"Grain Brain," authored by David Perlmutter, MD, argues that carbohydrates and gluten, combined with a sedentary lifestyle and lack of sleep, are detrimental to brain health, potentially leading to Alzheimer's disease, headaches, depression, attention deficit hyperactivity disorder (ADHD), and various other brain disorders. The book proposes a solution: a very-low-carbohydrate ketogenic diet rich in vegetables and some berries, regular exercise, adequate sleep, and specific supplements.
Target Audience and Popularity
"Grain Brain" is designed for a general audience seeking to prevent brain disorders, particularly Alzheimer's disease and other late-life dementias. The book's popularity is evident in its #1 ranking on the New York Times bestseller list. It also capitalizes on the recent popularity of the ketogenic diet.
Key Claims and Scientific Accuracy
"Grain Brain" received a scientific accuracy score of 0.8, indicating that key claims are very poorly supported by evidence.
Claim 1: Carbohydrate Increases the Risk of Dementia
The book suggests that carbohydrate consumption increases the risk of dementia by causing insulin resistance and diabetes, which in turn promotes dementia. While it's true that insulin resistance, diabetes, and elevated blood sugar levels may increase dementia risk, there is limited evidence that carbohydrate per se causes insulin resistance. "Grain Brain" cites no evidence to support this claim.
A large scientific trial demonstrated that a calorie-controlled low-fat, high-carbohydrate diet combined with exercise reduces the risk of developing diabetes by more than half. However, very-low-carbohydrate diets can cause weight loss, which increases insulin sensitivity. It's possible that very-low-carbohydrate diets, including the "Grain Brain" diet, can indirectly increase insulin sensitivity.
Read also: The science behind the Grain Brain Diet.
Claim 2: High Levels of Blood Cholesterol are Healthy for the Brain
"Grain Brain" claims that high levels of blood cholesterol, including LDL cholesterol, are beneficial for the brain. This claim is probably incorrect and potentially dangerous. The book cites evidence that high blood cholesterol late in life is associated with better brain health and greater longevity but fails to consider that dementia develops progressively over a long period.
A meta-analysis examining the association between blood cholesterol levels and dementia in midlife and late life found that high blood cholesterol in midlife is strongly associated with the later development of Alzheimer's disease, while high blood cholesterol in late life has no association with risk.
Furthermore, observational evidence cannot tease out cause-effect relationships effectively. A study examining people with cholesterol-increasing genes reported that they are not protected from Alzheimer's disease, nor is their risk increased. Additionally, meta-analyses suggest that cholesterol-lowering statin drugs have no impact on dementia risk.
Claim 3: Gluten is a Major Cause of Brain Conditions
"Grain Brain" asserts that gluten, found in wheat and some other grains, is a major cause of many brain conditions, including dementia, depression, ADHD, schizophrenia, anxiety, epilepsy, movement disorders, and migraine. The book states that "gluten sensitivity represents one of the greatest and most under-recognized health threat [sic] to humanity."
One key study cited in the book compares rates of anti-gluten antibodies in people with brain illnesses of unknown cause, people with known brain illnesses, and people without brain illness. The study reported that the group with brain illness of unknown cause had higher levels of anti-gluten antibodies. However, the group with known brain illnesses, including epilepsy, movement disorders, and dementia, had the lowest rate of gluten antibodies.
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Another issue with this study is the reliance on immunoglobulin G (IgG) as a marker of gluten sensitivity, which is not an established marker of food sensitivity.
These studies suggest that a small subset of people with specific types of brain illnesses may respond to a gluten-free diet, but this does not support the sweeping claims in "Grain Brain."
Accuracy of References
Grain Brain tends to cite references accurately when making claims that are prevalent in the mainstream scientific community. However, reference accuracy deteriorates when the book attempts to support its more questionable claims.
For example, the book states that an exercise intervention in elderly people caused an "1,800 percent improvement on measures of memory, language ability, attention, and other important cognitive functions." The study actually reports a "modest improvement" in cognitive function.
To support the argument that cholesterol-lowering statin drugs may increase the risk of Alzheimer's disease, the book cites a webpage containing a non-peer-reviewed article by a scientist who isn't an Alzheimer's disease researcher.
Read also: Nutri-Grain for Weight Loss
Additional Points
- "Grain Brain's" four-week plan promotes reduced calorie intake without explicitly counting calories and suggests limiting carbohydrate intake to fewer than 60 grams.
- The book inaccurately states that 60 grams of carbohydrate is equivalent to one piece of fruit.
- The book claims that we are genetically and physically identical to Paleolithic people and that brain diseases originate from high-carbohydrate diets.
- "Grain Brain" advocates for ketosis, asserting that it is safe because we have evolved to handle ketones.
- The book presents some accurate scientific information but also includes vague connections and unsupported claims.
Whole Grains, Cognition, Mood, and Anxiety
A systematic review examined the relationship between whole-grain intake, cognition, mood, and anxiety. The review included 23 studies (4 randomized controlled trials and 19 observational studies). The overall evidence for an association between whole-grain intake and cognition is inconclusive. However, evidence from RCTs, prospective cohort, and case-control studies suggests that higher intake is linked to improved outcomes for mood and depression, although the evidence is mixed for cross-sectional studies.
The Atkins Diet Connection
"Grain Brain" and "Wheat Belly" take a backdoor approach to the Atkins low-carbohydrate method. These books suggest that all starchy foods are unhealthy and should be minimized or avoided. Low-carbohydrate diets can cause weight loss, but the goal should be to live longer and stay healthy.
Inflammation
Promoters of low-carbohydrate diets claim that dietary carbohydrates are packed with inflammatory ingredients. However, the evidence linking carbohydrates to inflammation is convoluted, theoretical, and largely limited to Celiac disease.
Research does not support the theory that carbohydrates from wheat, other grains, or starchy vegetables are the source of injury that leads to chronic inflammation.