 Natural immuno-modulators are getting more and more popular, things that might naturally regulate our immune system. That popularity, however, often brings over-optimistic claims and mediocre effects. Such mythical beasts have been sought after for centuries. The current market is full of all sorts of supplements promising the golden fleece inexpensive no-sat effects, yet actively boosting our immune system. Many simply repeat unjustified claims with hardly any science to support them. On the other hand, there is beta-glucan, which has undergone 10,000 scientific studies in clinical trials. Wait, what? Beta-glucan is the fiber in nutritional yeast I talked about before, able to decrease episodes of common illnesses in young children. But what about in adults? Well, why can't they just come up with a vaccine against the common cold virus? Because there is no single common cold virus. There are hundreds of different viruses implicated in causing cold-like symptoms. So that's why there's so much interest in finding a general non-specific immune booster across the board. Beta-glucan supplementation can increase the levels of immunoglobulin A in the saliva within four days, a daily dose of 400 milligrams, but not 100 milligrams. So the amount found in about two teaspoons of nutritional yeast today, but not a half teaspoon. IGA is an antibody that plays a crucial role in the immune function of our moist membranes, like eyes, nose, and mouth. One teaspoon's worth didn't do much until they exercised. Two hours after a strenuous 50-minute bout of strenuous cycling in a hot human environment, those who had been on the yeast beta-glucan did get that IGA boost. Beta-glucans failed, however, to boost the antimicrobial activity of white blood cells taken from subjects who had been taking, like, a tablespoons worth a day. What we care about, though, are clinical outcomes. Do those consuming beta-glucan suffer significantly fewer infections? OK, how about a double-blind, randomized, placebo-controlled nutritional study to see if yeast beta-glucan can improve our immune defense system? A hundred people fall for 26 weeks, 50 getting about a tablespoon of nutritional yeast worth of beta-glucan a day, 50 getting placebo, and they just counted how many episodes of the common cold they got, and there was no significant difference. Now, if you just look at the first half of the time during cold season, there did appear to be fewer infections in the active group, meaning the beta-glucan group, but this is what's called a post-hoc analysis, where you go back and look at your data after the fact, which is frowned upon by the scientific community, because it increases the likelihood that your findings are just due to chance. But those who did end up getting sick while on the beta-glucan did genuinely appear to suffer milder symptoms. A similar larger study had similar findings. Maybe the severity of the colds was lessened, but in the main analysis, no significant difference in the number of times people got colds in the first place. Same in other studies, no significant differences in the number of symptomatic respiratory infection episodes, no significant effect on upper respiratory tract infection outcomes, so overall pretty disappointing results. But wait a second, what about my video about preserving immune function in athletes with nutritional yeast? They found a significant drop in cold symptoms, two weeks and four weeks after a marathon at both one teaspoon of yeast worth of beta-glucan a day and two teaspoons. Yeah, but they had just run a marathon. Remember this study where the effect only seemed to emerge after strenuous exercise? That's where beta-glucan seems to shine, counteracting the toll extreme physical exertion can have on our immune function. In an athlete that just may mean some lost practice days or something, but for soldiers or firefighters maintaining one's health, even in the context of heavy physical stress, could be critical. Okay, but that's counteracting the effects of physical stress. What about mental stress? Stressful life events can impair our moist membrane defenses, such that psychological stress has also been shown to increase susceptibility to the common cold, getting more colds and worse colds than people under less stress. So let's see if we can help, and indeed in this study of healthy women under moderate levels of perceived psychological stress, those taking about a teaspoon of nutritional yeast a day worth of beta-glucan for 12 weeks were 60% less likely to report experiencing symptoms like sore throat, stuff to runny nose, or cough, strongly suggesting that bakers, brewers, and nutritional yeast beta-glucan is able to counteract the negative effects of stress on the immune system. And they experienced 41% greater vigor, which is a measure that encompasses physical energy, mental acuity, and emotional well-being, so they just felt better too. Put all the studies together, and yeast beta-glucans do appear to have immune strengthening effects, at least in children, and those under physical or mental stress.