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.

In 1989, the late Charles Janeway gave a presentation that was to revolutionize our understanding of the immune system. He proposed that we must have some ancient, innate first-line-of-defense. We knew about vaccinations for centuries—how our bodies can learn from past infections, but he figured that’s not good enough. Our body must have evolved some way to recognize foreign invaders the first time they invade. He proposed that the way our immune cells discriminate between self and non-self—our own cells vs. invading microbes—may arise from pattern-recognition receptors; we’re just born with the ability to “recognize patterns of microbial structure.”

For example, there’s a unique component of fungal cell walls that naturally stimulates our immune system, called beta-glucan. Our own cells don’t produce it, but fungal pathogens, like candida, do. Candida is a type of yeast that can cause serious blood infections; so, it’s a good idea our immune system recognizes it right off the bat. So yeah, you could stimulate your immune system injecting candida into your veins—but then, you also might die. Luckily for us, non-disease-causing yeasts, like Saccharomyces cerevisiae, which is what baker’s yeast is, and brewer’s yeast, and nutritional yeast, also have that same molecular signature, that beta-glucan. So, the drug industry is all excited about capitalizing on this “powerful immunostimulatory response” to develop new anti-infection, anti-cancer therapies. Yeah, but does it have to be injected into the vein? What happens if you just eat some nutritional yeast?

Our digestive tract is our largest point of contact with the outside world—more surface area exposed than our lungs and skin put together. And so, not surprisingly, most of our immune cells are concentrated along our intestinal wall. But, they don’t just stay there. Once they’re tipped off to what’s happening in the gut, they can go off to defend other parts of the body. That’s why you can give an oral cholera vaccine, for example, and end up with cholera-fighting immune cells in your salivary glands, pumping out antibodies into your saliva to protect against infection.

So, what if we sprinkled some nutritional yeast on our kids’ popcorn for a snack? Might that help marshal defenses throughout their bodies? Adults tend to just get a few colds a year, but “the average schoolchild” can come down with a cold every other month. And, what can we really do about it? Modern medicine has “little to offer for” run-of-the-mill common colds. Nevertheless, doctors still commonly prescribe antibiotics, which can do more harm than good. “Clearly, there is a need for effective, safe, and inexpensive treatment[s].” And, “β-Glucan [may] be just the right solution.” But, you don’t know, until you put it to the test.

So, researchers performed “a randomized, double-blind, placebo-controlled trial” of about a half-teaspoon of nutritional yeast worth of beta-glucan in children who suffered from like repeated respiratory infections, and after a month, found a significant increase in salivary lysozyme levels, compared to control. Lysozyme is an important protective immune component of our eyes, nose, and mouth. But, a larger follow-up study reported the opposite findings—an apparent drop in salivary lysozyme levels. Though the researchers claimed this was “accompanied by pronounced improvements in…general physical health,” no data are given.

But the only reason we cared about the lysozyme levels, though, was because we were hoping it would result in fewer infections. But, that had never been directly studied—until now.

The title kinda gives it away, but basically, a “randomized, double-blind, placebo-controlled trial” was performed to see if just a dusting of nutritional yeast worth of beta-glucan a day could reduce the number of episodes of common childhood illnesses. “During the 12-week course of the study, 85% of children in the placebo group experienced one or more episodes of infectious illness.” Here it is, graphically: 85% got ill in the sugar-pill group, but just taking like an eighth of a teaspoon of nutritional yeast worth of beta glucans, or even just a 16th of a teaspoon’s worth, appeared to cut illness rates in half. And, those on the yeast that did come down with a cold only suffered for about three days, compared to more than like nine days in the placebo group.

The researchers conclude that by giving kids the yeast beta-glucans, we “could decrease the incidence and severity of infectious illness during the cold [and] flu season,” and thereby benefit the parents as well.

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