Beta-Carotene Supplements, Smokers and the ATBC and CARET Trials
The ATBC and CARET trials found beta-carotene pills raised lung cancer risk in smokers and asbestos-exposed workers. What the trials, follow-ups and reviews found, and who should ask a clinician.
Content last updated . This page has not been medically reviewed.
What is Beta-carotene good for?
What the body uses it for, and how strong the evidence is. A normal job in the body is not proof that extra supplements add benefit; each card says which.
Source of vitamin A (provitamin A)
Established roleBeta-carotene is a plant pigment that the body converts into vitamin A after it is eaten. Vitamin A helps vision in dim light and keeps the eye surface, skin and immune system healthy.
Supplements: The sources read do not show that beta-carotene supplements help people who already get enough vitamin A. Food is the usual source.
Antioxidant activity in the laboratory
Lab or animal research onlyBeta-carotene is grouped with antioxidants, compounds that can neutralise reactive molecules in laboratory settings. That does not show a pill protects health.
Supplements: Laboratory antioxidant activity is not evidence of benefit; large trials of beta-carotene supplements found harm in some groups.
Diets rich in fruit and vegetables versus beta-carotene pills
Preliminary or mixedEating plenty of colourful fruit and vegetables is linked to lower disease risk, but taking the pigment as a pill has not reproduced that effect.
Supplements: Food findings cannot be transferred to supplements.
Part of the original AREDS eye formula (later removed)
Preliminary or mixedThe first AREDS eye formula contained beta-carotene; the improved AREDS2 formula dropped it and added lutein and zeaxanthin.
Supplements: Support is for the combined formula in people with intermediate age-related macular degeneration, not for beta-carotene alone. Current and former smokers are advised by the NEI to avoid the formula containing beta-carotene.
Connected topics
Open a group to see how each topic connects and how strong the evidence is.
Body systems (3)
- Respiratory HealthDocumented risk
High-dose beta-carotene pills raised lung cancer risk in smokers and asbestos-exposed workers in two large trials. This is a risk, not a benefit.
- Respiratory SystemDocumented risk
High-dose beta-carotene pills raised lung cancer risk in smokers and asbestos-exposed workers in two large trials. This is a risk, not a benefit.
- Cardiovascular SystemDocumented risk
NCCIH says high doses of beta-carotene may increase death from cardiovascular disease, and the USPSTF recommends against it for preventing heart disease. Not shown to protect the heart.
Body parts (3)
- LungsDocumented risk
High-dose beta-carotene pills raised lung cancer risk in smokers and asbestos-exposed workers in two large trials. This is a risk, not a benefit.
- HeartDocumented risk
NCCIH says high doses of beta-carotene may increase death from cardiovascular disease, and the USPSTF recommends against it for preventing heart disease. Not shown to protect the heart.
- SkinDocumented risk
Very high intake can turn skin yellow or orange; this fades when intake is reduced and is not a skin benefit.
Functional actions (1)
- AntioxidantLab or animal research only
Beta-carotene is grouped with antioxidants in laboratory terms. That does not show that supplements prevent disease; trials found harm in some groups.
Conditions & symptoms (2)
- Lung NeoplasmsDocumented risk
Beta-carotene supplements raised lung cancer risk in smokers and asbestos-exposed workers in the ATBC and CARET trials; they do not prevent cancer.
- Cardiovascular DiseasesDocumented risk
NCCIH says high doses may increase death from cardiovascular disease; the USPSTF recommends against beta-carotene for preventing it.
Documented risks and interactions (6)
- Higher lung cancer risk with high-dose pills in smokers and asbestos-exposed workers. In two large trials, smokers and asbestos-exposed workers who took beta-carotene supplements had more lung cancer than those on placebo.
- No proven protection against cancer or heart disease; recommended against. A US expert panel recommends against beta-carotene supplements for preventing heart disease or cancer in healthy adults, because the harms outweigh the benefits.
- Possible increase in overall death risk in pooled trials. A Cochrane review of trials found beta-carotene supplements were linked to slightly higher risk of death from any cause.
- Yellow or orange skin colour with very high intake. Very high intake of beta-carotene can turn the skin yellow or orange. It is not described as dangerous and fades when intake is reduced.
- Caution during cancer treatment. Antioxidant supplements may interfere with some cancer treatments, so anyone in treatment should check with their cancer care team first.
- Possible reduction of cholesterol-drug effect (combination study). In one study, a combination of vitamins E and C, selenium and beta-carotene reduced the cholesterol-lowering effect of two drugs taken together.
If you smoke, used to smoke or worked with asbestos
High-dose beta-carotene supplements increased lung cancer risk in smokers and asbestos-exposed workers in two large randomized trials. The NCCIH says the strongest evidence of an increase was in people at high risk of lung cancer, meaning smokers and people with occupational asbestos exposure. [1] The US Preventive Services Task Force (USPSTF, 2022) concluded with moderate certainty that the harms of beta-carotene supplements outweigh the benefits for preventing cardiovascular disease or cancer in nonpregnant adults. [2] Talk to a clinician or pharmacist before taking any product containing beta-carotene, and check multivitamin and eye-health labels. Do not stop a prescribed medicine because of this page. This page is information, not personal advice.Beta-carotene from food versus pills
Beta-carotene is a carotenoid that the body can convert to vitamin A. The NHS lists yellow, red and green (leafy) vegetables such as spinach, carrots, sweet potatoes and red peppers, and yellow fruit such as mango, papaya and apricots, as the main food sources. [3] The trials below tested supplements. The ATBC investigators started from epidemiology showing that diets high in carotenoid-rich fruits and vegetables, and high blood beta-carotene, were linked with lower lung cancer risk; the trial of pills did not reproduce that. [4] The NCCIH notes high doses in supplements may have different effects from the smaller amounts in foods. [1]Evidence labels: evidence of harm, no good evidence of benefit, mixed.
The trials
| Trial | Who and what | Result | Label |
|---|---|---|---|
| ATBC (Finland, 1994) | 29,133 male smokers aged 50 to 69; beta-carotene 20 mg a day (alone or with alpha-tocopherol 50 mg) versus placebo; 5 to 8 years. [4] | Lung cancer incidence 18% higher with beta-carotene (3% to 36%); total mortality 8% higher (1% to 16%). [4] | Evidence of harm |
| CARET (US, 1996) | 18,314 smokers, former smokers and asbestos-exposed workers; beta-carotene 30 mg plus retinol 25,000 IU a day versus placebo; mean follow-up 4.0 years. [5] | Lung cancer relative risk 1.28 (1.04 to 1.57); death from any cause 1.17; death from lung cancer 1.46. The trial was stopped 21 months early. [5] | Evidence of harm |
| CARET after the pills stopped (2004) | About 6 more years of follow-up. [6] | Lung cancer relative risk 1.12 and all-cause mortality 1.08, no longer statistically significant but still above 1.0; cardiovascular mortality risk fell to 1.0. [6] | Evidence of harm, fading |
| Physicians' Health Study I (US) | Male physicians; beta-carotene 50 mg every other day for 12 years, as summarized by the US National Cancer Institute. [7] | No effect on cancer incidence, cancer mortality or all-cause mortality in smokers or non-smokers. [7] | No good evidence of benefit |
| AREDS2 (US eye trial) | People with intermediate AMD, beta-carotene included in some formulas. [8] | More lung cancers with beta-carotene (2.0% versus 0.9%), mostly in former smokers; ten years on, lung cancer odds were 1.82 times higher with beta-carotene and not significantly higher with lutein/zeaxanthin. [8][9] | Evidence of harm |
The ATBC investigators called the finding unexpected and said it raised the possibility that supplements may have harmful as well as beneficial effects. [4] The sources we read for this page do not explain the reason, so we do not offer a mechanism.
What reviews of all the trials found
- A 2023 meta-analysis of 8 randomized trials found no association between beta-carotene supplements and overall cancer incidence (risk ratio 1.02), but a higher lung cancer risk (1.19; 1.08 to 1.32), and increased risk in smokers. [10]
- A 2022 meta-analysis of 8 studies with 167,141 participants found lung cancer risk 1.16 times higher with beta-carotene, 1.21 times higher in smokers and asbestos workers, and no relationship between dose and size of the effect. [11]
- A Cochrane review of 78 antioxidant trials found that in trials with low risk of bias, beta-carotene significantly increased death from any cause (risk ratio 1.05). [12]
- Beta-carotene also did not prevent AMD in a Cochrane review of eye trials. [13]
- USPSTF 2022 recommends against beta-carotene (and vitamin E) supplements to prevent cardiovascular disease or cancer. [2][1]
Findings from these supplement trials should not be transferred to food carotenoids, to lutein or lycopene, or to the AREDS2 formula; see AREDS2 formula vs lutein and zeaxanthin alone.
Amounts and official limits
| Figure | Population, form, source and year |
|---|---|
| 20 mg a day | ATBC study amount: male smokers in Finland, beta-carotene, 5 to 8 years (NEJM 1994). [4] |
| 30 mg a day plus 25,000 IU retinol | CARET study amount: smokers, former smokers and asbestos-exposed workers, mean 4.0 years (NEJM 1996). [5] |
| 1.5 mg (1,500 mcg) a day of vitamin A | NHS (UK) advice on total vitamin A (retinol) from food and supplements; high intakes over many years may affect bones. [3] |
| A tolerable upper level for beta-carotene | A 2023 meta-analysis said establishing one should be considered. [10] We did not find an official figure in sources we could read; NIH ODS could not be read. |
Study amounts are not recommendations. For vitamin A itself see vitamin A.
Frequently asked questions
Is beta-carotene safe for smokers?
Not as a high-dose supplement. ATBC and CARET found more lung cancer with beta-carotene pills in smokers, and the NCCIH identifies smokers and asbestos-exposed people as the groups at greatest risk. [4][5][1]
Is beta-carotene in carrots and vegetables harmful?
These trials tested supplements, not food, and the NHS lists vegetables and fruit as beta-carotene sources. [3] Our sources do not show harm from food.
Why was CARET stopped early?
Because participants on beta-carotene plus vitamin A had more lung cancer and more deaths; the trial stopped 21 months earlier than planned. [5]
Does beta-carotene prevent cancer or heart disease?
No good evidence of benefit. The USPSTF recommends against it for preventing either, and a large meta-analysis found no effect on overall cancer. [2][10]
Does the risk continue after stopping?
In CARET, excess lung cancer risk stayed above 1.0 for about six years after stopping, though no longer statistically significant. [6]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Other safety points
- Yellow skin. A review says high intake of carotenoid-rich foods or beta-carotene supplements (over 30 mg a day) for months can cause yellowing of the skin, especially palms and soles. [14]
- Cancer treatment. The NCCIH says it may not be OK to take antioxidant supplements during cancer treatment and to check with the team managing it. [1] See antioxidants and cancer.
- Pregnancy and children. On its vitamin A page the NHS says to avoid liver and liver products in pregnancy. [3] The NCCIH advises talking to a provider if pregnant, nursing or giving a child a supplement. [1] Beta-carotene supplement cautions for kidney or liver disease and before surgery were not described in the sources we read; ask a clinician. See supplements before surgery.
- Medicines. In one study, a combination of vitamin E, vitamin C, selenium and beta-carotene reduced the cholesterol-lowering effects of two drugs taken together. [1] See medication interactions.
- Eye products. Current and former smokers with intermediate AMD should take the AREDS2 formula and avoid the AREDS formula with beta-carotene, says the NEI. [15]
More: antioxidants, smoking and higher-risk groups and high-dose antioxidant risks by compound.
References
- National Center for Complementary and Integrative Health, Antioxidants: In Depth. Read 2026-10-22.
- US Preventive Services Task Force, Vitamin, mineral, and multivitamin supplementation to prevent cardiovascular disease and cancer: recommendation statement (JAMA 2022). Read 2026-10-22.
- NHS, Vitamin A. Read 2026-10-22.
- ATBC Cancer Prevention Study Group, The effect of vitamin E and beta carotene on the incidence of lung cancer and other cancers in male smokers (N Engl J Med 1994). Read 2026-10-22.
- Omenn et al., Effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular disease (CARET, N Engl J Med 1996). Read 2026-10-22.
- Goodman et al., The Beta-Carotene and Retinol Efficacy Trial: incidence of lung cancer and cardiovascular disease mortality during 6-year follow-up after stopping supplements (J Natl Cancer Inst 2004). Read 2026-10-22.
- National Cancer Institute, Antioxidants and Cancer Prevention. Read 2026-10-22.
- AREDS2 Research Group, Lutein + zeaxanthin and omega-3 fatty acids for age-related macular degeneration: AREDS2 randomized clinical trial (JAMA 2013). Read 2026-10-22.
- Chew et al., Long-term outcomes of adding lutein/zeaxanthin and omega-3 fatty acids to the AREDS supplements: AREDS2 Report 28 (JAMA Ophthalmol 2022). Read 2026-10-22.
- Association between beta-carotene supplementation and risk of cancer: a meta-analysis of randomized controlled trials (Nutr Rev 2023). Read 2026-10-22.
- Kordiak et al., Role of beta-carotene in lung cancer primary chemoprevention: systematic review with meta-analysis and meta-regression (Nutrients 2022). Read 2026-10-22.
- Bjelakovic et al., Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases (Cochrane Database Syst Rev 2012). Read 2026-10-22.
- Evans and Lawrenson, Antioxidant vitamin and mineral supplements for preventing age-related macular degeneration (Cochrane Database Syst Rev 2017). Read 2026-10-22.
- Insights of hypercarotenaemia: a brief review (Clin Nutr ESPEN 2018). Read 2026-10-22.
- National Eye Institute, About AREDS and AREDS2. Read 2026-10-22.