How to Prevent & Treat Colds & Flu

High-Level Overview

In this solo episode, Andrew Huberman explains what colds and flu actually are, how they spread, how your immune system fights them, and which behaviors, foods and supplements have real scientific support for preventing them or getting over them faster. He clears up common myths, including that cold weather gives you a cold and that you stop being contagious once you have "had it for a few days," and walks through the three layers of immune defense: physical barriers, the fast but general innate immune system, and the precise, memory-forming adaptive immune system.

With that foundation, he turns to practical tools: being mindful of touching your eyes and face, nasal breathing, supporting the gut and nasal microbiome, sleeping enough, exercising at the right intensity and duration (and not too much), eating carbohydrates after long fasted workouts, and using the sauna. He then grades the popular remedies, from vitamin C and echinacea to vitamin D, zinc and N-acetylcysteine. The tone is practical and myth-busting, occasionally blunt about people who go to work sick, and grounded in personal experience alongside studies. The episode moves from virology to immunology to a clear list of do's and don'ts.

The Discussion Explores:

• Why there is no cure for the common cold, and why cold temperatures do not cause colds
• How colds and flu spread, how long they survive on surfaces, and when you are contagious
• Flu types, the Spanish flu, H1N1, and how effective flu shots are
• The three layers of the immune system: physical barriers, innate immunity and adaptive immunity
• Why we touch our faces after shaking hands, and why nasal breathing and the microbiome matter
• How exercise can strengthen or weaken the innate immune system, depending on dose
• Sauna as a tool for boosting innate immune activity
• What the evidence says about vitamin C, vitamin D, echinacea, zinc and NAC

Deep Dive into Main Ideas

Why there is no cure for the common cold

Huberman opens with the bad news: there is no cure for the common cold, because "the cold" is really more than 160 different serotypes of rhinovirus, each with a different shape on its surface. Antibodies your body made against one serotype cannot latch onto the next, which is why you can catch several colds in a single year or season.

He also dispels the classic parental warning that going outside without a jacket will make you "catch cold." Cold temperatures do not cause colds. Colds are more common in winter because people spend more time indoors, touching each other and shared surfaces and breathing on one another. The virus spreads through breathing, sneezing and coughing, and from hands to surfaces to other people's hands, and it can survive on skin, tables, glasses or door handles for up to 24 hours. That does not mean touching a contaminated handle will make you sick; your skin is an excellent barrier with its own antiviral substances. The virus mostly needs to reach your eyes, and less commonly your mouth.

When you are contagious, and the flu

People typically develop cold symptoms one to two days after exposure, and exposure does not guarantee infection if your immune system fights the virus off. You are most contagious when you feel your worst but can still be contagious as you improve; roughly five to six days past the worst point, you are probably leaving the contagious phase. Huberman is blunt about people who show up at the gym or work still sneezing and coughing while insisting they are no longer contagious: they are essentially walking virus vectors, and "you're lying." If you have symptoms, stay home and away from others as much as possible. Colds can range from mild to severe, with real financial and health costs.

Influenza comes in A, B and C types, with strains named for their surface proteins, such as H1N1. The Spanish flu, an A-type H1N1 virus that he notes probably did not originate in Spain, killed somewhere between 17 and 50 million people in four waves between 1918 and 1920, and some H1N1 cases have been reported this season. Flu viruses survive only about two hours on surfaces, so they spread mainly person to person. People start shedding the virus about 24 hours before their first symptoms and are most contagious during the three days they feel worst.

Because fewer flu strains circulate each year, seasonal flu shots are possible. Huberman says studies show they reduce the risk of catching the targeted strains by about 40 to 60% and can reduce severity, but do nothing against other strains or colds. He personally does not usually get one, since he does not work in a hospital or interact with large numbers of people daily, but says others, such as teachers or those with immune-compromised family members, should weigh it with their physician.

Tracking your own patterns

Huberman keeps a quick daily log of workouts, their intensity and his sleep, taking about 30 seconds, which lets him look back at what preceded each serious cold or flu. His colds have become less frequent over the years, from about once a year a decade ago to roughly once every 18 to 24 months. The patterns that preceded getting sick: two hard workouts in one day, hard workouts followed by cold exposure while traveling, especially overseas, and nights of two hours of sleep or less. He recommends everyone try this kind of simple self-tracking.

The immune system's three layers

The first layer is physical: skin plus its openings. The eyes have tears and antibacterial agents (the crust you wipe away in the morning is, he says, dead bacteria from a battle won overnight), and the retina at the back of the eye is actually brain tissue, not far from the outside world. The nose and mouth have sticky mucosal linings with chemicals and microbiota that trap and neutralize viruses. ("Get your fingers out of your nose please," he jokes.) The genital and rectal openings have their own linings, but the main entry points for colds and flu are the eyes, nose and mouth.

The second layer is the innate immune system, a fast, nonspecific response that does not care whether the invader is a cold, a flu, a bacterium, a fungus or even a physical object. Viruses hijack your cells' genetic machinery to replicate, and white blood cells such as neutrophils, natural killer cells and macrophages rush to the site. The complement system marks infected cells with an "eat me signal, while damaged cells release a help me" signal that draws in cytokines like interleukin-1, interleukin-6 and TNF-alpha. Blood flow increases, mast cells release histamine, and the area swells, much like emergency crews converging on a car crash. Often, the innate system beats the virus before you ever get full-blown symptoms.

The third layer is the adaptive immune system. It first produces IgM antibodies that fit the invader's surface fairly well, then refines the fit and produces highly specific IgG antibodies. It also keeps a memory of the battle in stem cell populations, such as in the bone marrow, so if the same serotype or strain returns it can be neutralized immediately. The lymphatic system works alongside the blood, filtering material and helping produce useful chemicals, which becomes important when talking about exercise.

Hands, faces and nasal breathing

Studies from Noam Sobel's lab at the Weizmann Institute show that after shaking someone's hand, people very often touch their eyes, the area around them, or their upper lip, likely to unconsciously sample the other person's chemical signals. Sobel's work also suggests we smell ourselves throughout the day. Being aware of this reflex, especially in the roughly 30 seconds after a handshake, and perhaps using hand sanitizer even if it feels awkward, can reduce infections. Huberman stresses he is not telling people to stop touching, since touch is important for connection, but "just like you can't get eaten by a shark if you never go in the ocean," less contact means fewer infections.

Nasal breathing is another zero-cost tool. The nasal microbiome appears to be the most effective at fighting incoming viruses, and nasal breathing keeps that environment healthy and warms incoming air in a way that makes it harder for viruses to embed. He cites a study on altered oral and nasopharyngeal microbiota in mouth-breathing children, who tend to get more upper respiratory infections, a paper on the human nasal microbiota, and the book Jaws by his Stanford colleagues on the importance of nasal breathing. His advice is to breathe through your nose whenever you are not talking, eating or exercising hard.

Sleep, stress, nutrition and the gut microbiome

The basics are the bedrock: enough quality sleep (even getting only 50 to 75% of what you need weakens innate immunity), adequate nutrition (a prolonged caloric deficit, like dieting through winter, can compromise immunity, though brief fasting has been implicated in some improvements), and stress management with nuance. Chronic stress and stress that disrupts sleep impair immunity, but short bouts of stress can enhance it. Cortisol, he says, is not simply bad; it is needed early in the day, and too little is bad for immune function because glucocorticoids help activate natural killer cells and deploy interleukins. Inflammation is a tool you want available, just not so much that it wrecks sleep and gut health.

For the gut microbiome, which runs from the mouth all the way through the digestive tract, he repeats Justin Sonnenburg's recommendation of two to four servings per day of low-sugar fermented foods such as refrigerated sauerkraut with live cultures, kimchi, kefir, kombucha, pickles kept refrigerated and yogurt with active cultures. He also shares an unusual habit he started about four months earlier: on waking, before brushing, take a sip of water, swish it around and swallow it, to carry oral bacteria that accumulated overnight into the gut. He admits there are no randomized controlled trials and that it may be a placebo effect, but says it is free, logical and does not taste bad.

Exercise: the right dose helps, too much hurts

If you feel whole-body malaise, unexplained fatigue or a throat tickle, Huberman advises against exercising: take a hot shower or bath and get into bed early, because pushing through will likely make you sicker. That sleepiness is itself part of the immune response, as interleukin-1 and interleukin-6 act on serotonin neurons in the dorsal raphe nucleus, which in turn act on sleep-promoting areas of the hypothalamus. If you are already sick with symptoms, do not exercise at all, even at home.

When you feel well, exercise can prime the innate immune system. Citing a 2019 review in the Journal of Sport and Health Science titled The compelling link between physical activity and the body's defense system, he explains that sessions of 60 minutes or less at a hard but not all-out effort increase exchange between blood and lymph and raise baseline innate immune activity for many hours, perhaps up to 24. Even 60 minutes of brisk walking increases T cell and natural killer cell activity and macrophage function, with mild increases in cytokines and stress hormones. Benefits can come from as little as 20 minutes a day, or even 12 minutes if it is very high intensity, like his weekly sprint session.

By contrast, people who have just run a marathon, or are deep into marathon training, are severely immune compromised, with T cell and natural killer cell function well below baseline and stress hormones and cytokines very high. He is not discouraging marathons, only urging people to understand the trade-off. His own approach: warm up 5 to 10 minutes, keep workouts to about 50 to 60 minutes, be careful about exceeding 75 minutes, avoid two hard sessions in one day, and take one day a week off. After a single bad night of sleep, going back to sleep is better if possible; if not, exercise early at 25 to 50% reduced intensity and duration, never sacrificing sleep for exercise. After long fasted morning workouts, especially beyond 60 to 75 minutes, eating complex carbohydrates like rice, oatmeal or pasta and some fruit within about an hour can reduce inflammatory markers by about 30 to 40% compared with water alone.

Sauna for immune support

A 2023 study on Finnish sauna sessions in trained and untrained men used ten sessions over three weeks, each consisting of three 15-minute rounds separated by two-minute cool showers. Huberman suggests roughly 176 to 210 degrees Fahrenheit depending on heat adaptation, with the usual safety cautions, and not for pregnant women or children. Each session raised cortisol, and white blood cell (leukocyte) counts increased, though in trained athletes the change only reached significance after the final session, likely because heat-adapted people need a stronger stimulus. He explains that the discomfort in a hot sauna, partly from dynorphin release, is the trigger for later adaptations and feelings of well-being. His takeaway: regular sauna, in three 15-minute rounds or one or two longer rounds of 20 to 30 minutes, can boost innate immune activity, but not if you are already feeling run down or sick.

What to take: vitamin C, vitamin D and echinacea

Asking on Instagram and X, he received thousands of answers, from chewing raw garlic cloves daily to fermented garlic, echinacea, vitamin C and zinc. Vitamin C, championed by Linus Pauling, has weak evidence at best: perhaps six to eight grams a day might modestly delay or shorten a cold, and doses that high often cause gastric distress. He points to a 2023 paper whose title begins with the word Retraction: a meta-analysis of nine randomized controlled trials suggesting extra vitamin C shortens colds was retracted after placebo groups were double counted. If you get enough vitamin C from food or a foundational supplement, high doses are probably not worth it for immunity.

Vitamin D deficiency is linked to weaker immune function and more respiratory infections, and a large meta-analysis of 25 randomized controlled trials found supplementation reduced acute respiratory infection risk to a small to moderate degree. But low vitamin D may partly reflect less sunlight, which has many immune-supporting effects of its own. He suggests 1,000 to 2,000 IU a day is probably safe for most people, some need 5,000 to 10,000 IU based on blood tests, and very high doses can be harmful if levels are already sufficient. Echinacea, he says, does not do much if anything according to the data, and high-dose continuous use may even impair innate immunity, so if people insist on using it, they should limit it to periods of feeling run down and no more than four weeks at a time.

Zinc and N-acetylcysteine

Zinc has pretty good data, especially for colds, but the dose matters: under 75 milligrams does not work, and 100 milligrams or more does. Take it with a meal, since he once felt nauseous after 50 milligrams on an empty stomach, and consider splitting it into two 50-milligram doses. One study found people taking 90 milligrams a day of zinc acetate recovered from colds three times faster. People over 65 may benefit most, while children under 15 and pregnant women should be careful and consult a doctor. Most evidence is for colds, but a physician he consulted saw no reason not to take zinc for flu.

N-acetylcysteine (NAC) is a precursor to glutathione, the master antioxidant that counters reactive oxygen and nitrogen species that rise during infection, and it is a powerful mucolytic that loosens mucus. During a nasty cold last winter, Huberman took 600 to 900 milligrams three times a day and found it relieved his sinus pressure, though it produced what he calls a "post nasal waterfall," so he stopped taking it close to bedtime. He prefers it to over-the-counter alpha-1 agonist decongestants, which can cause rebound congestion and be habit-forming. A 1997 study of 600 milligrams twice daily for six months found that 79% of infected people in the placebo group developed clinically apparent flu versus only 25% in the NAC group. An intensive care physician who deals with H1N1 patients told Huberman that he and colleagues take NAC preventively. Huberman notes more randomized trials are needed, that NAC is still available over the counter in the US after an FDA challenge tied to unsupported marketing claims, and that people can reasonably choose simpler remedies like sleep, a hot shower, chicken soup or ginger tea instead.

Conclusion

Huberman's playbook for cold and flu season is mostly behavioral and mostly free. Understand that colds and flu spread through people and surfaces rather than cold weather, that you can be contagious before symptoms and while still symptomatic, and that the eyes, nose and mouth are the main doors in. Keep your hands away from your face after contact, breathe through your nose, feed your microbiome with low-sugar fermented foods, protect your sleep, and exercise regularly at moderate to high intensity for about an hour or less, while avoiding marathon-level efforts and never training through illness. Sauna can add an immune boost. Among supplements, zinc at 90 to 100 milligrams with food has the best support for colds, NAC is promising, vitamin D helps those who are low, and high-dose vitamin C and echinacea largely fail to deliver. And if you are sick, rest, recover and stay home.

This is a summary of "How to Prevent & Treat Colds & Flu" from Huberman Lab, giving you the GIST so you can decide if you want the REST. Listen to the full episode.