Beta-carotene is a plant pigment found in many yellow, orange and dark-green leafy vegetables and some fruits (Albanes et al., JNCI 1996). It is a “provitamin A” carotenoid: the body can split it to make vitamin A. It is sold as a dietary supplement, used as a food coloring, and was once a prescription drug (Solatene) for a rare light-sensitivity disorder.

The most important fact about it is a negative one. In two large randomized trials, high-dose beta-carotene supplements increased lung cancer in smokers and asbestos-exposed workers, and the US Preventive Services Task Force (USPSTF) now recommends against beta-carotene supplements for preventing cancer or heart disease. Beta-carotene from food has not shown this harm.

This page summarizes what the National Academies nutrient reports, randomized trials and regulators report. It is for education only and is not medical advice.

Property	Detail
Class	Provitamin A carotenoid (plant pigment)
Formula / weight	C₄₀H₅₆; 536.9 g/mol
Vitamin A value	2 µg supplemental beta-carotene in oil, or 12 µg from food, = 1 µg retinol activity equivalent (RAE)
Doses in major trials	15–30 mg/day, or 50 mg every other day; 15–180 mg/day in protoporphyria studies
Plasma half-life	About 5–7 days (pharmacokinetic review)
Upper intake level	None set; the Institute of Medicine judged supplements “not advisable” for the general population
US status	Dietary supplement ingredient; listed food color additive and GRAS nutrient; former Rx drug Solatene 30 mg (NDA 017589, discontinued)
USPSTF	Recommends against use to prevent cardiovascular disease or cancer (grade D, 2022)

What it is

Beta-carotene is a 40-carbon hydrocarbon with a long chain of alternating double bonds capped by a ring at each end (PubChem). It has no oxygen atoms, and this hydrocarbon structure makes it insoluble in water (IOM 2000).

Of the six carotenoids most common in North American diets, three can be turned into vitamin A: alpha-carotene, beta-carotene and beta-cryptoxanthin. Lycopene, lutein and zeaxanthin cannot (IOM 2000). The Institute of Medicine (IOM) concluded that the only known function of carotenoids in humans is as a vitamin A source. Antioxidant and other effects are proposed actions, not established functions.

An enzyme in the gut wall, beta-carotene 15,15′-dioxygenase, cleaves the molecule in the middle to make vitamin A (retinal). Other “off-center” cleavage routes produce a range of smaller breakdown products.

How much vitamin A beta-carotene provides depends strongly on its source. The IOM set these conversion factors (IOM 2001):

Source	Amount equal to 1 µg RAE
Retinol (preformed vitamin A)	1 µg
Supplemental beta-carotene in oil	2 µg
Beta-carotene in food	12 µg
Other provitamin A carotenoids in food	24 µg

The 6-fold gap between supplements and food reflects how poorly beta-carotene is released from the plant matrix.

How it works in the body

Beta-carotene must be dissolved into bile-acid micelles to be absorbed, so dietary fat improves uptake (IOM 2000). Inside gut cells, part is converted to vitamin A and part is packed intact into chylomicrons (fat-carrying particles) that enter the lymph. In the fasting blood it travels mainly in LDL particles and is stored mainly in fat tissue and the liver.

Parameter	Finding	Source
Time to peak after a single dose	24–48 h	IOM 2000
Absorption from a highly bioavailable source	60–75% converted to vitamin A, plus about 15% absorbed intact	IOM 2000
Absorption from some foods	As low as 2%	IOM 2000
Elimination half-life	About 5–7 days	Schwedhelm et al., Clin Pharmacokinet 2003
Conversion at 6 mg vs 126 mg doses	About 27% vs 2%	Schwedhelm et al. 2003

Conversion to vitamin A falls as the dose rises. In a crossover study, 7 volunteers took 20 mg and 40 mg of deuterium-labeled beta-carotene (Novotny et al., J Nutr 2010). Doubling the dose doubled blood beta-carotene exposure but raised the vitamin A made from it by only 36%.

This built-in brake is why the IOM noted that long-term beta-carotene supplements do not raise serum retinol in people who already have adequate vitamin A. The vitamin A upper limit of 3,000 µg/day applies to preformed vitamin A, not to beta-carotene (IOM 2001).

Regulatory status

Dietary supplement and food ingredient. FDA lists beta-carotene as a color additive exempt from certification for coloring foods generally (21 CFR 73.95). It is also affirmed as generally recognized as safe (GRAS) as a nutrient supplement, with no limit other than good manufacturing practice (21 CFR 184.1245).
Former prescription drug. Roche’s Solatene, 30 mg oral capsules, was approved under NDA 017589 and is listed as discontinued (Drugs@FDA).
No upper intake level. The IOM found the data too inconsistent to set a UL. Instead it concluded that beta-carotene supplements are not advisable for the general population, except as a vitamin A source where deficiency is a risk, or for erythropoietic protoporphyria (IOM 2000).
USPSTF grade D. In 2022 the Task Force concluded with moderate certainty that the harms of beta-carotene supplements outweigh the benefits for preventing cardiovascular disease or cancer (USPSTF, JAMA 2022).

What the research shows

Cancer and heart disease prevention trials

Observational studies found that people who eat more carotenoid-rich produce, or have higher blood beta-carotene, get less lung cancer. Four large randomized trials then tested supplements directly:

Trial	Population	Dose	Main result
ATBC (Finland)	29,133 male smokers aged 50–69; 5–8 years	20 mg/day	Lung cancer +18% (95% CI 3–36%); total mortality +8% (95% CI 1–16%)
CARET (US)	18,314 smokers, former smokers and asbestos workers; mean 4 years	30 mg/day plus 25,000 IU retinyl palmitate	Lung cancer RR 1.28 (1.04–1.57); death from any cause RR 1.17 (1.03–1.33); stopped 21 months early
Physicians’ Health Study (US)	22,071 male physicians; 12 years	50 mg every other day	No effect: any cancer RR 0.98 (0.91–1.06); no difference in heart attack, stroke or death
Women’s Health Study (US)	39,876 women aged 45 or older; median 2.1 years of treatment	50 mg every other day	No effect: any cancer RR 1.03 (0.89–1.18)

Sources: ATBC Study Group, NEJM 1994; Omenn et al., NEJM 1996; Hennekens et al., NEJM 1996; Lee et al., JNCI 1999.

In ATBC, the extra deaths were mainly from lung cancer and ischemic heart disease. The pattern is consistent: no benefit in anyone, and harm concentrated in people with heavy lung exposure to smoke or asbestos.

Pooled analyses

The evidence review behind the 2022 USPSTF recommendation pooled the beta-carotene trials, with or without vitamin A (O’Connor et al., JAMA 2022):

Outcome	Odds ratio (95% CI)	Trials (n)
Lung cancer	1.20 (1.01–1.42)	4 (94,830)
Cardiovascular death	1.10 (1.02–1.19)	5 (94,506)

A Cochrane review of antioxidant supplements reached a similar conclusion. In trials at low risk of bias, beta-carotene was linked to higher all-cause mortality: RR 1.05 (95% CI 1.01–1.09), 26 trials (Bjelakovic et al., Cochrane 2012).

The original AREDS trial randomized 3,640 people aged 55–80 with signs of age-related macular degeneration (AMD) and followed them for an average of 6.3 years (AREDS Research Group, Arch Ophthalmol 2001). The antioxidant tablet contained vitamin C 500 mg, vitamin E 400 IU and beta-carotene 15 mg; zinc was tested separately and in combination.

Antioxidants plus zinc lowered the odds of advanced AMD: OR 0.72 (99% CI 0.52–0.98).
Antioxidants alone did not reach significance: OR 0.80 (99% CI 0.59–1.09).

AREDS2 then tested removing beta-carotene from the formula in 4,203 participants (AREDS2 Research Group, JAMA 2013). Removing it had no apparent effect on AMD progression. Lung cancer was more common with beta-carotene than without it (23 cases, 2.0%, vs 11 cases, 0.9%; nominal p = 0.04), mostly in former smokers. The investigators suggested lutein plus zeaxanthin as a substitute carotenoid.

Erythropoietic protoporphyria

Erythropoietic protoporphyria (EPP) is an inherited disorder in which a light-activated compound, protoporphyrin, builds up and causes painful skin reactions to sunlight. Beta-carotene was the original drug treatment.

Early open studies were positive. In an uncontrolled series of 133 EPP patients given 15–180 mg/day, 84% tripled or more their tolerance of sunlight (Mathews-Roth et al., Arch Dermatol 1977).
A controlled trial was negative. A placebo-controlled crossover trial found no significant difference between beta-carotene and placebo; symptoms tracked hours of sunshine instead (Corbett et al., Br J Dermatol 1977).
Current reviews. A 2023 systematic review of 40 studies found that controlled trials showed no effect of oral beta-carotene, while an afamelanotide implant (see Melanotan I) and inorganic sunscreen had moderate positive effects (Heerfordt et al., Biomed Pharmacother 2023).

Muscle, performance and recovery

We found no randomized trial testing beta-carotene alone on muscle mass, strength, exercise performance or recovery. Claims that it aids training recovery rest on its antioxidant chemistry, not on outcome data. As noted above, the IOM does not consider antioxidant activity an established function of carotenoids in humans.

Side effects and risks

Lung cancer in smokers and asbestos-exposed people

This is the main documented harm, and it appears with supplements, not food. In ATBC, the excess risk looked stronger in men who smoked at least 20 cigarettes a day (RR 1.25, 95% CI 1.07–1.46) and in those drinking at least 11 g of alcohol a day, just under one drink (RR 1.35, 95% CI 1.01–1.81) (Albanes et al., JNCI 1996). The investigators described these effects as stronger, but not substantially different, than in the other subgroups.

The harm faded after the pills stopped. In ATBC post-trial follow-up of 25,563 men, the excess risk was no longer evident 4–6 years after supplementation ended (Virtamo et al., JAMA 2003). The ATBC investigators concluded that smokers should avoid beta-carotene supplements. AREDS2 adds a signal in former smokers.

Carotenodermia

High intakes can turn the skin yellowish. The IOM describes this carotenodermia as harmless and reversible once intake stops, and notes it may occur with 30 mg/day or more taken for long periods (IOM 2000). It differs from jaundice because the whites of the eyes stay white.

The IOM also reported no toxic effects at the very high doses (about 180 mg/day) used for protoporphyria, and no evidence of birth defects, mutations or cancer in long-term animal studies.

Interactions

Orlistat (Xenical). The weight-loss drug reduced beta-carotene supplement absorption by 30% in a pharmacokinetic study. The label advises a daily multivitamin containing vitamins A, D, E, K and beta-carotene (Xenical label).
Combined vitamin A products. CARET combined beta-carotene with 25,000 IU of retinyl palmitate daily, so its results reflect both. Preformed vitamin A has its own upper limit and toxicity, unlike beta-carotene.

Who should avoid supplements

Based on the trial evidence and the IOM and USPSTF positions, the groups with documented harm are:

current smokers, especially heavy smokers;
former smokers (the AREDS2 lung cancer signal);
people with past asbestos exposure (CARET).

Key takeaways

A vitamin A precursor, not an essential nutrient in itself. The body converts it to vitamin A as needed, and conversion falls as the dose rises.
Food and supplements differ. Supplemental beta-carotene in oil is about 6 times more available than beta-carotene in food, and only supplements have been linked to harm.
No preventive benefit. Four large trials with over 100,000 participants found no protection against cancer or heart disease.
Real harm in smokers. Lung cancer rose by 18% in ATBC and 28% in CARET, and the USPSTF recommends against beta-carotene supplements for prevention.
Weak evidence for its one drug use. Early protoporphyria studies were positive, but controlled trials did not confirm a benefit.
No evidence for training or recovery. No randomized trial has tested beta-carotene alone on muscle or performance outcomes.

Sources

Institute of Medicine. β-Carotene and other carotenoids. In: Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. Washington, DC: National Academies Press; 2000:325–382. doi:10.17226/9810. NAP.
Institute of Medicine. Vitamin A. In: Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academies Press; 2001. doi:10.17226/10026. NAP.
National Center for Biotechnology Information. Beta-Carotene, PubChem CID 5280489. PubChem.
US Food and Drug Administration. 21 CFR 73.95, β-Carotene (color additive), and 21 CFR 184.1245, Beta-carotene (GRAS). eCFR 73.95; eCFR 184.1245.
US Food and Drug Administration. Solatene (beta carotene) 30 mg capsule, NDA 017589, Roche. Drugs@FDA.
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Alpha-Tocopherol, Beta Carotene 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;330(15):1029–1035. PubMed.
Albanes D, Heinonen OP, Taylor PR, et al. Alpha-Tocopherol and beta-carotene supplements and lung cancer incidence in the alpha-tocopherol, beta-carotene cancer prevention study: effects of base-line characteristics and study compliance. J Natl Cancer Inst. 1996;88(21):1560–1570. PubMed.
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Heerfordt IM, Lerche CM, Philipsen PA, Wulf HC. Experimental and approved treatments for skin photosensitivity in individuals with erythropoietic protoporphyria or X-linked protoporphyria: a systematic review. Biomed Pharmacother. 2023;158:114132. PubMed.
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Beta Carotene