The symptoms of vitamin D deficiency include bone pain and muscle weakness, according to WebMD. Vitamin D deficiencies are difficult to detect, but low blood levels often correlate with a higher risk of heart disease, asthma in children, cancer and cognitive impairment in older people. Conversely, adequate vitamin D levels support the prevention and treatment of diabetes, glucose intolerance, multiple sclerosis and hypertension.
In children vitamin D deficiency is a common cause of rickets, which is a condition that softens or weakens the bones, as explained by Mayo Clinic. In adults, the deficiency causes osteomalacia, which weakens bone and muscle. Elderly and obese people who receive limited sun exposure are among those who have a higher risk of deficiency.
Humans derive vitamin D from food sources such as eggs, fish, fortified milk and cod liver oil as well as exposure to natural sunlight, according to Mayo Clinic. At least 10 minutes of sunlight a day can provide adequate levels of the nutrient in most people. Vitamin D2 and vitamin D3 are the two specific forms of vitamin D that play a role in human nutrition. Vitamin D2 is made by plants, while D3 is produced by humans when the skin absorbs the sun's rays. Vitamin D is responsible for maintaining levels of calcium and phosphorous for proper bone density and overall health, and it also helps to prevent osteoporosis and high blood pressure.