This post is a little different from my usual posts. It’s still about food, but it’s also about new research showing that what you eat affects your immune response. I regularly browse through the scientific journals (for work, I swear) and this article caught my eye.
Here’s what the research says in a nutshell:
Less fiber = Fewer of the good bacteria in your intestines = Greater risk of allergies and asthma
Here’s what the research says in a little more detail:
Lower fiber intake, as in, the amount of fiber that is now typical in American diets, affects the types of microbes in your intestines. Less fiber means less of an important group of bacteria that eat the fiber and then produce molecules called short-chain fatty acids, or SCFAs. These SCFAs appear to help regulate your immune system–that’s the system that fights off illnesses, but also the part responsible for allergies, asthma and autoimmune diseases. As we are all probably aware, the typical Western diet today is composed of a lot of processed foods. We eat much less fiber than we did 40 years ago and less than people in developing countries eat today. A group of bacteria called Bacteroidetes appear to be responsible for producing SCFAs.
On a related note, the Lactobacillus bacteria, well-known for their role in yogurt, may also help reduce allergies. In regions of the world that regularly eat fermented foods and do not use antibiotics, allergies and asthma are much less common. And if that’s not enough for you, changes in gut microbiota are also associated with rheumatoid arthritis and inflammatory bowel disease.
If it seems strange to you that the bacteria in our gut would have such a critical role in our body’s function, it’s not. Over millenia, as we have evolved, we have done so in the company of our friendly gut bacteria. We require these bacteria to produce essential vitamins from our food and to digest fiber for us.
Lastly, the fiber hypothesis is compared with the hygiene hypothesis, which states that the extreme cleanliness of modern society is to blame for the rise in allergies. Anecdotal evidence for the hygiene hypothesis includes the fact that people raised on farms, in large families, or developing countries–basically, environments that tend to be less clean–have lower rates of allergies than their Western, urban counterparts. However these urbanized groups also tend to have lower fiber intake.
Interestingly, Japanese people do not have high rates of allergies, despite being quite urbanized and clean. However, the Japanese regularly eat beans and pickled and fermented foods, which leads to lots of SCFAs when they are broken down during digestion. This is compelling but I’m not ready to throw out the hygiene hypothesis in favor of the fiber hypothesis. I think there is probably a degree of truth to both of them.
This is my summary of a recent journal article. If you would like to read it, here’s the reference: Maslowski, K. M. & Mackay, C. R., Nature Immunology, v. 12, no. 1, p. 5, Jan 2011.