Dr. Dawn explains the 2025 Nobel Prize in Physiology awarded to Shimon Sakaguchi, Mary Brunkow, and Fred Ramsdell for discovering T regulatory cells. Previously, medical teaching held that the thymus only eliminated self-attacking T cells, but Sakaguchi found that removing the thymus from newborn mice caused autoimmune disease, suggesting protective regulatory cells existed. He identified CD4+CD25+ cells that suppress inflammation and can convert other T cells. Brunkow and Ramsdell discovered the FOXP3 gene that controls these cells, linking mutations to severe autoimmune diseases like IPEX syndrome. Tissue-specific Tregs regulate metabolism in fat, maintain gut microbiome tolerance, promote wound healing in skin, and control muscle regeneration. Therapeutic applications include stopping type 1 diabetes, preventing organ rejection, and treating multiple sclerosis.

An emailer asks about a study linking soft drinks to depression through gut bacteria changes. Dr. Dawn critiques the cohort association study for establishing only correlation, not causation, with a weak risk ratio of 1.1 representing just 10% increased association. She explains that bacteria can influence food cravings, making it unclear whether sodas change bacteria levels or bacteria drive soda consumption. Without Koch's postulates—isolating bacteria, growing them, and reproducing disease—the causal direction remains uncertain despite statistical significance.

Dr. Dawn reads David Whyte's essay on injury as invitation to transformation, exploring how pain reveals vulnerability, changes identity, requires patience, and teaches compassion. She notes this perspective may come easier to men who reach midlife believing they control their bodies, while menstruation disabuses women of that illusion earlier. As a physician, she emphasizes the ego crisis when people transition from healthy to "person with disease," requiring identity restructuring that can shake foundations but also mature and strengthen individuals.

A caller responds enthusiastically to the injury essay, citing quotes from André Gide, James Hillman, and Norman O. Brown about how illness opens doors to reality closed to healthy mindedness, how the soul sees through affliction, and how vulnerability is inherent to being human. Dr. Dawn agrees that many religions embrace wounds as paths to spiritual enlightenment and commits to deeper reflection on suffering's role in the human condition.

Dr. Dawn discusses cognitive functional therapy for chronic back pain, describing firefighter Joe Lawrence who believed his spine was irreparably damaged until physical therapist Peter O'Sullivan challenged those beliefs. The therapy addresses psychological aspects by teaching that backs need movement, not protection, and that tensing muscles worsens pain. The three-step approach examines pain origins including emotional context, gradually reintroduces avoided activities while learning relaxation, and establishes healthy sleep and exercise routines.

GLP-1 drug prices have dropped dramatically to $499 monthly at Costco due to compounding pharmacy competition.

Dr. Dawn urges immunizations, noting studies show shingles vaccination reduces dementia risk by 20% over seven years, possibly by generating T regulatory cells that reduce brain inflammation. Natural experiments in England where vaccine rollout occurred at different times in different regions provided strong evidence. She explains that chickenpox vaccination in childhood prevents both chickenpox and future shingles. Even tetanus shots appear to lower dementia risk, suggesting vaccines activate immune responses that reduce chronic inflammation.

She concludes with practical advice to reduce microplastic exposure by avoiding plastic cups and containers, especially with heat. Eight-year-old coffee makers contain twice the microplastics of six-month-old machines due to deterioration. She recommends ceramic cups, glass or metal kettles, removing food from plastic before cooking, and washing polyester clothing on low heat to minimize microplastic generation.