How we rate
“Strong” = several concordant meta-analyses or systematic reviews. “Moderate” = one synthesis, or several controlled trials. “Limited” = early trials only. The rating is about the quality of the studies, not about how useful the supplement is.
Beta-carotene
Orange pigment from carrots, which the body converts into vitamin A. As a dietary supplement, large trials find no protection against cancer, heart disease or diabetes, and in smokers, 20 to 30 mg per day increased lung cancers.
Benefits
- Sunburn: in a meta-analysis of seven studies, beta-carotene protects against sunburn, provided it is taken for at least 10 weeks; the protection increases with each additional month of intake.
- Pregnancy in an undernourished country: in Nepal, among nearly 45,000 women, 42 mg of beta-carotene per week (or low-dose vitamin A) reduced pregnancy-related mortality by 40 to 49%.
- Elderly defenses: after 10 to 12 years at 50 mg every other day, natural killer (NK) cell activity was higher in elderly men supplemented than under placebo (59 men).
- Eyes, in combination: in the AREDS trial, the combination of vitamins C and E, beta-carotene and zinc reduced the risk of advanced age-related macular degeneration (AMD) and moderate vision loss.
Precautions
Smokers and asbestos workers: in nearly 30,000 smokers, 20 mg of beta-carotene per day for 5 to 8 years increased lung cancers by 18% and total mortality by 8%. In over 18,000 smokers, former smokers and workers exposed to asbestos, 30 mg per day with vitamin A increased lung cancers (risk multiplied by 1.28), all-cause deaths and cardiovascular deaths: the trial was stopped early. Two meta-analyses find this excess of lung cancers, and an increase in stomach cancers at 20 to 30 mg per day. After stopping, the excess of lung cancers and deaths took 4 to 6 years to disappear in smokers; the authors recommend that they avoid beta-carotene. Heart: in smokers who had already had a heart attack, beta-carotene increased deaths from coronary heart disease. Mortality: a meta-analysis of 68 trials (over 232,000 participants) concludes that beta-carotene, alone or combined with other antioxidants, increases mortality in the most reliable trials. Limitations: in over 22,000 physicians followed for 12 years and nearly 40,000 women, no effect, neither good nor bad, on cancers, cardiovascular diseases or mortality; no effect on type 2 diabetes (12-year trial and meta-analysis of trials), cataracts, non-melanoma skin cancers or colon polyps.
Recommended dosage
15 to 30 mg per day, or 50 mg every other day, in trials; to be avoided if you smoke.
How to take it
- Who it is for: most trials in this dietary supplement profile sought to prevent cancer, heart disease or diabetes in adults, and did not succeed.
- If you smoke: no beta-carotene. In nearly 30,000 smokers, 20 mg per day increased lung cancers by 18%; in smokers and asbestos workers, 30 mg per day with vitamin A did the same.
- Dose: 50 mg every other day in large trials in physicians and women, without benefit or harm on cancer or the heart; 15 mg per day in the AREDS mixture.
- Duration: protection against sunburn requires at least 10 weeks of intake; the effect on memory only appeared after an average of 18 years.
- What does not work: type 2 diabetes, cataracts, non-melanoma skin cancers and colon polyps (adenomas) do not change in trials.
- Time of day: no study in this dietary supplement profile compares morning and evening, nor intake with or without a meal.
Did you know?
In men over 65, a few years of beta-carotene changed nothing for memory. Those who had been taking it for an average of 18 years (50 mg every other day) did, however, have better cognitive and verbal memory scores than the placebo group.
What the studies say
This systematic review and meta-analysis explored the relationship between antioxidants (vitamins C, E, and beta-carotene) and type 2 diabetes (T2D). Observational studies showed an inverse association between dietary beta-carotene intake and the risk of T2D. However, beta-carotene supplementation (based on randomized controlled trials) had no protective effect on T2D. This suggests that adequate dietary intake, rather than high-dose supplementation, may play a role in the prevention of T2D.
Lampousi AM, Lundberg T, Löfvenborg JE, Carlsson S. — Advances in nutrition (Bethesda, Md.) (2024) — View the source study
For information only: not a substitute for medical advice. Dietary supplements are not a replacement for a varied, balanced diet. Learn more