Flashback Friday: Best Food to Counter Stress-Induced Immune Suppression

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

“Natural immunomodulators 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 side 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…and…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?

First of all, 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, nonspecific immune booster, across the board.

Beta-glucan supplementation can increase the levels of immunoglobulin A in the saliva within four days, at a daily dose of 400mg, but not 100mg. So, the amount found in about two teaspoons of nutritional yeast a day; 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 serious 50-minute bout of strenuous cycling in a hot, humid 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 tablespoon’s worth a day. What we care about, though, are clinical outcomes. Do those consuming beta-glucans suffer significantly fewer infections?

Okay. How about a double-blind, randomized, placebo-controlled nutritional study to see if yeast beta-glucan can improve our “immune defense system.” 100 people followed for 26 weeks; 50 getting about a tablespoon of nutritional yeast worth of beta-glucan a day; 50 getting a 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. 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-glucans for 12 weeks were 60% less likely to report experiencing symptoms, like sore throat, stuffed or runny nose, or cough—strongly suggesting that baker’s, brewer’s, 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.

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Original layout with photos from Andrew Gaines, skeeze, and MasimbaTinasheMadondo. Images have been modified.

Motion graphics by Avocado Video