Chapter 129
Eating for a Healthy Brain
In my follow-up video see.nf/alsdiet, I report that some scientists consider BMAA to be one of the main causes of Alzheimer’s, especially after Alzheimer-like symptoms developed in the brains of monkeys that ate BMAA-enriched food. The biggest objection to this theory, however, is that in some autopsy studies—including the most comprehensive—no trace of BMAA was found in Alzheimer’s brains. This is part of an ongoing debate about the susceptibility of the various testing methods. Until the question is resolved, some consider it advisable not to commit too strongly.
In addition to fish and shellfish, BMAA is also found in concentrated form in shark products and certain algae supplements. Shark fins (used to make soup) have one of the highest BMAA levels ever measured, and 15 of 16 shark cartilage dietary supplements were contaminated. 8 of 18 blue-green algae (A. flos-aquae) and spirulina dietary supplements contained toxins in amounts above the daily allowed dose, but only two contained BMAA. By contrast, four of five tested protein powder supplements with spirulina were contaminated.
Eating for a Healthy Brain
It is important to know which components or specific foods we should consume to protect our brain function, but what does the best diet look like to preserve our mind?
Pointing the Finger
What if, given the obvious effectiveness of various individual lifestyle interventions, we combine some of them? The first major randomized controlled trial of a multi-domain lifestyle intervention for at-risk older adults was the Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (or FINGER, for FINnish GERiatric). It was published in 2015. More than 1000 men and women over 60 and over 70, respectively, were randomized to receive either a combination of dietary counseling, exercise, cognitive training, and risk-factor management or, in the control group, only regular general health counseling. After two years, the improvement in cognitive abilities in the lifestyle intervention group was significantly better, although the effect size was small (0.13). (Effect size is calculated as a “standardized mean difference” [SMD]. An SMD of 0.2 is considered small, 0.5 moderate, and 0.8 large.) At the population level, even small effects can have important public health implications. But why was the effect so small?
The rather modest results of intervention studies like FINGER have been cited as an argument against an important role for lifestyle in dementia prevention, but they may actually be because the studies did not go far enough. For example, the “brain-healthy diet” recommended in the FINGER study consisted only of the advice to eat four servings of fruits and vegetables per day and to choose low-fat versions of meat and dairy products. It is true that the participants did better the more closely they adhered to this, but small changes can only produce a small effect.
Mediterranean Diet
Couldn’t we make more comprehensive changes right away and switch to a Mediterranean diet, for example? There are dozens of observational studies that followed a total of nearly 100,000 people for three to twelve years. They found that those who adhered more closely to a Mediterranean diet tended to experience less decline in global cognitive function. However, the effect size was again relatively small, and dementia as well as mild cognitive impairment did not occur noticeably less often. About a dozen randomized controlled trials of the Mediterranean diet recorded 72 test results, but only a small portion of them—8 of 72—showed a statistically significant benefit.
To find out how to improve the Mediterranean diet, scientists tried to pick out the useful components. Fish consumption showed no benefit, and moderate alcohol consumption didn’t either. The two linchpins were apparently the vegetables and the better ratio between unsaturated and saturated fats—that is, essentially the balance of plant and animal fats. Of all the assessed features of the Mediterranean diet, reduced meat consumption is most strongly associated with better cognitive performance and greater total brain volume.
MIND Diet
To develop an eating pattern tailored to brain health, scientists at Rush University Medical Center took components from successful diets and developed a dietary plan called the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND). DASH stands for Dietary Approaches to Stop Hypertension. Their original goal was to protect the cardiovascular system. From it, the scientists adopted the reduction of saturated fats, sweets, and meat (including fish). From the Mediterranean diet, they adopted the lower amounts of dairy products, placed more emphasis on beans and nuts, and, instead of potatoes, the MIND diet centers on leafy green vegetables at least six times a week. And instead of fruit in general, they recommended berries. The MIND diet gives extra points for less fast food or fried foods—that is, at most once a week. The Academy of Nutrition and Dietetics summarizes: “MIND combines the two eating plans. It emphasizes natural, plant-based foods and encourages increased consumption of berries and leafy green vegetables while limiting consumption of animal foods and foods high in saturated fatty acids.”
Take a look at see.nf/mind to see what can be achieved with the MIND diet. In short, there are about a dozen studies on it, and all of them found that stricter adherence benefits at least one aspect of cognition. Seven of the nine studies that measured overall cognitive function consistently found advantages, including up to a 53 percent lower Alzheimer’s risk. As a side effect, one presumably also lives longer. Compared with subjects who were in the bottom third of the MIND score scale, the average 70-year-olds in the top third had a 37 percent lower risk of dying over the next twelve years. So far, however, there has been only a single randomized controlled trial in which the diet was tested thoroughly. So far it looks good, because in the three-month pilot study, the randomized participants who followed MIND performed significantly better on six of eight cognitive measures.
The Harvard Nurses’ Health Study was large enough to determine which component of the MIND diet was primarily responsible for the benefit, and the researchers concluded: it was the reduction of saturated and trans fats. If lower meat consumption is the central component of the Mediterranean diet, and the core point of the MIND diet appears to be reducing saturated fats and trans fats in butter and junk food, then how about a whole-food plant-based diet?
Whole-Food Plant-Based Diet
In my video see.nf/antiaging, I explore the possible reasons why long-term vegetarians have up to a threefold lower risk of dementia. It could be because they are exposed to less saturated fat, cholesterol, animal protein, or AGE gerontotoxins. Simply moving away from animal foods seems to protect against cognitive impairment, aside from plant-based substitute products. However, adherence to MIND recommendations correlates more closely with cognitive performance than mere reduction of animal products, suggesting that consuming primarily healthy plant foods such as leafy greens and berries may be beneficial.
Perhaps it is also because a plant-based diet protects against oxidative stress and inflammation. Dietary factors can also influence the effects of stress on cognitive decline. A diet in which a lot of animal proteins, saturated fats, and refined sugar are consumed but few plant foods can increase the release of stress hormones like cortisol from the adrenal glands, and that in turn promotes the development of dementia.
The most important tips for Alzheimer’s prevention through diet are: Reduce added sugar, added salt, saturated fats, animal products, and processed foods in general; eat more plants (especially leafy greens and beans) and fruit (especially berries).