The CNBC headline. “A Harvard nutritionist and brain expert says she avoids these five foods that ‘weaken memory and focus.” She is also the author of “This Is Your Brain on Food,” an Amazon #1 bestseller in obsessive-compulsive disorders. I haven’t read the book, but it would be pointless based on her article, which appeared on many other news outlets.
I am well aware of the extensive junk science in the field of nutrition, and her article is just another reflection of it. It is the standard attempt
- to extrapolating rodent’s studies to humans
- to equate correlations as a cause-and-effect relationship
- unwarranted chemophobia
- cherry-picking the variable you would like to demonize.
Her first claim states
“existing studies point to the idea that we may be able to reduce the possibility of dementia by avoiding foods that can compromise our gut bacteria and weaken our memory and focus.”
The study was conducted on mice and involved a treatment method for chronic vascular inflammation and the possible prevention of CVD in humans. There was no mention of dementia, memory, or focus, which of course would likely be a tad bit difficult to measure in mice, so, to extrapolate this study to any meaningful information on the prevention of dementia seems a bit odd.
Also, consider the following points, both from peer-reviewed studies.
- “Coronary lesions are either naturally rare or hard to be fast induced in these models, hence, coronary heart disease induction mostly relies on surgical or pharmaceutical interventions with no or limited primary coronary lesions, thus unrepresentative of human coronary heart disease progression and pathology. [1]
- “Rodents are phylogenetically very distant from humans, and some pathophysiological features of disease and their response to pharmacological treatments may not be reliable predictors.” [2]
“Here are the foods I try to avoid or cut back on to fight inflammation and promote brain health, sharp thinking and good decision-making”
Before critiquing her claims, you may wish to review my prior writing on the gross misunderstanding of the purported “inflammatory” foods.
Added sugars
No one will argue that most Americans, or anyone living in an industrialized society, can ease up on the added sugars. Most are far too sedentary to frequently indulge in the extra calories they have no capacity to utilize. The increased rates of overweight and obese adults with the often-related dysfunction of sugar metabolism are well established. However, the author refers to a study on Malaysian older adults, all age 60 or greater, to support her position that the added sugar may be precipitating dementia. Here are some additional relevant considerations
- Malaysia has the highest prevalence of obesity among adults in South East Asia. Obesity reflects lifestyle dietary and activity choices. A sedentary lifestyle has the same negative impacts as additional dietary sugar. A sedentary lifestyle, which was not measured for but likely prevalent, confounds added sugar as the sole cause of dementia.
- A dietary history questionnaire was used to assess food intake, which is highly unreliable. You have no idea what your population group actually consumed.
- The subjects most negatively affected by the added sugars were also the same ones with the lowest plant-based diet, another indicator that their whole lifestyle choices were the issue rather than a cherry-picked variable from the mix of causative variables.
- The study provides no objective evidence of smoking habits, alcohol, or drug use, which of course, would play a dominant role.
- The second study used to support her recommendation was a rodent study, and as pointed out above, cannot be directly applied to humans. Mice are not little people.
Fried Foods
“In fact, one study including 18,080 people found that a diet high in fried foods was linked to lower scores in learning and memory. The likely reason: These guilty pleasures cause inflammation, which can damage the blood vessels that supply the brain with blood.” Emphasis added
- Food frequency questionnaires were again used, so what was actually consumed is impossible to evaluate objectively.
- The authors of the study she references as support state, “as expected, greater consumption of the plant-based dietary pattern that loaded highest in many different types of vegetables, fruits and legumes was associated with higher cognitive performance,” which illustrates what? It is the totality of the diet, not the cherry-picked fried chicken variable, that may affect your health and aging - not the result of a possible consumption of fried chicken.
High-glycemic-load carbohydrates
Her referenced study again uses the undependable food frequency questionnaire. Sugar-sweetened beverages are among the foods with the highest glycemic index. [3] But the authors of the cited study state, “No significant association between sugar-sweetened beverage consumption and depression risk was found.”
Alcohol
Yes, the author refers to it as one of the “foods” to avoid. To her credit, she does not say to abstain but to prevent overindulgence. The advice she provides should be common sense. But do you think anyone who overindulges in alcohol would be reading her piece in the first place?
Nitrates
Nitrates are not food; they are used as a preservative and enhance the color of cured meats. Based on this study, she states, “nitrates may be connected with depression.”
The study's authors did not evaluate nitrates at all; they looked at a blood biomarker, nitric oxide (NO). Nitric oxide is involved in many cell processes, and nearly every cell produces it naturally, far more than any dietary source. One of its roles is as a vasodilator. So, theoretically, nitric oxide should help prevent dementia if dementia is related to vascular constriction, not exacerbate it.
As the authors report, “Plasma nitrate concentrations were significantly higher in depressed patients than in patients with an anxiety disorder or in controls.” But the study group is small, and as the authors note, “The source of the surplus production of NO (nitric oxide) in patients with major depressive episode remains unclear.”
- She extrapolates an associated blood marker, nitric oxide, as the cause-and-effect relationship to depression and then further exacerbates the cherry-picking fiasco with the processed meats as the source of it, even though the authors of the study clearly disagree.
- Approximately a 1/4 cup of cooked spinach naturally contains 370 mg of nitrate. So, if processed meats are going to precipitate dementia, then spinach will make you appear to have had a lobotomy.
- She closes with, “if you simply can’t live without salami and sausages, seek out those containing buckwheat flour, which is used as a filler. Buckwheat flour contains important antioxidants that can counter some of the negative health effects of these meats.”
- You can read more on the misguided antioxidant holy grail fallacy or my commentary on nitrates and processed meats in the British Journal of Cancer.
It is rather sad to say, but this Harvard-trained nutritionist does not appear to grasp some basic nutrition science concepts, which I would have taught in my beginning nutrition course at the junior college level.
[1] Animal models of coronary heart disease The Journal of Biomedical Research
[2] Small mammalian animal models of heart disease American Journal of Cardiovascular Disease
[3] A glycemic index of 55 or less is both low and good; indices of 70 or higher are bad. Coca-Cola has an index of 63, essentially the same as table sugar. Fruits typically have a low glycemic index
