By Indre Viskontas, Ph.D., University of California, San Francisco
We have all heard that the secret to a better brain lies in a diet rich with superfoods like fish oil, vitamins, power drinks, and antioxidants. But what are the truths behind these claims?
The key ingredient in fish oil is omega-3 polyunsaturated acid— specifically, docosahexaenoic acid (DHA)—and claims have been made that it’s good for your brain. You can find it in oily fish such as salmon, mackerel, and sardines, or you can take it as a supplement. DHA is thought to play a role in brain development by increasing the expression of brain-derived neurotrophic factor (BDNF).
Work with rodents has shown that omega-3 fatty acids turn on genes that help keep the signaling system between brain cells working properly and enable neuroplasticity, or the types of physical changes that drive learning.
DHA is the most prevalent fatty acid in brain cell membranes—the protective covering that keeps the good stuff in the cell and the bad stuff out—but it also plays a major role in signaling between cells.
There’s some evidence that our ability to add DHA to our diets was a turning point in our evolutionary history, helping our brains grow in size compared with the rest of our body—increasing the brain-to-body-mass ratio, or encephalization quotient. DHA is also an antioxidant.
The American Heart Association recommends DHA supplements because they seem to reduce the risk of coronary artery disease and cardiovascular problems contribute to cognitive decline. Eating a lot of fish also seems to be associated with a lower risk of stroke.
This is a transcript from the video series Brain Myths Exploded: Lessons From Neuroscience. Watch it now, on Wondrium.
They also reduce inflammation, which has been associated with neurodegenerative diseases such as Alzheimer’s. Omega-3 fatty acids might even play a direct role in decreasing Alzheimer’s pathology because they reduce amyloid production and the plaques that are a signature of the disease are made up of amyloid.
Fish oil likely won’t make a difference unless you’re pregnant, under one year of age, or at risk of showing cognitive impairment, either in childhood or in old age.
There also doesn’t seem to be any evidence that DHA can make you smarter.
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Antioxidants are involved in helping brain cells get nutrients from the blood and in neuroplasticity. But they’re best known for defusing the little bombs that result from normal chemical reactions: Free radicals.
Oxygen is the stuff of life, but too much of it can be toxic. While you can’t breathe yourself to death, if you are getting oxygen from a supplemental source—for example, when scuba diving—you can take in too much oxygen, which can ultimately cause problems, such as seizures.
You need oxygen to extract energy from food, a process that leaves behind metabolic byproducts such as free radicals. These are atoms that are electrically unstable; they have an unpaired electron. Because of this instability, free radicals can strip an electron from another molecule nearby. As they travel through the body, they can wreak havoc by creating more unstable molecules in their wake.
This domino effect is how free radicals can damage cells and too many free radicals in a person’s body can become a problem. That’s why the body has natural defenses to protect against the proliferation of these little bombs. Cells can keep free radicals penned in with physical boundaries. Our bodies have enzymes that neutralize oxygen gone awry.
Antioxidants from our diet can donate their electrons to stop the chain reaction. This is part of the normal metabolic process. But the question at hand is whether more antioxidants will enhance brain function, or even protect it from decline.
Studies in animal models show some positive effects of adding antioxidants to the diet, but the data from human studies are mixed. Smaller studies have reported some effects, but once those studies are replicated with larger sample sizes, the effects diminish. This means that there are likely other variables affecting the results in the smaller samples.
Studies have also shown that taking too much of an antioxidant, such as vitamin E, can have negative side effects, such as an increased risk of prostate cancer.
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In 1988, an influential placebo-controlled study of 12- to 13-year-olds showed an improvement in nonverbal IQ for those who took vitamins. But since then, the evidence is building that adding vitamins to a healthy diet doesn’t help the brain.
Even so, research indicates that poor nutrition can harm cognitive function. For children who are in danger of not getting enough nutrients from their diet, vitamins are a good idea. For everyone else, it doesn’t seem to make a measurable difference.
You might have seen bottles in your local health-food store of brain-boosting drinks, marketing better sleep, sharper wits, and less stress. Some of these even contain neurotransmitters and hormones.
But these drinks are classified as dietary supplements, not food or drugs, so they don’t need FDA approval or even safety testing to tout their benefits.
It’s difficult to say if coffee staves off disease yet, but coffee most likely does leave a person more alert and able to complete cognitive tasks and thus score higher on such measures.
There’s not much evidence that you can drink your way to a better brain—unless your drink is laced with caffeine. It’s difficult to say if coffee staves off disease yet, but coffee most likely does leave a person more alert and able to complete cognitive tasks and thus score higher on such measures. It probably does not prevent plaques and tangles, which are the pathological markers of Alzheimer’s disease.
Caffeine might have a protective effect, but it remains unclear whether it’s a direct physiological mechanism, such as reducing inflammation, for example, or more related to increasing cognitive resources, such as helping you focus better on the task at hand.
However, this story is one of moderation. Sleep deprivation can lead to increased Alzheimer’s pathology, so if too much caffeine is interfering with your sleep patterns, it can have harmful effects on your energy through the day.
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There does seem to be some evidence that caloric restriction— eating substantially less than most people do—may enhance cognition and even extend your lifespan.
In mouse models, restricting calories significantly, by having them fast every other day, has been shown to improve cognitive function and protect against Alzheimer’s, Parkinson’s, and Huntington’s diseases, as well as strokes.
Fasting—while maintaining essential vitamins and other nutrients via supplements—can induce the growth of more new neurons, or neurogenesis, in mice. It can also positively affect their neuroplasticity, which might stave off age-related cognitive declines and restore function if the brain is injured.
Even just delaying the next meal seems to enhance intelligence in mice, even when the ultimate calorie intake is the same. It seems that fasting can stimulate the production of certain proteins and hormones that improve function, such as BDNF.
Evidence for the cognitive benefits of caloric restriction is plentiful among rodents. There’s some encouraging evidence from studies involving humans and other primates, but the data here are mixed.
One reason why we still don’t know how caloric restriction affects primates is that our diets are so variable. Not enough food is bad for your brain, and too much unhealthy food is also bad for your brain. But we don’t yet know whether restricting calories in total can keep your brain young.
Learn more about how dieting is the area most prone to myths and misinformation
Exercise does seem to reliably stave off cognitive decline, trigger the production of BDNF and other helpful proteins, and boost your brain. In humans, exercise increases BDNF, and that might be the mechanism by which it protects against neurodegenerative diseases.
Consistent aerobic exercise increases the amount of gray matter in your brain, especially in the hippocampus and prefrontal cortex, which are responsible for memory and cognitive control.
In 1995, a meta-analysis was designed to examine the effects of sugar on the behavior and cognition of children. By then, 23 studies had already been conducted to address the issue. When studies were carefully controlled for expectation effects, and measures were objective, consuming sugar had no effect on most children.
Long-term studies do find negative effects of junk food on cognition. This has social implications because children of lower socioeconomic status tend to consume more junk food. Indeed, the problem may not be about too much sugar but about malnutrition in general, because these same children are more likely to have little or no omega-3 fatty acids, for example, in their diets.
Pills that enhance your brain—so-called nootropics, or “smart pills”—seem to be more and more commonly used by healthy people, and the billion-dollar industry that supplies them is blossoming.
Most nootropics are stimulants that boost cognition essentially by staving off fatigue and thereby increasing mental focus. These include drugs such as Adderall, Ritalin—traditionally prescribed for the treatment of attention deficit hyperactivity disorder (ADHD)—and modafinil.
They prevent brain cells from reabsorbing the neurotransmitters norepinephrine and dopamine, which leaves more of them available for use by the cells.
They might seem harmless, but they do have side effects, including sleep problems, anxiety, headaches, dizziness, and an increased heart rate, among others.
Learn more about what placebos can and cannot do
The truth is this: Eating a healthy diet is certainly important for brain health. The brain, of course, is metabolically expensive.
But so far, there aren’t any foods that consistently improve brain functions.
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While eating a certain food may not directly lead to an increase in intelligence, eating a healthy diet will certainly improve your brain health. This includes antioxidant-containing foods such as kale, spinach, blueberries, pecans, and goji berries.
Not only can eating healthy foods positively impact your brain health but eating an unhealthy diet can negatively affect your cognition. This includes sugar (leads to memory problems), fried foods (can damage brain cells), and salty foods (interfere with your thinking).
Ways that you can enhance your cognitive abilities include learning a new skill, engaging in vigorous exercise, debating someone, and observing the world around you.
To heal brain damage without the use of drugs, you should ease back into activity, take note of items that you have difficulty recalling, eliminate alcohol and unhealthy foods from your diet, and get a full night’s sleep.