Beta-Carotene
Beta-carotene
TL;DR
Beta-carotene from food is fine. As a supplement it failed decisively: two large trials found it increased lung cancer incidence and mortality in smokers, and AREDS2 removed it from the eye formula for that reason.
Ideal For
- Erythropoietic protoporphyria, at high dose under specialist care
- Vitamin A repletion in non-smokers with poor vegetable intake
Avoid If
- Current smokers — increased lung cancer risk
- Former smokers and asbestos-exposed workers
- Heavy alcohol use
- Seeking eye protection — use lutein and zeaxanthin instead
Frequently Asked Questions
Are carrots dangerous then?
I quit smoking ten years ago — is it safe now?
What should I take for eye health instead?
Why did an antioxidant increase cancer?
Overview
Beta-carotene is the canonical example of why a nutrient that looks protective in observational data can prove harmful when isolated and given at high dose. Epidemiology repeatedly found that people eating more carotenoid-rich vegetables had less lung cancer, so two large trials tested the pill. The ATBC trial in Finnish male smokers found 18% more lung cancer in the beta-carotene arm. CARET, testing beta-carotene with retinol in smokers and asbestos-exposed workers, was terminated early with 28% more lung cancer and 17% higher overall mortality. These are not ambiguous results. The proposed mechanism involves beta-carotene oxidation products in the high-oxygen, oxidant-rich smoker lung acting to promote rather than prevent carcinogenesis. The consequence is visible in the AREDS programme: the original AREDS eye formula contained beta-carotene, and AREDS2 replaced it with lutein and zeaxanthin, which performed at least as well without the cancer signal. Dietary carotenoids remain unambiguously good, and beta-carotene is still useful for erythropoietic protoporphyria and, at modest doses, as a vitamin A source in people who do not smoke. But as a general antioxidant supplement it should not be taken.
How It Works
- Converted to retinal by BCMO1, with feedback regulation
- Quenches singlet oxygen at low oxygen tension
- Becomes pro-oxidant at high oxygen tension, as in smoker lung
- Cleavage products disrupt retinoic acid signalling
Quick Facts
- ATBC: 18% more lung cancer in smokers
- CARET: stopped early, 28% more lung cancer, 17% higher mortality
- AREDS2 replaced it with lutein and zeaxanthin
- Food carotenoids remain entirely safe
Health Concerns Addressed
Vitamin A Deficiency
Likely helps correct and prevent vitamin A deficiency, but less reliably than preformed vitamin A, and not as a self-treatment for eye signs.
Macular Degeneration
Superseded and unsafe in smokers. Use the AREDS2 formulation with lutein and zeaxanthin instead.
Skin Cancer
A clear negative, with documented harm in one population.
Supporting Research30 studies
Vitamin and mineral supplements for the primary prevention of cardiovascular disease and cancer: US Preventive Services Task Force review
O'Connor EA, Evans CV, Ivlev I +3 more
No consistent benefit was found for multivitamins or most single nutrients; beta-carotene increased lung cancer risk in high-risk groups.
Vitamin and mineral supplementation for maintaining cognitive function in cognitively healthy people in mid and late life
Rutjes AWS, et al.
Cochrane review of 28 trials (about 83,000 cognitively healthy adults) found no evidence that vitamin or mineral supplementation - including B vitamins, antioxidant vitamins C and E, beta-carotene, selenium, zinc or multivitamins - preserves cognitive function in mid or late life; the only weak signals (beta-carotene and selenium after many years) were of doubtful clinical significance.
Long-term Outcomes of Adding Lutein/Zeaxanthin and ω-3 Fatty Acids to the AREDS Supplements on Age-Related Macular Degeneration Progression: AREDS2 Report 28
At 10 years, lutein/zeaxanthin substitution for beta-carotene was associated with reduced progression to late AMD and lower lung cancer risk.
Secondary analyses of the effects of lutein/zeaxanthin on age-related macular degeneration progression: AREDS2 report No. 3
AREDS2 Research Group, Chew EY, Clemons TE
In participants with the lowest dietary lutein/zeaxanthin intake, supplementation reduced progression to advanced AMD; lutein/zeaxanthin was a safer substitute for beta-carotene.
Lutein + zeaxanthin and omega-3 fatty acids for age-related macular degeneration: the Age-Related Eye Disease Study 2 (AREDS2) randomized clinical trial
Age-Related Eye Disease Study 2 Research Group, Chew EY, Clemons TE +8 more
In 4,203 participants at high risk of progression, adding lutein 10 mg + zeaxanthin 2 mg to the AREDS formulation did not significantly reduce progression to advanced AMD overall, but in secondary analyses lutein/zeaxanthin outperformed beta-carotene (HR ~0.82) and benefited participants with the lowest dietary lutein intake. Omega-3 (DHA+EPA) showed no effect. Beta-carotene raised lung cancer risk in former smokers.
Vitamin, mineral, and multivitamin supplementation to prevent cardiovascular disease and cancer: US Preventive Services Task Force recommendation statement
US Preventive Services Task Force
The evidence is insufficient to recommend multivitamins for preventing cardiovascular disease or cancer, and beta-carotene and vitamin E are recommended against.
A randomised controlled trial to test equivalence between retinyl palmitate and beta carotene for vitamin A deficiency
Carlier C, Coste J, Etchepare M +2 more
the two treatments were statistically equivalent
Vitamin A or beta-carotene supplementation reduces but does not eliminate maternal night blindness in Nepal
Christian P, West KP, Khatry SK +4 more
beta-Carotene supplementation had less of an effect
Double blind, cluster randomised trial of low dose supplementation with vitamin A or beta carotene on mortality related to pregnancy in Nepal. The NNIPS-2 Study Group
West KP, Katz J, Khatry SK +4 more
vitamin A or beta carotene lowered mortality by 44%
Daily consumption of Indian spinach (Basella alba) or sweet potatoes has a positive effect on total-body vitamin A stores in Bangladeshi men
Haskell MJ, Jamil KM, Hassan F +4 more
approximately 6:1 for synthetic beta-carotene
Lack of improvement in vitamin A status with increased consumption of dark-green leafy vegetables
de Pee S, West CE, Muhilal +2 more
a similar amount of beta-carotene from a simpler matrix produced a strong improvement
Effects of vitamin A or beta carotene supplementation on pregnancy-related mortality and infant mortality in rural Bangladesh: a cluster randomized trial
West KP, Christian P, Labrique AB +4 more
did not reduce all-cause maternal, fetal, or infant mortality
Bioconversion of plant carotenoids to vitamin A in Filipino school-aged children varies inversely with vitamin A status
Ribaya-Mercado JD, Solon FS, Solon MA +4 more
Bioconversion of plant carotenoids to vitamin A varies inversely with vitamin A status
Zinc plus beta-carotene supplementation of pregnant women is superior to beta-carotene supplementation alone in improving vitamin A status in both mothers and infants
Dijkhuizen MA, Wieringa FT, West CE +1 more
Breast-milk beta-carotene concentrations were higher in all women supplemented with beta-carotene
Low-dose beta-carotene supplementation and deworming improve serum vitamin A and beta-carotene concentrations in preschool children of Bangladesh
Haque R, Ahmed T, Wahed MA +3 more
Low-dose beta-carotene supplementation, along with an antihelminthic therapy, synergistically improved vitamin A status
Beta-carotene-rich orange-fleshed sweet potato improves the vitamin A status of primary school children assessed with the modified-relative-dose-response test
van Jaarsveld PJ, Faber M, Tanumihardjo SA +3 more
Consumption of OFSP improves vitamin A status
Orange fruit is more effective than are dark-green, leafy vegetables in increasing serum concentrations of retinol and beta-carotene in schoolchildren in Indonesia
de Pee S, West CE, Permaesih D +3 more
the equivalent of 1 RE would be 12 microg beta-carotene
Two common single nucleotide polymorphisms in the gene encoding beta-carotene 15,15'-monoxygenase alter beta-carotene metabolism in female volunteers
Leung WC, Hessel S, Méplan C +4 more
may provide an explanation for the molecular basis of the poor converter phenotype
Recovery from impaired dark adaptation in nightblind pregnant Nepali women who receive small daily doses of vitamin A as amaranth leaves, carrots, goat liver, vitamin A-fortified rice, or retinyl palmitate
Haskell MJ, Pandey P, Graham JM +3 more
women who received vitamin A as liver, amaranth leaves, carrots, or retinyl palmitate
Responsiveness of dark-adaptation threshold to vitamin A and beta-carotene supplementation in pregnant and lactating women in Nepal
Congdon NG, Dreyfuss ML, Christian P +4 more
a placebo-controlled trial of vitamin A and beta-carotene
Carotenodermia in men with elevated carotenoid intake from foods and beta-carotene supplements
Micozzi MS, Brown ED, Taylor PR +1 more
Definite carotenodermia was observed only in the five subjects who took 30 mg
Vitamin A and beta (β)-carotene supplementation for cystic fibrosis
de Vries JJ, Chang AB, Bonifant CM +2 more
no clear conclusions on β-carotene supplementation can be drawn
Effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular disease (CARET)
Omenn GS, Goodman GE, Thornquist MD +1 more
The trial was stopped early: participants receiving beta carotene plus retinyl palmitate had a 28% higher incidence of lung cancer and 17% higher death rate than placebo.
Protection from sunburn with beta-Carotene--a meta-analysis
Kopcke W, Krutmann J
Beta-carotene protected against sunburn only after at least 10 weeks of supplementation
The Effect of Vitamin E and Beta Carotene on the Incidence of Lung Cancer and Other Cancers in Male Smokers
The Alpha-Tocopherol, Beta Carotene Cancer Prevention Study Group
Male smokers receiving beta carotene had an 18% higher incidence of lung cancer and 8% higher total mortality than those not receiving it.
Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases
Bjelakovic G, Nikolova D, Gluud LL +2 more
Beta-carotene and vitamin E supplementation were associated with increased all-cause mortality in analyses of low-bias-risk trials.
The Beta-Carotene and Retinol Efficacy Trial: Incidence of Lung Cancer and Cardiovascular Disease Mortality During 6-Year Follow-up After Stopping Beta-Carotene and Retinol Supplements
Goodman GE, Thornquist MD, Balmes J +1 more
Excess lung cancer risk in the supplement arm diminished after supplementation stopped, though risks remained elevated among women.
Drugs for preventing lung cancer in healthy people
Cortés-Jofré M, Rueda JR, Asenjo-Lobos C +1 more
Some studies have suggested a protective effect of antioxidant nutrients and higher dietary levels of fruits and vegetables on lung cancer.
Antioxidant vitamins and magnesium and the risk of hearing loss in the US general population
Choi YH, Miller JM, Tucker KL +2 more
High intakes of beta-carotene or vitamin C combined with high magnesium compared with low intakes of both nutrients were significantly associated with lower (better) PTAs at high frequencies.
A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E, beta carotene, and zinc for age-related macular degeneration and vision loss: AREDS report no. 8
Age-Related Eye Disease Study Research Group
Antioxidants plus zinc reduced progression to advanced age-related macular degeneration by about 25% in higher-risk participants.
Safety Information
Potential Side Effects
Carotenodermia, a harmless yellow-orange skin discolouration, at high intake. The serious concern is not a side effect but an outcome: increased lung cancer incidence and mortality in smokers at supplemental doses.
Contraindications
Current or former smoking and asbestos exposure are effective contraindications to supplemental beta-carotene at doses of 20 mg/day or more.
Drug Interactions
- Statins and niacin — beta-carotene combinations blunted HDL response in one trial
- Orlistat and cholestyramine — reduced absorption
- Alcohol — may worsen hepatotoxic potential of retinoid pathways
Pregnancy & Breastfeeding
Pregnancy: Likely safe
Breastfeeding: Likely safe
Dosage Guidelines
Dosage Used in Studies
3-6 mg
Best Time to Take
With a fat-containing meal, if taken at all
Best Form
Dietary carotenoids from food; mixed carotenoids if supplementing
Bioavailability
Absorption from supplements is far higher than from raw vegetables; cooking and dietary fat substantially improve food-source absorption.
Dosing by Goal
| Goal | Dose | Notes |
|---|---|---|
| Typical range | 3-6 mg/day if used, well below the 20-30 mg trial doses | |
| Starting dose | Not generally recommended as an isolated supplement | |
| Timing | With a fatty meal | |
| Notes | Absolute avoidance in current and former smokers |
Forms Compared
Dietary beta-carotene
From carrots, sweet potato, dark leafy greens — safe and preferred
Synthetic beta-carotene
The form used in ATBC and CARET; avoid at high dose
Mixed carotenoids
Closer to food; still not recommended at high dose in smokers
Lutein and zeaxanthin
The AREDS2 replacement for eye health
Food & Timing
Fat-soluble — requires dietary fat for absorption.
Medical Disclaimer
The information provided on this website is for educational and informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any supplement regimen.
Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.