Can diet lower depression risk

Used with permission by the Academy of Nutrition and Dietetics

Decades ago, depression was frequently characterized as a problem of the worried well, people who had the time and money to consult with a psychiatrist about their mental state.  It was something to joke about.  Now depression is recognized as the most common psychiatric diagnosis in developed countries, affecting 300 million+ people, costing $1 trillion in lost productivity per year.  Nothing to joke about from a global perspective, and nothing to joke about for the person whose life is severely affected by one’s own depression or that of a family member or friend.  Unfortunately, pharmacological and psychological treatment only work in about 1/3 of cases, and relapse is common even after successful treatment.  What to do?

Over the past few years, nutrition and diet have been on the depression cause-and-treatment radar screen.  Is there a certain nutrient that can “fix” depression or prevent it?  Is there a type of diet that predisposes someone to depression?  Part of the problem with this type of research is choosing a sufficiently large study group of people with clearly defined measures of depression, and then tracking them for a sufficiently long time to track changes related to a nutrient or diet.  Another big logistical problem would be controlling the diets of the study groups.  The only fool-proof way to do that would be to confine people to a study facility; who would volunteer for that?  So we’re left to use less direct methods of measuring any potential benefits of diet or nutrition.

A new review attempts to make some sense out of studies that have already been done on this topic.  The authors sorted through over three thousand studies done since 1946 on diet and depression.  They picked studies that had a clear set of characteristics:

  • a thorough diet assessment, done using standard and reliable food intake measurement questionnaires
  • a diagnosis of depression and/or report of depressive symptoms
  • a statistically reliable study design
  • study subjects who were free-living, in other words not institutionalized.  People with bipolar disorder or stress were excluded, as were pregnant women or hospitalized patients.

Just to show how strict the criteria were, out of the 3000+ studies found by the initial search, only 51 met the standards to be included in the analysis.

The studies used different diet scoring systems to identify different diet patterns.  Some common examples are:

  1. Mediterranean diet
  2. The Healthy Eating Index, which is based on the US Dietary Guidelines
  3. The high fruit and vegetable DASH diet, which is recommended for hypertension.
  4. The Dietary Inflammatory Index, which is based on the inflammatory potential of 45 different food measurements.
  5. American Heart Association diet
  6. vegetarian diets

Were any of these associated with depression?  The Mediterranean diet had most significant link to lower risk for depression.  Studies using the Dietary Inflammatory Index score showed that lower inflammatory scores were linked to lower risk for depression.  This isn’t surprising, since Mediterranean diets are known to have lower inflammatory potential.  This isn’t to say a DASH diet or vegetarian diet wouldn’t also be beneficial, just that the Mediterranean diet showed a stronger effect.

So what does this mean?

Here’s what it does not necessarily mean: that a Mediterranean diet will “cure” depression.  Rather, the diet is linked to a lower risk for depression.  Is that because less depressed people choose this type of diet?  Maybe.  Or perhaps there’s something about the mix of food and nutrients in a Mediterranean style diet that is beneficial to brain function.  Brain and nerve function are adversely impacted by inflammation, so diets that suppress inflammation would be expected to be beneficial, or at least not damaging.  The Mediterranean diet includes anti-inflammatory nutrients like anti-oxidants and omega-3 fats.  The other possibility is that a plant-based Mediterranean diet has a beneficial effect on gut microbe populations, which benefit brain function.  You can find a more detailed discussion of these possibilities in my latest book “Food Wisdom for Women“.

Take Away Message

Depression can be a debilitating disease, impacting quality of life.  A Mediterranean style diet might help lower risk for this problem.  It’s also known to be a healthy diet, with benefits for plenty of other chronic diseases.  If you’re dealing with depression, diet can be a valuable part of your intervention program.  Given the range of health benefits, there’s no downside, so why not try it.

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