BOSTON, MASSACHUSETTS. Age-related macular degeneration (AMD) is a leading cause of blindness for which treatment options are limited.
Researchers at the Harvard Medical School have just released a major study that points to a close association between the development of AMD and the consumption of certain fats and fatty acids, such as those found in oily fish and fish oils. The study involved 42,743 female nurses enrolled in 1984 and 29,746 male health professionals enrolled in 1986. The nurses completed 130-item food frequency questionnaires in 1984, 1986 and 1990 and the men completed them in 1986 and 1990.
By 1996 a total of 567 study participants (351 women and 216 men) had developed AMD with visual loss of 20/30 or worse. The researchers found that women with a high fat intake (fifth quintile) had a 63 per cent greater risk of AMD than women with a low intake (first quintile). For men, the increased risk was 36 per cent. The major contributors to the increased risk were high intake of linolenic acid and trans-fatty acids. In contrast, a high intake of docosahexaenoic acid (DHA), a main component of fish oils, was found to lower the risk of AMD by about 30 per cent. More than one serving per week of beef, pork or lamb as a main dish was associated with a 35 per cent increased risk of AMD when compared to an intake of less than three servings per month. Fish, especially canned tuna, was found to have a protective effect, with the participants who ate fish (thus, consuming fish oils) more than four times per week having a 35 per cent lower risk of AMD than people eating fish three times per month or less.
The researchers conclude that a high intake of linolenic acid may increase the risk of AMD. They caution though that their finding contradicts other studies that have shown that linolenic acid is protective against coronary heart disease.
Cho, Eunyoung, et al. Prospective study of dietary fat and the risk of age-related macular degeneration. American Journal of Clinical Nutrition, Vol. 73, February 2001, pp. 209-18.
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