& Joannie Dobbs Monday,
Fish is good for the brain, study shows
Grandma used to say, "Fish is brain food." The idea has passed down without any real explanation of why.
Researchers at Chicago's Rush-Presbyterian-St. Luke's Medical Center have put the fish theory to the test, and their results indicate that Grandma just might have been right.
During a four-year period, people over the age of 65 were evaluated for Alzheimer's disease. Those who ate fish at least once a week were about half as likely to develop Alzheimer's as those who never ate fish. The study agrees with others that have considered the link between eating fish and Alzheimer's.
Question: Why might fish be good for the brain?
Answer: Fish oils contain omega-3 fatty acids that may benefit the brain. Various studies with animals find that the those with diets containing adequate omega-3 fatty acids have superior learning and memory skills compared with those with low levels of these fatty acids. Also, people with Alzheimer's disease typically have lower levels of omega-3 fatty acids in their blood.
Although these studies do not prove that omega-3 fatty acids are the protective factor, researchers are focusing future work on this area. One of these fatty acids -- docosahexaenoic acid, or DHA for short -- is a major component of the brain.
Q: Are there other possible explanations?
A: Certainly. Fish contain many other important nutrients, and people who eat more fish may tend to eat more of other healthful foods. Other studies have reported that people who eat more fruits and vegetables are less likely to develop Alzheimer's.
Q: Is there more than one type of omega-3 fatty acid?
A: Three are commonly found in foods. They differ by the length of their molecules. Some plant oils, such as flaxseed oil, contain shorter molecules, whereas fish oils contain the longer ones commonly called EPA and DHA. In the Rush-Presbyterian study, DHA was the fatty acid most directly associated with reduced risk of Alzheimer's.
Q: Can you get too much omega-3 fatty acids?
A: Yes. Even moderately high doses of fish oil over time can suppress the immune system and increase the risk of bleeding and hemorrhagic stroke. People taking blood-thinner medications should consult their physician before taking fish oil supplements.
Q: Do omega-3 fatty acids have other benefits or risks?
A: Adequate DHA may decrease the risk of developing age-related macular degeneration. But omega-3-rich plant oils may not provide the same benefit. In fact, some studies have found that excess intake of plant-oil omega-3s increases the risk of macular degeneration and prostate cancer.
The bottom line: Over time, too much or too little of any one type of fatty acid can produce significant health problems. Again, variety and balance are the spices of life.
Alan Titchenal, Ph.D., C.N.S. and Joannie Dobbs, Ph.D., C.N.S.
are nutritionists in the Department of Human Nutrition, Food and Animal Sciences,
College of Tropical Agriculture and Human Resources, UH-Manoa.
Dr. Dobbs also works with the University Health Service
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