What are they and why do we care? Probiotics are microorganisms that have beneficial properties for the host (that's us). Probiotics are an important way we can alter intestinal bacterial flora. Most are derived from food sources like cultured milk products. The list of probiotics is long, but some familiar names are: lactobacillus, clostridium butyricum, stept salvarius, and a strain of E Coli called E Coli Nissle 1917.
In what kind of illnesses have we studied the use of probiotics? Several studies have shown that probiotics can be effective for many gastrointestinal illnesses (Crohns, ulcerative colitis, irritable bowel syndrome, antibiotic associated diarrhea) and allergies. There was a very compelling study looking at pregnant women treated with probiotics prenatally and it showed a decreased incidence of allergy and asthma in their children. Many ongoing studies on pregnant women and children for prevention of allergy and asthma will soon be published so stay tuned but the evidence for the GI illnesses is quite significant already.
Ok, so how do I take probiotics? The easiest way to incorporate probiotics in to your diet is through fermented milk products, which is the same thing as cultured milk or dairy products. These are dairy products that have been cultured with lactic acid bacteria. Yogurt (plain Turkish yogurt being rich in cultures among others), kefir, sour cream, and crème fraiche are your easy options.
Are all probiotics created equally? No, and benefits observed in one study for one ailment may not be applicable to another. Having said that, yogurt is commonly recommended and make sure it's a yogurt with "live and active cultures". Several are readily available in stores: Activia by Dannon, Columbo, Horizon, Stonyfield, etc. Please buy PLAIN yogurt and avoid the added sugar. There are many probiotic capsules and powders available on the internet but the only real evidence is for the active cultures listed above. One preparation called VSL#3 which comes in powder or capsules (made by Nature Pharmaceuticals) has been studied and shown to be effective for several GI illnesses.
Ahhh the science--how do probiotics work?
Here are our best guesses at how they work:
1) suppression of growth or epithelial binding/invasion by harmful bacteria.
2) Improvement of intestinal barrier function
3) Modulation of the immune system by inducing protective cytokines and suppressing harmful ones.
4) Changing pain perception in the gut.
In my primary care practice who do I recommend give probiotics a try? Aside from the obvious well defined GI illnesses that benefit (Crohns, IBS, etc.) I suggest many of my patients who suffer from low grade symptoms of nausea, loose stools, increased gas pains, abdominal bloating, and "gurgly stomach" give it a try. My women who suffer from chronic vaginal yeast infections also do well when they incorporate the probiotics into their diet and no, you don't have to put the yogurt inside of the vagina you can eat it.