How to Enhance Your Immune System | Dr. Roger Seheult
Summary
Dr. Roger Seheult, a board-certified pulmonologist, critical care, and sleep medicine physician at Loma Linda University, outlines the foundational pillars of immune health and explains the powerful but underappreciated role of sunlight — particularly infrared and red light — in supporting mitochondrial function, reducing inflammation, and protecting against infectious disease. The conversation covers practical strategies for maximizing light exposure, the science behind phototherapy, and why modern indoor lifestyles are driving chronic disease.
Key Takeaways
- Sunlight is the most accessible and effective form of red/infrared light therapy — no device can fully replace it, and even 15–20 minutes daily produces measurable biological benefits.
- Infrared light penetrates deep into the body (up to ~8 cm via scattering), stimulates mitochondrial melatonin production, and reduces oxidative stress inside cells.
- Mitochondrial function declines ~70% by age 40, and this dysfunction underlies virtually all major chronic diseases including diabetes, hypertension, dementia, and heart disease.
- Green spaces dramatically amplify infrared exposure — chlorophyll-rich leaves reflect infrared light, potentially multiplying your dose 2–4x compared to open environments.
- Latitude and sunlight duration — not temperature or humidity — predicted COVID-19 surge timing across European countries, reinforcing sunlight as a critical immune factor.
- Americans spend 93% of their time indoors, creating a chronic deficit of infrared and red light that correlates with seasonal disease surges peaking 1–3 weeks after the winter solstice.
- A randomized controlled trial showed 15 minutes/day of 940 nm infrared light for 7 days improved oxygen saturation, respiratory rate, lymphocyte counts, and shortened hospital stays in COVID-19 patients.
- Shifting from incandescent to LED lighting has removed red and infrared wavelengths from indoor environments, leaving people exposed predominantly to blue/green short-wavelength light.
Detailed Notes
The “New Start” Framework for Immune Health
Dr. Seheult references a mnemonic coined by Dr. Neil Nedley as his foundational approach to health:
- N — Nutrition: Whole, minimally processed foods
- E — Exercise: Mild to moderate exercise reduces inflammation; elite-level exercise can temporarily suppress immunity (J-curve relationship)
- W — Water: Includes external water therapies such as sauna and cold plunge, which activate the innate immune system and stimulate interferon production
- S — Sunlight: Detailed extensively below
- T — Temperance: Avoiding toxins (smoking, alcohol, etc.)
- A — Air: Fresh air and phytoncides (chemicals released by trees) — linked to forest bathing research from Japan showing improvements in innate immune function
- R — Rest: 7–8 hours of quality sleep strongly associated with better antibody response to vaccines and fewer annual illnesses; connected to cortisol and beta-adrenergic receptor regulation
- T — Trust/Community: Stress reduction via social connection or spiritual practice
Sunlight and Infrared Light: The Deep Biology
The infrared spectrum is largely overlooked:
- Only 38% of solar energy is visible light; 52% is in the infrared spectrum
- Infrared photons have long wavelengths, low energy, and high tissue penetration — analogous to how low-frequency sound travels through walls
- A single infrared photon can scatter up to ~8 cm through tissue, illuminating organs, not just skin surface
- Infrared light penetrates clothing and can be felt through multiple layers
Key paper: “Melatonin and the Optics of the Human Body” — Zimmerman & Ryder, 2019, Melatonin Research
Mitochondria produce melatonin on-site:
- Mitochondrial melatonin is produced in concentrations 20x higher than pineal-derived melatonin in blood
- This melatonin is not secreted into circulation — it acts locally as an antioxidant
- It neutralizes reactive oxygen species (ROS) produced during ATP synthesis
- It also upregulates the glutathione system
- At night, pineal-derived melatonin enters the bloodstream, diffuses into cells and mitochondria, and performs the same antioxidant function — likely a key reason sleep is so restorative
Infrared light also:
- Activates cytochrome c oxidase (Complex IV of the electron transport chain)
- Increases nitric oxide availability
- Directly improves mitochondrial efficiency and ATP output
Sunlight and Infectious Disease
Influenza seasonality:
- Influenza peaks 1–3 weeks after the winter solstice in the Northern Hemisphere and in late June/July in Australia — directly inverse
- In Singapore (near equator), flu peaks are non-seasonal and essentially random
- The 2009 H1N1 pandemic, which peaked in summer, allowed researchers to decouple flu from winter variables — Harvard Kennedy School analysis found sunlight strongly protects against influenza
COVID-19 surge timing:
- A 2021 European study found temperature and humidity showed flat correlations with surge onset
- Latitude produced a near-perfect correlation — countries further from the equator (Finland first, Greece last) experienced surges in exact sequential order as daylight shortened
Vitamin D context:
- UVB light drives vitamin D synthesis — already well accepted
- Infrared light effects on mitochondria represent a parallel and equally important solar benefit
Green Spaces and Inflammation
Louisville, Kentucky tree study:
- 8,000+ mature trees planted in a 4-square-mile area
- 2–3 years later: hsCRP (high-sensitivity C-reactive protein) dropped by 13% — comparable to exercising 3x/week
- No changes in income, diet, or exercise programs in the same area
- Mechanism proposed: chlorophyll reflects infrared light, substantially increasing ambient infrared exposure in green spaces
Red Light Research: Clinical Evidence
Glen Jeffrey, University College London (Ophthalmology):
- 3 minutes of 670 nm red light in the morning → 17% increase in color sensitivity lasting for days in older subjects
- Mechanism: retina has the highest mitochondrial density of any tissue; red light boosts ATP production in those mitochondria
- Effect was morning-specific in this study
Glucose metabolism study (Jeffrey):
- 30 subjects given 75g glucose load
- Blinded red light (670 nm) applied to backs
- Intervention group: lower peak glucose and higher exhaled CO2 — indicating mitochondria were consuming more fuel more efficiently
Oxford / University of Leiden study (~10,000 subjects):
- Sunlight exposure in prior 7 days predicted improved insulin sensitivity and reduced triglycerides on a per-hour basis
Swedish Women’s Study (~30,000 women, 20-year follow-up):
- High sun exposure group: lower all-cause mortality, lower cardiovascular mortality, lower cancer mortality
- Dose-response curve (Bradford Hill criteria suggesting causation)
- Striking finding: women who got lots of sun and smoked had similar mortality to women who avoided sun and didn’t smoke
- Replicated in UK Biobank with ~400,000 subjects (both sexes)
Brazil COVID-19 RCT:
- 940 nm infrared light jacket, 2.9 mW/cm², 15 min/day for 7 days
- Placebo-controlled, double-blinded
- Results: improved oxygen saturation, deeper breaths, lower heart rate and respiratory rate, improved lymphocyte counts, shorter hospital stay (control avg: ~12 days vs. intervention group)
Desktop infrared lamp study:
- 850 nm infrared light, 4 hours/day for 8 weeks
- No effect in summer (participants already getting sufficient outdoor infrared)
- Statistically significant benefit in winter only
Practical Recommendations
Daily sunlight exposure:
- 15–20 minutes is the target threshold; diminishing returns beyond that
- Time of