High-fat diets may speed up AMD

AMD & Cardiovascular Disease: Common Risks

Approximately 25-30 million people in industrialized countries over the age of 50 are affected by age-related macular degeneration (AMD). Since individuals with early or intermediate stages of the disease make up a growing segment of the elderly U.S. population, there's great interest in identifying dietary and lifestyle factors that can reduce the risk for AMD. The AREDS trial found that high dose antioxidants and zinc can slow down AMD progression. Studies suggest that higher intake of lutein and zeaxanthin can also reduce AMD risk.

Researchers have long theorized that AMD and cardiovascular disease share some common risk factors. Just as fatty foods can clog arteries and raise the risk of heart disease, it's believed that a high fat diet could also affect the eye's blood vessels and lead to advanced stages of AMD. To test that theory, a team of Harvard investigators examined the relationship between dietary habits and the risk of AMD progression to advanced stages associated with loss of vision and quality of life (1).

High Fat Diets May Lead to Vision Loss

In this five year study of 261 patients who already had signs of early to intermediate AMD, the risk that the disease would progress more than doubled for those eating the highest amount of fat compared to those consuming the least. Specifically, higher intake of vegetable fat, and to a lesser extent animal fat, increased the rate of progression. Diets rich in meat and dairy also heighten the risk, but not as much as processed baked goods which are often a source of LDL cholesterol-raising trans fatty acids.

The Good News: Fish and Nuts Are Protective

One exception among the fat-containing food categories was nuts, which were found to be protective. Among those AMD patients whose intake of the omega-6 fatty acid, linoleic, was lowest, a protective effect was also seen for those who consumed plenty of fish. Fish is a rich source of the omega-3 fatty acids, particularly DHA which is found abundantly in the eye's retina. Nuts also contain an omega-3 fatty acid called linolenic acid, which the body can convert into the more potent DHA and EPA fatty acids.

The finding that eating fish reduced the risk of AMD progression is consistent with the results of other studies linking higher fish consumption with a lower risk of advanced AMD (2). In one large scale study, fish - especially DHA-rich Tuna - was associated with risk reduction (3).

Other studies, too, have a reported a protective role for nuts and cardiovascular disease. In the Physician's Health Study, for example, men who included nuts in their diet twice or more weekly, reduced their risk of sudden cardiac death by half (4). Additionally, The Nurses' Health Study reported a 35% lower risk of heart disease among women who consumed nuts at least five times weekly compared to those who eat none (5). In addition to omega-3's, nuts contain other cardio-protective nutrients such as vitamin E, magnesium, fiber, and resveratrol - the antioxidant and anti-inflammatory compound also found in red wine.

What's the Take Home Message?

For eye health, watch your overall fat intake, cutting back on fat laden foods such as processed baked goods. Bring on the nuts, fish, and - for lutein and zeaxanthin - the green leafy vegetables. Your heart will be healthier too!

References

1. Seddon JM et al. Progression of Age-Related Macular Degeneration: Association with dietary fat, trans-unsaturated fat, nuts and fish intake. Arch Ophthalmol 121:1728-37, 2003.
2. Seddon JM et al. Dietary fat and risk for advanced age-related macular degeneration. Arch Ophthalmol 119:1191-99, 2001.
3. SanGiovanni JP et al. Abstract 811/B786 presented at ARVO Annual Meeting, May, 2003
4. Albert CM et al. Nut consumption and decreased risk of sudden cardiac death in the Physician's Health Study. Arch Intern Med 162:1382-87, 2002.
5. Hu FB et al. Frequent nut consumption and risk of cornoray heart disease in women: prospective cohort study. British Med J 317:1341-45, 1998.