The role of probiotics and fermented foods
As we saw in an earlier post, approximately one-third of the dry weight of our stool is bacteria. Shortly after birth, promoted by bacterial growth factors in human breast milk, the digestive tract gradually gets colonized with about thirty to fifty different species of beneficial bacteria. These bacteria serve a host of useful functions, including repressing the growth of harmful organisms, training the immune system to respond to only pathogenic bacteria, detoxifying and removing cancer-causing toxins, and producing immune system–supporting nutrients. The natural, native bacterial flora of humans also protect against allergies and immune disorders by decreasing absorption of incompletely digested proteins.
The term “probiotics” is used both for the beneficial bacteria that are native to our intestinal tract and for supplemental live bacterial organisms that are thought to be beneficial when ingested. However, the (limited) bacteria in supplemental probiotics and fermented foods are not the same as the indigenous bacterial flora that live in the gut. Supplemental probiotics serve a beneficial role—but mostly when the normal native bacteria have been harmed or removed with antibiotic use or perverted with a diet of sweets and processed foods.
There is no published evidence that probiotic supplements are able to effectively replace all the functions of the body’s natural flora when these have been killed off. Probiotics are useful after taking antibiotics, as noted; but it can still take months to reestablish the normal type and amount of gut flora. Healthy foods promote healthy bacteria to live in the gut; unhealthy foods promote unhealthy bacteria and yeast forms. However, unless a healthy diet, rich in various fibers, is continually maintained, the probiotic bacterial levels achieved by supplements drop within days when supplementation ceases. So what we eat is still the most important factor in maintaining our intestinal flora.
“Good” bacteria feast on fiber and resistant starch, while “bad” bacteria and yeast feast on refined sugar and animal fat. There is no substitute for a healthy diet; and if you are eating health-promoting foods and avoiding junk foods and antibiotics, it is not necessary for you to take probiotics or fermented foods. Your body will grow the right kind of bacteria automatically.
One of the complications of antibiotic therapy is secondary infection—a huge problem in hospitals. Until recently there hasn’t been a good understanding of how and why this occurs. Now researchers have identified the way that normal gut flora keep the immune system “primed” to recognize the cell walls of bacteria so that the slightest change from a normal to a pathogenic bacterium will stimulate an immediate attack. Antibiotics shut this recognition ability down, leaving the body without one of its defense systems. Probiotics can help turn this safeguard back on again.
If you are taking antibiotics more than once per year, then of course the continual use of probiotics is recommended, as it could take a year or more to reestablish normal bacterial protection each time. Otherwise, probiotics should be used for at least three months after each use of antibiotics. Fortunately, most healthy people eating a healthy diet should never need an antibiotic—not once in their life—because dangerous bacterial infections are exceedingly rare in people with excellent immunity.
Probiotic supplements may be indicated and helpful for certain other conditions as well, such as irritable bowel syndrome, autoimmune diseases, allergies, headaches, and excessive yeast in the gut. They are also helpful for those who are not eating properly for good health.
More than a dozen studies on the effectiveness of probiotics in preventing viral infections such as colds and flu have been conducted, with mixed results. Most studies have shown some decrease in the severity and number of illness days in participants randomly assigned to treatment groups.31 The inconsistency of the evidence demonstrates that probiotics are more useful for unhealthy people eating unhealthfully, and less helpful for those eating healthfully and in good general health.
A healthy diet with plenty of raw vegetables, mushrooms, and beans, in the absence of antibiotics, will provide enough of the favorable bacteria in your gut to you keep you healthy and functioning at your highest levels. It is not necessary to eat fermented foods such as yogurt and kefir to have beneficial bacteria in the digestive tract. However, the more a person consumes sweets and processed foods and utilizes antibiotics, the more likely it is that he or she will require ongoing supplementation with probiotics.
Probiotics are well tolerated in adults, children, pregnant women, and even premature infants. However, they should be avoided in severely immune-compromised patients with HIV or advanced cancer or people undergoing chemotherapy.