What are Probiotics?
Probiotics are live microbial organisms that are naturally present in the digestive tract and vagina.
The digestive tract maintains a balance between healthy and potentially harmful micro-organisms. Healthy micro-organisms, also called microflora, are residents of the digestive tract that have a protective role in our bodies. There are over 400 species of microorganisms in the human digestive tract, including Lactobacillus and Bifidobacterium.
As we age, the proportion of healthy microflora in our bodies declines and is less able to protect us from disease.
Probiotics are considered beneficial and are sometimes referred to as "friendly" bacteria. Some of the ways they are thought to promote health include suppressing the growth of potentially harmful bacteria, improving immune function, enhancing the protective barrier of the digestive tract, and helping to produce vitamin K.
A number of medical, diet, and lifestyle factors are believed to disturb the balance in the colon. This imbalance is called dysbiosis. Factors include:
- Inadequate dietary fiber
- Oral antibiotic therapy
- Infant formula feeding
- Ingestion of environmental toxins
No longer kept in check, less healthy bacteria and yeast may flourish, which is thought to increase the likelihood of conditions such as infectious diarrhea and vaginal yeast infections.
Health Benefits of Probiotics
A literature review on probiotics found 185 studies published in what they deemed to be credible journals between 1980 and 2004. The most commonly studied condition was diarrhea (41 or 22% of the 185 studies).
Seven studies looked at probiotic use in adults, focusing on the strains Lactobacillus reuteri, Lactobacillus GG, L casei, L acidophilus, and Saccharomyces boulardi. Although they varied in dose and probiotic strain, in six of the studies, probiotics shortened the course of diarrhea or decreased its severity.
Many studies have looked at probiotic use in children. Once again, there is a wide range of doses and probiotic strains. The most commonly used strains were Lactobacillus acidophilus, L casei, L GG, and Bifidobacteria. In 20 of the studies published between 1980 and 2004, all of the studies found an improvement.
Seven out of 12 controlled trials reported a definite prevention of antibiotic-associated diarrhea. In addition, a meta-analysis looked at 9 randomized, double-blind, placebo controlled trials with a total of 1214 patients. Six of the nine trials showed a significant benefit of probiotics.
Probiotics are thought to combat oxidative stress, believed to play a major role in the development and progression of diabetes. A study assessed the effectiveness of probiotics and yogurt on blood glucose and antioxidant status in people with type 2 diabetes.
For the study, 64 people with type 2 diabetes were assigned to two groups. One group took 300 grams/day of probiotic yogurt containing Lactobacillus acidophilus La5 and Bifidobacterium lactis Bb12 and people in the control group tool 300 grams per day of conventional yogurt for six weeks.
Fasting blood tests, 24 hour diet recalls and anthropometric measurements were collected before and after the six week study period. After six weeks, fasting blood glucose and hemoglobin A1c were decreased compared to the baseline measurement and glutathione peroxidase, erythrocyte superoxide dismutase, and total antioxidant status increased compared to the control group, indicating that probiotic yogurt may be a promising functional food for the management of diabetes.
Functional Bowel Disorders
Studies on probiotics for functional bowel disorders have had inconsistent results, which might be due to differences in probiotic strains used in the studies.
A study examined the probiotic bacterias Lactobacillus acidophilus NCFM and Bifidobacterium lactis Bi-07 twice a day in people with functional bowel disorders excluding constipation.
Primary outcomes were relief of gastrointestinal symptoms and treatment satisfaction. Secondary outcomes were changes in the severity of symptoms, well-being, and quality of life.
After four and eight weeks, abdominal bloating improved in the group taking the probiotics compared with those taking the placebo.
Common Uses for Probiotics
- Diarrhea Due to Antibiotic Use
- Traveler's Diarrhea
- Side Effects of Radiation Therapy
- Irritable Bowel Syndrome
- Vaginal Yeast Infections
- Ulcerative Colitis
- Crohn's Disease
- Immune Support
- Lactose Intolerance
- Prevention of Colds
- Allergic Rhinitis / Hayfever
- Colon Cancer Prevention
- Small Intestine Bacterial Overgrowth
- Canker Sores
Sources of Probiotics
Probiotics can be found in capsule, liquid, powder, or tablet form. Acidophilus drinks can be found in health food stores and some grocery stores and Asian grocers.
Probiotics can also be found in cultured dairy products such as yogurt or kefir, however, the number of live organisms varies greatly from product to product due to differences in processing methods. Fermented foods such as sauerkraut also contain probiotics.
Related: Kefir: What You Need to Know
Once ingested, probiotics colonize the intestines and other parts of the body and can sustain themselves unless they are destroyed by antibiotics or other factors.
Although they are thought to be essential for health, because they can sustain themselves in the body under normal circumstances, there is no recommended daily intake of probiotics.
"Prebiotics" are also thought to improve the balance of probiotics in the intestines. They are non-digestible carbohydrates that stimulate the growth of beneficial bacteria in the intestines. Sources of prebiotics include fructo-oligosaccharides (FOS) and inulin, found in onions, asparagus, chicory, and banana. FOS is also available as a supplement and is sometimes combined with probiotic dietary supplements.
Safety Concerns of Probiotics
Side effects of probiotics may include mild, temporary digestive complaints, such as gas and bloating.
People who are immunosuppressed should seek medical advice before using probiotics. It is possible that the probiotic itself may cause a serious infection. One death was reportedly linked to probiotic use in a person taking immunosuppressant medication.
Potential Drug Interactions
Probiotics may interact with immunosuppresant medication (see above). Probiotics are recommended by some health practioners during and/or after antibiotic use.