A recent study published in the Nutrition Journal reports that eschewing animal products in favor of plant-based foods helps improve mood in just a few weeks. This short-term study incorporated thirty-nine omnivores. Each participant was randomly assigned to a control group consuming meat, fish and poultry daily, a group consuming fish 3-4 times per week but avoiding meat and poultry or a vegetarian group avoiding meat, fish and poultry. At the outset of the study and after two weeks of making assigned dietary transitions, participants were asked to complete a Food Frequency Questionnaire, the Profile of Mood States questionnaire and the Depression Anxiety and Stress scales. By the conclusion of the study, mood scores remained constant for the omnivore and fish eating group but several mood scores for vegetarian participants improved significantly.1 These findings might be surprising given that people who eat fish regularly increase their intake of healthy eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) fatty acids, fats that are critical for optimal brain health. This is what makes the study’s results so surprising.
Research evidence has frequently linked long-chain omega-3 fatty acids, EPA and DHA, to mood- a substance primarily found in fish and shellfish. Conversely, meat and poultry are high in arachidonic acid (AA), a potentially neuroinflammatory long-chain omega-6 fatty acid. Omnivores who consume large amounts of meat and poultry and low amounts of fish, with their elevated AA to EPA/DHA ratio, have been known to be at increased risk of depression.2 Omnivorous diets rich in fish and low in meat and poultry have been linked to a lower risk of depression.3 Vegetarian and vegan diets tend to be low in both long-chain omega-3 and long-chain omega-6 fatty acids, but prior to this study, there has been limited research examining the effects of a vegetarian diet on mental well-being.
Potential confounding variables such as a prior history of mental disorder, alcohol or substance abuse, BMI, age, gender and exercise frequency were accounted for and a general health history was completed at baseline. After two-weeks, the vegetarian group’s levels of EPA, DHA and AA dropped to negligible amounts while the fish eating group exhibited a 95-100 percent rise in dietary EPA/DHA. This evidence is indicative that manipulation of fatty acid concentrations in each of the participants was successful. In every individual on the vegetarian plan, stress and anxiety scores decreased after the two weeks, indicative that those who eliminate meat, fish and poultry may be better able to cope with mental stress than omnivores. The results of this study support another cross-sectional study which found that vegetarians report significantly better moods than non-vegetarians.4
While warranting further investigation, the results may be due to increased antioxidant consumption on the vegetarian plan leading to a reduction in oxidative stress on the brain.5 These findings are fascinating and while we might not completely understand the mechanisms involved in why a vegetarian diet likely leads to enhanced mood, the results are certainly worth pondering. I know I feel good as I finish off my huge salad or green smoothie!
I know my father gets excellent results with those suffering with depression by combining his nutritarian diet with added EPA and morning light therapy. He always uses nutrition and lifestyle medicine as the primary intervention, not drugs, which can lead to dependency, side effects and long-term health problems. It is good to know that the scientific literature is slowly catching up to Dr. Fuhrman (my dad). Who knows, maybe next year some other study will show that combining green vegetables, onions and mushrooms prevent cancer (Ha Ha)!
1. Beezhold BL, Johnston CS. Restriction of meat, fish, and poultry in omnivores improves mood: A pilot randomized controlled trial. Nutr J. 2012 Feb 14;11:9.
2. Kiecolt-Glaser JK, Belury MA, Porter K, Beversdorf DQ, Lemeshow S, Glaser R: Depressive symptoms, omega-6:omega-3 fatty acids, and inflammation in older adults. Psychosom Med 2007, 69:217-224.
3. Colangelo LA, He K, Whooley MA, Daviglus ML, Liu K: Higher dietary intake of long-chain omega-3 polyunsaturated fatty acids is inversely associated with depressive symptoms in women. Nutrition 2009,25:1011-1019.
4. Beezhold BL, Johnston CS, Daigle DR: Vegetarian diets are associated with healthy mood states: a cross-sectional study in Seventh Day Adventist adults. Nutr J 2010, 9:26.
5. Szeto YT, Kwok TC, Benzie IF: Effects of a long-term vegetarian diet onbiomarkers of antioxidant status and cardiovascular disease risk. Nutrition 2004, 20:863-866