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PO Box 45409, Phoenix, AZ 85064-5409
Dear Sir:
Mares-Perlman recommended against lutein supplementation at this time for prevention of cataract, stating that we should learn a lesson from ß-carotene (1). She pointed out that studies have shown that ß-carotene supplementation does not appear to reduce the risk of cancer or cardiovascular disease and that it might even increase the risk of certain diseases. However, the studies she cited used synthetic ß-carotene, which consists almost entirely of all-trans-ß-carotene, whereas natural food sources contain a substantial amount of cis isomers as well (2). Recent evidence suggests that the cis isomers may be much more effective antioxidants in vivo than are the all-trans isomers (3). This could explain the lack of effectiveness of ß-carotene in these trials. Conceivably, a reduced ratio of cis to all-trans isomers in the tissues of people undergoing supplementation with all-trans-ß-carotene could have negative consequences, such as the increased risk of disease mentioned above. Thus, the real lesson we should learn from this is to perform trials by using carotenoid supplements that have the same proportions of the various isomers as are present in foods whose consumption has been linked with a reduced risk of disease.
I agree that routine lutein supplementation for prevention of cataract or age-related macular degeneration should not be advised until we obtain more definitive support from clinical trials. But can we also agree, in accordance with the adage "a dark, leafy green vegetable a day may keep the ophthalmologist away," to at least recommend consumption of more green vegetables to our patients? It couldn’t hurt. Supplements should be reserved for patients who are unable or unwilling to change their dietary habits, or for situations in which the desired intake of a given nutrient cannot be readily achieved by dietary means.
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