Of rats and men: The gut-brain axis can affect mood, behavior

Does it seem hard to believe that your gut, in particular the bacteria in your gut, can affect your mood and behavior? Indeed, the gut-brain axis has become increasingly well understood through studies on experimental rats.

We all are familiar with the relationship between gut and brain. We hear such expressions as “He makes me sick to my stomach,” “I have a bad feeling in my gut about this” or even “She is such a pain in the …” Such visceral, earthy metaphors give testimony to how our feelings and gut are related.

Through fascinating scientific research in germ-free rats, mechanisms are being discovered that offer promise for future gut and brain therapies. Our microbiota, the 1,000 or so species making up 3 to 6 pounds of protoplasm in our gut, turn out to be major players in this bidirectional communication between gut and brain.

Studies in germ-free rats, whose gut has been purged of all bacteria, are revealing that mood issues like anxiety and depression can be linked to gut bacteria profiles. Microbiota affect development of nerve sensitivity, contractility and immune processes in the developing gut. Cutting the vagus nerve blocks the effects of gut bacteria on the brain. The vagus is so-called because it wanders from the brain to the gut (think vagabond, vagrant, etc.) It has many important effects on gut function and is a direct satellite feed to the brain. Hormonal and neurochemical changes elicited by gut bacteria also communicate to the brain and affect mood mediated by, among other chemical signals, serotonin, the neurotransmitter targeted by mood altering drugs like Prozac.

Scientific studies have given strong evidence that irritable bowel syndrome, a bothersome condition known to be triggered by stress, is also related to abnormal microbiota. Changes in immune response, gut permeability, as well as activation and regulation of pain receptors in the gut result from changes in gut bacteria profiles. In some cases, reinoculating the gut bacteria with probiotics can improve this condition.

So the next time you have a gut feeling, you might want to trust it. Our bacteria have collectively more DNA than all our other cells combined and seem to be thinking and feeling for us.

How do we keep these bacteria and thus ourselves healthy and happy? Rat studies shown that alterations in food, stress management, birthing methods, breast feeding, antibiotic and drug use are significant.

Here is what can we do to support our gut-brain axis:

1. Eat more fermented foods, plant fibers and probiotics that support gut microbiota.

2. Eat probiotics like whole grains, bananas, onions, garlic, honey and artichokes that serve as food for our microbiota.

3. Avoid antibiotics, powerful antacids, steroids and anti-inflammatories whenever possible; if medically necessary, add probiotics to your diet for a month or more, usually 10 to 30 billion units daily.

4. Manage stress effectively to protect your gut; learn to meditate, practice mindfulness, engage in regular exercise, prayer and cultivate social support.

5. If you are a pregnant mom, do your best to have a safe vaginal birth rather than a C-section, and breast feed as long as possible.

Dr. Victor S. Sierpina is the WD and Laura Nell Nicholson Family Professor of Integrative Medicine and Professor of Family Medicine at UTMB.

By DR. VICTOR S. SIERPINA

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Of rats and men: The gut-brain axis can affect mood, behavior