Skin synthesis of vitamin D drops in winter. A 2017 meta-analysis found fewer respiratory infections with supplements, mostly in people who started deficient.
World Marathon Majors winners and mid-pack runners face the same physiology; the evidence shows carbohydrate intake and practiced absorption decide the final 10 kilometres.
Ten days into the 2026 World Cup, mandatory hydration breaks and documented venue heat have made player welfare a running storyline of the group stage.
Grand slam matches run past four hours in heat; the evidence on tennis fueling shows carbohydrate, fluids and practice — not stimulants — carry the fifth set.
Grand tour riders face the highest documented energy demands in sport; the evidence on how the peloton eats shows planning, not products, does the work.