Probiotics Help With Depression, Anxiety, Studies Find
Most probiotics are bacteria. Examples of the most common bacterial species used in a probiotic role include Lactobacillus acidophilus and other members of the Lactobacillus family, as well as certain members of a bacteria family called Bifidobacterium. Some species of yeasts also provide a probiotic benefit. Well-known foods and drinks that contain probiotic microorganisms include yogurt, pickles, sauerkraut, certain types of soft cheeses, sourdough bread, a yogurt-like fermented drink called kefir, a Korean pickled vegetable mixture called kimchi, a fermented soybean product called tempeh, a Japanese soup called miso, certain types of dark chocolate, and a form of fermented tea called kombucha tea. The theory of probiotic use is based on knowledge of the natural function of the human digestive system. Every living person has literally millions of bacteria and other types of microorganisms living in his or her digestive tract. While some of these microorganisms are neutral or harmful to human health, many of them play vital roles by assisting the breakdown of food and food wastes, as well as by keeping harmful species of microbes in check. Some of the species viewed as probiotic already exist in the human gut, while others bear a close resemblance to existing species. When probiotic species enter the digestive tract (especially the lower portion of that tract), they support the species already present and potentially improve digestive health. Scientists believe that probiotics may achieve their effects by doing such things as helping kill off harmful microorganisms and/or improving the function of the body’s immune system.
Role in Mental Health
At one point, doctors and researchers believed that the effects of probiotics were limited to the digestive tract and the immune system. However, a growing body of evidence indicates that the presence of probiotic species can also alter normal brain function. For example, in a study published in June 2013 in the journal Gastroenterology, a multi-institution research team gave probiotic-containing yogurt to a group of women who had no problems with their digestive health, then compared the brain function of these participants to a group of healthy women who didn’t consume any probiotics. After reviewing their findings, the authors of the study concluded that probiotic use reduces the brain’s tendency to react to emotionally stressful imagery, and also increases the rate of communication in an area of the brain that helps support conscious thought processes. Another study, published in 2011 in the Proceedings of the National Academy of Sciences, used animal testing to study the brain effects of one specific strain of probiotic Lactobacillus bacteria. The authors of this study concluded that use of this strain alters the body’s normal stress response and reduces the severity of a variety of behaviors associated with the onset of depression and a group of conditions called anxiety disorders. Inside the brain, the Lactobacillus species apparently achieves its effects by altering the same chemical system that’s altered by use of the sedative medication diazepam (Valium).
The authors of the study published in the Proceedings of the National Academy of Sciences believe that their findings may one day support the use of probiotics to either prevent or treat depression, anxiety, and (possibly) a number of other mental disorders. However, they stress that their findings are highly preliminary, and extensive testing of probiotics’ effects on the mental health of human beings (as opposed to the mice used in the study) will need to occur before anyone can accurately gauge the usefulness of probiotic substances in promoting or restoring mental health. The study’s authors also stress the fact that any treatment developed in the future will almost certainly differ significantly from the commonly available forms of probiotics found in everyday foods or in the supplement products currently marketed to consumers.