Fish consumption and its effect on the brain

If you eat broiled or baked fish daily, what effect does it have on your brain?

Scientific ethics prohibits a study in which subjects in one group of people would be fed fish for the last two decades of their lives while another group would be deprived of fish in order to eventually examine their brain tissue for differences.

This is where we call in laboratory mice to help us get a better idea of how a daily intake of fish might help our brains stay healthy and free of amyloids, the proteins that collect in strands of waxy fibers that are believed to be responsible for Alzheimer’s disease (AD).

“This is a sign”

In the e-Alert “Mercury Rising” (4/25/02) I told you about a Canadian study from the University of Guelph that found Alzheimer’s patients and elderly patients with various types of dementia all had lower levels of docosahexaenoic acid (DHA; an omega-3 fatty acid found most abundantly in fish) than subjects with normal cognitive functioning.

In a press release, Julie Conquer, director of the University of Guelph’s Human Nutraceutical Research Unit said, “Low DHA levels are already affiliated with several disorders. Given that our research indicates that decreased levels of DHA also appear to accompany cognitive impairment with aging, we think this is a sign we should all be eating more fish.”

Fish was also on the menu in a more recent study from Tufts University where researchers analyzed ten years of data taken from more than 1,100 elderly men and women who had participated in the Framingham Heart Study. The impressive results showed that those who had high levels of DHA and who also ate about three fish meals each week, had nearly 50 percent reduced risk of developing AD.

DHA enriched

The research from Tufts and Guelph demonstrates that DHA appears to help prevent Alzheimer’s disease. But these studies don’t prove a clear cause and effect. For something closer to that type of evidence we’ll take a look at new research from the University of California Los Angeles (UCLA).

As the name implies, amyloid precursor protein (APP) is a protein that prompts the production of amyloid fibrils in the brain. To assess the effect of dietary DHA on the processing of APP, the UCLA scientists divided mice into three groups to receive different diets: a low-DHA diet, a high-DHA diet and a DHA-free diet. At the outset, the mice were about a year and a half old. They were fed the special diets for about three months.

When the UCLA team analyzed tissue samples from different sections of the mouse brains they found that APP was significantly reduced in mice on the high-DHA diet, while total amyloid accumulation was more than 70 percent less in mice that received a high-DHA diet when compared to those in the DHA-free group.

Fish and fish only

For researchers, proof that DHA intake prevents Alzheimer’s disease is still a long way off. But for most of us out here in the real world there appears to be no downside to keeping DHA levels high.

In the e-Alert “Oil Rich” (9/25/03) I told you how dietary sources like walnuts and flaxseed deliver omega-3 fatty acids, but only fish contains both DHA and eicosapentaenoic acid (EPA). When combined, these two essential fatty acids have been shown to help prevent depression, as well as heart disease, arthritis, influenza, hyperactivity and even some forms of cancer.

For those who don’t feel comfortable eating fish for fear of mercury or other toxins, fish oil and cod liver oil supplements also provide good sources of omega-3 EPA/DHA. Unfortunately, some of these supplements may also contain traces of mercury and other pollutants. To insure the highest quality of uncontaminated fish oil, look for pharmaceutical grade fish oil that’s been molecularly distilled. The molecular distillation process effectively separates toxic heavy metals from the oil.

Sources:

 

“A Diet Enriched with the Omega-3 Fatty Acid Docosahexaenoic Acid Reduces Amyloid Burden in an Aged Alzheimer Mouse Model” The Journal of Neuroscience, Vol. 25, No. 12, 3/23/05, jneurosci.org

“Fatty Acid-Rick Diet May Block Alzheimer’s” Reuters Health, 3/22/05, reutershealth.com

“Development of a Comprehensive Dietary Antioxidant Index and Application to Lung Cancer Risk in a Cohort of Male Smokers” American Journal of Epidemiology, Vol. 160, No. 1, 7/1/04, ncbi.nlm.nih.gov

“New Data Finds Antioxidant Combo Decreases Smokers’ Cancer Risk” NutraIngredients.com, 8/9/04, nutraingredients.com