A 2025 study by the University of Bath found that regular indoor exercise helped people keep healthy vitamin D levels during the darker months, even without supplements or weight loss. Staying active supports your bones and immune system year-round.

A 2025 double-blind, placebo-controlled study by Laterza et al. in Nutrients found that taking a multistrain probiotic with vitamin D significantly improved gut barrier function and microbiota balance in people with IBS. Benefits even lasted after treatment stopped.