Explore Functional Foods
An A to Z directory of the foods in the Functional Foods library, with the collection, the main topic of each guide, any caution it names and a link to the full guide.
Content last updated . This page has not been medically reviewed.
Safety first. Natural products can cause side effects and interact with medicines. Read functional food safety before you use anything on this page.
Read this first
Food allergy comes before everything else on a food page. The U.S. FDA lists nine major food allergens: milk, eggs, fish, crustacean shellfish, tree nuts, peanuts, wheat, soybeans and sesame. [1] For trouble breathing or swelling of the face or throat after eating, call 911. Some foods can also change how a medicine works. The FDA says some medicines carry warnings against drinking grapefruit juice or eating grapefruit while taking them, [2] and MedlinePlus says foods with vitamin K can affect how warfarin works. [3] Ask a pharmacist or the prescriber about your own medicines. More on how foods and medicines interact and in How Interactions Work.How to use this directory
This page lists every food that has its own guide in the library, in alphabetical order. Each guide is about the food as eaten. It separates what randomized trials found from what large population studies found, and it names the comparison food where a study used one. The columns below show the topic named in each guide's title. They are not a verdict: the strength of evidence is labeled inside each guide, and food evidence is mostly observational. [4] A cell that says "See the guide" means the title does not name one main caution, not that none exists.A to Z directory
| Food | Collection | Main topic in the guide | Question or caution named | Guide |
|---|---|---|---|---|
| Almonds | Nuts, seeds and fats | Research and cautions | Tree nut allergy | More about Almonds → |
| Avocado | Nuts, seeds and fats | Research and cautions | See the guide | More about Avocado → |
| Barley | Fiber-rich foods | Beta-glucan and research | See the guide | More about Barley → |
| Beets (beetroot and beet juice) | Fruits and vegetables | Dietary nitrate and blood pressure | See the guide | More about Beets (beetroot and beet juice) → |
| Berries: strawberries, raspberries, blackberries | Fruits and vegetables | What research shows beyond blueberries | See the guide | More about Berries: strawberries, raspberries, blackberries → |
| Black pepper, cayenne and capsaicin foods | Spices as foods | Culinary use and what research shows | See the guide | More about Black pepper, cayenne and capsaicin foods → |
| Black tea | Drinks | Research and caffeine | Caffeine | More about Black tea → |
| Blueberries | Fruits and vegetables | What research shows | See the guide | More about Blueberries → |
| Bone broth | Protein foods | Claims checked | Marketing claims | More about Bone broth → |
| Broccoli and other cruciferous vegetables | Fruits and vegetables | Research | Thyroid questions | More about Broccoli and other cruciferous vegetables → |
| Chia seeds | Fiber-rich foods | What research shows | Choking | More about Chia seeds → |
| Cinnamon (cassia and Ceylon) | Spices as foods | Cassia vs Ceylon | Coumarin | More about Cinnamon (cassia and Ceylon) → |
| Citrus fruits and orange juice | Fruits and vegetables | Research | Grapefruit and medicines | More about Citrus fruits and orange juice → |
| Coffee | Drinks | Research reviews | Caffeine and pregnancy | More about Coffee → |
| Cranberries | Fruits and vegetables | Urinary tract infections: what Cochrane found | See the guide | More about Cranberries → |
| Dark chocolate and cocoa | Drinks | Research | Sugar and metals | More about Dark chocolate and cocoa → |
| Extra virgin olive oil | Nuts, seeds and fats | Use in the diet and research | See the guide | More about Extra virgin olive oil → |
| Flaxseed | Fiber-rich foods | Ground vs whole | See the guide | More about Flaxseed → |
| Fortified foods | Fortified foods | What fortification is, what labels tell you | See the guide | More about Fortified foods → |
| Fortified plant milks and cereals | Fortified foods | What is added and what labels show | See the guide | More about Fortified plant milks and cereals → |
| Fruit juice vs whole fruit | Fruits and vegetables | What research shows | See the guide | More about Fruit juice vs whole fruit → |
| Ginger (as a food) | Spices as foods | Fresh, dried and in cooking | See the guide | More about Ginger (as a food) → |
| Green, black, white and oolong tea | Drinks | What differs | See the guide | More about Green, black, white and oolong tea → |
| Kefir | Fermented foods | Research and live cultures | See the guide | More about Kefir → |
| Kimchi | Fermented foods | Research | Sodium | More about Kimchi → |
| Kombucha | Fermented foods | Research | Safety | More about Kombucha → |
| Leafy greens | Fruits and vegetables | Research | Vitamin K with warfarin | More about Leafy greens → |
| Legumes (beans, lentils, chickpeas) | Fiber-rich foods | Overview | See the guide | More about Legumes (beans, lentils, chickpeas) → |
| Matcha and green tea as drinks | Drinks | Research | Caffeine and liver | More about Matcha and green tea as drinks → |
| Miso | Fermented foods | Nutrition and research | Sodium | More about Miso → |
| Mushrooms as food | Fruits and vegetables | Where to read about mushrooms | See the guide | More about Mushrooms as food → |
| Natto | Fermented foods | Nutrition | Vitamin K and warfarin | More about Natto → |
| Oats | Fiber-rich foods | Beta-glucan and cholesterol | Gluten questions | More about Oats → |
| Oily fish | Fish, soy and protein foods | Heart research | Mercury advice | More about Oily fish → |
| Onions, garlic and other alliums (as food) | Fruits and vegetables | Culinary use | See the guide | More about Onions, garlic and other alliums (as food) → |
| Other nuts: pecans, cashews, Brazil nuts, macadamias | Nuts, seeds and fats | Overview | Tree nut allergy | More about Other nuts: pecans, cashews, Brazil nuts, macadamias → |
| Pickles (fermented vs vinegar) | Fermented foods | What counts as probiotic | See the guide | More about Pickles (fermented vs vinegar) → |
| Pistachios | Nuts, seeds and fats | Research and cautions | Tree nut allergy | More about Pistachios → |
| Plant milks: oat, almond, soy and others | Drinks | Comparison of types | Nut and soy allergy | More about Plant milks: oat, almond, soy and others → |
| Pomegranate and pomegranate juice | Fruits and vegetables | Research | Medicine cautions | More about Pomegranate and pomegranate juice → |
| Prebiotic foods: inulin, onions, garlic, chicory | Fiber-rich foods | What prebiotic means in foods | See the guide | More about Prebiotic foods: inulin, onions, garlic, chicory → |
| Pumpkin seeds | Nuts, seeds and fats | Nutrition and research | See the guide | More about Pumpkin seeds → |
| Resistant starch foods | Fiber-rich foods | Cooked-and-cooled starches, green bananas, beans | See the guide | More about Resistant starch foods → |
| Saffron, cloves and other whole spices | Spices as foods | Culinary use | See the guide | More about Saffron, cloves and other whole spices → |
| Sauerkraut | Fermented foods | Research and live cultures | See the guide | More about Sauerkraut → |
| Sourdough bread | Fermented foods | Claims checked | Marketing claims | More about Sourdough bread → |
| Soy foods | Fish, soy and protein foods | LDL, isoflavones and common concerns | Soy allergy | More about Soy foods → |
| Sweet potatoes, carrots and orange vegetables | Fruits and vegetables | Overview | See the guide | More about Sweet potatoes, carrots and orange vegetables → |
| Tart cherries and cherry juice | Fruits and vegetables | Sleep, gout and exercise research | See the guide | More about Tart cherries and cherry juice → |
| Tempeh | Fermented foods | Nutrition and research | See the guide | More about Tempeh → |
| Tomatoes and lycopene | Fruits and vegetables | Research | See the guide | More about Tomatoes and lycopene → |
| Turmeric (as a food) | Spices as foods | Spice vs supplement | Supplement risks differ | More about Turmeric (as a food) → |
| Walnuts | Nuts, seeds and fats | Cholesterol research | Tree nut allergy | More about Walnuts → |
| Whole grains and ancient grains | Fiber-rich foods | What research shows | See the guide | More about Whole grains and ancient grains → |
| Yogurt | Fermented foods | Research and live cultures | Milk allergy | More about Yogurt → |
Foods found inside a group guide
Some foods share a guide. Look up the name here, then open the row shown above.- Cashews, pecans, Brazil nuts and macadamias: see "Other nuts".
- Strawberries, raspberries and blackberries: see "Berries".
- Carrots and sweet potatoes: see "Sweet potatoes, carrots and orange vegetables".
- Onions and garlic: see "Onions, garlic and other alliums" and "Prebiotic foods".
- Beans, lentils and chickpeas: see "Legumes".
- Cloves and saffron: see "Saffron, cloves and other whole spices".
- Matcha: see "Matcha and green tea as drinks".
- Oat milk, almond milk and soy milk: see "Plant milks".
Foods with a guide in another section
Some foods are owned by other parts of AlternativeMed, so they are not repeated here.| Food | Where to read |
|---|---|
| Olive oil as a home or skin item | More about Olive oil as a home or skin item → |
| Cacao as an ingredient | More about Cacao as an ingredient → |
| Honey | More about Honey → |
| Seaweed, sea moss and kelp | More about Seaweed, sea moss and kelp → |
| Apple cider vinegar | More about Apple cider vinegar → |
| Colloidal oatmeal (skin) | More about Colloidal oatmeal (skin) → |
| Green tea as an herb | More about Green tea as an herb → |
| Garlic as an herb | More about Garlic as an herb → |
| Ginger as an herb | More about Ginger as an herb → |
| Turmeric as an herb | More about Turmeric as an herb → |
What is not in this directory
- Supplements. A pill, powder or capsule made from a food is not the food. See Food vs Supplement Sources of Nutrients. Results for one do not carry over to the other.
- Nutrients and compounds such as fiber, beta-glucan, polyphenols and nitrate have their own guide: Nutrients and Compounds in Foods.
- Goals, labels, preparation and claim checks are on By wellness goal, Reading food labels, Preparation and everyday use and Food claim checks.
- Foods with no guide. A food missing from the table has not been written up in this library. That says nothing about whether research on it exists.
Frequently asked questions
Does being on this list mean a food is proven to protect health?
No. The list shows which foods have a guide. Most research on foods is observational, and one review notes that the results of many nutritional epidemiology studies have not been replicated in later studies. [4] Each guide labels its evidence.
Is there a guide for every food?
No. Only the foods in the table have one. The group guides cover several related foods at once, as listed above.
I take warfarin. Which foods matter?
MedlinePlus says to eat consistent amounts of vitamin K-containing food from week to week and to talk to your doctor before changing your diet. [3] The leafy greens and natto guides are the ones that name vitamin K. Your prescriber or pharmacist decides what is right for you.
What should I do about a food allergy?
The FDA's list of nine major allergens includes tree nuts, soybeans, fish, milk and sesame. [1] A clinician can advise on testing and an action plan. Call 911 for trouble breathing or swelling of the face or throat. See Food Allergy Basics and Emergency Signs.
Are supplements made from these foods covered here?
No. Supplements are covered in Vitamins & Supplements. The FDA describes a dietary supplement as a product intended for ingestion that contains a dietary ingredient intended to supplement the diet. [5]
References
- U.S. Food and Drug Administration. Food Allergies. Read 2026-10-22.
- U.S. Food and Drug Administration. Grapefruit Juice and Some Drugs Don't Mix. Consumer Update. Read 2026-10-22.
- MedlinePlus. Warfarin. U.S. National Library of Medicine. Read 2026-10-22.
- Kamangar F, Karimi P. The state of nutritional epidemiology: why we are still unsure of what we should eat? Arch Iran Med 2013. PMID 23906255. Read 2026-10-22 (abstract).
- U.S. Food and Drug Administration. Questions and Answers on Dietary Supplements. Read 2026-10-22.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.