Chapter 106
Garlic
During World War II, garlic was called “Russian penicillin,” because the Soviet government turned to it when it ran out of antibiotics. Does garlic actually work? It appears to have two major advantages: It dampens an overreaction of the immune system by suppressing inflammation, and it strengthens protective immune functions such as natural killer cell activity. At see.nf/coldsandcancer there is information on placebo-controlled double-blind studies with garlic for the prevention of colds and cancer. (Garlic supplements did not appear to protect against Covid, but to get the same garlicky benefit as in a raw, crushed clove, you would have to take up to 54 capsules.)
What happens when you cook it? If you compare raw, chopped garlic with garlic cooked in various ways, you can see a dramatic decline in one of the presumed active components. After six minutes of boiling, the amount drops by 66 percent; after 15 minutes of simmering, by 94 percent; and after one minute of frying, it is destroyed 100 percent. And roasted garlic? Surprisingly, roasting—although hotter than boiling water—preserves about twice as much. Raw garlic has the highest amount, but some people may prefer to eat two or three cooked garlic cloves rather than the equivalent (half a clove) of raw garlic.
As I already said in How Not to Die, the only major caveat with garlic (aside from being less tempted to kiss) is that it has a blood-thinning effect, which is why you may not want to eat any for a week before a planned surgery. That is the result of a study in which participants were given 10 grams of garlic daily for two months, about three cloves a day. At a more “socially acceptable” dose of one to two cloves a day for a week, however, no changes in blood clotting have yet been found. And how do you get rid of garlic breath? Raw apple, raw head lettuce, and mint leaves have proven at least partially effective.
Mushrooms
As I show in the video see.nf/mushrooms, cooked white button mushrooms can also stimulate IgA production and, in addition, dampen overactivity of the immune system. A randomized placebo-controlled clinical double-blind study found an antiallergic effect of a component of oyster mushrooms in children who had suffered recurrent upper respiratory tract infections in the past.
Shiitake mushrooms have also been shown to improve immune defenses in humans. Eating just two or three large dried shiitake mushrooms per day for a month increased the proliferation of two cell types of the innate immune system while simultaneously lowering markers of systemic inflammation. Our biggest concern, however, is preventing infections.
Supplementation with white button mushrooms, for example, increases natural killer cell activity in old mice but does not protect them from a subsequent influenza infection. Oyster mushrooms seem to do that—at least in athletes. In elite athletes, natural killer cell activity can drop by 28 percent during the recovery phase after intense training. When they were given the daily equivalent of a special beta-glucan fiber from an oyster mushroom, not only did their natural killer cell count rise, but they also experienced fewer upper respiratory complaints over three months. In the placebo group, 84 percent suffered from four or more symptoms, whereas in the mushroom group, only 12 percent did.
Nutritional Yeast
That same immune-activating beta-glucan fiber is also found in brewer’s, baker’s, and nutritional yeast. Details at see.nf/nooch, but in short, the beta-glucan from about a heaping teaspoon of nutritional yeast a day can boost IgA in a way that reduces the frequency, duration, and severity of upper respiratory infections more than a placebo. And what is the downside—that your popcorn tastes better with yeast? Randomized controlled trials also found an anti-inflammatory effect sufficient to improve wound healing, reduce the severity of canker sores, and alleviate symptoms in ragweed allergy sufferers (ragweed), and it also helps with weight loss. None of the studies reported treatment-related side effects, but I would advise people with two particular autoimmune diseases against using any kind of yeast: Crohn’s disease (see.nf/crohns) and the skin disease hidradenitis suppurativa (see.nf/hidradenitis).
Green Tea
Our bodies are constantly on the lookout for PAMPs, pathogen-associated molecular patterns. These are foreign molecules that indicate infections, such as components of bacterial cell walls. We have immune cells with pattern-recognition receptors that recognize these “non-self” signatures. But since not all bacteria are pathogenic, the term was refined to MAMPs (microbe-associated molecular patterns). The beta-glucans in yeast and mushrooms are important MAMPs. They make up fungal cell walls and therefore act as nonspecific immune stimulants (in contrast to a specific immune stimulant like a vaccine). In short, when our bodies detect beta-glucans in the system, they play it safe and don’t celebrate the shiitake stir-fry—they diagnose a fungal infection. This heightened vigilance benefits us.
Some plants mimic MAMPs. Bacteria, fungi, parasites, and tumor cells release a group of MAMP compounds called alkylamines. Theanine, the unique amino acid that gives tea its pleasant (umami) flavor, is broken down in the gut into the alkylamine ethylamine, which then circulates in the body. You can tell whether someone is a tea drinker by testing their urine for ethylamine. Alkylamines are also found in apple peels (n-butylamine), wine (isoamylamine), and healthy vaginal secretions (isobutylamine).
Alkylamines enhance the proliferation and activity of gamma-delta T cells, a cell type of the innate immune system. The “priming” of these cells by ethylamine could explain why gamma-delta T cells are more active in tea drinkers than in coffee drinkers. If white blood cells are taken before and after a week of tea drinking, two to four times more interferon is released in vitro after bacterial exposure. The daily low-level ethylamine exposure appeared to keep immune cells in a constant state of readiness. It has even been speculated that primate immune systems evolved to take advantage of the immune-boosting properties of alkylamines and their precursors in plant foods.
Tea drinkers have been shown to get the flu less often, and their risk of dying from pneumonia is only half as high. A randomized placebo-controlled double-blind study found that those who took capsules of green tea concentrate had cold and flu symptoms on only about two thirds as many days as the placebo group, though the dose used was equivalent to ten cups of tea per day. A subsequent similar study in health care workers found that those randomized to receive the equivalent of only one and a quarter cups of green tea per day for five months were three times less likely to get the flu (4 percent versus 13 percent in the placebo group). How low can you go with the dose? In 2020, researchers wanted to push the limit and found that even the equivalent of half a cup of green tea per day (that is, about a small teacup) cut the risk of an upper respiratory infection in half, but less than a quarter cup per day no longer did anything.
Does it help to gargle with green tea?
In a study in which oral swabs were taken from volunteers 10, 40, and 60 minutes after drinking tea, it was shown that even an hour after drinking, an antiviral concentration of the tea’s components was present in the oral cavity. The studies mentioned above found that infection risk also declines when you swallow capsules of green tea extract, so direct contact with the throat is not even necessary. And the opposite of that? If you only gargle green tea and then spit it out, so there is only oral contact?