Beta Carotene

What does beta-carotene do?

Beta-carotene, a substance from plants that the body can convert into vitamin A, also acts as an antioxidant and immune system booster. Other members of the antioxidant carotene family include cryptoxanthin, alpha-carotene, zeaxanthin, lutein, and lycopene; however, unlike beta-carotene, most of these nutrients do not convert to significant amounts of vitamin A.

What is the difference between natural and synthetic beta-carotene?

Most, but not all, beta-carotene in supplements is synthetic, consisting of only one molecule called all trans beta-carotene. Natural beta-carotene found in food is made of two molecules—all trans beta-carotene plus 9-cis beta-carotene.

Researchers originally saw no meaningful difference between natural and synthetic beta-carotene. This view was questioned when the link between beta-carotene-containing foods (all natural) and lung cancer prevention was not duplicated in studies using synthetic pills. In smokers, synthetic beta-carotene has apparently caused an increased risk of lung cancer in double blind research. Animal research has begun to identify the ways in which synthetic beta-carotene causes damage to lungs, particularly when animals are exposed to cigarette smoke.

Much of natural beta-carotene is in the all trans molecule form—the same as synthetic beta-carotene. Moreover, much of the 9-cis molecule found only in natural beta-carotene converts to the synthetic molecule before it reaches the blood stream. Also, absorption of 9-cis beta-carotene appears to be poor, though some researchers question this finding.

Despite the overlap between natural and synthetic forms, natural beta-carotene may possibly have activity that is distinct from the synthetic form. For example, the natural form has antioxidant activity that the synthetic form has been reported to lack in both animals and in people. Also, in one trial, precancerous changes in people reverted to normal tissue with natural beta-carotene supplements, but not with synthetic supplements. Increasingly, nutritionally oriented doctors recommend that people supplement only natural beta-carotene. However, no animal research has yet explored whether the precancerous effects caused by synthetic beta-carotene might result from a combination of cigarette smoke plus natural beta-carotene supplements. Until more is known, smokers should avoid all beta-carotene supplements and others should avoid synthetic beta-carotene.

In supplements, the natural form can be identified by the phrases “from D. salina,” “from an algal source,” “from a palm source,” or as “natural beta-carotene” on the label. The synthetic form is identified as “beta-carotene.”

Where is beta-carotene found?

Dark green and orange-yellow vegetables are good sources of beta-carotene which is also available in supplements.

Who is likely to be beta-carotene deficient?

Individuals who limit their consumption of beta-carotene-containing vegetables could be at higher risk of developing a vitamin A deficiency; however; because beta-carotene is not an essential nutrient, deficiencies do not occur.

How much beta-carotene is usually taken?

The most common beta-carotene supplement intake is probably 25,000 IU (15 mg) per day, though some people take as much as 100,000 IU (60 mg) per day. Whether the average person would benefit from supplements with beta-carotene remains unclear.

Are there any side effects or interactions?

Beta-carotene does not cause any side effects; however, excessive intake (more than 100,000 IU, or 60 mg per day) sometimes gives the skin a yellow-orange hue. Individuals taking beta-carotene for long periods of time should also supplement with vitamin E, as beta-carotene may reduce vitamin E levels. As noted above, synthetic beta-carotene has now been linked to increased risk of lung cancer in smokers. Precancerous changes to lungs have appeared in animals given synthetic beta-carotene supplements, particularly those exposed to tobacco smoke. Though some research suggests that differences between synthetic and natural supplements may exist, conclusive proof of such a difference has not yet been shown.