Role: Regulates calcium and phosphorus levels by regulating their intestinal absorption, retention by the kidneys, deposition into bone, and absorption from bone when calcium and phosphorus blood levels dip. Required for bone/teeth growth and maintenance.
Deficiency: Growth retardation. Rickets (bowed legs, knocked knees, other skeletal deformities) develop in childhood. Adults develop osteomalacia (excessive loss of calcium from bones) with risk of bone fracture. Severe deficiency due to illness or metabolic error causes twitching and muscle spasms.
Sources: Synthesis by the body when skin is exposed to sunlight, vitamin D-fortified milk, fish and liver oils.
Toxicity: Impairs kidney function; excessive urination and thirst. Kidney stones and calcium deposition in other soft tissues – heart, blood vessels, and membranes in bone joints. Joint pain. Bone loss. Growth retardation.