In 2025, Aleksandra Skoczek-Rubińska and a team from Poznan University of Physical Education reviewed 13 studies from 2009-2025 on how vitamin D helps BDNF (a brain protein for nerve growth), mood, and thinking in adults. They looked at human and animal studies from big databases to see how vitamin D levels or supplements affect people’s brains and feelings.

Despite marketing claims, major studies show no clear link between UV exposure and melanoma, and outdoor workers may even have lower melanoma rates than those indoors. Meanwhile, most conventional sunscreens contain seed oils that oxidize under heat, hormone-disrupting chemicals like oxybenzone, and titanium dioxide nanoparticles that can reach your brain.

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.