It is fairly common knowledge that serotonin and dopamine, neurotransmitters that help regulate our moods, do their magic by stimulate our brain’s pleasure and reward centers. We know too that many scientists believe low levels of serotonin and dopamine may contribute to depression. Mood-altering drugs like LSD and Ecstasy cause an enormous spike in serotonin levels. Most antidepressant medications (i.e. Prozac, Zoloft, Celexa) work by keeping the serotonin in our brains from being reabsorbed, which increases the available serotonin in our brains. Several addictive drugs such as cocaine and methamphetamine use dopamine to create feelings of euphoria. Addiction to caffeine, sugar, video games, alcohol and other addictive behaviors also involve stimulation by dopamine.
What may not be so widely known is that 80-90% of the serotonin in our bodies and 50% of the dopamine has an intestinal source. The mesentery, an organ that surrounds and supports the intestine, produces these vital neurotransmitters, but the mesentery itself is
influenced by the microbiome—the billions of bacteria, archaea, fungi, single celled eukaryotes and even viruses that live in our guts. That’s why what we eat can have such a profound effect on our mood.
Researchers are just beginning to develop theories about how the gut microbiome is involved in brain development, learning, memory and mood. One researcher (Dr. Premysl Bercik) began with two strains of mice: the first group were from a strain bred to be anxiety prone, and the second group were from a strain bred to be intrepid. They kept these mice from receiving a normal microbiome from their mothers through a caesarian birth, then raised them in a sterile environment. They then introduced the normal microbiome of the anxiety prone strain into the intrepid mice, and vice versa. The result was a reversal of normal behavior. The normally anxious mice exhibited bold behavior, and the normally bold mice became anxious. The microbiome had a greater influence on mood than genetics.
The link between Autism Spectrum Disorder (ASD) and the microbiome has only recently been explored. Several papers on the subject were published just a few years ago in book form, under the title Bugs, Bowels, and Behavior: The Groundbreaking Story of the Gut-Brain Connection edited by Teri Arranga and Claire I. Viadro. In it researchers explore a long understood, but neglected connection between bowel issues (like chronic constipation and Irritable Bowel Disease) and autism. The connecting link has only recently been a subject of research, since the discovery of the importance of the gut microbiome to brain development. This may explain why babies born by caesarean section are more likely to develop ASD or ADHD than babies delivered vaginally—where they are exposed to the maternal microbiome.
The microbiome has been linked to cognitive processes such as learning, memory and decision making. So, it is not surprising that researchers have found an association between the gut microbiome and eating behavior. Some scientists have gone as far as to suggest that microbes may be able to communicate with our brains via the vagus nerves. These two nerves are the communication channel between our digestive tract and our central nervous system. The vagus nerves signal to our brains to communicate hunger, satiation, or illness in the digestive tract. However, some researchers are speculating that the microbiome may also tap into this system to influence how much we eat and to send craving signals to influence our choice of food. It has been suggested that it may even stimulate our brains to take action to satisfy these cravings.
Whether the microbiome can influence actions through the vagus nerves is pure speculation at this point, but the notion is fascinating. We have all experienced moments when our bodies seem to react in a zombie like fashion to seek out foods that we would otherwise avoid. It would certainly explain how we can end up in front of the refrigerator without any conscious thought. However, it is far too soon to accept this a scientific theory.
Given how pivotal the microbiome is to our brain’s healthy function, it is imperative that we take care of it, so that it can take care of us. The saturated fat, and animal protein in meat and dairy damage the microbiome and should be avoided, they encourage the growth of Bacteroidetes species that are harmful to our colon. These are decay organisms that basically rot our gut along with the meat. The way to care for our gut microbiome is by feeding it plenty of fiber rich foods like whole grains, nuts, seed, fruits and vegetables. These encourages the growth of Firmicutes species that feed our colon lining butyrate to make it strong. A whole foods plant based diet is the ideal diet for a healthy gut microbiome, and a healthy brain. Feed yours today.