Vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol) are the two major forms of vitamin D – a secosteroid.9 In this article, the term vitamin D will refer to both forms..

Three types of health-related behaviour are described:7.

Nutrition is defined by the World Health Organization as ‘the intake of food, considered in relation to the body’s dietary needs'.4 Diet is simply what an organism eats, but good nutrition involves...