Which Comes First, Cardio or Weights_ - Alex Hutchinson [89]
A number of studies have shown that certain probiotic strains can help boost immune function. For instance, antibiotics often kill off some of the beneficial bacteria that live in your gut, an outcome that can leave you susceptible to gastrointestinal problems like diarrhea. A recent analysis of 34 different studies concluded that several strains of probiotics (S. boulardii, L. rhamnosus, L. acidophilus, and L. bulgaricus) all reduced the risk and severity of antibiotic-related and traveler’s diarrhea. There’s also some evidence that probiotics can enhance the mucous lining of the respiratory tract, to help prevent viral infections like colds and coughs.
Because the extreme effort associated with something like marathon training can leave your immune system temporarily depleted (see Chapter 1), athletes have been particularly interested in the potential benefits of probiotics. In a 2008 study at the Australian Institute of Sport, 20 elite runners spent four months of winter training taking capsules containing either Lactobacillus fermentum or a placebo. By the end of the study, the number of days during which the runners reported symptoms of respiratory infection was 2.4 times higher in the placebo group than in the probiotic group, and the symptoms were more severe on average in the placebo group. The researchers also took blood samples that showed elevated levels of interferon gamma, a marker of immune function, in runners taking the probiotic.
Another study monitored 141 runners training for the Helsinki marathon, giving them capsules containing either Lactobacillus rhamnosus or a placebo for three months leading up to the race and monitoring them for a further two weeks afterwards. In this case, there was no difference in the number of respiratory infections or gastrointestinal “episodes” reported by the two groups. However, there was a trend for GI problems to clear up more quickly in the probiotic group (2.9 days for problems before the marathon and 1.0 day after the marathon) compared with the placebo group (4.3 days before and 2.3 days after).
These results are definitely encouraging—the problem is that every individual strain of probiotic bacteria has different effects, and there’s not yet any consensus about which ones are best or how much we need to take. Fortunately, this is one of those cases where it makes sense to incorporate foods like yogurt with live bacterial cultures into your diet even though the scientific research is still incomplete. Even if the probiotics don’t do anything for you, you’ll still have eaten a bunch of nutritious (and tasty) food.
Will vitamin D make me a better athlete?
In a 2009 study, researchers from the University of Manchester in Britain asked 99 adolescent schoolgirls to perform a series of one- and two-legged jumps, then took blood tests to see how much vitamin D they had in their bodies. There was a clear correlation: the more vitamin D, the higher, faster, and more powerful the jumps. To many, this was confirmation of what they’d suspected for some time: the “sunshine vitamin” could turn out to be the ultimate natural performance enhancer. But it’s not quite that simple.
D has been the star vitamin of the past few years, piling up study after favorable study even as the claims of its fellow vitamins are steadily being debunked. According to various studies, vitamin D fights cancer, builds bones, combats heart disease, tunes up your immune system, and provides a long list of other benefits. Since it’s produced in the body as a response to ultraviolet light from the sun, people who live far from the equator are particularly at risk of deficiency in winter—which may explain why diseases like lung cancer and breast cancer are most likely to kill you if you’re diagnosed during those gloomy months. You can get some vitamin D from sources like fatty fish and fortified milk, but the vast majority comes from either sunlight or supplements.
Interest in the sun’s potential as a performance booster dates back at least to a rudimentary Russian study in 1938 in which four students