Low vitamin D levels have been linked to cancer, cognitive impairment in older adults, and increased risk of death from cardiovascular disease, according to WebMD. Children with a deficiency can develop severe asthma. Low levels can also lead to rickets, a condition that makes bones soft, creating skeletal abnormalities.
Increased amounts of vitamin D may also be helpful in preventing some conditions, WebMD reports. Some research suggests that sufficient vitamin D may prevent multiple sclerosis, high blood pressure, glucose intolerance, and both type 1 and type 2 diabetes.
Most of the time, the symptoms of vitamin D deficiency are subtle, explains WebMD. Some patients may experience bone pain or muscle weakness.
Several factors lead to a lack of sufficient vitamin D, states WebMD. People with darker skin have less ability to make vitamin D from sunlight because of the increased amount of melanin in the skin. Another factor is not getting enough sunlight exposure in general. Some people do not consume enough vitamin D from food sources, which include animal-based food such as fish, fortified milk, egg yolks and beef liver. Other factors include the inability to absorb vitamin D through the digestive tract, or to convert it into an active form in the kidneys.