Dr. Roger Seheult is a physician specializing in pulmonary and critical care medicine and is widely recognized for his expertise on vitamin D and sunlight’s role in human health. He is the co-founder of MedCram, where he explains the science behind vitamin D, immune function, sleep, and metabolic health in a clear, evidence-based way. Dr. Seheult is known for translating complex medical research into practical guidance that helps people optimize health and resilience.

In our conversation we discuss:

(0:00) – Sunlight benefits beyond vitamin D
(3:39) – Can sunlight increase lifespan
(6:36) – Sunlight versus outdoor activity benefits
(13:20) – Best time of day for sunlight
(19:52) – Morning cortisol: wake time versus sun timing
(21:01) – Is sunlight best cortisol trigger
(22:56) – Front-loading cortisol and workout timing
(27:26) – Blue light effects on circadian rhythm
(33:36) – Why earlier sleep improves energy
(39:12) – Can late sleepers fully adapt
(40:26) – Ideal sleep and wake schedule
(44:01) – Can weekend sleep make up deficits
(45:39) – Daily melatonin use safety
(51:04) – Recommended sleep supplements
(1:00:30) – Are chronotypes fixed or flexible
(1:00:53) – Sunscreen risks and benefits
(1:05:39) – Face sunscreen with body sun exposure
(1:08:38) – Sun exposure needed for vitamin D
(1:11:44) – Optimal vitamin D dosage and toxicity
(1:14:05) – Other key immune system boosters
(1:19:47) – Hot and cold therapy for immunity
(1:25:52) – Sauna and cold exposure guidelines

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