Almost half of the adult population in the United States will experience a mental illness at some point in their lives, and one out of four will suffer a mental disorder in any given year, although not all will seek a doctor’s help and be officially diagnosed.

While many people believe the term “mental illness” defines only conditions such as schizophrenia or depression, those are only the beginning. Mental illness includes any health condition that involves changes for the worse in emotion, thinking or behavior — separately or in combination—and this broad category can include dementia and other neurological conditions.

No matter how you define mental illness, one thing’s for certain: treatments offered in conventional medicine are almost always drugs and psychotherapy, with very little attention given to nutrition.

That’s a mistake, because a new study reveals that any treatment for mental health problems should begin with treating your gut with probiotics.

Probiotics, of course, are live bacteria and yeasts that support the health of the digestive tract. You’ve heard them called “good” bacteria. They support nerves that control the muscles used to move food through your gut as well as keep “bad” bacteria in balance.

Natural doctors have long believed that supplementing with probiotics can improve overall health, even mental health. Two food scientists in India set out to see if this is true.

They analyzed all of the research related to mental health and your gut microbiome, the term used for the complex population of microorganisms found in your intestinal tract.

The Gut-Brain Connection

Japanese scientists first demonstrated the link between gut microorganisms and the nervous system in 2004, with a study in mice.

Since then, studies in animals have demonstrated probiotics can improve symptoms of anxiety, stress, depression, chronic fatigue, autism, Alzheimer’s, and vascular dementia. But the real test of probiotics is whether they can achieve similar results in humans.

In the review, the researchers presented a number of studies showing probiotics, either in foods or as supplements, can significantly improve human brain function compared to placebo. For example, probiotics helped:

  • Improve mood in healthy volunteers.
  • Decrease anxiety symptoms.
  • Reduce psychological distress, depression and anger or hostility.
  • Diminish negative thoughts associated with a sad mood.
  • Improve depression, anxiety, and stress scores.
  • Relieve stress in healthy medical students prior to sitting for their exams as measured by a reduction in salivary cortisol and physical symptoms of stress.

Writing in The Open Microbiology Journal, the food scientists report that these and other studies “show a clear indication that lack of healthy gut microbes is linked to mental ailments…Probiotics that change the population of gut bacteria…alleviate depression and influence brain activity related to emotion regulation and mood upliftment [their term], motivation, reward, and happiness.”

They conclude that “it is highly beneficial and recommended to consume a probiotic-rich diet and, wherever recommended, probiotic supplements for boosting brain and body – the key to sound mental health and wellbeing.”

But How Do Probiotics Help Your Mental Health?

A huge amount of research is currently directed at the remarkable four pounds of bacteria, viruses, fungi and protozoa that reside in the intestinal microbiome.

When these microbes are in healthy balance, all hundred trillion of them, they produce compounds that positively influence the brain. These compounds are called psychobiotics.

For instance, as much as 95 percent of the “happy” hormone serotonin is produced in the gut.

The microbiome also produces other neurotransmitters such as acetylcholine and glutamate, which are involved with learning and memory; the amino acid GABA, which calms nerve activity; and the sleep hormone, melatonin.

It’s important to note that deficiencies of some or all of these compounds are seen in people with anxiety, depression, mood disorders and dementia.

It’s also no surprise that the research shows people suffering from these problems can have impaired amounts and composition of gut bacteria compared to the mentally healthy. Fortunately, the microbiome is not set in stone. You can change your microbiome for the better by simply consuming probiotics.

Taking Probiotic Foods and Supplements

The most popular and accessible probiotic food is yogurt, so long as the label states that it contains live cultures and minimal sugar. Others include kefir, fermented soybeans (miso, natto and tempeh), fermented black tea (kombucha) and cultured vegetables such as sauerkraut and kimchi.

Instead of, or in in addition to the foods, there’s a wide-range of supplements available, from capsules and liquids to powders and chewable products.

Probiotics are measured in colony forming units (CFU), which indicate the number of viable cells. Most supplements contain between one and ten billion CFU, but some contain much more.

Most of the research on human brain performance used one billion CFU of lactobaccillus and bifido probiotic cultures. These studies suggest that while results don’t happen overnight, positive effects on mood and memory do appear in about four weeks.