Food for mood: A Wall Street Journal article makes bold claims with little evidence

A Wall Street Journal article published last week (‘The Food That Helps Battle Depression‘) had this subheading:

“The right kind of diet may give the brain more of what it needs to avoid depression, or even to treat it once it’s begun”

It’s a bold claim for which the story provides little in the way of compelling evidence. Experts we spoke to said the story goes way beyond the science in this emerging field.

Allen Frances, MD

“The fact that almost no research has been done on the topic gives free rein to wildly speculative and potentially harmful hype,” said Allen Frances, MD, a former chairman of the psychiatry department at Duke University.

“It makes great sense to have a healthy diet for many reasons, but preventing or treating depression would not rate high among them. Except for a placebo effect, eating your way out of depression is likely to be an ineffective distraction from real treatment. By way of contrast, there is substantial evidence that exercise is effective.”

For evidence that a “healthy diet” can both prevent and treat depression the article points to three pieces of research that — in no way — can conclude that any kind of diet can either prevent or treat depression:

‘SMILES’ trial (2017)

Over 3 months, 33 people receive dietary support (diet advice + counseling) and 34 people in a control group attend social support groups on neutral topics. What the dietary group actually eats is not recorded. Of the 56 individuals who complete the study, a small number of subjects in both groups show modest improvements in depressive symptoms as self-reported in a questionnaire.

HELFIMED (2017)

182 adults with self-reported depression are randomized to a MedDiet group (free Mediterranean ingredients + cooking workshops + fish oil supplements) or a control group attending twice-monthly social support meetings. After a significant number of drop-outs and exclusions, depressive symptoms are self-reported at three (n= 95) and six months (n= 85) with questionnaires. Both groups show modest improvements in depressive symptoms.

Low Sodium DASH

Preliminary and unpublished observational data sourced from an American Academy of Neurology press release. We reviewed this in February, explaining why the cause-and-effect language used by many reporters was not justified.

Common limitations in diet/depression studies

The published (and unpublished) studies above exemplify common limitations that preclude making cause-and-effect conclusions about diet being able to either prevent or treat depression:

• Small sample sizes are difficult to generalize to the general public because they lack statistical power.
• Observational studies (like the DASH study mentioned above) are not randomized, cannot control for other influencing factors, and therefore can’t draw cause-and-effect conclusions.
• Randomized, controlled studies (such as SMILES and HELFIMED above) that are not completely blinded mean subjects are aware of which intervention they are receiving. This can introduce bias.
• Actual food intake is unknown – often because it is either not measured (SMILES), or incomplete because it relies on subjects having to self-report it (HELFIMED). The latter is not completely reliable.
• Questionnaires for depression are not only highly subjective but, as with food questionnaires, not always reliable or reproducible.

Given these limitations you can see why certain questions are inevitable. Most notably, in the SMILES and HELFIMED studies, was the modest improvement in mood directly related to dietary intake or advice? Couldn’t it simply be attributed to being helped by a social support group (regardless of the type of support)? Then there’s the chicken-and-egg question: Are people with poor diets more likely to report feeling depressed … or … are people reporting depression more likely to be unmotivated to follow healthy diets? (since lack of motivation is a common symptom in depression).

Bold claims, no evidence

Susan Molchan, MD

The above studies — which are the only ones cited — do not justify the hyperbolic, cause-and-effect language used throughout the article.

“I think the author oversteps with statements such as ‘it’s really about an unhealthy brain, and too often people forget this’,” said psychiatrist Susan Molchan, MD, a former NIH researcher and one of our regular contributors.

“That’s a rather meaningless and arrogant thing to say. There are many reasons for depression. And, no, it’s not healthy. And who forgets this?”

And here are some other statements for which no evidence is given:

• “processed or deep-fried foods often contain trans fats that promote inflammation, believed to be a cause of depression.”
• “the good and bad bacteria in our gut have complex ways to communicate with our brain and change our mood … we need to to maximize the good bacteria and minimize the bad.”
• “can a good diet replace medicine or therapy? Not for everyone. But people at risk for depression should pay attention to the food they eat.”

The reporting implies cause-and-effect relationships between trans-fats, the microbiome, and depression. These statements are presented unequivocally, even though much of the research to support them not only remains equivocal, but has mostly been done in mice, not humans.

And supporting quotes come exclusively from researchers heavily invested in establishing links between diet and mental health. No critiques by independent voices are included.

Does this give readers a balanced perspective to help guide them in making informed decisions regarding diet and mood? And does it even inform readers about what’s controversial or unknown when it comes to research on this topic?

Closing the deal or deal-breaker?

The closer to the article — arguably what some writers intend as their take-home message — is a protracted anecdote of a depressed 60-year-old woman who has tried a host of antidepressants and psychotherapy, yet remains depressed. Her suffering drives her to the internet in search of some kind of solution, and there she finds … cashews. She buys, freezes, and presumably eats 100 pounds worth. Further research leads to more promising foods — mostly in line with a Mediterranean diet, the type of diet the article implies as being the best for depression. She changes her diet, gets better, and we’re told her depression “has never come back.”

Here’s my take-home message: Scientific research on diet and mood disorders is important, in its adolescence, and is in need of larger, longer term, randomized controlled trials. As we’ve pointed out before, nutritional research is an area of scholarship in which conflicts of interest are not uncommon and need to be sought out. There is a double jeopardy here — mood disorders are common and news coverage of diet is very popular. Reporting is prone to featuring more fads than evidence.

This Wall Street Journal article highlights these issues in spades. In doing so it runs a huge risk of misinforming — and in doing so misleading — a very vulnerable group of people.