維生素D (vitamin D)是一群脂溶性的維生素，是維持人體正常生長及健康的重要營養素。人體可由攝取食物取得維生素D，也可由皮膚接受紫外線照射而自行合成維生素D。維生素D是具有多重生理作用的荷爾蒙，其傳統的功能為維持鈣磷的平衡及骨骼健康(skeletal health)，除此之外，也有許多非骨骼健康(extra-skeletal health)方面的功能，包括腎臟保護的功能、心臟血管保護的功能、免疫調節的功能及預防癌症的功能等。維生素D缺乏(vitamin D deficiency)或不足(insufficiency)與許多疾病相關，也與死亡率較高相關。維生素D缺乏或不足並不少見，因此維生素D的的需求及補充也越來越被重視。本篇文章主要整理維生素D與人體健康的關係，包括骨骼健康及非骨骼健康，維生素D缺乏或不足對人體健康的影響與維生素D補充(vitamin D supplementation)可能的臨床效益。

Vitamin D is a group of fat-soluble secosteroids, and it is an important nutrient for human’s normal growth and health. Humans obtain vitamin D from the intake of food containing it. Human body can also synthesize vitamin D in the skin by ultraviolet B radiation from sunlight. Vitamin D is a pleiotropic hormone, its classical function is to maintain calcium and phosphate homeostasis and skeletal health. Vitamin D also has many extra-skeletal functions, such as renoprotection, cardiovascular protection, immune modulation and cancer prevention. Vitamin D deficiency is associated with many acute and chronic illnesses and diseases and is also associated with high mortality. Vitamin D deficiency is not uncommon and vitamin D supplementation may have some benefits for human health. This article reviewed the relationship of vitamin D and human health, including skeletal and extra-skeletal health, vitamin D deficiency and its associated illnessess, vitamin D supplementation and its potential benefits. (J Intern Med Taiwan 2014; 25: 250-260)