How to Become Smarter (26 page)

Going back to the effects of diets, several studies on laboratory animals have shown that a high-protein diet increases the level of dopamine in some regions of the brain. Interestingly, these are the same brain regions where psychostimulant drugs increase the dopamine level—the frontal cortex and the striatum [
329
,
330
]. One of those studies has also shown that a low-protein diet has the opposite effect: it lowers the level of dopamine in these brain regions [
329
]. These data suggest that a low-protein diet may worsen attentional performance because it has an effect that is opposite to that of attention-enhancing drugs.

High-protein diets increase the level of dopamine less than psychostimulant drugs do [
329
,
331
]. It is still intriguing that a dietary change produces effects that are similar to those of ADHD medication. Why do high-protein diets increase the level of dopamine in some brain regions? The likely reason is that brain cells make dopamine from the amino acids tyrosine and phenylalanine. Those are byproducts of digestion of dietary protein.
^H
It is likely that foods containing high-quality protein rich in essential amino acids, such as red meat, are more effective at improving attention function [
120
,
318
,
319
,
835
,
836
,
853
,
912
]. Food products containing lower quality protein, such as plant products, should be less effective.

Some studies have shown that high-protein diets or even a single high-protein meal can produce subjective changes that are similar to the effects of stimulants. For example, one study shows that a high-protein diet increases self-esteem in obese patients, which is unrelated to weight loss [
278
]. Another study showed that a high-protein meal makes a person feel “warmer;” that is, it increases production of heat in the body. The researchers did not see this effect with high-carbohydrate and high-fat meals [
117
]. The participants of the study also felt more alert and energetic after the high-protein meal compared to the high-fat or high-carbohydrate meal [
117
]. Finally, one study of the Atkins diet, which is a high-protein, high-fat, low-carbohydrate diet, has shown that this diet contributes to insomnia during the first month of this regimen [
277
]. Increased self-esteem, increased production of heat by the body, and increased wakefulness are common effects of amphetamine-like stimulants [
332
]. In summary, high-protein diets share several biological effects with attention-enhancing drugs, and therefore should have beneficial effects on attention function of healthy people.

So far, nobody has tested the effects of high-protein diets in clinical trials with ADHD patients. Therefore, the patients who are reading this book need to seek professional psychiatric treatment instead of experimenting with diets. My personal view is that the combination of a high-protein diet with pharmacotherapy should be more effective than either approach alone, especially in severe cases of ADHD. Further research is needed in this area.

• ADHD drugs, most often amphetamine-like stimulants, improve attention control both in ADHD patients and in healthy people.
  
• The attention-enhancing effect of ADHD drugs has to do with an increase in the level of a chemical called dopamine in several brain regions.
  
• High-protein diets produce chemical changes in the brain that are similar to the changes produced by ADHD medication. Therefore, these diets may enhance attention function in healthy people and in ADHD patients.
  
• Low-protein diets produce the opposite changes in the brain and therefore should worsen attention performance.
  
• Foods containing higher quality protein, such as red meat, should be more effective at improving attention.
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From the discussion in the previous sections it follows that low quality of dietary protein, impaired digestion of dietary protein, or both may be the cause of attention deficit hyperactivity disorder (ADHD). The validity of this hypothesis depends on whether a low-protein diet can reproduce symptoms of ADHD in healthy people. My personal experience suggests that the fruit-and-vegetable diet is a good experimental model of ADHD because it reproduces many symptoms: distractibility, hyperactivity, and impulsivity. I have not conducted statistically significant volunteer studies with the fruit-and-vegetable diet and have data for only one experimental subject (yours truly). Interestingly, anorexia nervosa, an eating disorder that involves severe protein malnutrition, correlates with hyperactivity and poor attention [
915
,
916
]. A recent study shows that protein malnutrition causes hyperactivity and impulsivity in young rats [
1002
].

To be precise, the fruit-and-vegetable diet is not a low-protein diet but an almost protein-free and fat-free diet. The amount of protein in this diet is tiny and quality of the protein is also low. This diet consists of fruits, vegetables, and juices only and excludes protein-rich plant foods (grains, nuts, and legumes) and all food additives, seasonings, pungent vegetables, and spices. The duration of the diet is 3 to 5 days. Participants in this study can eat any amounts of fruits and vegetables (raw and cooked) and a sample menu is shown below.

Breakfast
: 1-2 glasses of carrot juice, a salad made of cucumbers, dill, tomatoes, and boiled potatoes; 1-2 apples.

Lunch
: vegetable soup, a glass of orange juice, a salad, several dates.

Dinner
: 1-2 glasses of tomato juice, a salad, some fruit for dessert.

You can find some relevant recipes in
Appendix I
. Since this is a high-carbohydrate diet, it is not safe for diabetic patients. My experience suggests that this diet can cause muscle cramps, in which case, reducing consumption of fruit is helpful. This diet has several unusual effects: it reduces fatigue but at the same time causes reluctance to perform most types of work especially heavy manual and intellectual work. Due to poor attention control and distractibility, it is impossible to perform any work- or school-related reading or writing tasks on this diet. Hyperactivity manifests itself as unusual talkativeness and inability to sit still. The amounts of food consumed will increase 2-fold or more, compared to the mixed diet [
505
]. The person on the fruit-and-vegetable diet may still feel that the stomach is empty most of the time (but will not feel hungry). Because fruits and vegetables are not a filling type of food, following this diet is difficult in the presence of temptations, i.e. in the presence of disallowed types of food. It is possible to comply with this diet for a week or two but beyond that, periodic binging on disallowed food is inevitable. Other possible adverse effects include loss of work capacity, reduced stress-resistance, and increased sweating.

Adding fat to this diet will not reduce distractibility and impulsivity, but may reduce hyperactivity. If you continue the fruit-and-vegetable diet beyond 3-5 days, the symptom of hyperactivity seems to disappear, but impulsivity (low self-control) and poor attention control will persist. Further continuation of this diet results in a loss of interest in many activities
^F
and inability to perform most types of work, with a few exceptions. It is possible to extend the hypothetical experimental model of ADHD beyond 3-5 days. Add a glass of milk and half a glass of wheat extract (
Appendix I
) to each meal, starting on day 4. Reintroduction of normal amounts of good-quality protein (such as beef, fish, cheese, and nuts) into the diet reverses the symptoms of distractibility, hyperactivity, and impulsivity.

A diet consisting of boiled grains plus fruits and vegetables is a low-protein diet. The quality of protein in this diet is low too. This diet appears to cause attention deficit without hyperactivity. I am unable to concentrate on any type of work-related reading or writing while on this diet. The activity level is low-to-normal with this diet most likely because cooked grains have sedative properties, as we saw in Chapter Two.

• The fruit-and-vegetable diet contains tiny amounts of protein and quality of the protein is low.
  
• This diet may serve as an experimental model of ADHD because it induces distractibility, hyperactivity, and impulsivity.
  
• Reintroduction of high-quality dietary protein into this diet reverses all symptoms.
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Several studies on healthy human subjects and on laboratory animals have shown that high-protein diets and high-fat diets can have beneficial effects on mental health. Note that there are many variables that can differ among studies that investigate “a high-protein diet.” For example, the composition of a high-protein diet and the segments of population under study can be different between different research projects. Therefore, it is often difficult to draw a direct comparison or an easy conclusion. With these limitations in mind, we can take a look at some of the existing data from literature.

For instance, both high-protein and high-fat diets (separately) reduce anxiety in laboratory rats [
281
,
333
]. A high-fat diet reduces anxiety in human subjects [
280
]. Some studies suggest that meals consisting of fat only have a mild sedative effect on humans (reviewed in [
872
]). The above study on rats used a high-protein diet containing large amounts of a milk protein called casein. This diet is different from what most people consider a high-protein diet: a diet that contains lots of meat, fish, eggs, and cheese. In another report [
261
], a high-fat diet had an antidepressant effect in laboratory rats; this study used plant-derived oils as a main component of the high-fat diet.

We are discussing high-fat diets here because, as explained later, a high-protein diet that contains large amounts of lean meat can cause severe adverse effects. It seems necessary to use fatty meat in high-protein diets. This book’s high-protein diets contain large amounts of fatty meat and have few side effects. Strictly speaking, these diets should be called high-protein, high-fat diets. On the other hand, if you feel well on high-protein
low-fat
diets, then you can ignore my recommendations regarding fat content of meat.

On the subject of dietary fat, a study by Dr. Karina Fischer and colleagues in Switzerland [
117
] compared the effects of a single high-protein, high-fat, or high-carbohydrate meal. Overall, the high-fat meal, which consisted of equal parts of plant and animal fat, resulted in the best mental performance during the 3 hours after the meal.
ⁱ
The high-protein meal resulted in better attention and efficiency, whereas the high-carbohydrate meal improved working memory and accuracy during the 3 hours after the meal. On the other hand, an earlier study in the United Kingdom found that a single high-fat meal resulted in worse cognitive performance compared to a single balanced meal [
334
].

Another study led by Dr. Fischer compared the effects of a single high-protein and high-carbohydrate meal on various measures of attentional performance [
335
]. Overall, the high-protein meal resulted in better attentional performance during the 3 hours after the meal compared to the high-carbohydrate meal.

Earlier, during the discussion of the effects of food additives on attention, we talked about a study of a “few foods diet” on ADHD children [
67
]. That study shows that the diet consisting of rice, turkey, lamb, vegetables, fruits, margarine, vegetable oil, tea, pear juice, and water can improve ADHD symptoms of the patients. The main source of protein in this diet is turkey and lamb, which are the source of highest quality protein rich in essential amino acids [
120
,
318
,
319
,
835
,
836
,
853
,
912
]. The authors attributed the beneficial effects of the diet to elimination of all food additives. Yet it is possible that the benefits were in part due to the improved quality or amount of dietary protein compared to the patients’ regular diet.

A report out of the Netherlands [
336
] has shown that a high-protein meal in the evening improves attentional performance in the morning. The high-protein meal in that study included a tryptophan-rich protein called alpha-lactalbumin. These results lend further support to the idea that increased consumption of protein-rich foods has a beneficial effect on attention. The beneficial effects of high-protein diets on attention are likely to be the result of biochemical changes in several relevant regions of the brain.
^H
,
J