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 Eating several servings of seafood (especially fish) weekly has beneficial health effects throughout life, and now research finds another benefit in older adults. Seafood contains both EPA and DHA, which are two types of omega-3 fatty acids. DHA or docosahexanoic acid has "neuroprotective qualities" and is found in both the gray and white matter of the brain. Higher DHA levels (measured in the blood) was associated with better memory, less brain atrophy (better brain volume), and fewer amyloid plaques (which are associated with Alzheimer's) in cognitively healthy older adults. From Medscape:

Higher Serum DHA Linked to Less Amyloid, Better Memory

New research supports neuroprotectant effects of docosahexaenoic acid (DHA) in the aging brain. In a small cross-sectional study of cognitively healthy older adults, higher serum DHA levels were associated with less cerebral amyloidosis, better memory scores, and less regional brain atrophy.

"The interesting finding was the association of low serum DHA levels with cerebral amyloidosis (amyloid plaques) in older adults without evidence of dementia," Hussein N. Yassine, MD, Department of Medicine, University of Southern California, Los Angeles, told Medscape Medical News. "This association was predominantly driven by persons at the lowest quartile of serum DHA levels who likely have limited intake of seafood." "This study adds to the existing evidence on the benefit of seafood consumption on [Alzheimer's disease] AD risk factors," Dr Yassine added.

The study was published online August 8 in JAMA Neurology. In a linked editorial, Joseph F. Quinn, MD, Department of Neurology, Oregon Health and Science University, Portland, notes that DHA is "the most abundant polyunsaturated fatty acid in the brain, playing an important structural role in synapses while also modulating a number of signaling pathways. "Brain DHA levels are also modulated by dietary intake, so it is plausible for dietary DHA to alter brain concentrations and affect downstream targets including brain pathology and function."

Dr Yassine and colleagues assessed serum DHA levels, measures of amyloid burden based on positron emission tomography with Pittsburgh compound B, brain volume, and neuropsychological test scores in 61 adults without dementia in the Aging Brain Study.

They found that serum DHA levels (percentage of total fatty acids) were 23% lower in those with cerebral amyloidosis relative to those without. Serum DHA levels were inversely correlated with brain amyloid load, independent of age, sex, years of education, and apolipoprotein E genotype. They also noted a positive correlation between serum DHA levels and brain volume in several subregions affected by AD, in particular the left subiculum and the left entorhinal volumes.

Clinically, there was a significant association between serum DHA levels and nonverbal memory. This association persisted after adjustment for age but not after adjustment for apolipoprotein E genotype. Serum DHA levels were not associated with measures of global cognition, executive function, or verbal memory scores.

After reading this article, I looked over my last year's posts and realized that the recent studies posted all found that eating fish showed health benefits (and they did not look at supplements). Once again, a food shows benefits while the supplement is debatable. Current advice: try to eat fish at least twice a week. From the NY Times:

Fish Oil Claims Not Supported by Research

Fish oil is now the third most widely used dietary supplement in the United States, after vitamins and minerals, according to a recent report from the National Institutes of Health. At least 10 percent of Americans take fish oil regularly, most believing that the omega-3 fatty acids in the supplements will protect their cardiovascular health. But there is one big problem: The vast majority of clinical trials involving fish oil have found no evidence that it lowers the risk of heart attack and stroke.

From 2005 to 2012, at least two dozen rigorous studies of fish oil were published in leading medical journals, most of which looked at whether fish oil could prevent cardiovascular events in high-risk populations. These were people who had a history of heart disease or strong risk factors for it, like high cholesterol, hypertension or Type 2 diabetes. All but two of these studies found that compared with a placebo, fish oil showed no benefit.

In theory at least, there are good reasons that fish oil should improve cardiovascular health. Most fish oil supplements are rich in two omega-3 fatty acidseicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) — that can have a blood-thinning effect, much like aspirin, that may reduce the likelihood of clots. Omega-3s can also reduce inflammation, which plays a role in atherosclerosis. And the Food and Drug Administration has approved at least three prescription types of fish oil — Vascepa, Lovaza and a generic form — for the treatment of very high triglycerides, a risk factor for heart disease. But these properties of omega-3 fatty acids have not translated into notable benefits in most large clinical trials.

Like many cardiologists, Dr. Stein encourages his patients to avoid fish oil supplements and focus instead on eating fatty fish at least twice a week, in line with federal guidelines on safe fish intake, because fish contains a variety of healthful nutrients other than just EPA and DHA. “We don’t recommend fish oil unless someone gets absolutely no fish in their diets,” Dr. Stein said.

But some experts say the case for fish oil remains open. Dr. JoAnn Manson, the chief of preventive medicine at Brigham and Women’s Hospital in Boston, said the large clinical trials of fish oil focused only on people who already had heart disease or were at very high risk. Fish oil has also been promoted for the prevention of a variety of other conditions, including cancer, Alzheimer’s and depression. Dr. Manson is leading a five-year clinical trial, called the Vital study, of 26,000 people who are more representative of the general population. Set to be completed next year, it will determine whether fish oil and vitamin D, separately or combined, have any effect on the long-term prevention of heart disease, Type 2 diabetes, and other diseases in people who do not have many strong risk factors.

Dr. Manson says that although she recommends eating fatty fish first, she usually does not stop people from taking fish oil, in part because it does not seem to have major side effects in generally healthy people“But I do think people should realize that the jury is still out,” she said, “and that they may be spending a lot of money on these supplements without getting any benefit.”

Get your omega-3 fatty acids from either fish or flaxseed (or other seeds).From Science Daily:

Nothing fishy about health benefits of plant-based omega-3 fatty acid

Increasing the amount of omega-3s in your diet, whether from fish or flax, will likely decrease your risk of getting heart disease, according to Penn State nutritionists. A substantial amount of evidence exists supporting the heart-health benefits of eicosapentaenoic acid and docosahexaenoic acid (EPA and DHA), marine-derived omega-3 fatty acids. However, much less evidence exists to demonstrate the positive effects of alpha-linolenic acid (ALA), a plant-based omega-3 fatty acid.

EPA and DHA can be found in seafood and fish oil, and are often consumed in the form of dietary supplements. ALA is found in flaxseed and its oil, vegetable oils, and some nuts, and is now available in supplement form. EPA and DHA have been available for much longer. Other sources of ALA, EPA and DHA are fortified foods such as orange juice, eggs, peanut butter, margarine and bread, among others. While there are many other omega-3 fortified foods in the market place, most are relatively low in omega-3 fatty acids.

Omega-3 fatty acids are considered essential for human health, but the body does not produce them -- therefore they must be consumed in order to maintain appropriate levels.

In reviewing existing literature on the subject, the researchers have come to the conclusion that ALA is likely just as effective in preventing cardiovascular disease as EPA and DHA have proven to be, as they report on the current issue of Advances in Nutrition.