How to Prevent & Treat Colds & Flu

KEYPOINTS

• 01

  Cold viruses usually get in through the eyes

  Cold viruses are tiny, travel through the air and skin contact, and can survive on surfaces for up to 24 hours. Huberman says the most common route of infection is touching your eye region, and the mouth and lips much less often. Symptoms typically show up 1–2 days after exposure.

• 02

  Exposure doesn't guarantee infection

  Even with a serotype you've never encountered, a well-functioning immune system can fight off the virus before you get sick or pass it on. That's why most of the episode focuses on tools that strengthen innate immunity.

• 03

  'I'm past the contagious stage' is usually a myth

  You're most contagious when you feel worst, and still contagious as you start to recover. Most data suggest the contagious phase ends about 5–6 days after your worst symptoms. Anyone still sneezing, coughing, blowing their nose or waking up groggy is still a 'walking, talking' vector and should stay home where possible.

• 04

  A flu shot is a bet on which strains are circulating

  Huberman personally doesn't usually get the flu shot, but frames it as an individual decision to make with your physician. He suggests weighing it more heavily if you live with immune-compromised family, work in a school or have high exposure. He also notes most people can't reliably tell whether they have a cold or flu.

• 05

  Nasal breathing protects the upper airway

  Breathing through your nose, except when talking, eating or exercising hard, keeps the nasal microbiome healthy and diverse. Huberman cites a study of mouth-breathing children showing altered oral and nasal microbes and more upper-respiratory infections, plus the book 'Jaws' by Stanford colleagues. Nasal breathing also warms incoming air, which makes it harder for viruses to embed in the nasal lining.

• 06

  Up to 60 minutes of hard exercise boosts innate immunity; marathon-level loads suppress it

  Citing a 2019 review in the Journal of Sport and Health Science, Huberman says sessions of 60 minutes or less at high subjective effort (not all-out) improve exchange between blood and lymph and keep innate immune activity raised for up to 24 hours. Brisk 60-minute walks increase T-cell, natural killer cell and macrophage activity. People training for or just finishing a marathon show sharply reduced T-cell and NK function and very high stress hormones and inflammatory cytokines.

• 07

  After a bad night, sleep first; if you can't, train lighter

  If you can go back to sleep, that's the better choice. If you can't, exercising at 25–50% lower intensity and duration can offset some immune and blood-sugar effects of one night's sleep loss and help you fall asleep on time that night. Exercise is not a replacement for sleep.

• 08

  Zinc has the strongest supplement evidence, at the right dose

  Doses below about 75 mg don't seem to work; around 100 mg (once, or as two 50 mg doses) does, taken with a meal because zinc on an empty stomach causes nausea. Adults over 65 may benefit most. Children under 15 shouldn't take much zinc, and pregnant women should ask their doctor first.

• 09

  Vitamin C megadoses are probably not worth it

  There's weak evidence that 6–8 g a day might delay or shorten a cold, at the cost of likely stomach upset. A 2023 meta-analysis of nine randomized trials claiming a benefit was retracted because placebo groups had been double-counted. If your diet or a multivitamin covers vitamin C, extra is probably a poor immune investment.

• 10

  Vitamin D matters most if you're deficient

  An individual-participant meta-analysis of more than 20 randomized trials found supplementation reduced acute respiratory infections overall, and deficient people have weaker immune function. Huberman says most physicians would consider 1,000–2,000 IU a day safe for most people, but you need blood work to know whether you need more.