Vitamin D is produced as a result to the body’s exposure to the ultraviolet rays of the sun. Vitamin D also occurs naturally in fish, fish liver oil, egg yolks and fortified milk. It is essential for building strong bones because it helps the body utilize calcium from the diet. Low levels of the vitamin are associated with Rickets which is a condition that occurs when bone tissue doesn’t sufficiently mineralize, resulting in soft bones and skeletal deformities.

Symptoms of low levels include muscle fatigue and bone weakness. Over time this can increase one’s risk of cardiovascular disease. In some cases, there have been ties between insufficient levels of Vitamin D and asthma in children, cognitive impairment in older adults and even cancer.

Outside of diet and sun exposure, there are several factors that can contribute to insufficient Vitamin D levels in certain individuals. In some cases, the kidneys can’t convert the vitamin to its active form. Other people suffering from conditions like Crohn’s Disease, Cystic Fibrosis or Celiac Disease, can’t properly absorb it in their digestive tracts. Furthermore, obesity can cause issues since Vitamin D is extracted from the blood by fat cells. Individuals with a body mass index of over 30 tend to have low levels.

Sunscreen blocks the synthesis of vitamin D in the skin. Light skinned people need 10-15 minutes of exposure per day, while dark skinned individuals and the elderly require 20-30 minutes. If you follow a strictly plant based diet and do not meet these sun exposure minimums, supplementation is recommended.