We’ve only recently come to appreciate the importance of bacteria in our health. Microbes have traditionally been thought of as the enemy and while they certainly can cause disease, they also provide us with a host of health benefits we are still in the process of discovering.
Most research so far has focused on the GI tract (stomach and small and large intestines) because of the huge amount of bacterial diversity that exists there. The most recent research indicates that there are probably 500 to 1,000 different species of bacteria in the GI tract, most of which are in the large intestine. They help protect us from harmful bacteria that might try to invade and they produce nutrients and vitamins that we need to live, like short-chain fatty acids and vitamins B and K.
Increasingly, though, researchers are finding bacteria interact with our immune systems as well. The immune system normally kills invaders, but in some parts of the body it seems they learn to tolerate foreign organisms. This has fascinated researchers because understanding how this happens would help understand diseases where the body loses the ability to tell what’s good and what’s bad for the body. This is what happens in a food allergy: your body thinks something you’ve eaten is something dangerous and tries to destroy it.
A study out this week sought to further unravel the role bacteria play in food allergies. Using mice, they had three groups: one raised in a sterile environment who had no gut bacteria, a second who were treated with antibiotics to reduce the variety and number of bacteria in their gut and a third normal group. They then fed them parts of peanuts known to cause allergies to see how they would respond.
The immune systems of both the sterile and depleted mice reacted strongly to the peanuts by producing antibodies against the peanut allergens. The normal group showed only a mild reaction. They then reintroduced bacteria into the intestines of the sterile and depleted mice to see whether the renewed presence of these microbes would influence how the immune system reacted to subsequent doses of peanuts.
They found that mice that were given a mix of bacteria from the Clostridia family saw a reversal of the allergic response from the immune system, with antibodies significantly lower when allergens were given. This did not happen when the mice were given another group of bacteria called Bacteriodes. The researchers inferred from this that Clostridia have a unique effect on how the body handles allergens, perhaps because of their location in the gut. Clostridia sit along the innermost part of the intestinal lining, which puts them in close contact with immune cells.
It remains to be seen whether Clostridia have a similar effect in humans, so don’t expect to see it on health store shelves any time soon. What this study does show us is that bacteria are probably playing a more important role in allergies than we currently realize. As studies like this move into looking at humans, rather than other animals, we’ll gain a new possibly radically different understanding of how the microbes in our intestines determine our health and well-being.