Authors: Majid Fotuhi
In fact, the best recipe for a bigger brain starts with a healthy, balanced diet and then adds to it a serving of the key nutrients—DHA, plus select flavonoids and vitamins—we now know can grow the brain.
Your Brain . . . on Food
Let’s start with that basic healthy diet. Many studies have shown that the Mediterranean diet—a diet low in fat and cholesterol and high in fiber—omega-3 oils, vegetables, nuts, and fruit, can help stave off cognitive decline. People who adhere to such a diet have a much lower prevalence of age-related cognitive impairment than those who don’t.
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In one study, led by Columbia University neurology professor Nikolaos Scarmeas, this diet offered a roughly 28 percent lower risk of cognitive impairment and dementia.
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The Mediterranean diet also helped the already impaired elderly lower their risk of developing Alzheimer’s disease, at least during Scarmeas’s study period. Study subjects who had cognitive impairment and were in the top third for adherence to a Mediterranean diet had a 48 percent lower risk of progressing to Alzheimer’s disease, as compared to people with cognitive impairment who were in the lowest third of adherence.
When combined with exercise, the effect can be even more powerful. When Scarmeas and his team followed 1,880 elderly New Yorkers over a period of fourteen years, they found that those who exercised regularly
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adhered to a Mediterranean diet had a whopping 65 percent lower relative risk of developing Alzheimer’s disease.
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Of course, there may be other factors common to those who stay active and eat such a diet. Such people may be more inclined to engage their brains, or stay socially active and less stressed, or they are different in some other way that brings with it a neuroprotective benefit.
However, recent studies show certain foods do affect brain size, independent of other factors. Some of the more compelling research on this topic comes from Gene Bowman, an assistant professor of neurology at the Oregon Health and Science University, who studied the link between blood serum levels of specific vitamins and brain size and function.
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When I met Dr. Bowman during the 2012 Alzheimer’s Association meeting, his passion for the subject was evident. Bowman had just published the findings of his study in the journal
Neurology
and was eager to share the details. For the study, Bowman reported on 104 men and women in their eighties who were enrolled in the Oregon Brain Aging Study, which has tracked participants since 1989. Looking at their blood samples, MRIs, and cognitive tests, Bowman found that people with high blood levels of vitamins B, C, D, and E had larger brains and performed better on memory tests than those with lower levels of those vitamins. Those with higher levels of omega-3s in their blood also were more likely to have greater brain volume, and they scored better on tests of executive function.
Cut the Salt!
Our bodies require salt to survive, but the typical Western diet contains far more salt than we need. In fact, while the U.S. Centers for Disease Control and Prevention recommends a daily intake of 1,500 milligrams, with 2,300 milligrams being the maximum recommended upper limit, the national average salt consumption is more than 3,400 milligrams per day.
Processed and packaged foods tend to be especially high in salt. Consuming too much salt can raise your risk of high blood pressure, heart disease, and stroke, all of which can shrink the brain.
Drop the Donut
Perhaps most telling of all was what Bowman found in the blood of those who had the lowest brain volume and scored poorly on tests of memory, processing speed, attention, and language skills. Not only did those study subjects have lower levels of the key vitamins and omega-3s but they also had higher levels of trans fats in their blood. Trans fats, you probably know, are unsaturated fats that can occur naturally but are most often obtained through processed foods—think fast food, donuts, and mass-produced cookies and cakes—that contain partially hydrogenated vegetable oil. Trans fats raise the risk of cardiovascular disease by increasing LDL (the bad cholesterol) and decreasing HDL (the good cholesterol). And we now know, thanks to Dr. Bowman, that trans fats are linked with a brain that is shrinking rather than growing.
Of course, it’s not just trans fats that shrink the brain. Animal studies also show us the dangers of too much sugar in the diet. In one study, published in 2012 by researchers at UCLA, rats fed a steady diet high in fructose—and low in omega-3s—showed signs of developing insulin resistance and had the slowed cognitive performance that goes with it.
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For the study, researchers trained two groups of rats on a maze twice a day for five days. They then fed one group regular rat food plus a fructose-water solution for six weeks. A second group was fed regular rat food and a fructose-water solution plus omega-3 fatty acids in the form of DHA and flaxseed oil. After six weeks on the diet, the rats tried the maze again. The rats in the omega-3 group fared much better than their non-omega-3 peers, remembering the maze fairly well. The rats in the fructose group, meanwhile, struggled to find their way through the maze. In addition, their blood tests showed that they had developed resistance to insulin, a hormone that’s crucial to glucose regulation and brain cell function.
A diet high in saturated fat and sugar has also been shown to reduce hippocampal BDNF levels in animal studies.
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In addition, such a diet contributes to other conditions, such as diabetes, high cholesterol, high blood pressure, and stroke, which are known to shrink the brain. A poor diet also contributes to a greater risk of obesity, which, as you’ll read in
chapter 11
, also inhibits the body’s production of BDNF.
Even in the short term, however, poor food choices can affect how you think. The blood-sugar rush you get from devouring a brownie, for example, may be followed by a crash, leaving you low on energy and thinking sluggishly.
That’s all the more reason to stick to a low-carb, high-protein, balanced diet and steer clear of brain-shrinking foods. I recommend shunning foods that are high on the glycemic index (for a list, visit the American Diabetes Association at www.diabetes.org), which will help you avoid the sugar spikes that mimic diabetes. In addition, I strongly encourage adding brain-building nutrients to your diet to help grow your brain. The end result will be increased energy and cognitive performance today and a bigger brain for the future.
So, what are those brain-building nutrients? While there’s much debate—and much research under way—I’ve selected the best of them to discuss next.
Omega-3s: Adding DHA to Your Diet
The nondescript commercial strip twenty miles south of Baltimore doesn’t look like much. Outside there’s a simple sign that reads “DSM,” a parking lot, some tidy shrubbery. It is tranquil, even a bit dull. Looks, of course, can be deceiving. Inside, there’s plenty going on.
The first clue is an assortment of consumer products just inside the front door: yogurt, baby formula, milk, orange juice, bread, crackers—the list goes on. They come in different shapes and sizes, and from different manufacturers, but they all have one thing in common: each product has been supplemented with docosahexaenoic acid, a long-chain polyunsaturated omega-3 fatty acid better known as DHA.
In this case, it’s not just any DHA but a type of DHA cultivated from algae in a process the scientists here developed in the late 1980s. Those scientists were all members of a team working for a Washington-area defense contractor and assigned to study potential uses of algae in long-term space flight for NASA. As they probed for possible applications of algae as a food source, the team began to identify the distinct health benefits DHA offered. DHA, they began to prove, had clear rewards for the heart, the eyes, and the brain. Before long they had their own company, called Martek Biosciences Corporation (now part of DSM), and were well on their way to ensuring DHA would make its way into consumer products across the globe.
A believer in the benefits of DHA, I have served as a consultant to Martek and watched as the company developed its products and spread the word about the benefits of DHA. Their research facility in Columbia, Maryland, has carefully compiled evidence, and researchers worldwide have added their own proof, that DHA delays cognitive decline and improves cognitive health in both children and adults.
By the mid-2000s, DHA’s role as a key health product was solidly established. In health food stores and even in regular grocery stores, sales of fish oil, omega-3s, and other fatty acids shot up as people got the message that better cognition might be within their grasp. By 2011, Martek—which launched in 1985 with just a handful of employees—had been snapped up by Netherlands-based DSM for a whopping $1.08 billion.
Martek’s success was part of a huge rise in the supplement market in general. But behind the company’s spectacular growth is increasing scientific evidence that its marquee product offers very real cognitive benefits throughout life.
Forget the Pyramid
In 2011, the U.S. Department of Agriculture said good-bye to the long-familiar food pyramid, replacing it with a new dietary guideline called My Plate (www.choosemyplate.gov).
My Plate uses a dinner plate graphic to give you a visual idea of what a balanced diet looks like—fruit and vegetables make up half the plate, proteins and starch share the other half and are complemented by a small portion of dairy.
A Fish Oil That Stands Above the Rest
DHA is just one type of omega-3 fatty acid. And while omega-3s in general have been shown to reduce the risk of heart disease and stroke—two benefits that have their own brain health implications—DHA is the only one that comes with robust proof that it’s a brain builder.
Found in certain fish, algae, and supplements, DHA is a vital component of brain health in adults and brain development in children. DHA is also crucial for eye and heart health, and has shown promise as a protection against depression, cancer, and diabetes.
Like many other brain boosters, DHA helps to reduce inflammation in the brain and may reduce the aggregation of amyloid plaques associated with Alzheimer’s disease, although we can’t yet say that it helps to prevent the disease. Researchers have also tied low DHA levels to serious conditions and problems—lower-than-typical levels are found in adolescents who are incarcerated and have behavior problems, in children with ADHD, and in people with dementia and Alzheimer’s disease.
On the flip side, we have ample evidence that its presence is beneficial—DHA, along with another omega-3 called EPA (eicosapentaenoic acid), has a proven effect on heart health, increasing oxygen flow throughout the body, including the brain,
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and has also been shown to increase BDNF and neurogenesis in the hippocampus.
In short, DHA helps to grow the brain. The result, of course, is improved memory and enhanced learning.
The evidence is laid out in a host of studies. One, published in 2009, was the type of randomized, controlled interventional study that scientists love best. It showed the effects of DHA on ninety-one South African schoolchildren, who for six months ate a bread spread enriched with 127 milligrams of DHA. By the end of the study, the children showed higher blood levels of DHA and significant improvement on cognitive tests that measured short-term memory and processing speed.
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The ninety-two children in a control group, who did not eat the bread spread, showed no such improvement.
In another study, published in 2010, researchers in Gothenburg, Sweden, tracked the academic achievements of 9,448 schoolchildren and their dietary intake of fish.
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What did they find? Children who ate more than one serving of fish per week had an overall school grade 15 percent higher than those who consumed less than one serving per week. Even eating just one serving of fish a week proved beneficial. Those students (about 56 percent of the total group) also scored higher than students who ate less than one serving a week.
University of Pittsburgh researchers found similar results in their study of 280 adults between the ages of thirty-five and fifty-four.
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That study’s participants underwent cognitive testing and had blood samples drawn to check omega-3 levels. Those with higher DHA levels scored better on nonverbal reasoning and mental flexibility tests as well as on working memory and vocabulary measurements.
One of the best studies to show the benefits of DHA was MIDAS (Memory Improvement with Docosahexaenoic Acid Study), conducted at nineteen centers across the United States and funded by Martek Biosciences.
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MIDAS was a randomized, double-blind, placebo-controlled study—the gold standard in scientific clinical trials.
For the study, the research team enrolled 485 healthy adults over the age of fifty-five who were experiencing mild memory problems and gave half the participants 900 milligrams of DHA each day for twenty-four weeks. The remainder of the participants took a placebo. All took cognitive tests at the start of the trial and again at the end of the six-month study period. What researchers found was that both groups had improved their performance, reducing their memory errors, but the DHA group showed remarkable improvement, halving their memory errors over the study period. As expected, the DHA group had doubled their blood level of DHA.