Dietary DHA Protects Against Cognitive Decline and Alzheimer’s Disease

by Nils Osmar. April 1, 2022

DHA IDocosahexaenoic acid) plays an important role in brain function. This isn’t surprising when you consider that approximately 60 percent of a healthy human brain is comprised of fat, and that omega-3 fatty acids — especially DHA — are highly concentrated in our brain tissues. According to a study called Docosahexaenoic Acid and Cognition throughout the Lifespan, DHA makes up over 90% of the n-3 polyunsaturated fatty acids in the brain and 10%–20% of its total lipids. 

Evolutionary biologists note a connection between DHA consumption and the development of intelligence. As the human diet expanded to include seafood, gray matter in the cerebral cortex began to expand and the physical size of the brain increased:

Modern humans have evolved with a staple source of preformed docosahexaenoic acid (DHA) in the diet. An important turning point in human evolution was the discovery of high-quality, easily digested nutrients from coastal seafood and inland freshwater sources. Multi-generational exploitation of seafood by shore-based dwellers coincided with the rapid expansion of grey matter in the cerebral cortex, which characterizes the modern human brain.

Source: Docosahexaenoic Acid (DHA): An Ancient Nutrient for the Modern Human Brain

DHA and Alzheimer’s

Alzheimer’s is a complex medical condition. At this point. there are no medications that can be reverse it. But there’s evidence that it can be prevented, and that symptoms of cognitive decline can be reversed, by making changes in our diet.

One change that would likely be beneficial would be to reduce our consumption of sugars, including fructose. According to the authors of an article entitled “Sugar-Sweetened Drinks May Increase the Risk of Alzheimer’s Disease“:

“Researchers found that in the 2,664 individuals included in the study, those who consumed (one or more) servings of sugar-sweetened beverages per week were 1.91 times more likely to develop Alzheimer’s disease than those who consumed no sugar-sweetened beverages.”

Lower DHA Correlates With Lower Cognitive Ability

Another intervention which studies suggest could help would be increasing our consumption of fatty fish. Decreases in the level of DHA in our plasma are associated with cognitive decline both in healthy elderly adults and in patients with Alzheimer’s disease — and high dietary intake of DHA is inversely correlated with a lower risk of Alzheimer’s disease.

Can Cognitive Decline be Reversed?

In a double-blind 2010 study entitled “Beneficial effects of docosahexaenoic acid on cognition in age-related cognitive decline“, researchers set out to clarify the effects of DHA on cognitive functions in older adults. The people in the study were “otherwise healthy,” but had begun experiencing what was considered age-related cognitive decline. (I would question whether it was really caused by aging, since they were able to reverse it by making changes in the participants; diets.)

There were 485 healthy participants in the study.  After 24 weeks of supplementation with 900 mg per day of DHA, researchers found improved learning and memory function. They concluded that DHA is a beneficial supplement that supports cognitive health with aging.

For people able to eat fish, the best sources of DHA are foods such as salmon, trout, sardines, mackerel, anchovies and herring Both sardines and anchovies contain high amounts of these beneficial fats, compared to other fish species. Anchovies canned in oil contain about 2 grams of omega-3s, while sardines have about 1.6 grams of omega-3s..Note: Pregnant women are advised to avoid fish that are high in mercury.

What I’m Doing

I eat foods rich in EPA and DHA every day. Wild Pacific sockeye salmon, anchovies and sardines are my key staples. I also take a krill oil supplement. One three ounce can of sardines has about  740 milligrams of DHA and 450 milligrams of EPA (which is also beneficial to the brain). I would estimate that I get around 2,500 mg of omega 3s a day, of which around 900 mg are DHA. I also eat organic grass-fed beef once or twice a week, another good source of the nutrient. For vegans, Algal oil, a type of oil derived from algae, appears to be the best source.

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