How to Enhance Your Immune System

High-Level Overview

Andrew Huberman talks with Dr. Roger Seheult, a board-certified physician in internal medicine, pulmonary disease, critical care and sleep medicine who works in the intensive care unit at Loma Linda University and teaches through his MedCram channel. The conversation is a practical guide to avoiding colds, flu and other infections, and to getting through them faster when they strike. Dr. Seheult organizes health around the NEWSTART pillars (nutrition, exercise, water, sunlight, temperance, air, rest and trust) and spends much of the episode on a surprising mechanism: infrared light from the sun penetrates deep into the body, where it helps mitochondria make their own melatonin, a powerful antioxidant that protects cellular energy production. From there they cover evidence linking sunlight to lower rates of influenza, COVID and death, the history of sun and fresh-air therapy in hospitals, darkness at night, the flu shot, masks and handwashing, fever and hydrotherapy, N-acetylcysteine (NAC), zinc, eucalyptus oil, forest air, indoor lighting, long COVID, mold and the role of trust and forgiveness in recovery.

The tone is enthusiastic and nerdy but grounded: Dr. Seheult repeatedly separates randomized trials and dose-response data from anecdotes, and Huberman, clearly in his element when discussing light, adds his own mechanisms and protocols. The conversation swings between cellular biology, clinical stories from the ICU, medical history and simple, low-cost tools anyone can use.

The Discussion Explores:

• The NEWSTART pillars of health as the foundation for resisting infection
• How infrared light penetrates the body, boosts mitochondrial melatonin and counters oxidative stress
• Evidence tying sunlight and green spaces to lower inflammation, influenza, COVID severity and mortality
• Practical sunlight doses, winter strategies, indoor LED lighting, low-E windows and darkness at night
• The flu shot, the Swiss cheese model of protection, masks and handwashing
• Fever, hot and cold hydrotherapy, interferon and white blood cells
• NAC, zinc and eucalyptus oil for respiratory infections
• Forest air, long COVID, smell training, mold, and the role of trust, forgiveness and self-advocacy in the hospital

Deep Dive into Main Ideas

The NEWSTART Pillars of Health

Asked how to avoid getting sick, Dr. Seheult says the answer is the same as avoiding illness of any kind. He uses a mnemonic, NEWSTART, coined by Dr. Neil Nedley of Weimar University. Nutrition means eating food as natural as possible and avoiding processed foods. Exercise follows a J-shaped curve: doing none raises inflammation, mild to moderate exercise lowers it, and very intense training can leave elite athletes more vulnerable to getting sick. Water includes both drinking it and using it externally, as in sauna and cold plunges, which affect the innate immune system and interferon.

Sunlight is the pillar he's most passionate about. Temperance means avoiding toxins that make you sick. Air includes not only avoiding pollutants but breathing air with beneficial compounds, such as phytoncides released by trees. Rest means seven to eight hours of sleep, which he says improves both vaccine antibody responses and how often people get sick. Trust includes faith in a higher power and community, which help relieve stress.

Infrared Light, Mitochondria and Melatonin

Dr. Seheult explains that roughly 38% of the sun's energy is visible light, while about 52% is infrared. Everyone accepts that invisible ultraviolet B light makes vitamin D; what's less known is what infrared does. He cites a 2019 paper in Melatonin Research by Scott Zimmerman and Russel Reiter showing that long-wavelength infrared light scatters deep into the body, up to about eight centimeters. His analogies: the bass from a car stereo shaking your steering wheel, or distant thunder rumbling across the Grand Canyon. An infrared photo of a hand by astrophysicist Bob Fosbury shows light illuminating the whole hand. You can test it yourself by standing outside in several layers with your eyes closed and noticing you can still feel where the sun is.

Why does it matter? Mitochondria generate ATP but also reactive oxygen species (free radicals), much as a car engine makes heat. Left unchecked, that oxidative stress damages mitochondria, and he says mitochondrial dysfunction lies at the root of diabetes, hypertension, heart disease and dementia; he adds that mitochondrial output falls by about 70% after age 40. Research shows mitochondria make their own melatonin on site, in concentrations orders of magnitude higher than the pineal gland, and it acts as a powerful antioxidant that upregulates the glutathione system. He describes it as the mitochondria's cooling system: by day, infrared light boosts local melatonin; at night, melatonin from the pineal gland diffuses into cells, which he thinks is part of why sleep is so restorative. Infrared also acts on cytochrome c oxidase and nitric oxide, improving mitochondrial efficiency. Huberman stresses that no device replaces the sun as the best source of red and infrared light.

The Evidence: Trees, Red Light and Sunlight

Leaves and grass strongly reflect infrared light, so green spaces can deliver two to four times more of it, which is why the shade under a tree is the coolest spot in a garden. People living in green spaces have less diabetes, hypertension and mortality. In a Louisville, Kentucky study, planting over 8,000 mature trees in a four-square-mile area, with no change in income or exercise programs, lowered residents' hs-CRP, an inflammation marker, by 13%, which he says is almost on the order of exercising three times a week.

For interventional evidence he turns to Glen Jeffery at University College London. Three minutes of 670-nanometer red light in the morning improved color sensitivity in older adults by 17% for days; the retina has the highest concentration of mitochondria in the body. In another study, red light on the back of 30 subjects, done without their knowledge, lowered blood glucose after a 75-gram glucose drink and raised exhaled carbon dioxide, a sign of more active mitochondria. Observational studies add more: an Oxford and Leiden study of about 10,000 people linked more sunlight in the prior week to better insulin sensitivity and lower triglycerides; a 20-year Swedish study of about 30,000 women found sun-seekers had lower all-cause, cardiovascular and cancer mortality in a dose-response pattern, with sun-seeking smokers having the same mortality as sun-avoiding non-smokers (he stresses he is not encouraging smoking); and a UK Biobank study of about 400,000 people found similar results. He notes dermatologist Richard Weller's paper titled "Sunlight: time for a rethink."

Huberman adds that his dermatologist guest Dr. Teo Soleymani said there is no evidence sunlight causes the deadliest skin cancers like melanoma, though it does age skin and cause other skin cancers. Both suggest using a UV index app and avoiding excessive midday UV, and Dr. Seheult adds that fair-skinned people can wear a broad-brimmed hat and long sleeves, since clothing blocks ultraviolet while infrared still passes through.

Sunlight, Influenza and COVID

Why is flu seasonal? Holidays, cold and time indoors all coincide with short days, so researchers struggled to separate them until the 2009 H1N1 pandemic peaked in summer across varied climates. A Harvard Kennedy School analysis using solar radiation data concluded, in Dr. Seheult's words quoting it, that "sunlight strongly protects against getting influenza." A 2021 study of Europe's autumn COVID surge found temperature and humidity did not predict when each country surged, but latitude did perfectly, starting with Finland and ending with Greece. US flu deaths peak one to three weeks after the shortest day, Australia's peak in late June or early July, and Singapore near the equator has non-seasonal flu. He adds that deaths from heart disease, kidney disease and Alzheimer's also rise and fall on the same yearly schedule.

A randomized, double-blind trial in Brazil put hospitalized COVID patients in LED jackets emitting 940-nanometer infrared light at only about 2.9 milliwatts per square centimeter (full sunlight delivers roughly 20 milliwatts of infrared) for 15 minutes a day for seven days. Patients had better oxygen saturation, breathing, heart and respiratory rates and lymphocyte counts, and average stays fell from about 12 days to eight.

How Much Sunlight, and the Winter Problem

Jeffery told Dr. Seheult that benefits level off after about 15 to 20 minutes, across bees, insects and humans. Dr. Seheult doesn't think time of day matters much for this purpose, except that fair-skinned people should cover up at midday. The problem is that in winter people drive to work in the dark, work indoors and drive home in the dark, sometimes going weeks without 15 minutes of sun, and he believes this helps explain the winter flu surge. An EPA study found Americans spend 93% of their time indoors (86% in buildings, 6 to 7% in vehicles). His simplest advice: take your lunch break outside. For places with little sun, a study of an 850-nanometer infrared lamp at a desk found benefits to well-being only in winter, but he warns red and infrared light has a biphasic response, so more is not better; match what the sun provides.

Huberman insists there is sunlight all year round, even on rainy, overcast days, which are far brighter than night, and he goes out every morning regardless of weather. He describes his own setup of a 10,000-lux light box plus a red and near-infrared light for the first minutes of the day, and suggests hospitals could easily do something similar. Dr. Seheult guesses that sunlight habits might account for something like 20 to 30% of metabolic dysfunction, and points to a study showing dark days and bright nights are both associated with higher mortality.

Hospitals, History and the Power of Getting Outside

Huberman notes a Nobel Prize was awarded in the early 1900s for phototherapy, so this isn't new-age biohacking. Dr. Seheult traces the history: tuberculosis sanitariums at high altitude, Florence Nightingale writing that fresh air and, a close second, direct sunlight most helped wounded soldiers recover, and Ellen G. White, founder of Loma Linda, urging sunlight and calling lights left on after nine o'clock "a wretched health destroying habit." Hospitals once had rooftop sun decks. He blames scientific reductionism: because UV can cause cancer, we treated all sunlight as dangerous, even though humans never experienced blue or UV light without accompanying infrared until artificial lighting.

Today's ICU patients are much sicker, so taking them outside requires oxygen tanks and monitoring, but he has done it with patients close to needing intubation who then improved. He tells the story, shared by mother Amy Hanmeyer, of her 15-year-old son with leukemia and a severe fungal lung infection (mucormycosis). After losing one lung, he was declared DNR and asked, as a dying wish, to go outside. Staff wheeled him out on BiPAP and oxygen for five hours a day; his fever vanished, oxygen needs fell, and five days later a CT scan showed the disease almost gone. Dr. Seheult stresses this is an anecdote, not proof, but shows "if there is a will there's a way to do it." Huberman adds that ICU psychosis is well known and that patients near windows fare better; Dr. Seheult says they are also discharged faster, and proposes a simple trial of 20 to 30 minutes outdoors for hospitalized patients.

Darkness at Night and Meal Timing

Huberman cites a PNAS study showing that even dim 100-lux light in a sleeping room worsened morning blood glucose. Dr. Seheult recommends blackout measures (even aluminum foil on windows for night-shift workers) and an eye mask, since light passes through closed eyelids. Huberman notes that just 15 seconds of artificial light at night can significantly suppress melatonin, per research from Charles Czeisler's lab. For nighttime bathroom trips, use a phone flashlight pointed at the floor rather than looking at a screen, or dim red lights. He also mentions a brightly lit wall thermostat or night light can emit 100 to 400 lux, while a campfire or full moon delivers only around one to ten, and that overhead lights affect the circadian system more than low lamps, which is why Scandinavians often use table-level lighting in the evening.

Huberman recounts that chronobiologist Dr. Samer Hattar lost over 80 pounds by getting sunlight by day, darkness at night and going to bed earlier. Glen Jeffery's glucose data make Dr. Seheult suspect we should eat only while the sun is up; he likes dinner around 6 to 6:30. But he cautions that these rules shouldn't become so rigid they cause anxiety.

The Flu Shot, Masks and Handwashing

Huberman says he has never had a flu shot and took heat for saying so. Dr. Seheult, who works around flu patients constantly, gets one every year, once at the start of the season. He explains it is a best guess based on strains circulating in the other hemisphere six months earlier, and that it doesn't necessarily prevent infection but reduces severity, so people who say it didn't work can't know how bad their illness would have been. He recommends it for immunocompromised or metabolically unhealthy people and those with heavy exposure, describing an ICU patient with severe diabetes who developed flu and a near-fatal fungal infection. His family gives flu shots to their kids starting in the teen years, a personal choice.

He frames prevention with the Swiss cheese model: each layer has holes, but stacking many layers, like the multiple sterile precautions in an operating room, blocks what gets through. NEWSTART habits are layers, and a flu shot can be an additional one after discussing risks and benefits with your doctor. Risks include allergic reactions and, in one European season, a rash of narcolepsy cases associated with one vaccine formulation. Surgical masks mainly stop wearers from spreading droplets, while N95s protect the wearer but add breathing effort for people with lung disease; he masks in clinic when local flu rates rise. On handwashing, he says study data are mixed, but we constantly touch our eyes, nose and mouth, and surface spread matters for influenza droplets, rotavirus and C. difficile, even if COVID spread mainly through the air.

Water, Fever, Hydrotherapy and Interferon

Drinking water matters; blood sodium concentration mostly reflects water intake, and higher sodium concentration is associated with higher mortality, though eight glasses may be more than needed. But he focuses on water's external use. The immune system has an adaptive branch (specific antibodies) and an innate branch, whose key weapon is interferon, which works broadly against viruses regardless of variant. Viruses need countermeasures against it, and SARS-CoV-1 and SARS-CoV-2 both carry genes that suppress interferon. In lab studies, raising lymphocytes to 39 degrees Celsius (about 102.2 degrees Fahrenheit) increased interferon secretion tenfold, and a newer mouse study found a jump in interferon-related signaling at just 38 degrees (about 100.4 degrees Fahrenheit), driven simply by temperature increasing transcription. An infusion of interferon lambda in a New England Journal of Medicine trial cut COVID hospitalizations by 50%.

That makes him wary of reflexively suppressing fevers, and he notes heavy aspirin use during the 1918 flu may have been harmful. Because water holds so much heat, it's an effective way to raise body temperature: hot baths, saunas, hot showers, or the historic "hot fomentations," hot damp towels applied over a protective layer for about 20 minutes until sweating. He cites a 1919 report by Wells Ruble, medical director of the New England Sanitarium, comparing Adventist sanitariums using hydrotherapy and sunlight with army hospitals in 1918: far fewer flu patients progressed to pneumonia, though once pneumonia set in, mortality was similar. Julius Wagner-Jauregg won a Nobel Prize in 1927 for curing neurosyphilis by inducing fevers with malaria.

The Battle Creek Sanitarium protocol was about 20 minutes of heat followed by a very brief cold application with rubbing, similar to Russian banya and Finnish traditions. Cold causes vasoconstriction, which pushes white blood cells off vessel walls into circulation (demargination) and helps lock in the heat. Huberman adds that wearing a wool hat in a sauna lets you tolerate more heat, that pregnant women should avoid saunas, and that many gray-market peptides are contaminated with LPS, which can trigger inflammation and fever. Both note how different cultures, from hot sand in Iraq to grandma's hot water bottle, arrived at the same remedies.

NAC, Zinc and Eucalyptus Oil

N-acetylcysteine replenishes glutathione and is standard hospital treatment for Tylenol overdose. Dr. Seheult explains that its sulfur groups break disulfide (S-S) bonds, which is why it thins mucus. He also links it to COVID and possibly flu: viral binding to ACE2 receptors in the lung's blood vessels removes an antioxidant pathway, oxidative stress damages vessel linings, and von Willebrand factor polymerizes through S-S bonds into platelet-trapping "white clots," which autopsies found in COVID patients. NAC may help by breaking those bonds. In a multicenter, double-blind, placebo-controlled trial, 600 milligrams of NAC twice daily through a winter didn't reduce flu infections but sharply reduced symptoms, especially runny nose and sore throat; Huberman recalls severe symptoms dropping from the high 70s to about 28 percent. Dr. Seheult takes 600 milligrams twice a day during flu season for no more than about three months, and considers in-vitro concerns about NAC feeding cancer cells overstated. Huberman takes higher doses short-term when he feels something coming on and likes it as a decongestant.

On zinc, Dr. Seheult says the data look supportive and mentions 40 milligrams of elemental zinc as a recommendation he has heard, noting labels list the whole compound and that copper levels should be checked. Huberman takes high doses and monitors blood work. For eucalyptus oil, an in-vitro study showed small amounts dramatically increased immune cells' gobbling up of particles, and it is the main ingredient in Vicks VapoRub. He stresses it should never be ingested, since overdoses have caused deaths; instead, use a few drops on the skin or upper lip, or in a bowl of steaming water with a towel over your head.

Air: Vaping, Nicotine and Forest Bathing

Don't inhale anything but air or lung medicine. Vaping may have fewer toxins than smoking but is still harmful, can carry higher nicotine concentrations, and before COVID he saw many young people on ventilators from homemade vapes. Nicotine gum is a safer tool he uses to help patients quit smoking; Huberman occasionally uses a milligram or two and notes it is habit-forming and a vasoconstrictor.

Japanese forest bathing research took Tokyo executives to Hinoki cypress forests for three days and found immune improvements lasting about seven days, linked to phytoncides from trees. Diffusing Hinoki oil in a hotel room reproduced much of the immune effect, but cortisol was lower in the actual forest, suggesting something about the whole experience matters. He sees a lesson against reductionism, citing lung cancer trials where high-dose vitamin A supplements made outcomes worse. Indoors, LED bulbs lack infrared and red, and low-E window glass is designed to block infrared, which you can test by whether you feel the sun's warmth through it. Huberman adds that aquarium and reptile keepers understand that living things fail under narrow-spectrum light.

Long COVID, Smell Loss and Mold

Long COVID means symptoms such as fatigue, headaches, shortness of breath or loss of taste and smell lasting more than 12 weeks. It's heterogeneous, but research shows downregulated fat metabolism (beta oxidation) in mitochondria of long COVID patients. After ruling out blood clots, heart failure and lung scarring, Dr. Seheult had one patient with a year of shortness of breath rated 8 out of 10 stop eating after 5:30 p.m. (to give the body time to clear damaged cells and regenerate mitochondria) and get outside more. A month later, his reflux was gone and his breathlessness was 3 out of 10, though Dr. Seheult says this doesn't happen for everyone. He also notes infrared light can reduce the toll-like receptor inflammation involved in COVID, and some patients may carry residual virus.

Smell loss happened because supporting cells around olfactory neurons carry many ACE2 receptors; a randomized controlled trial showed smell training with scented sticks (orange, lemon, chocolate and so on) helps recovery. On mold, he says it's real but it's both germ and terrain: "it's not or it's and." Aspergillus can cause allergic disease treated with steroids and antifungals, or invasive disease that may require surgery. Mold in a home raises the burden you inhale, and whether it causes illness depends on your immune strength. True lung infection should be visible on CT and confirmed by biopsy or culture before targeted antifungals.

Trust, Forgiveness and Getting Good Hospital Care

On trust, Dr. Seheult says people with faith and community weather illness better. Writing thank-you letters to mentors improved outcomes even when letters weren't delivered. A Texas survey of 1,500 Christians found those who forgave conditionally had more anxiety about death, more physical complaints and lower well-being than those who forgave unconditionally, and the strongest predictor of unconditional forgiveness was feeling forgiven by God. With permission, he gently asks anxious ICU patients whether something is weighing on them, and says helping them feel forgiven within their own beliefs makes a world of difference.

Huberman's final question: how can ordinary people get better hospital care? Dr. Seheult says yelling or insulting staff makes things worse. The most effective step is for family to learn about the condition and ask informed, intelligent questions about treatment plans, which puts doctors on their game. His MedCram site offers courses explaining lab tests like blood counts and metabolic panels and conditions like heart failure for exactly this purpose.

Conclusion

Dr. Roger Seheult's message is that the strongest defenses against infection are foundational and often free: the NEWSTART pillars of good food, moderate exercise, water inside and out, sunlight, avoiding toxins, fresh air, rest and trust. His most striking argument is that infrared light from the sun reaches deep into the body and helps mitochondria defend themselves with melatonin, which may explain why sunlight and green spaces are tied to lower inflammation, seasonal flu, COVID severity and mortality, so 15 to 20 minutes outdoors daily, especially in winter, and real darkness at night matter. When illness strikes, heat and water can harness fever and interferon, brief cold can mobilize white blood cells, and NAC, zinc and eucalyptus steam may ease symptoms, with vaccines as an optional extra layer of Swiss cheese. Throughout, he balances randomized evidence with honest anecdotes and a humane view of healing that includes community, forgiveness and informed family advocates.

This is a summary of "How to Enhance Your Immune System" from Huberman Lab, giving you the GIST so you can decide if you want the REST. Listen to the full episode.