Low Fat Diet Increases ARM; High Omega-3 Fatty Acid Reduces ARM Risk

In a recent study - the large Blue Mountains Eye Study in Australia, 2335 elderly patients were screened for early (dry) and late (wet) age-related maculopathy (ARM), or age-related macular degeneration (AMD) at baseline and after five years using pictures of their retinas. Their diets were assessed using a standardized questionnaire which was corroborated by physically measuring the daily food intake in 70 patients.

After correcting for smoking, age, sex, and vitamin C intake, the screening showed that low fat diets (less than 27% calories from fat) including low unsaturated fat, increased the likelihood of dry ARM by 50 -70%. A low Omega-3 unsaturated fat diet also slightly increased the likelihood of dry ARM. Contrary to previous studies, high unsaturated fat intake did not correlate with increased incidence of early or late ARM. In fact, diets high in n-3 unsaturated fats decreased the incidence of late ARM by 60%.

High or low fat, per see, is not the issue. The type of fat is critical. Omega-3 polyunsaturated fat from fish or krill oil is anti-inflammatory. Omega-6 fats are pro-inflammatory. High omega-3 fat diets decrease the risk of ARM; high omega-6 fat diets increase the risk of ARM. Older studies did not differentiate between the type of fat included in a low- or high-fat diet, thus their often conflicting and confusing results.

When the food origin of fat intake was compared, the researchers found that one fish meal a week (except fish sticks and farmed fish) could reduce the incidence of early ARM by 40%. Three or more fish meals per week could reduce the incidence of late ARM by 75%. Fish oil contains essential n-3 fatty acids and is known to promote cardiovascular health.

Loss of vision in the elderly is often the result of macular degeneration or a breakdown in central vision - the macula being the retinal area in the center of the eye. In 85 – 90% of cases it is known as the “dry” form caused by the buildup of fatty tissue called drusen. In 10-15% of cases it is the “wet” form which usually follows the dry form, where blood vessels grow extensively behind the retina and then hemorrhage.

Some common risk factors for macular degeneration include other symptoms of inflammation - hypertension, cardiovascular disease, high fat diets, oxidative stress and exposure to intense sunlight. Wet macular degeneration can be treated with laser cauterization, but few treatments are available for the early dry form.

As indicated by the known risk factors for ARM and the known benefits of n-3 fatty acid intake, consuming three or more fish meals per week may help keep elderly eyes healthy. Alternatively, fish oil supplements demonstrate the same benefit.

In a related study, Eating fish and Omega-3 fish oils may protect against age-related macular degeneration (AMD).

Reference:

Chua B, Flood V, Rochtchina E, Wang JJ, Smith W, Mitchell P. Dietary Fatty Acids and the 5-Year Incidence of Age-Related Maculopathy. Arch Ophthalmol. 2006;124:981-986.

Key concepts: omega-3, omega-6 fatty acids, ARM, age-related maculopathy