You know you’re mostly not human, right?
When you count the microorganisms living in your gastrointestinal tract, skin, and respiratory tract will, there are ten times as many bacterial cells as human cells in your body. We are ecosystems, rather than single organisms. If 20th century nutrition was the discovery of vitamins, proteins, carbohydrates, and other nutrients, 21st century nutrition will be the study of how nutrients affect those 90% of nonhuman cells within us.
These friendly bacteria (also known as normal flora or probiotics) play an important role in our gastrointestinal health, allergies, normal immune system functioning, and maintaining a normal body weight. Some intriguing early animal studies found that probiotics could even decrease symptoms of depression. In the June issue of the journal Gastroenterology, researchers at UCLA published the first study showing a direct effect of probiotics on the human brain. And no, this does not mean that people were shoving yogurt into their ears.
Researchers divided a group of 36 healthy women into three subgroups: the first received two servings of yogurt with probiotics daily; the second subgroup received non-fermented milk products; and the third subgroup received no special foods.
After four weeks, these women underwent psychological testing while in a functional MRI (fMRI) — an imager that examines real-time brain activity, rather than just taking a static image. The probiotic subgroup showed significantly reduced activity in brain areas associated with emotional variability and pain. Translation? Probiotics made them less moody!
The importance of this study is that it proves that gut bacteria can have a direct impact on human brain functioning, specifically in the areas of emotions and pain perception. It did not examine what the exact mechanism of action is. We also have to be a bit cautious with this study, because these were healthy volunteers, with no gastrointestinal or psychological disorders.
Nevertheless, this just adds another piece of evidence that indicates that tending to the complex “rain forest” within us, with fermented foods and lots of dietary fiber, is probably more important than taking high doses of any single nutrient.
Tillisch K et al. Consumption of Fermented Milk Product With Probiotic Modulates Brain Activity. Gastroenterology June 2013; 144(7):1394-1401.