As the most commonly prescribed vitamin, it is perhaps worth briefly reviewing the functions of vitamin D in maintaining good health. Its main role is to regulate calcium and phosphorous metabolism, necessary for bone mineralisation. It also helps regulate extracellular fluid calcium levels, important for neuromuscular function.⁹

In infants, prolonged vitamin D deficiency during periods of bone growth means the osteoid or bone matrix is not mineralised sufficiently, resulting in rickets. The problem may also arise with calcium and phosphorous deficiencies.

Rickets is most notable in infancy, but when there is a further major growth spurt at puberty or through adolescence, it may mean bones do not achieve peak bone mass. For adults, deficiency may result in osteomalacia, or ‘soft bones’, with severe bone pain and muscle weakness.⁹