Food and the Pursuit of Happiness

Wiser dietary indulgences may promote improved health and boost mood.

Posted Jul 08, 2018

Aaron Burden/Unsplashed
Source: Aaron Burden/Unsplashed

“Let food be thy medicine and medicine be thy food.” Often attributed to Hippocrates, this quote shines an incontrovertible light on a common sense statement. We are all aware that poor dietary choices have the ability to harm, and a high quality diet has healing potential. Evidence is solid regarding the negative impact of highly processed foods and their relationship with cancer, and overindulging in trans fatty acids and associated risk for cardiovascular disease, stroke, and type 2 diabetes.

Over the past several decades, as obesity rates have risen, so have cases of major depressive disorder offering not one, but two public health crises. In 2010, the Obama administration launched the Let's Move campaign to target childhood obesity. Unfortunately, obesity has been associated with a number of mental health concerns in people of all ages.

But are we paying enough attention to the idea that what we eat might indeed affect our mental health? And is it possible that starting off our day with a sugary coffee lavished with gobs of whipped cream, microwaving a highly processed frozen lunch, and indulging in our favorite takeout dinner could actually cause depression the way it causes heart disease?  Many mental health care professionals are advocating for the importance of dietary modifications for an improved mood, as patients are asking for these issues to be addressed. Columbia University psychiatrist and author Drew Ramsey navigates this topic seamlessly and often addresses the importance of brain food in mental wellness.

Let us now turn to the evidence, but first, understand the murky nature of this topic. It is broad and even the best study designs are vulnerable to multiple confounding factors. As we navigate the world of Green Psychiatry, I acknowledge that recent studies exploring the relationship between diet and mood, although promising, are not yet definitive. Many of these studies are weakened by a cross-sectional approach, which although points out an association between dietary quality and mood does not definitively establish a causal relationship. Which came first, the chicken or the egg? That being said, some experts may exploit areas where the studies fall short; however, with the evidence as it stands, I see progress and a good foundation to build upon.

Let us begin with the SMILES trial, an Australia-based study published in 2017 that followed 67 patients for 12 weeks who met baseline criteria for major depressive disorder (Jacka). Patients were divided into two groups. One group received seven nutritional consult sessions and they were started on a Mediterranean diet. The other group was placed in a social support protocol. At baseline, all patients’ dietary quality was gauged as relatively poor by a dietary screening tool. By the end of the study, 32% of patients eating a Mediterranean-style diet were no longer meeting criteria for depression verses 8% in the social support group. I like this study for two reasons: Primarily, it is one of the first randomized control trials targeting the relationship between diet and mood, and secondly, it takes a truly integrative approach in incorporating dietary modifications with medications and psychotherapy rather than forgoing the standard of care altogether. Patients in the study who were already receiving antidepressant medications or psychotherapy continued to receive those treatments, and with dietary modifications many of them got better. This is great news.

Another study compared treating depressed patients with low dose Prozac (20 mg/day), the omega 3 fatty acid eicosapentaenoic acid or EPA (1,000 mg/day) or a combination of both (Jazayeri). Forty-eight patients were analyzed and the combination group (Prozac plus EPA) had a greater reduction in depressive symptoms after eight weeks. The American Heart Association recommends eating at least two servings of fish per week. Mackerel, salmon, and albacore tuna contain high amounts of EPA and its sister omega-3 fatty acid docosahexaenoic acid (DHA). A third type of omega-3 fatty acid, alpha-Linolenic acid (ALA), commonly found in flaxseeds and chia seeds, is converted to EPA and DHA, albeit somewhat inefficiently.

Traveling now to Spain, the PREDIMED trial followed almost 4,000 patients who were at high risk for cardiovascular disease (Sanchez-Villegas). Patients were divided into three groups. The first was placed on a Mediterranean diet. The second adhered to a Mediterranean diet plus 30 grams/day of mixed nuts (15 g walnuts, 7.5 g hazelnuts and 7.5 g almonds), and the third was encouraged to follow a low-fat diet. Participants were all provided dietary counseling and support throughout the observation period and followed for several years. Results revealed that in a specific subset of patients — those with diabetes — incorporating a Mediterranean style diet plus 30 grams of mixed nuts/day had a statistically significant protective factor when it came to developing major depressive disorder during the follow-up period. This is interesting, to say the least, but I can hear the skeptics loud and clear, so let's address some concerns with these studies head on:

The SMILES trial was single-blinded. This means that patients were obviously aware if they were in the Mediterranean diet group or not, which created an opportunity for response bias. If a patient thought he was supposed to get better by eating a Mediterranean diet, then he may have reported feeling better when he actually did not.

Could the placebo effect have played a role in results of the SMILES trail? Absolutely. It is possible that depressed patients studied in the trial actually did feel better, but not because the Mediterranean diet was reducing inflammatory markers, boosting mood elevating neurotransmitters, or eradicating vitamin and mineral deficiencies, but because patients perceived that eating a cleaner diet was healthier and was expected to improve their mood. I would also acknowledge that antidepressants have their own well-documented placebo effect, which in my view is not necessarily a bad thing as long as patients are feeling better and tolerating treatment with limited side effects. Finally, the number of participants in the SMILES trail was relatively small. In medicine we like to see large studies, which can be quite expensive, but in turn support more robust results. Consider that the STAR-D trial, a hallmark study for treatment-resistant depression, followed over 4,000 patients and took place over a five-year period.

Regarding the PREDIMED trial, we are left with more questions than answers. A statistically significant reduction in depression risk was only seen in a specific subset of patients (diabetics). And the opportunity for confounders contributing to the results is rampant. The authors understand that further research needs to be done.

So what does all of this mean?

I believe questions about diet should be an integral part of every psychiatric encounter. We do not need to wait for a perfect study to solidify a causal correlation between diet and mood because the risk of recommending dietary modifications is exceedingly low and the benefits are substantial.

Consider this: In the 1960s, only one-third of medical doctors were willing to recognize a causal association between smoking cigarettes and lung cancer despite 20 years of convincing evidence. Establishing an evidence-based standard of care often moves at a snail's pace. In the meantime, we can improve our overall health by making better decisions about what we eat. Who knows, we might even feel a little bit happier along the way.


Jacka, F., et al. A randomised controlled trial of dietary improvement for adults with major depression (the 'SMILES' trial). BMC Medicine 2017. 15:23. 

Jazayeri, S., et al. Comparison of therapeutic effects of omega-3 fatty acid eicosapentaenoic acid and fluoxetine, separately and in combination, in major depressive disorder. Australian and New Zealand Journal of Psychiatry 2008; 42: 192-198.

Sanchez-Villegas, A., et al. Mediterranean dietary pattern and depression: the PREDIMED randomized trial. BMC Medicine 2013. 11:208.