A friend of mine was kind enough to lend me some DVDs of a BBC series called The Truth About Food. So far I have been able to watch about two episodes and am enjoying the questions that they are raising about how certain foods might actually help improve disgestive function, sexual function, etc. One of the questions that was raised was whether or not yogurt (or yoghurt, depending on which side of the Atlantic you are spelling it in), which contains pro-biotics or "good" bacteria, can actually help increase the "good" bacteria in your digestive system.
Sidebar: While I am finding this show interesting, and somewhat entertaining, so far, I have one major quibble about this show. All of the little "experiments" that they are doing are not necessarily double blind, and they are usually so small as to not be able to extract that information to the general public. I think they are missing out on a huge opportunity to explain how the scientific method works, how to look at news reports critically, etc. Curmudgeon duties over.
First of all, let me point you back to this article, which I have quoted before, for a little primer on probiotics from ScienceBasedMedicine.org: Probiotics. Read it? Good. What I would like you to remember for this situation is that the body sees the bacteria in the yogurt as a foreign object, and since the digestive system works as a "first defense" in your immune system, then your body is going to try to push the foreign objects out. So it was no surprise to me that on the TV show the small group of people that ate yogurt for a week (and pooped into a bucket so the sample could be collected) did not increase the favorable bacteria in the gut. The group that ate a lot of leafy greens (that happend to be high in pre-biotic fiber), actually did have an increase in "good" bacteria. And though this was a small study, there has been more research that indicates that eating a variety of plants seems to be more beneficial for feeding the favorable gut. So it looks like eating yogurt won't help increase the general favorable bacteria in your gut.
But my doctor told me to eat yogurt when I was put on antibiotics for an infection!
Right, and Dr. Crislip mentioned this in the above listed blog post. He reminds us that antibiotics can "kill off" the good bacteria as well as the bad, leaving room for the "even worse" bacteria, like C. difficile, from moving in. Think of the probiotics in the yogurt or capsule as a placeholder, albeit a temporary one, that keeps the bad guys out until you can replenish your good guys.
What about those advertisements that tell you to eat yogurt to keep things "regular?"
I'm sure you are thinking of Activia, and the reason that I don't usually watch TV is so that I don't have to hear more than I wanted to know about celebrity digestive systems. Remember what I said about your body trying to push the "foreign objects" out? When you eat the yogurt, you will likely experience an increase in your bowel movements because your body is trying to push the foreign object out. So, if you eat the Activia light, you just ate 70 calories and 11 grams of carbohydrate that you may or may not have needed to have, when you could have just taken a laxative or a probiotic capsule. If you have trouble with constipation, defined as less than three bowel movements per week, you might need to increase your vegetable intake, exercise more, and/or cut out your refined flours. (In my patients, we also have to consider what medications they are taking that might be causing a problem, and if they have a longstanding history of diabetes, we have to consider more serious conditions like gastroparesis).
But I like yogurt!
That's ok, foods that are fermented are often more easily digested by those of us that have Irritable Bowel Syndrome or other digestive conditions; therefore, people who are lactose intolerant can usually tolerate yogurt because the good bacteria breaks down the lactose. Yogurt is also a good source of protein and calcium, and the creamier yogurts are quite satiating/satisfying. Just avoid the yogurts that have sugar added; your best bet is to get plain Greek yogurt and sweeten it yourself so you don't wind up with a bunch of extra calories or carbodrates,
Take home message--No sugar added yogurt can be a good snack, but maybe not for the reasons you think.