Vitamin D is essential for strong bones, because it helps the body use calcium from the diet. Traditionally, vitamin D deficiency has been associated with rickets, a disease in which the bone tissue doesn’t properly mineralize, leading to soft bones and skeletal deformities. Another potential issue stemming from vitamin D deficiency is osteoporosis, which is seen most prevalent in the elderly—particularly women. This is because all our bones naturally lose calcium over a lifetime, but the process of creating a healthy baby adds an extra toll on women’s bones. Additionally, low blood levels of the vitamin have been associated with the following:

- Increased risk of cardiovascular disease

- Cognitive impairment in older adults

- Severe asthma in children

Vitamin D toxicity is a rare but potentially serious condition that occurs when you have excessive amounts of vitamin D in your body. Vitamin D toxicity is usually caused by megadoses of vitamin D supplements—not by diet or sun exposure. The main consequence of vitamin D toxicity is a buildup of calcium in your blood, which can cause poor appetite, nausea, and vomiting.