How does diet affect our mood?
Some scientists believe that what we eat encourages certain types of microbes to thrive in our gastrointestinal tract, and these microbes can affect our mood, skin, weight, immune system and risk for chronic diseases such as autoimmune disease and cancer. The “gut-brain-skin” theory has been around since 1930 when dermatologists John H. Stokes and Donald M. Pillsbury noted that skin conditions such as acne are often associated with mood disorders and gastrointestinal disturbances—which increase gut permeability and lead to systemic inflammation.
Since the 1930’s, animal and human research has supported the idea that mental health disorders are frequently associated with low levels of Lactobacillus and Bifidobacterium, an omega-3 deficient diet and low stomach acid (hypochlorhydria). The microflora of our GI tract is intimately involved in gut permeability—which when breached can allow foreign proteins across the gut’s barrier and trigger immune reactions and systemic inflammation, leading to inflammatory acne lesions and depressed mood/ anxiety. In fact, it has been shown in animal studies that a circulating endotoxin, E. coli lipopolysaccharide (LPS)—which is usually not present in blood but can be if the intestinal barrier is not working proprerly—can itself produce depression-like behavior in animals. In addition, if the gut is not populated with beneficial microbes (or they’re not in the appropriate location), small intestinal bacterial overgrowth (SIBO) can result—which has been associated with fibromyalgia, chronic fatigue syndrome, constipation, depression and anxiety. One cause of this disturbance of normal gut microflora is hypochlorhydria, sometimes caused by medication (e.g. proton pump inhibitors, H2 blockers), hypothyroidism, atrophic gastritis, naturally occurring with age, or other less common conditions such as tumors, mucolipidosis or pellagra (niacin deficiency).
Probiotics including Lactobacillus and Bifidobacterium species have been shown to limit systemic oxidative stress and reduce inflammatory cytokines in various tissues of the body, inhibit the release of substance P and decrease monoamine oxidase activity—resulting in decreased anxiety- like behavior in animals. Stress hormones and substance P are known to cause anxiety, depression and aggression. The addition of probiotics to lab animal feed increases tissue levels of omega-3 fatty acids, peripheral tryptophan levels, and increase serotonin and dopamine turnover in the frontal cortex and limbic system—which can have a positive impact mental health.
This “gut-brain-skin” theory also works in reverse—stress and anxiety can adversely affect the gut microflora, as can a poor diet. In the Western diet, which is typically high in fat, sugar as well as processed foods, the loss of Bifidobacteria can lead to increased intestinal permeability, encroachment of LPS endotoxins through the intestinal barrier, low grade inflammation, insulin resistance and mood disorders. As we learn more about the prebiotic-probiotic-mood relationship, perhaps physicians will consider treating mood disorders with a prescription for a certain diet or HCl supplement, as opposed to a psychopharmaceutical drug.
BOTTOM LINE: Prebiotics and probiotics can have a positive impact on mood. Anyone who wishes to lead a healthier lifestyle and promote a normal mood state should eat a healthy diet and consider consuming fermented dairy products daily (see PROBIOTICS overview).