There is an increasing amount of information about probiotics and the human microbiome in both the scientific and public media. If you visit your neighborhood supermarket pharmacy aisle you will likely see a dizzying array of probiotics. Let’s start by defining these terms.
Probiotics are live microorganisms that are either the same as or similar to microorganisms found naturally in the human body and may be beneficial to health. A probiotic can be any microorganism although current products contain only bacteria or yeast. Probiotics are available as supplements in the form of capsules, tablets and powders and in dairy foods such as yogurts with live active cultures. Probiotics commonly used in the United States include the bacteria Lactobacillus and Bifidobacterium. There are many specific types of bacteria within each of these two broad groups, and health benefits associated with one type may not hold true for others.
A prebiotic is a nondigestible carbohydrate that stimulates the growth and activity of beneficial microorganisms in the gastrointestinal (GI) tract. In essence, it’s food for the probiotic organisms. Examples include inulin and lactulose. Foods containing prebiotics include oats, wheat, bananas, honey, artichokes and many others.
A synbiotic is simply a combination of a prebiotic and a probiotic and can be found in such foods as yogurt, kefir, pickles, some cheeses, and increasingly available in dietary supplements.
The microbiome represents the total collection of microorganisms in the human body and include bacteria, fungi including yeast, and viruses. The main reservoir of the microbiome is in the GI tract and is often referred to as the gut microbiome. The microbiome in the average adult weighs a kilogram (about 2 pounds) and is very important in maintaining health. Alterations in the microbiome can lead to diseases involving the intestines including diarrhea, small intestinal bacterial overgrowth (SIBO) and inflammatory bowel disease as well as diseases outside the intestines including fatty liver, heart disease and even cancer.
More about probiotics
The U.S. consumer market for probiotics is growing rapidly. The global market for probiotics is expected to reach over $32 billion in 2014 and growing. Japan currently accounts for half of the world’s consumption of probiotics.
The rapid growth in marketing and consumer interest and use has outpaced the scientific research. The scientifically demonstrated benefits of probiotics are surprisingly limited. Although some probiotic formulations have shown promise in research, strong scientific evidence to support specific uses of probiotics for most conditions is lacking. Studies suggest that probiotics usually have few side effects. However, the data on safety are limited, and the risk of serious side effects may be greater in people who have underlying health conditions. My take is that probiotics are safe but there might be risks for anyone with a serious underlying medical condition including those with compromised immunity.
Various mechanisms may account for the effects of probiotics on human health. Possible mechanisms include reducing harmful organisms in the intestine, producing antibiotic-like compounds, and stimulating the body’s immune system.
Although the FDA has not approved any health claims for probiotics, they are used for a variety of GI and non-GI conditions. Currently, good evidence exists for the use of probiotics in infectious diarrhea, diarrhea associated with using antibiotics, reducing the risk of necrotizing enterocolitis (a severe intestinal condition of premature newborns) and atopic eczema (a skin condition commonly seen in infants). Studies show that probiotics may reduce side effects associated with treatment for Helicobacter pylori infection, the cause of most stomach and duodenal ulcers. Other potential uses include the treatment of: elevated cholesterol levels, obesity, the irritable bowel syndrome and inflammatory bowel disease, which includes ulcerative colitis and Crohn’s disease.
Concerns have also been raised about the quality of probiotic products. Some products have been found to contain smaller numbers of live microorganisms than expected. In addition, some products have been found to contain bacterial strains other than those listed as ingredients. Most probiotics on the store shelves have no evidence of benefit.
Some points to keep in mind before taking a probiotic:
- Before using probiotics, learn as much as you can by talking to your health care provider and researching reliable sources of information.
- Do not use a probiotic as a reason to postpone seeing your health care provider about any health problem.
- Anyone with a serious underlying health problem should be monitored closely for potential negative side effects while taking probiotics.
Here’s to your colon health!
Frank Farrell, MD, MPH, AGAF