Flashback Friday: Should We Take DHA Supplements to Boost Brain Function?

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

The concept of vitamins was first described by none other than Dr. Funk, in his landmark paper in 1912: the concept that there were complex compounds that our body couldn’t make from scratch, and so had to get from our diet. By the mid-twentieth century, all of the vitamins had been discovered and isolated.

But it wasn’t until the 60s that we realized that certain fats were essential, too. In 1929, the necessity for fat was definitively settled in the diet of the rat. But, when one of the researchers tried a 99% fat-free diet on himself for six months, ironically, he felt better. His high blood pressure went away; he felt more energetic; his migraines disappeared. This one-man experiment fortified the medical profession’s doubt that essential fatty acids had any relevance to human nutrition, until TPN was developed in the 60s—Total Parenteral Nutrition, meaning feeding someone exclusively through an IV: initially developed for babies born without working intestines.

But, the first preparations were fat-free, because we didn’t think humans needed fat. And so, they rapidly induced severe essential fatty acid deficiencies, ultimately convincing the medical community that some fats are, indeed, essential. They started out using safflower oil. But, as they discovered in a young girl they were giving it to after an abdominal gunshot wound, we don’t just need fat, but specific fats, like omega-3s. And so, when they switched to soybean oil instead, she was restored to normal.

The fact that it took so long, and under such extreme circumstances, to demonstrate the essential nature of omega-3s illustrates how hard it is to develop overt omega-3 deficiency. Of course, the amount required to avoid deficiency is not necessarily the optimal amount for health. A spoonful of orange juice worth of vitamin C would be enough to avoid scurvy (the overt vitamin C deficiency disease). But no one considers that enough vitamin C for optimum health.

What would optimal omega-3 status look like? Well, doubt has been cast on its role in heart health—which appears to be based on a faulty premise in the first place. And so, taking extra omega-3s for our heart might not make any sense.

But what about for our baby’s brain? Extra DHA may not help pregnant or breast-feeding fish-eaters. But, those who want to avoid the contaminants in fishes can take supplements of pollutant-free algae oil to get the best of both worlds for their babies.

But what about adults? No apparent psychological or neurological benefit of DHA supplementation for the general public. But what about in those who don’t eat fishes?

Take the famous Alpha Omega Trial, with thousands of people randomized for over three years to get either long-chain omega-3s from fishes, short-chain omega-3s from plants, or placebo. And, they found no significant benefits for any kind of omega-3 supplementation on global cognitive decline. But, most were eating fishes; already getting preformed DHA in their diet.

And so, general population studies like this, that found no benefit, can’t fully inform us about the role of DHA in brain health—any more than giving half of these people oranges, finding no difference in scurvy rates (zero in both groups), and concluding that vitamin C plays no role in scurvy.

In 2013, for the first time, DHA supplementation was found to improve memory and reaction time among young adults who rarely ate fishes. Previous randomized, controlled trials failed to find such a benefit among, like, 18- to 45-year olds. But they all only lasted a few months at most, whereas the 2013 study lasted six months. So, if all the studies either showed no effect, or a positive effect, one might give it a try.

But in one of those shorter trials, DHA supplementation didn’t just fail to show benefit; it appeared to make things worse. After 50 days, those who consumed the DHA had worse memory than those taking the placebo. So, out of the six randomized controlled trials, four showed nothing; one showed a benefit; one showed a harm.

So, if it was just about boosting brain function in the short-term, I’d err on the side of caution, and spend my money elsewhere.

But what about preserving brain function over the long run? I’ll address that, next.

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Image thanks to dierk schaefer via flickr