The Powerful Link Between Nutrition and Depression

by Grant H. Brenner

“You are what you eat” is an oft-repeated anthem, a quick way for us to say that what we eat matters on an essential level to our health and well-being. It's far too easy to ignore or dismiss, given the power of emotional, or stress, eating. Increasingly, and compellingly, a growing body of research identifies connections between diet (along with other lifestyle elements) and how we feel physically and psychologically.

What we eat has a direct effect in terms of nutritional richness, as well as affecting interrelated factors, including gut bacteria (the microbiome and use of psychobiotics to address mental health), inflammation; energy metabolism (e.g. mitochondrial function and nutritional supplementation), antiaging medicine; and effect on memory and cognition—sometimes subsumed under the rubric "nutritional psychiatry".

Eating and nutrition are, of course, critical aspects of social behavior—breaking bread—and for many reasons, social life is as integral to health as are individual efforts, adding a layer of nuance to food choices. It's easier to be healthy when we partner with others to achieve our goals. While smaller studies are interesting and often drive individual behavior (e.g. changing diet or taking a supplement after reading something online), population-based studies provide more robust data to inform decision-making.¹

Enlightened Eating

There are two sides to the nutrition/well-being coin: one is how poor eating habits and consuming junk food negatively affect health; the other is how enlightened eating, sometimes referred to as “food as medicine,” can enhance health and longevity while preserving or enhancing pleasure. The Mediterranean diet, for instance, associated with reduced depression risk, is also delicious.

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The Leading Edge

Our understanding of food, lifestyle, and health is growing by leaps and bounds, reflecting greater collective awareness. A recent article on NPR, for example, calls for a coordinated, multipronged approach with seven elements:

1. Treat food as medicine.
2. Focus on the quality of calories, not just quantity.
3. Expand access to dietary and lifestyle counseling.
4. Support food entrepreneurs.
5. Increase the number of new farmers growing healthy foods using regenerative farming techniques.
6. Make school meals free for all students.
7. Establish a federal food czar.

Underlying many of the above initiatives is the need to better understand the role of proper nutrition as well as the detrimental effects of inadequate nutrition. To date, in spite of increasing research on the psychiatric impact of diet, there have been limited population-based studies on the role of nutrition on depression. However, a recent study reported in the Journal of Affective Disorders (2022) addresses this gap in the literature.

Researchers Owczarek, Jurek, Nolan, and Shevlin, using the U.S. National Health and Nutrition Examination Surveys (NHANES) for 2017-2018, included data from about 5,000 U.S. adults. In this study. They focused specifically on nutrition and depression, although the NHANES study covers a broad range of measures.

The NHANES survey collects participant dietary habit information over the course of two detailed interviews to estimate the nutritional quality of the foods they ate. This data was used to determine levels of daily intake of calories, fiber, folate (vitamin B9), vitamin B1, vitamin B12, vitamin K, calcium, magnesium, iron, zinc, copper, and selenium, benchmarked to recommended daily amounts required for adequate nutrition. For each nutrient, participants were noted to be either meeting or not meeting daily requirements. Depressive symptoms were measured using the Patient Health Questionnaire-9 (PHQ-9).

Statistics included age, gender, marital status, education level, weight, income, and related factors, along with medical data such as tobacco use and diagnosis of conditions including diabetes, high blood pressure, and arthritis. The data were analyzed to identify the best fit of nutritional status with depression. In studies of this type, the goal is to build a model based on how many categories best explain the overall pattern—technically, a “latent class analysis.”

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Broad Classes of Nutrition Influence Depression Risk

Nearly 10 percent of the NHANES sample were above the cutoff point suggesting clinically-significant depression. Four classes of nutritional status tracked with depression.

1. Low Nutrient Class (35.3 percent), with low folate, fiber, vitamin K and magnesium, and medium to high levels of the other nutrients measured, had higher depression scores relative to the Sufficient Nutrient Class (#2).
2. Sufficient Nutrient Class (27.6 percent), with high values of nutrients aside from lower fiber and vitamin K, had lower depression scores on average. This group was also associated with higher educational levels.
3. Low Fiber and Magnesium Class (22.6 percent), similar to the Sufficient Nutrient Class, with lower fiber and magnesium. had lower depression scores on average. People in this group were more likely to have higher weights compared with Class 4.
4. Nutrient Deprived Class (14.5 percent), with low nutrients across the spectrum, had the highest average depression scores. This was the only class with a significantly increased risk of meeting at least a moderate depression score per the PHQ-9. Men were more likely to be in this class.

Nutrition class contributed to up to 10 percent of the difference in depression scores, suggesting that diet has a significant but circumscribed impact on depression.

Nutritional deficiency was associated with the highest level of depression. Age and income protected against nutritional deficiency. Study authors report that prior research has found that psychiatric illness is associated with a lower intake of vitamins and minerals, a finding in the current data as well.²

Implications for Diet and Future Directions for Nutritional Psychiatry

The strongest association with depression was in the Nutrient Deprived Class, underlining the importance of overall nutritional status. In short, general insufficiency of a range of vitamins and minerals has a high impact.

This work supports the overall notion that a balanced diet is important for the maintenance of mood, while highlighting that for individuals, specific factors such as fiber and magnesium intake (associated with obesity) may be important.

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The relationship between nutritional status and depression is complex. This early population-based research provides the groundwork for understanding how nutrition relates to depression. Future work ideally would be prospective, similar to the Framingham Study, following a large group of people over the course of generations to identify strong causal nutritional factors that can be addressed in order to reduce the general risk of psychiatric illness and inform a rational treatment regimen.

In the meantime, eating a balanced diet and following best recommendations for overall healthy eating, addressing individual factors including inflammation and other medical conditions, reducing identified risk factors, and taking a holistic, personalized approach with attention to many lifestyle factors, are most likely to result in greater well-being.

Overall nutrition was more important in this study than any specific factors. There is no magic bullet, so far.

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