allergy and associated food allergy to hazelnut, carrot or both | Blood tests of antibodies and T cells against birch (Bet v 1), hazelnut (Cor a 1) and carrot (Dau c 1) proteins Protein |
Most hazelnut Cor a 1-reactive IgE antibodies also reacted to birch Bet v 1. T cells primed with one protein responded to the other in all patients in the study, showing cross-reaction between birch and hazelnut allergens. Cross-reactivity found in all patients studied (Not applicable) Methods, limits and fundingOutcomes: IgE and T-cell cross-reaction between birch pollen and hazelnut proteins Limitations: A laboratory method study in a small group of patients; it does not say how often reactions happen. Funding and conflicts: Not stated in the abstract. The record lists non-U.S. government research support. Read: abstract |
| Masthoff 2014 Hazelnut allergy differs between children and adults in frequency of severity, aetiology and relevance of diagnostic parameters Clin Exp Allergy · PMID 25333730 · DOI |
Cross sectional |
271 Adults (120, challenged) and children (151, from an earlier study) challenged with hazelnut, Netherlands |
Double-blind placebo-controlled hazelnut food challenge Kernel Challenge doses not stated in the abstract Single challenge · vs Comparison of adults and children |
Hazelnut allergy was confirmed in 95 of 120 adults (79%). Of those, 77% had only subjective symptoms and 23% had objective symptoms. In children, 63% had objective symptoms. Birch pollen allergy also occurred in 82% of the adults and 39% of the children with hazelnut allergy. Adults: allergy confirmed 79%; objective symptoms 23%. Children: objective symptoms 63%. Birch pollen allergy 82% vs 39%. (Not given in the abstract) Methods, limits and fundingOutcomes: Confirmed hazelnut allergy, symptom type, birch pollen allergy, usefulness of tests Limitations: People sent for challenge testing, so not the general public. Children and adults came from different studies. Funding and conflicts: Not stated in the abstract. Read: abstract |
| Nilsson 2020 Allergen components in diagnosing childhood hazelnut allergy: Systematic literature review and meta-analysis Pediatr Allergy Immunol · PMID 31301691 · DOI |
Meta-analysis |
635 Mostly children suspected of hazelnut allergy (7 of 8 studies), confirmed by food challenge |
Blood IgE tests to hazelnut components (Cor a 1, 9, 14) and whole extract Protein · vs Oral food challenge as the reference |
Tests for Cor a 14 and Cor a 9 were more specific than tests for Cor a 1 or whole-hazelnut extract. In children, specificity was 81.7% for Cor a 14, 67.3% for Cor a 9, 22.5% for Cor a 1 and 10.8% for hazelnut extract. Specificity: Cor a 14 81.7%; Cor a 9 67.3%; Cor a 1 22.5%; extract 10.8% (Cor a 14 95% CI 77.1 to 85.6) Methods, limits and fundingOutcomes: Diagnostic accuracy of blood tests for hazelnut allergy Limitations: This is about testing, which belongs to an allergist. Mostly children. Funding and conflicts: The record lists non-U.S. government research support. Read: abstract |
| Perna 2016 Effects of Hazelnut Consumption on Blood Lipids and Body Weight: A Systematic Review and Bayesian Meta-Analysis Nutrients · PMID 27897978 · DOI |
Meta-analysis |
425 Adults in 9 hazelnut diet studies; 3 randomised studies pooled for lipids |
Whole hazelnuts as part of the diet Kernel 29 to 69 g a day (trial detail, not advice) 28 to 84 days · vs Control diet without hazelnuts |
Across 3 randomised studies, LDL cholesterol was lower on the hazelnut diet by 0.150 mmol/L. Total cholesterol showed a trend down. HDL, triglycerides and BMI did not change. LDL -0.150 mmol/L; total cholesterol -0.127 mmol/L (trend); HDL +0.002; triglycerides +0.045; BMI +0.062 kg/m2 (LDL 95% HPD -0.308 to -0.003; total cholesterol -0.284 to 0.014; BMI -0.293 to 0.469) Methods, limits and fundingOutcomes: LDL, total and HDL cholesterol, triglycerides, BMI Limitations: Only 3 randomised studies could be pooled; the LDL range almost touches zero. Short diets (28 to 84 days). Funding and conflicts: The authors declare no competing interests. Read: abstract |
| Salvatore 2023 Mycotoxin Contamination in Hazelnut: Current Status, Analytical Strategies, and Future Prospects Toxins (Basel) · PMID 36828414 · DOI |
Narrative review |
Review of mycotoxin research in hazelnuts | Not applicable Kernel and nut |
The review says hazelnuts are a potential source of mycotoxins, that contamination can occur during fruit development or after harvest, and that European safety regulation has prompted many tests for aflatoxin B1 and total aflatoxins. Other mycotoxins have also been detected in hazelnuts. Narrative review, no pooled numbers in the abstract (Not applicable) Methods, limits and fundingOutcomes: Mycotoxins detected in hazelnuts and control methods Limitations: Narrative review. The abstract gives no contamination rates. Funding and conflicts: The authors declare no conflict of interest. Read: abstract |
| s-fda-food-allergies FDA: Food Allergies · Source |
Health agency n/a |
Methods, limits and fundingRead: full-text | ||
| s-gbif-corylus-avellana GBIF species match: Corylus avellana L. · Source |
Reference database n/a |
Methods, limits and fundingRead: full-text | ||
| s-medlineplus-vite MedlinePlus: Vitamin E in diet · Source |
Health agency n/a |
Methods, limits and fundingRead: full-text | ||
| s-nhs-food-allergy NHS: Food allergy · Source |
Health agency n/a |
Methods, limits and fundingRead: full-text | ||
| s-nhs-foods-avoid NHS: Foods to avoid giving babies and young children · Source |
Health agency n/a |
Methods, limits and fundingRead: full-text | ||
| s-nhs-pregnancy-foods NHS: Foods to avoid in pregnancy · Source |
Health agency n/a |
Methods, limits and fundingRead: full-text | ||
| s-pubchem-alpha-tocopherol PubChem: alpha-Tocopherol (CID 14985) · Source |
Reference database n/a |
Methods, limits and fundingRead: full-text | ||
| s-pubchem-beta-sitosterol PubChem: beta-Sitosterol (CID 222284) · Source |
Reference database n/a |
Methods, limits and fundingRead: full-text | ||
| s-pubchem-oleic-acid PubChem: Oleic acid (CID 445639) · Source |
Reference database n/a |
Methods, limits and fundingRead: full-text | ||
| s-usda-fdc-170581 USDA FoodData Central: Nuts, hazelnuts or filberts (FDC 170581) · Source |
Reference database n/a |
Methods, limits and fundingRead: full-text | ||
| s-who-mycotoxins WHO: Mycotoxins fact sheet · Source |
Health agency n/a |
Methods, limits and fundingRead: full-text |
What we do not know yet
- Only 3 randomised hazelnut studies could be pooled for cholesterol, and all were short.
- No trial of hazelnuts on heart attacks, stroke or death was found; those data are for nuts in general.
- No trial of hazelnut oil, skin extract, flour or supplements was read.
- Blood pressure, blood sugar and inflammation findings are weak and mostly from small studies.
- Pesticide residues, heavy metals, oxalate, FODMAP and breastfeeding were not researched.
How new research is added
New studies are found by a saved PubMed search and placed in a review queue before the page changes.
Lab markers
What changed in blood or saliva tests during trials. A changed number is not the same as feeling or being healthier, and we give no "normal ranges".
Metabolic 1
LDL cholesterol
Lowered in trials
The cholesterol carried in low-density lipoprotein particles, often called "bad" cholesterol.
Low certaintyResults and what it means
Why it was measured
Higher LDL is linked to a higher risk of heart disease.
Statistical vs. clinical meaning
A small change in a blood test. It does not show fewer heart attacks.
Safety implication
None specific, apart from nut allergy.
| Study | Result | People | Product |
|---|---|---|---|
| 13 | Pooled LDL -0.150 mmol/L (95% HPD -0.308 to -0.003) on a hazelnut diet vs control, 3 randomised studies. | Adults | Hazelnut-enriched diet, 29 to 69 g a day for 28 to 84 days |
| 4 | LDL -4.8 mg/dL (95% CI -5.5 to -4.2) per serving of tree nuts a day, 61 trials; no significant difference between nut types. | Adults without cardiovascular disease | Tree nuts, all types |
Other 3
HDL cholesterol and triglycerides
No change in trials
HDL is the "good" cholesterol carrier. Triglycerides are a blood fat.
Low certaintyResults and what it means
Why it was measured
Part of a standard blood fat panel.
Statistical vs. clinical meaning
No clear hazelnut effect on HDL or triglycerides. The small triglyceride fall is for all nuts pooled.
Safety implication
None specific.
| Study | Result | People | Product |
|---|---|---|---|
| 13 | HDL +0.002 mmol/L and triglycerides +0.045 mmol/L, both with wide intervals around zero, on a hazelnut diet. | Adults | Hazelnut-enriched diet |
| 4 | For all tree nuts pooled, triglycerides were 2.2 mg/dL lower per serving a day; HDL was not significantly changed. | Adults without cardiovascular disease | Tree nuts, all types |
Body mass index (BMI)
No change in trials
Weight divided by height squared, a rough measure of body size.
Moderate certaintyResults and what it means
Why it was measured
Used to check for weight gain on a diet.
Statistical vs. clinical meaning
No weight gain found in these trials.
Safety implication
None specific.
DNA damage in blood cells (lab marker)
Lowered in trials
A test of strand breaks and oxidative damage in the DNA of white blood cells.
Very low certaintyResults and what it means
Why it was measured
Used as a marker of oxidative stress.
Statistical vs. clinical meaning
A lab marker in one small trial. It does not show benefit for health.
Safety implication
None specific.
| Study | Result | People | Product |
|---|---|---|---|
| 7 | Endogenous DNA damage fell 18.9% (hazelnuts with skin) and 23.1% (without skin); oxidised LDL did not change. | 60 children and adolescents with primary hyperlipidaemia | Hazelnuts, 15 to 30 g a day for 8 weeks |
Safety
What studies and official sources say about side effects, medicines and who should check first. Each point shows what kind of evidence it comes from.
Main points to know 4
- Hazelnut is a tree nut allergen, and reactions can be severe. The NHS lists hazelnuts among tree nuts that can cause food allergy. In the US, tree nuts are one of nine major food allergens (FDA). A 2025 review says eating hazelnuts may be quite dangerous for people who are allergic. In a Dutch study, hazelnut allergy was confirmed by challenge in 79% of 120 adults sent for testing, and objective symptoms were more common in children (63%) than adults (23%). Call emergency services for swelling of the lips, mouth, throat or tongue, fast or hard breathing, a tight throat or fainting. Authoritative guidance 18 15 3 11
- Itchy mouth from raw hazelnut in people with birch pollen allergy. In a laboratory study of people with birch pollen allergy and hazelnut allergy, most antibodies against a hazelnut protein (Cor a 1) also reacted to the main birch pollen protein. In the Dutch study, 82% of adults and 39% of children with hazelnut allergy also had birch pollen allergy. This often causes itching in the mouth and throat. A doctor or allergist should sort out what kind of allergy you have. Laboratory research 10 11
- Whole nuts can cause choking in children under 5. The NHS says whole nuts should not be given to children under 5 because they can choke on them. Crushed or ground nuts can be added to food from about 6 months, and nut butter should be spread thinly, not given on its own. If there is a family history of food allergy, the NHS says to talk to a GP or health visitor before introducing any type of nut. Authoritative guidance 19
- Mould toxins (aflatoxins) can contaminate hazelnuts. WHO names hazelnuts among nuts that are regularly contaminated with aflatoxins. Large doses can cause life-threatening liver damage, and there is evidence that aflatoxins can cause liver cancer in humans. WHO advises inspecting nuts and discarding any that look mouldy, discoloured or shrivelled. A 2023 review says hazelnuts can pick up mycotoxins during growth or after harvest. The sources read do not say how much people usually take in. Authoritative guidance 25 14
Side effects 4
| Effect | How often | Severity and recovery | Evidence |
|---|---|---|---|
| Allergic reaction to hazelnut, from itching or swelling in the mouth to severe anaphylaxis The Dutch study found objective symptoms in 23% of allergic adults and 63% of allergic children; those people were referred for testing, so the figures are not for the general public. | Not established | mild to severe Not stated in the sources read | Authoritative guidance 18 11 3 |
| Itchy mouth and throat after raw hazelnut in people with birch pollen allergy The laboratory study shows the protein link. How mild or common it is was not stated in these abstracts. | Not established | usually mild Not stated in the sources read | Laboratory research 10 11 |
| Choking on whole nuts by young children NHS advice is to avoid whole nuts under age 5. | Not established | potentially life-threatening Not applicable | Authoritative guidance 19 |
| Bleeding in the brain (hemorrhagic stroke) with high-dose vitamin E supplements This is about supplements, not food. MedlinePlus says eating vitamin E in foods is not risky. | Not established | severe Not stated | Authoritative guidance 17 |
Liver
No liver injury from eating hazelnuts that are free of mould was found in the sources read. WHO says large doses of aflatoxins, which can contaminate hazelnuts, can cause life-threatening liver damage, and there is evidence that they can cause liver cancer in humans. LiverTox was not checked. 25
How often. No frequency was found.
Monitoring. No agency monitoring advice was found.
This is a safety connection. It is not evidence that Hazelnuts supports liver health.
Medicines and supplements 3
| With | Why it matters | Importance | Evidence | What to do |
|---|---|---|---|---|
| Prescription and over-the-counter medicines in general prescription | No source read describes hazelnuts changing how any medicine works. | Absence of a warning in the sources read is not proof of safety. | Authoritative guidance Not enough evidence | Ask a pharmacist about your own medicines. |
| High-dose vitamin E supplements supplement | MedlinePlus says high doses of vitamin E supplements (alpha-tocopherol) might raise the risk of bleeding in the brain. Hazelnuts contain vitamin E, but MedlinePlus says eating it in foods is not risky. | This concerns supplements, not hazelnuts as food. | Authoritative guidance Low certainty 17 | If you take vitamin E supplements or blood thinners, ask your doctor or pharmacist. |
| Warfarin (vitamin K) prescription | USDA lists 14.2 micrograms of vitamin K per 100 g of raw hazelnuts, a small amount compared with green leafy vegetables. Whether this matters for warfarin was not looked up. | Not researched; no source read links hazelnuts to warfarin. | Reference database Not enough evidence 24 | If you take warfarin, follow your clinic's advice about food. |
Who should check first 5
| Situation | Advice | Evidence |
|---|---|---|
| Known allergy to hazelnuts or other tree nuts | Avoid hazelnuts and ask an allergist about other nuts and about testing. A 2020 review found that blood tests for different hazelnut proteins differ in how well they avoid over-diagnosing allergy in children, so testing belongs to an allergist. Call emergency services for trouble breathing or swelling of the lips, mouth, throat or tongue. | Authoritative guidance 18 15 12 |
| Allergy to macadamia nut | In a laboratory study of 7 people allergic to macadamia, hazelnut extract blocked IgE binding to a macadamia protein, which suggests cross-reaction. Ask an allergist before eating hazelnuts. | Laboratory research 9 |
| Children under 5 (choking) | No whole nuts. Crushed or ground nuts and thinly spread nut butter are the NHS options from about 6 months. If there is a family history of allergy, talk to a GP or health visitor first. | Authoritative guidance 19 |
| Pregnancy | The NHS says peanuts and other nuts are safe to eat in pregnancy unless you have been told not to by a doctor or midwife, or you have an allergy. | Authoritative guidance 20 |
| Breastfeeding | No hazelnut-specific source was read. Ask your doctor or midwife if you or your baby has a nut allergy. | Unknown |
Overdose, product quality and regulators
Summary. No toxicity from eating clean hazelnuts as food was found in the sources read. The concerns are allergy, choking in young children and mould toxins.
Animal. Not reviewed.
Human doses studied. Hazelnut trials gave 15 to 69 g a day for 4 to 12 weeks. The abstracts read do not report side effects.
Overdose response. Not found.
Genotoxicity. Aflatoxins from mouldy nuts are genotoxic (WHO). Not researched for clean hazelnuts.
Toxic or hazardous parts. No toxic part was identified in the sources read.
Aflatoxins and other mould toxins can be present in hazelnuts. Pesticide residues and heavy metals in hazelnuts were not researched.
Aflatoxins (mould toxins). WHO names hazelnuts among nuts regularly contaminated with aflatoxins. It advises inspecting nuts, discarding any that look mouldy, discoloured or shrivelled, buying nuts as fresh as possible, and storing them dry and not too warm without keeping them for long. 25
Other mycotoxins. A 2023 review says hazelnuts may be infected by several fungi, and that other mycotoxins have also been detected, including ochratoxins and trichothecenes. It notes that European regulation has led to many tests for aflatoxin B1 and total aflatoxins. 14
| Body | Action | Date |
|---|---|---|
| NHS (UK) (United Kingdom) | Food allergy page lists tree nuts, including hazelnuts, as common food allergens and gives emergency signs source | 2026-08-20 |
| NHS (UK) (United Kingdom) | Whole nuts should not be given to children under 5; crushed or ground nuts can be added to food from about 6 months source | 2026-02-18 |
| NHS (UK) (United Kingdom) | Foods to avoid in pregnancy: peanuts and other nuts are safe unless a doctor or midwife has told you not to, or you have an allergy source | 2026-06-15 |
| FDA (US Food and Drug Administration) (United States) | Food allergy page: the nine major food allergens are milk, eggs, fish, crustacean shellfish, tree nuts, peanuts, wheat, soybeans and sesame source | 2026-03-11 |
| WHO (International) | Mycotoxins fact sheet names hazelnuts among nuts regularly contaminated with aflatoxins and gives advice to inspect, discard mouldy nuts, buy fresh and store dry source | 2023-10-02 |
| MedlinePlus (US National Library of Medicine) (United States) | Vitamin E page: names hazelnuts/filberts as a vitamin E food; eating vitamin E in foods is not risky; high-dose vitamin E supplements might raise the risk of bleeding in the brain source | 2025-01-21 |
When to get medical help
- Trouble breathing, a tight throat or trouble swallowing, or swelling of the lips, mouth, throat or tongue after eating hazelnuts (NHS lists these as reasons to call emergency services)
- Lips, tongue or skin turning blue, grey or pale, sudden confusion or drowsiness, or fainting and not waking, after eating a nut (NHS)
- A child under 5 choking on a nut
- Any new symptoms after eating nuts: the NHS says to see a GP if you think you or your child may have a food allergy
Stop using the product and contact a clinician or emergency service. In the US, Poison Control is 1-800-222-1222.
General information only, not medical advice. Ask a clinician or pharmacist before use, especially with medicines, in pregnancy or with a health condition. See the Natural Remedy Safety guide.
Frequently asked questions
What are hazelnuts good for?
Do hazelnuts lower cholesterol?
Do hazelnuts prevent heart disease?
Will hazelnuts make me gain weight?
Do hazelnuts lower blood pressure or blood sugar?
Why do raw hazelnuts make my mouth itch?
Is hazelnut allergy the same as peanut allergy?
Can young children eat hazelnuts?
Not whole nuts under age 5, because of choking (NHS). Crushed or ground nuts can be added to food from about 6 months, and nut butter should be spread thinly. Talk to a GP or health visitor first if allergy runs in the family.
Are hazelnuts safe in pregnancy?
The NHS says nuts are safe to eat in pregnancy unless you have an allergy or a doctor or midwife has told you not to. Ask your midwife or doctor if unsure.
Can hazelnuts carry mould toxins?
Do hazelnuts interact with medicines?
No source read names a medicine that hazelnuts affect, but that is not proof of safety. High-dose vitamin E supplements, which are not food, may raise bleeding risk (MedlinePlus). Ask a pharmacist.
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Editorial transparency
- Written by
- AlternativeMed editorial team. Research compiled with AI assistance, then checked against the sources listed.
- Medical review
- None. This page has not been reviewed by a physician or pharmacist.
- First published
- 2026-10-26
- Last substantive update
- 2026-10-26
- How we research
- We started from our existing hazelnut summary, re-checked nutrition at USDA FoodData Central, and re-read the abstracts of the cited reviews and trials at PubMed. We also read the NHS, FDA, WHO and MedlinePlus pages named. Only abstracts were read for studies. Items we could not verify are flagged in the research gaps.
- How we rate evidence
- See "How we rate evidence" in the Evidence tab.
- Independence
- No product is promoted on this page. No affiliate links are shown.
Sources 25
Each source was opened and checked. Where we read only the abstract, it says so. The small numbers in the text point here.
- Aune D, Keum N, Giovannucci E, et al.. Nut consumption and risk of cardiovascular disease, total cancer, all-cause and cause-specific mortality: a systematic review and dose-response meta-analysis of prospective studies. BMC Med. 2016. PMID 27916000. DOI 10.1186/s12916-016-0730-3. (abstract)
- Brown R, Ware L, Tey SL. Effects of Hazelnut Consumption on Cardiometabolic Risk Factors and Acceptance: A Systematic Review. Int J Environ Res Public Health. 2022. PMID 35270573. DOI 10.3390/ijerph19052880. (abstract)
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- . FDA: Food Allergies. . . (full-text)
- . GBIF species match: Corylus avellana L.. . . (full-text)
- . MedlinePlus: Vitamin E in diet. . . (full-text)
- . NHS: Food allergy. . . (full-text)
- . NHS: Foods to avoid giving babies and young children. . . (full-text)
- . NHS: Foods to avoid in pregnancy. . . (full-text)
- . PubChem: alpha-Tocopherol (CID 14985). . . (full-text)
- . PubChem: beta-Sitosterol (CID 222284). . . (full-text)
- . PubChem: Oleic acid (CID 445639). . . (full-text)
- . USDA FoodData Central: Nuts, hazelnuts or filberts (FDC 170581). . . (full-text)
- . WHO: Mycotoxins fact sheet. . . (full-text)
Where to buy
Check the label first. Whatever you buy, look for these:
- Raw or roasted, and salted or unsalted
- A best-by date, since nuts and seeds turn rancid
- Tree nut and peanut allergy warnings
- A resealable bag, and cool storage once opened
Talk to a pharmacist or doctor before you start any supplement, especially if you take medicines. See the Safety tab for interactions.
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