Looking through a microscope will make something tiny look big. It blows the teeny-weeny out of proportion. As it turns out, you don’t even need a microscope to do that.
The book This Is Your Brain on Food makes rather bold claims. “Until we solve nutritional problems,” its author writes, “no amount of medication and psychotherapy is going to be able to stem the tide of mental issues in our society.” Said author doesn’t limit herself to stress and mild anxiety; the book has chapters on post-traumatic stress disorder, schizophrenia, and bipolar disorder.
The book came out in August 2020 and was written by Dr. Uma Naidoo. Her credentials will leave a mark on her readers. She was trained in psychiatry at Harvard Medical School and is now a member of its faculty. She completed a nutrition program at Cornell University. She is also a professional chef, having graduated from the Cambridge School of Culinary Arts. Who would be better positioned to write about how nutrition might cause, exacerbate, and help treat mental disorders?
I am not a psychiatrist. I am not even a medical doctor. If we only care about diplomas to answer questions of trust, she wins hands down.
But there is something that I can do, something that a journalist can do, something that even a casual reader can do with a bit of time and access to the scientific literature.
We can see if Dr. Naidoo is accurately reporting on the studies that form the building blocks of her thesis. Because when I read that certain foods “relieve anxiety” or that others “deepen trauma,” and see blueberries and curcumin being heralded as solutions for serious psychiatric conditions, my skeptical alarm bells go off.
Do the studies Dr. Naidoo cite in support of her claims even say what she claims they say?
A series of unfortunate misrepresentations
The framework Dr. Naidoo is using in her book has a name: nutritional psychiatry. She writes in chapter 1 that “in 2015, Jerome Sarris and his colleagues established that ‘nutritional medicine’ was becoming mainstream in psychiatry.” That is not quite what they wrote in the paper she cites. The article, labelled “Personal View” by the journal Lancet Psychiatry, concludes that “nutritional medicine should now be considered as a mainstream element of psychiatric practice” (all italics in quotes will be mine unless specified, to highlight keywords). Sarris and colleagues were writing on behalf of the International Society for Nutritional Psychiatry Research, whose aim is to grow the field of nutritional psychiatry research. They were asking for recognition, not stating that nutritional considerations in psychiatry were now mainstream.
You may think I am splitting hairs, but further examples of distortions and exaggerations in Dr. Naidoo’s book will show this example was just an early illustration of a much larger problem.
Dr. Naidoo is a big believer in the brain-gut connection, and she argues that probiotics—“live bacteria that convey health benefits when eaten”—are key to fighting depression. She references a study in which people were randomized to a probiotic supplement or a placebo and concludes that the brains of the participants in the first group were “less depressed and less stressed” (italics hers). She uses this study as a springboard to recommend the consumption of yogurt and fermented foods. In actuality, 26 healthy people took the probiotic in the study she quotes and 29 got the placebo. The study was financed by a company that makes probiotics and the authors of the study remark that “these data are preliminary.” This is thin gruel. The bacteria living in our gut are an active object of research, but we should all beware of premature conclusions about how specific strains impact our health.
Meanwhile, the most expensive spice in the world, saffron, can apparently help combat depression, according to Dr. Naidoo, and she cites a study so great it deserved an exclamation mark. “A study in 2017 demonstrated that 15 milligrams of saffron was as effective as 20 milligrams of Prozac in decreasing depressive symptoms!” The authors of said study are not as enthusiastic in their write-up. “The trial is not well powered and should be considered a preliminary study.” They point out the absence of a placebo group, the small number of participants, the short follow-up, and the lack of patients with severe depression. You wouldn’t know it from Dr. Naidoo’s book, which goes on to recommend adding saffron in combination with “the antidepressant foods shared previously for double the mood-boosting effect.”
For those suffering from anxiety, Dr. Naidoo believes they may want to pay attention to their magnesium consumption. “In humans, magnesium deficiency is associated with high anxiety levels,” she writes. She recommends embracing foods rich in magnesium. After all, a 2017 review “found that magnesium supplementation can help especially if you are vulnerable to anxiety.” It is funny how she does not quote the following from the conclusion of the review: “There is suggestive but inconclusive evidence for a beneficial effect of magnesium supplementation in mild anxiety.” The authors point out that the quality of the studies they looked at was “generally poor.” Hardly a solid enough foundation from which to issue recommendations.
Likewise, she recommends turmeric and its yellow pigment curcumin, writing that its “positive effect on anxiety has been confirmed by […] three trials in humans.” The reference she cites highlights the small number of studies and the lack of long-term investigations and calls for more robust studies to be done. Curcumin’s effect on anxiety has not been “confirmed” by these three trials.
Dr. Naidoo then tackles chamomile to help with sleep. She says a 2017 study showed the herb “improved sleep quality significantly.” But the chamomile-versus-placebo study was done in two groups of 30 elderly people in a single nursing home, where the doctors and nurses knew what each participant was receiving and also did not ask how much sleep medication they were taking. She brings up a meta-analysis that apparently concluded chamomile was “very effective” for sleep. But its authors list a number of important issues plaguing the few published studies, including their quality which ranges from “very low to low” (italics theirs). I find it hard to reconcile Dr. Naidoo’s many enthusiastic endorsements with the actual studies she references.
If you are not a scientist, you may be wondering why there seems to be a scourge of small studies in the literature. The reason is simple: small studies are easier and cheaper to do. Large, informative clinical trials are costly and they take years and a hefty infrastructure to manage. Recruiting thirty people instead and calling the results “preliminary” and “promising” is simply more straightforward for researchers working in an ever more competitive granting system. This reality, however, is no excuse for settling for inadequate studies as a bolster for tall claims when writing for a lay audience.
This trend toward exaggerating the strength of the evidence Dr. Naidoo reports on unfortunately continues with even more serious conditions, like post-traumatic stress disorder (PTSD) and schizophrenia.
Hippocratic ventriloquy
Glutamate is one of the many building blocks of proteins and one of the most abundant neurotransmitters in our nervous system. It can also be found bound to an atom of sodium in the unfairly maligned flavour enhancer MSG. Dr. Naidoo points to a recent study that shows that a low-glutamate diet was “effective at reducing anxiety and symptoms of PTSD.” The study in question is a poster presentation at a conference of a preliminary analysis of an on-going trial, in which 17 veterans with Gulf War Illness had been recruited to date. Colour me unimpressed. The final paper was actually published this June, and the pilot trial managed to test a total of 40 veterans whose psychiatric symptoms were not clinically evaluated (instead relying on a questionnaire) and who were all put on a one-month low-glutamate diet. There was no placebo control group to compare the diet to.
For patients dealing with schizophrenia, Dr. Naidoo’s recommendations are to avoid the Western diet, caffeine, sodium, alcohol, and gluten. “Clearly,” she writes, “all patients with schizophrenia should at least try a gluten-free diet.” She also recommends a list of nutrients she distressingly calls “reality-resetting foods.” It is worth calling attention to the fact that schizophrenia can be accompanied by delusions and hallucinations, and the risk of suicide for people dealing with it is 12 times higher than the general population. And before you think Dr. Naidoo’s nutritional suggestions are made in the shadow of much more important pharmaceutical interventions, she instead clarifies that “pharmaceuticals like lithium and antipsychotics are powerful weapons in fighting bipolar disorder and schizophrenia. But equally powerful are the changes to diet that can work alongside medications to help people suffering from these debilitating illnesses.”
The unsaid principle underlying This Is Your Brain on Food is “let food be thy medicine,” a misconception wrongfully attributed to Hippocrates and often recited as a credo by believers in alternatives to medicine. In fact, Dr. Naidoo, convinced of the all-encompassing link between our gut and our brain, points out that Hippocrates warned that “death sits in the bowels” and that “bad digestion is the root of all evil.” “Now,” she concludes, “we are figuring out how right he was.” While these two quotes are frequently presented in the probiotic literature and on wellness websites, I could not find them in a long list of Hippocrates’ aphorisms or in Professor Elizabeth Craik’s collection of the Hippocratic corpus. The scientific papers that cite them end up referencing other papers that quote them liberally, in a printed game of telephone. They are yet another potential misrepresentation of Hippocrates, who is so often ventriloquized into endorsing pseudomedical ideas.
Dr. Naidoo complains that medicine is no longer holistic and that it has lost its focus. It’s no wonder, as the back of her book states, that she speaks frequently for Goop audiences. She has one foot in the medical world and another in the venerated natural world, whose promises often remain unfulfilled. Stories that would make physicians shake their head are presented in the book as instances of open-mindedness. An orthopedic colleague reaches out to her because one of his patients wants to delay surgery for severe knee pain. The patient has heard of turmeric and wants to try it first.
Throughout the book, mediocre evidence is spun as confirmatory. Science is used to make claims appear more reasonable than they are, but ultimately, Dr. Naidoo is all about trying things out for yourself. In a statement that could be interpreted as poisoning the well of evidence-based medicine, she writes that randomized clinical trials are good but “they give you data on a group of individuals, not the individuals themselves.” Her solution? “The only way to truly know what works for you is to experiment on your own.” This is a red flag. Trials exist to minimize the biases of anecdotes and personal experimentations. In the wellness world, however, they get in the way of making exaggerated claims. Every individual is a unique snowflake, we are told, hence the “no trial for snowflakes” gambit.
This Is Your Brain on Food is littered with unearned causal language. She lists “foods that increase” and “relieve anxiety.” She defines a “memory-boosting menu” (featuring turmeric and chickpea) and a “libido-lifting menu” (which includes Cajun spice and chocolate-dipped strawberries). Meanwhile, the overall diet she recommends is not bad. She warns against the excesses and deficiencies of the modern Western diet and praises fruits, vegetables, nuts, fibre-rich foods, and plant-based proteins. It is fair to say that improving your diet will have a positive impact on your mental health and we should properly research the contributions nutrition can make to quality of life when dealing with mental illness.
But she manufactures certainty where there is none and attributes to a healthy diet the power to treat serious medical conditions, distorting small and uncertain studies into appearing larger and more robust to give her thesis credibility.
Through the microscope, tiny things look much bigger than they really are. This Is Your Brain on Food is one heck of a microscope.
Take-home message:
- Dr. Uma Naidoo, a Harvard psychiatrist, wrote a book called This Is Your Brain on Food in which she claims there are foods to consume and others to avoid in order to fight a variety of mental problems, like depression and schizophrenia
- She frequently exaggerates the reliability of the studies she references, using small, preliminary studies of low quality to derive specific nutritional recommendations
