Studies have found a correlation between low blood levels of vitamin D and an increased risk of depression. Taking vitamin D in doses higher than 20 mcg (800 IU) per day plus calcium may raise blood pressure for those who are overweight or obese. Research has also suggested that vitamin D supplements may help reduce cholesterol levels and high blood pressure, two of the main risk factors for heart disease. Treatment for vitamin D deficiency may include taking oral ergocalciferol (vitamin D) at 50,000 IU per week for eight weeks.
Clinical trials have indicated that while vitamin D supplements (with or without calcium) may not affect the risk of cancer, they may slightly reduce the risk of dying from this disease. Other studies have shown that vitamin D supplements don't stop most people with prediabetes from developing diabetes. Vitamin D deficiency in adults is defined as a serum 25-hydroxyvitamin D level of less than 20 ng per ml (50 nmol per L), and deficiency is defined as a serum 25-hydroxyvitamin D level of 20 to 30 ng per ml (50 to 75 nmol per L). If serum levels of 25-hydroxyvitamin D have not yet increased, the most likely cause is lack of adherence to treatment or poor absorption.
A randomized study of men and women aged 65 to 85 who lived in the community found that people taking vitamin D had a statistically significant decrease in osteoporosis fractures, particularly in women. In the United States, 61% of the elderly population is deficient in vitamin D, while 90% in Turkey, 96% in India, 72% in Pakistan and 67% in Iran were deficient in vitamin D. Vitamin D is a fat-soluble vitamin that the body uses for normal bone development and maintenance by increasing the absorption of calcium, magnesium and phosphate. People with chronic liver disease, such as cirrhosis, may have defective 25-hydroxylation that causes a vitamin D deficiency.
Fortunately, due to vitamin D-fortified infant formula and fortified cow's milk, rickets are very rare in the United States. In the United States, 47% of African-American babies and 56% of Caucasian babies are vitamin D deficient, while more than 90% of babies in Iran, Turkey, and India are vitamin D deficient. Even mild chronic vitamin D deficiency can cause chronic hypocalcemia and hyperparathyroidism, which may contribute to the risk of osteoporosis, falls and fractures, especially in the elderly population. The Institute of Medicine guidelines increased the recommended daily allowance (RDA) of vitamin D to 600 international units (IU) for all people ages 1 to 70, and raised it to 800 IU for adults over 70 years of age to optimize bone health.