News Bites: Fish as Food for the Brain & Exercise for Eye Health

DHA, Fish Lower Risk for Alzheimer's

Coldwater, fatty fish are a concentrated source of the omega-3 fats docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). Population health studies have consistently shown positive health effects from fish consumption and, now, a study published in the November issue of The Archives of Neurology, links greater fish intake to a lower risk of developing Alzheimer's and other dementias (1). And in this study, DHA was most important for cutting risk.

Using data from the Framingham Heart study, researchers followed about 900 healthy participants for an average of more than 9 years. During that time, 99 people developed dementia including 71 cases of Alzheimer's. Researchers quantified the amount of DHA and fish the participants typically consumed by dietary questionnaires, and measured the level of fatty acids in their blood.

DHA Cuts Risk of Dementia by Nearly 50%

The top 25% of study volunteers with the highest blood levels of DHA reduced their risk of developing dementia by 47%. They were about half as likely to develop dementia as the 75% of participants with lower levels of DHA in their blood. The risk reduction was seen even after controlling for other known or suspected risk factors for dementia such as smoking, overweight, high blood pressure and diabetes.

Participants who ate two or more servings of fish weekly reduced their dementia risk by 39%, while those who ate less had no risk reduction.

According to the study's authors, the observation that DHA seems to be key in lowering dementia risk is consistent with earlier data showing high levels of DHA in healthy brain tissue and low levels in the brains of people with Alzheimer's. The next step will be to conduct placebo controlled trials of DHA in people who don't yet have Alzheimer's to see whether DHA can help protect against this disease.

Active Lifestyle Could Protect Against AMD

Exercise may help protect against age-related macular degeneration (AMD) according to the results of a large study supported by the NIH and published in the British Journal of Ophthalmology (2). The authors examined the relationship between physical activity and AMD because heart disease and AMD appear to share common risk factors. And regular exercise, as we all know, is good for the heart and arteries.

Participants in the Beaver Dam Eye Study were followed for 15 years. During that time they were given eye exams periodically, and they filled out questionnaires at the beginning of the study to assess their level of activity. They were asked how many flights of stairs they climbed daily, how many city blocks they walked each day, and how often each week they engaged in physical activity that involved working up a sweat.

Compared with sedentary people, those who participated in regular activity 3 times weekly were less likely to develop wet AMD. Those with an active lifestyle - defined as engaging in an activity that resulted in sweating 3 or more times each week - reduced their risk of wet AMD by 70%. Walking 12 or more blocks daily lowered that risk by 30%.

Walk Daily, Put More Fish on Menu

Can't get to the gym or participate in vigorous exercise? Try walking at least a mile daily. Though each city and each block vary in length, walking 8-12 city blocks is roughly equivalent to a mile. It's certainly good for heart and may help your eyesight as well.

For better mental function as we age, remember that fatty fish is best, and frying fish can cause some deterioration of its DHA content. You can also consider augmenting your intake of DHA and EPA with supplemental fish oil.

References

1. Schaefer EJ, et al. Plasma phosphatidylcholine docosahexaenoic Acid content and risk of dementia and Alzheimer disease: the Framingham Heart study. Arch Neurol. 63:1545-50, 2006.
2. Knudtson MD, et al. Physical Activity and the 15-year Cumulative Incidence of Age-related Macular Degeneration: The Beaver Dam Eye Study. British J of Ophthalmology, published online Oct. 31, 2006.