Also indexed as: Carotenes
Carotenoids are a highly colored (red, orange, and yellow) group of fat-soluble plant pigments. All organisms, whether
bacteria or plants, that rely on the sun for energy contain carotenoids. Their antioxidant effects enable these compounds to play a
crucial role in protecting organisms against damage during photosynthesis—the process of
converting sunlight into chemical energy.
Where are they found?
Carotenoids are found in all plant foods. In general, the greater the intensity of color,
the higher the level of carotenoids. In green leafy vegetables, beta-carotene is the predominant carotenoid. In the
orange colored fruits and vegetables—such as carrots,
apricots, mangoes, yams,
winter squash—beta-carotene concentrations are high, but other pro-vitamin A
carotenoids typically predominate. Yellow vegetables have higher concentrations of yellow
carotenoids (xanthophylls), hence a lowered pro-vitamin A activity; but some of these
compounds, such as lutein, may have
significant health benefits, potentially due to their antioxidant effects. The red and purple vegetables and
fruits—such as tomatoes, red cabbage,
berries, and plums—contain a large
portion of non-vitamin A–active carotenoids. Legumes,
grains, and seeds are also significant
sources of carotenoids. Carotenoids are also found in various animal foods, such as salmon,
egg yolks, shellfish, milk, and poultry. A variety of carotenoids is also found in
carrot juice and “green drinks”
made from vegetables, dehydrated barley greens, or wheat grass.
Synthetic beta-carotene is available as a supplement. Mixed carotenoids (including the
natural form of beta-carotene) are also available in supplements derived from palm oil, algae,
and carrot oil.
Carotenoids have been used
in connection with the following conditions (refer to the individual
health concern for complete information):
Who is likely to be deficient?
Carotenoid deficiency is not considered a classic nutritional deficiency like scurvy or
beri-beri (severe vitamin C and vitamin B1 deficiencies, respectively). However, given
the possible health benefits of carotenoids, most doctors recommend adequate intake. People
who do not frequently consume carotenoid-rich foods or take carotenoid supplements are likely
to be taking in less than adequate amounts, though optimal levels remain unknown. Also,
deficiency may be found in people with chronic
diarrhea or other disorders associated with impaired absorption.
How much is usually taken?
Whether people who already consume a diet high in fruits and vegetables would benefit further from supplementation
with a mixture of carotenoids remains unknown. While smokers clearly should not supplement
with isolated synthetic beta-carotene, the
effect in smokers of taking either natural beta-carotene or mixed carotenoids is not
clear.
Nonetheless, based on health-promoting effects associated with these levels in preliminary
research, some doctors recommend that most people supplement with up to 25,000 IU (15 mg) per
day of natural beta-carotene and approximately 6 mg each of alpha-carotene, lutein, and lycopene.
Are there any side effects or interactions?
Carotenoids are generally regarded as safe, based primarily on studies with beta-carotene. Increased consumption of carotenoids
may cause to the skin to turn orange or yellow—a condition known as
“carotenodermia.” This occurrence is completely benign and is unrelated to
jaundice—the yellowing of the skin that can result from liver disease or other
causes.
Until more is known, people especially smokers should not supplement with synthetic
beta-carotene. Two double-blind studies have shown that supplementation with isolated
synthetic beta-carotene may increase the risk of
lung cancer in people who smoke.1 2 Moreover, three of four studies
have found small increases in the risk of heart
disease in people assigned to take synthetic beta-carotene compared with those assigned to
take placebo.3 4 5 6
Are there any drug
interactions?
Certain medicines may interact with carotenoids. Refer to drug interactions for a list of those medicines.
References:1. Albanes D, Heinone 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;88:1560–70.
2. Omenn GS, Goodman GE, Thornquist MD, et al. Effects of a combination
of beta carotene and vitamin A on lung cancer and cardiovascular disease. N Engl J
Med 1996;334:1150–5.
3. Greenburg ER, Baron JA, Karagas MR, et al. Mortality associated with
low plasma concentration of beta carotene and the effect of oral supplementation.
JAMA 1996;275:699–703.
4. Omenn GS, Goodman GE, Thornquist MD, et al. Effects of a combination
of beta carotene and vitamin A on lung cancer and cardiovascular disease. N Engl J
Med 1996;334:1150–5.
5. The 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;330:1029–35.
6. Hennekens CH, Buring JE, Manson JE, et al. Lack of effect of long-term
supplementation with beta carotene on the incidence of malignant neoplasms and cardiovascular
disease. N Engl J Med 1996;334:1145–9.