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Carotenoids

Also indexed as: Carotenes

Illustration

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 anti-oxidant 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 colour, 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 anti-oxidant 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. Pulses, 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):

Science Ratings Health Concerns
1Star

Cataracts (prevention)

Heart disease (prevention)

Macular degeneration (prevention) (lutein, zeaxanthin, lycopene)

Sickle cell anaemia
3Stars Reliable and relatively consistent scientific data showing a substantial health benefit.
2Stars Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
1Star For a herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support and/or minimal health benefit.

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 diarrhoea 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.