Surprising Benefits of Probiotics

Probiotics—the “good” bacteria in yogurt and fermented foods—may be the new Prozac, helping to control depression, anxiety and other mental disorders, groundbreaking new research suggests.

Among the more unexpected findings is that we have “stress receptors” in our gut, according to Acadia University researchers who have launched a national study of whether probiotics might be a natural antidepressant and stress-reducer.

Scientists are also investigating the role probiotics may play in warding off colds, skin rashes, obesity, diabetes, and heart disease. How can bacteria in the gut combat such a wide range of disorders? Here’s a closer look at the new studies.

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Mind-Altering Microbes?

There’s increasing evidence that the unique mix of bacteria in our gut—which is as distinctive as a fingerprint—may affect mental health. For example, people with major depression, panic disorder and generalized anxiety disorder have high rates of irritable bowel syndrome (IBS), a 2009 study reported, while an earlier study also linked IBS to obsessive-compulsive disorder.

In a 2011 intriguing experiment aimed at finding out if changing gut bacteria influences brain chemistry, researchers fed mice a probiotic broth containing Lactobacillus rhamnosus JB-1, a type of bacteria that’s found in yogurt and also in the guts of healthy animals and people. 

The bacteria-fed mice showed significantly less behavior associated with stress, anxiety and depression than mice fed a plain broth. The bacteria-fed mice also had much lower levels of the stress hormone corticosterone during anxiety-inducing situations, such as being lost in a maze, and were also less likely to drift haplessly while dropped in water (a test for depressive symptoms in animals). 

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Potential to Treat Psychiatric Disorders with Yogurt

The study also found that probiotics boosts activity of GABA, a calming  brain neurotransmitter, increasing the number of receptors in brain areas associated with emotional control, memory and learning. The GABA system contributes to several stress-related mental disorders in people. One common type of anti-anxiety drugs (benzodiazepines) enhances the effects of GABA.

While these drugs, which include Xanax and Valium, are widely used, with about 100 million prescriptions written for them in the US, they can have a number of adverse effects and may be addictive. Therefore, a natural alternative would be a huge boon to psychiatry, the researchers point out.

Potential to Use “Yogurt Instead of an Antidepressant”

“These findings [open] up the intriguing opportunity of developing unique microbial-based strategies for treatment of stress-related psychiatric disorders such as anxiety and depression,” senior study author John F. Cryan said in a statement. Should probiotics be shown to have similar effects on people, he added, “You could take a yogurt with a probiotic in it instead of an antidepressant.”

The research, conducted by scientists from the Alimentary Pharmabiotic Centre in University College Cork in the UK and the Brain-Body Institute at McMaster University in Canada, was published in Proceedings of the National Academy of Sciences.

How Do Gut Bacteria Affect the Brain and Emotions?

Another 2011 study, published in Gastroenterology, was the first to link gut bacteria with depression and other mental disorders. In that study, which also involved mice, some of the animals were bred to be germ-free. The scientists observed that mice without normal gut flora were passive, but became lively, daring and interested in exploring after receiving bacteria from active mice. 

Conversely, the active mice became anxious, passive, and appeared depressed if their gut flora were altered with antibiotics. These animals also had a rise in brain-derived neurotrophic factor (BDNF), a substance that researchers have previously linked to major depression in humans. Once the antibiotics were halted, the mice’s gut bacteria, brain chemistry and behavior soon returned to normal.

Surprising Range of Probiotic Benefits

While further investigation, such as the Acadia study discussed above, is needed to see if “good” bacteria could be a useful therapy for certain psychiatric conditions, recent studies suggest that these friendly bugs may have the potential to boost health in surprising ways:

  • Lower cholesterol. A study presented at the American Heart Association scientific session this month shows that taking two doses of a probiotic supplement daily may reduce both total and LDL (bad) cholesterol. The placebo-controlled trial included 127 adults with high cholesterol.
  • Fewer colds. As I reported recently, a Cochrane review pooling data from 10 randomized studies (the gold standard of scientific research) found that people who consume probiotics for more than a week had 12 percent fewer upper respiratory infections than those treated for less than a week or given a placebo.
  • Protecting babies against eczema. Women who take probiotics during pregnancy and breastfeeding are less likely to have babies who develop the itchy skin rash eczema, a Finnish study reported this month. It’s thought that the healthy bacteria may cross the placenta and be present in breast milk.
  • Controlling diabetes. A 2010 study published in PloS One found that people with type 2 diabetes have very different intestinal flora than those with normal blood sugar levels, leading the researchers to recommend that probiotics be explored as a strategy to help control the disease.
  • Combatting obesity. There’s some evidence that the microbial mix in your gut may influence body weight. For example, farmers have long used low-dose antibiotics to fatten up cattle. Conversely, researchers are now using probiotics to help people who had gastric bypass surgery slim down more quickly. 

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