Diet - Possible Protective Factors: Alzheimers

Content provided by the Faculty of the Harvard Medical School

Diet

Just as some dietary fats can protect against cardiovascular disease and others can increase the risk, several studies suggest that the same is true for Alzheimer's disease. Diets that are high in damaging saturated fats and trans fats appear to increase the risk of Alzheimer's disease, whereas diets that are high in heart-healthy monounsaturated and polyunsaturated fats appear to decrease the risk. Saturated fats come mainly from meat and dairy, and trans fats from processed foods made with partially hydrogenated oils. Sources of healthy unsaturated fats include nuts, olive oil, canola oil, and fish.

A 2003 study in Archives of Neurology, for example, followed 815 cognitively normal people ages 65 and older for four years. By the end of the study, the people who ate the most saturated and trans fats were twice as likely to have Alzheimer's disease as the people who consumed the least. However, the people who ate the most mono- and polyunsaturated fats were 70% less likely to develop Alzheimer's than the people who ate the least of these healthy fats.

Several other studies have found a benefit specifically from eating fish that is rich in omega-3 fatty acids, a type of polyunsaturated fat. Salmon, mackerel, and sardines are good sources. One 2005 study in Neurology found that people who ate fatty fish more than twice a week had a 28% lower risk of dementia and a 41% lower risk specifically of Alzheimer's disease than people who ate fatty fish less than once a month. This study did not find a protective effect from eating lean fried fish.

Many unanswered questions about diet remain, however. It is unclear whether fish oil supplements are also beneficial. If fish does reduce the risk of various types of dementia, it could be because of its protective effect against cardiovascular disease. But fish may also benefit the brain directly. In a 2005 study reported in Neurobiology and Aging, researchers found that a diet supplemented with omega-3 fatty acids limited the accumulation of beta-amyloid in the brains of mice bred to develop Alzheimer's disease. Whether people would enjoy the same benefit remains to be seen, but in the meantime, it can't hurt to replace the unhealthy fats in your diet with healthy ones.

Last updated:	January 23, 2007