Peat Archive

Ray Peat viewed vitamin D as an important hormone precursor but warned against the supplementation craze. He noted that vitamin D is produced from cholesterol in the skin with sunlight exposure, and that supplementation can be useful in deficiency but that megadosing can cause calcium dysregulation and soft tissue calcification. He emphasized that vitamin D works in concert with vitamins A and K2, and that supplementing one without the others can cause imbalances.

Peat recommended moderate sun exposure as the primary source, with supplementation of 1,000-2,000 IU daily in winter or for those with limited sun. He noted that hypothyroid patients often have low vitamin D because thyroid hormone is needed for its activation.