Do DHA Supplements Improve Brain Function?

The concept of vitamins was first described by none other than Dr. Funk. In his landmark paper in 1912, he discussed the notion that there were complex compounds our body couldn’t make from scratch, so we had to get them from our diet. By the mid-20th century, all the vitamins had been discovered and isolated, but it wasn’t until the 1960s 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 percent fat-free diet on himself for six months, ironically, he felt better. His high blood pressure went away, he felt more energetic, and his migraines disappeared. This one-man experiment “fortif[ied] the medical profession’s doubt that essential fatty acids had any relevance to humans,” until TPN—Total Parenteral Nutrition, meaning feeding someone exclusively through an IV—was developed in the 1960s. TPN was initially developed for babies born without working intestines. Because we didn’t think humans needed fat, “the first preparations were fat free, and they rapidly induced severe EFA [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 given the oil after an abdominal gunshot wound, we don’t just need fat—we need specific fats like omega-3s. So, when they switched from safflower oil to soybean oil, she was restored to normal.

The fact 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. The vitamin C in a spoonful of orange juice would be enough to avoid scurvy (the overt vitamin C deficiency disease), but no one considers that enough vitamin C for optimal health.

As I discuss in my video Should We Take DHA Supplements to Boost Brain Function?, what would optimal omega-3 status look like? Well, doubt has been cast on its role in heart health (see Is Fish Oil Just Snake Oil?), which appears to have been based on a faulty premise in the first place (see Omega-3s and the Eskimo Fish Tale), so taking extra omega-3s for our heart might not make any sense (see Should We Take EPA and DHA Omega-3 for Our Heart?). But what about for our baby’s brain (see Should Pregnant and Breastfeeding Women Take DHA?)? 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 (see Should Vegan Women Supplement with DHA During Pregnancy?). What about adults? There doesn’t appear to be any apparent psychological (see Fish Consumption and Suicide) or neurological (see Is Fish “Brain Food” for Older Adults?) benefit of DHA supplementation for the general public, but what about in those who don’t eat fish?

The famous Alpha Omega Trial randomized thousands of people over three years to get either long-chain omega-3s from fish, short-chain omega-3s from plants, or placebo. The result? The study found no significant benefits for any kind of omega-3 supplementation on global cognitive decline. However, most of the subjects were eating fish, thereby already getting pre-formed DHA in their diets. General population studies like this, that find no benefit, can’t fully inform us about the role of DHA in brain health. It would be akin to giving half these people oranges, finding no difference in scurvy rates (zero in both groups), and concluding 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 fish. Previous randomized, controlled trials failed to find such a benefit among18- to 45-year-olds, but they only lasted a few months at most, whereas the 2013 study lasted for six months. If all the studies showed either 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 for DHA supplementation, four showed nothing, one showed a benefit, and one showed a harm. If it were just about boosting brain function in the short term, I’d err on the side of caution and spend my money elsewhere.


What about the long term though? See Should Vegans Take DHA to Preserve Brain Function?.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

 

The Healthiest Way to Eat Paleo

There have been about a half dozen studies published on Paleo-type diets, starting around 20 years ago. For example, in what sounds like a reality TV show: ten diabetic Australian Aborigines were dropped off in a remote location to fend for themselves, hunting and gathering foods like figs and crocodiles.

In Modern Meat Not Ahead of the Game, my video on wild game, I showed that kangaroo meat causes a significantly smaller spike of inflammation compared to retail meat like beef. Of course, ideally we’d eat anti-inflammatory foods, but wild game is so low in fat that you can design a game-based diet with under 7 percent of calories from fat. Skinless chicken breast, in comparison, has 14 times more fat than kangaroo meat. So you can eat curried kangaroo with your cantaloupe (as they did in the study) and drop your cholesterol almost as much as eating vegetarian.

So, how did the “contestants” do? Well, nearly anything would have been preferable to the diet they were eating before, which was centered on refined carbs, soda, beer, milk, and cheap fatty meat. They did pretty well, though, showing a significantly better blood sugar response—but it was due to a ton of weight loss because they were starving. Evidently, they couldn’t catch enough kangaroos, so even if they had been running around the desert for seven weeks on 1,200 daily calories of their original junky diet, they may have done just as well. We’ll never know, though, because there was no control group.

Some of the other Paleo studies have the same problem: They’re small and short with no control groups, yet still report favorable results. The findings of one such study are no surprise, given that subjects cut their saturated fat intake in half, presumably because they cut out so much cheese, sausage, or ice cream. In another study, nine people went Paleo for ten days. They halved their saturated fat and salt intake, and, as one might expect, their cholesterol and blood pressure dropped.

The longest Paleo study had been only 3 months in duration, until a 15-month study was conducted—but it was done on pigs. The pigs did better because they gained less weight on the Paleo diet. Why? Because they fed the Paleo group 20 percent fewer calories. The improvement in insulin sensitivity in pigs was not reproduced in a study on people, however. Although, there were some benefits like improved glucose tolerance, thanks to these dietary changes: The Paleo group ate less dairy, cereals, oil, and margarine, and ate more fruits and nuts, with no significant change in meat consumption.

A follow-up study also failed to find improved glucose tolerance in the Paleo group over the control group, but did show other risk factor benefits. And no wonder! Any diet cutting out dairy, doughnuts, oil, sugar, candy, soda, beer, and salt is likely to make people healthier and feel better. In my video Paleo Diet Studies Show Benefits, you can see a day’s worth of food on the Standard American Diet, filled with pizza, soda, burgers, processed foods, and sweets, versus a Paleo diet, which, surprisingly, has lots of foods that actually grew out of the ground.

But the Paleo diet also prohibits beans. Should we really be telling people to stop eating beans? Well, it seems hardly anyone eats them anyway. Only about 1 in 200 middle-aged American women get enough, with more than 96 percent of Americans not even reaching the minimum recommended amount. So telling people to stop isn’t going to change their diet very much. I’m all for condemning the Standard American Diet’s refined carbs, “nonhuman mammalian milk”, and junk foods, but proscribing legumes is a mistake. As I’ve noted before, beans, split peas, chickpeas, and lentils may be the most important dietary predictor of survival. Beans and whole grains are the dietary cornerstones of the longest living populations on Earth. Plant-based diets in general and legumes in particular are a common thread among longevity blue zones around the world.

The bottom line may be that reaching for a serving of kangaroo may be better than a cheese danish, “but foraging for…[an] apple might prove to be the most therapeutic of all.”


I’ve reported previously on Paleo’s disappointing results in Paleo Diets May Negate Benefits of Exercise.

The underlying philosophy behind “caveman” diets may be flawed in the first place. See:

So, What’s the Natural Human Diet? Watch the video!

The wild game video I mentioned is Modern Meat Not Ahead of the Game. Kangaroo is kind of the Australian version of venison. Note that it also matters how the animals are killed. See Filled Full of Lead and Lead Contamination in Fish and Game.

And, for more on the musical fruit, see:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

Meat Can Cause Stress Hormone Levels to Rise and Testosterone levels to Drop

A critique of the scientific validity of the dietary advice in Men’s Health magazine discovered nuggets claiming meat can give men “a testosterone boost,” but we’ve known for a quarter century that a meal with that much fat can drop testosterone levels by nearly one-third within hours. In fact, a significant drop of both free and bound testosterone in the bloodstream occurs within just one hour of it going in one’s mouth, whereas a low-fat meal of mostly carbs has no such effect. Based on in vitro studies on the effects of fat on testicle cells in a petri dish, researchers suspect fat in the blood may actually suppress testosterone production in real time. If you feed people lots of eggs and meat, including fish and poultry, and then switch them to a diet with bread, fruit, vegetables, and sugar—but about the same amount of fat—all their testosterone levels go up. Even more importantly, however, all their levels of cortisol, a stress hormone produced by our adrenal glands, go down.

Having low stress hormone levels is good, because high cortisol levels may “strongly predict cardiovascular death” in men and women both with and without pre-existing cardiovascular disease. In fact, this may help explain “death from a broken heart,” the heightened heart attack and stroke risk in the immediate weeks following the loss of a spouse. Higher cortisol levels days, months, or even years after losing someone you love may increase cardiac risk and reduce immune function. And, the rise in stress hormone levels from the loss of a spouse, a bump of about 50 points, is less than the bump you get by eating high-meat diet.

Cortisol may also help explain why those who are depressed tend to put on abdominal fat. The reason obesity around the middle is associated with elevated cortisol secretion may be that abdominal fat kind of sucks it up, so the accumulation of fat around our internal organs may be an adaptation by which our body deals with excess stress.

These spikes in stress hormone levels every time we eat a lot of meat may not just affect our health, but that of our children, which I discuss in my video Maternal Diet May Affect Stress Responses in Children. “Substantial evidence now suggests that maternal diets of high protein density have adverse effects on the fetus.” For example, back in the 1960s, an experiment was performed on pregnant women in Motherwell, Scotland, in which they were told to eat a high-meat diet in hopes of preventing preeclampsia, a disease of pregnancy. It didn’t work. In fact, the lowest preeclampsia rates I’ve ever seen were among women eating strictly plant-based diets—only 1 case out of 775 pregnancies. Preeclampsia normally strikes about 5 percent of pregnancies, so there should have been dozens of cases, suggesting a plant-based diet could alleviate most, if not all, of the signs and symptoms of this potentially serious condition. So what did happen when pregnant women went from eating about one daily portion of meat to about two portions a day? Mothers who ate more meat and fewer vegetables during pregnancy gave birth to children who grew up to have higher blood pressures.

“One explanation proposed for the adverse effects of high-meat/fish consumption is that this may increase maternal cortisol concentrations, which, in turn, affect the developing fetus,” resetting his or her stress hormone thermostat to a higher level. But, we don’t know until we put it to the test. And indeed, researchers found higher blood cortisol levels “in both the sons and daughters of women who had reported higher meat/fish” consumption, about a 5 percent increase for every meat serving per day. Such diets may present a metabolic stress to the mother and kind of reprogram the adrenal axis of their children, leading to lifelong hypercortisolemia, elevated levels of stress hormones in the blood. This may help explain why every daily portion of meat during late pregnancy may lead to a 1 percent greater fat mass in their children by the time they reach adolescence. So, this could increase the risk of their children becoming obese later in life and thus has “important implications for public health and in terms of prevention of obesity.”

What if they’re already born? We may be able to bring down children’s stress hormone levels with similar dietary changes, but this is just baseline stress hormone levels. Do children of mothers who eat more meat during pregnancy also have exaggerated responses to life stressors? Researchers put them through a stressful challenge—public speaking and mental arithmetic—and then measured their cortisol responses. If their mom ate less than two servings of meat/fish a day while she was carrying them, they got little shots of stress hormones from their adrenal glands. Those whose moms ate more really got stressed out, and those whose moms ate the most—17 or more servings a week, which is more than 2 servings each day—appeared to be really quaking in their boots. In a way, you are what your mother ate.


Want more craziness from Men’s Health magazine? Check out my video Changing a Man’s Diet After a Prostate Cancer Diagnosis.

Here are some other popular videos about eating healthfully during pregnancy:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations: