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:

 

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:

How to Avoid BPA

The purported link between obesity and hormone-disrupting plastics chemicals like bisphenol A (BPA) was initially based in part on observations that the rise in chemical exposure seemed to coincide with the rise of the obesity epidemic, but that may only be a coincidence. Many other changes over the last half century, like an increase in fast-food consumption and watching TV, would seem to be simpler explanations. But why are our pets getting fatter, too? Fido isn’t drinking more fries or drinking more soda. Of course, the more we watch Seinfeld reruns, the less we may walk the dog, but what about our cats? They’re also getting fatter. Are we giving both them and our kids a few too many treats? That would seem to be an easier explanation than some pervasive obesity-causing chemical in the environment building up in the pet and person food chains.

How then do we explain the results of a study of more than 20,000 animals from 24 populations, showing they are all getting fatter? The odds that this could happen just by chance is about 1 in 10 million. The study’s “findings reveal that large and sustained population increases in body weight” are occurring across the board, even in those without access to vending machines or getting less physical education in schools. Perhaps some environmental pollutant is involved. I discuss this in my video How to Avoid the Obesity-Related Plastic Chemical BPA.

We’re exposed to a whole cocktail of new chemicals besides BPA, but the reason researchers have zeroed in on it is because of experiments showing that BPA can accelerate the production of new fat cells, at least in a petri dish. This was at more than a thousand times the concentration found in most people’s bloodstream, though. We didn’t know if the same thing happened at typical levels…until now. Most people have between 1 and 20 nanomoles of BPA in their blood, but even 1 nanomole may significantly boost human fat cell production. So, even low levels may be a problem, but that’s in a petri dish. What about in people?

Why not just measure the body weights of a population exposed to the chemical compared to a population not exposed to the chemical? There is virtually no unexposed population: BPA is everywhere. In that case, how about those with higher levels compared to those with lower levels? This is what researchers at New York University did, and the amount of BPA flowing through the bodies of children and adolescents “was significantly associated with obesity.” However, since it was a cross-sectional study, a snapshot in time, we don’t know which came first. Maybe instead of the high BPA levels leading to obesity, the obesity led to high BPA levels, since the chemical is stored in fat. Or, perhaps BPA is a marker for the same kinds of processed foods that can make you fat. What we need are prospective studies that measure exposure and then follow people over time. We never had anything like that…until now! And indeed, researchers found that higher levels of BPA and some other plastics chemicals were significantly associated with faster weight gain over the subsequent decade. So, how can we stay away from the stuff?

Though we inhale some from dust and get some through our skin touching BPA-laden receipts, 90 percent of exposure is from our diet. How can we tell? When we have people fast and drink water only out of glass bottles for a few days, their BPA levels drop as much as tenfold.

Fasting isn’t very sustainable, though.

What happens with a three-day fresh foods intervention, where families switch away from canned and packaged foods for a few days? A significant drop in BPA exposure. If we do the experiment the other way, adding a serving of canned soup to people’s daily diet, we see a thousand percent rise in BPA levels in their urine compared to a serving of soup prepared with fresh ingredients. That study used a ready-to-serve canned soup, which, in the largest survey of North American canned foods, was found to have about 85 percent less BPA than condensed soups, but the worst was canned tuna.


I previously touched upon bisphenol A in BPA Plastic and Male Sexual Dysfunction. Some companies make canned foods without BPA, for example, Eden Foods. (See Do Eden Beans Have Too Much Iodine? for more information.) You can also buy aseptic packaged beans or boil your own. Personally, I like pressure-cooking them.

For more on BPA, see:

Phthalates are another concerning class of plastics chemicals. I covered those in Avoiding Adult Exposure to Phthalates and What Diet Best Lowers Phthalate Exposure?.

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: