Vitamin D is naturally present on very few foods but many foods are commonly fortified with it. It is also produced when ultraviolet rays hit the skin, which triggers Vitamin D synthesis in the body. Vitamin D’s main functions in the body are promoting calcium absorption in the gut and bone growth and repair. Vitamin D also modulates cell growth, neuromuscular and immune function and reduces inflammation.
Salmon, tuna, swordfish and fish liver oils are the best dietary sources of Vitamin D. There are also small amounts present in cheese, eggs and beef liver. Fortified foods are responsible for most of the dietary Vitamin D consumed in the United States. Nearly all milk is fortified with it, as well as many breakfast cereals and some orange juices.
Most people get at least some of their Vitamin D from sun exposure. Under normal sun conditions most people are able to get enough Vitamin D in 30 minutes twice a week of unprotected sun exposure when the sun is at its peak between 10 a.m and 3 p.m. Though sun exposure is vital when it comes to getting adequate Vitamin D, ultraviolet radiation is a carcinogen that is responsible for skin cancer and melanoma.
Rickets is the disease that is most commonly associated with Vitamin D deficiency. The disease is characterized by the failure of bone tissue to properly materialize which causes soft bones and skeletal deformities. The government mandated milk to be fortified with Vitamin D in the 1930s in order to combat rickets. While there are still documented cases they have become exceedingly rare.
There are many different groups that are at risk of insufficient Vitamin D intake. Breast fed infants who don’t receive supplements will have low Vitamin D as there is very little available in breast milk. Older people are also at an elevated risk because their skin does not synthesize Vitamin D as efficiently; they also tend to get less sun exposure than younger people. People with darker skin also don’t receive as much Vitamin D from the sun due to lower levels of melanin, which is responsible for skin pigment. Those who are obese or have had gastric bypass surgery also may need more Vitamin D than others, as it is absorbed through the intestine; part of which is no longer part of the digestive system after gastric bypass surgery.
Adequate Vitamin D levels are linked to many benefits. It helps the body with the absorption of calcium which can lower the risk of osteoporosis. Studies also indicate that Vitamin D supplementation can lead to a lower incidence of cancer among individuals who are of average weight. There are also indications that Vitamin D plays many roles in the prevention and treatment of many different conditions but more studies are needed.