Five Questions About Vitamin D

Sometimes known as the “sunshine vitamin” because it’s produced by the body in response to sunlight, vitamin D is important for maintaining strong bones and ensuring healthy functioning of the lungs, cardiovascular system, immune system, and brain. Because of concerns that excessive sun exposure can lead to skin cancer, some people may avoid spending much time outdoors – potentially lowering their vitamin D levels if they don’t get enough of the vitamin through diet or supplements. Here are some vitamin D basics: 

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How does vitamin D work in the body?

It plays an important role in regulating the amounts of calcium and phosphorous in the blood. It also enables the body to absorb these minerals, which are essential for strong bones.


What are the primary sources of vitamin D?

The body makes vitamin D in response to the ultraviolet B rays in sunlight. According to the Vitamin D Council, exposing the skin to the sun for only a short time is sufficient for most people (those with pale skin tend to make vitamin D more quickly than those with dark skin). The council advises exposing the skin for about half the time its takes the skin to turn pink or begin to burn. While vitamin D is added to some foods, like milk, few foods naturally contain any of the vitamin – and the foods that do have the vitamin generally have only small amounts. For that reason, the Vitamin D Council recommends taking a vitamin D supplement each day.


How much vitamin D do people need?

Different organizations recommend different amounts. The Vitamin D Council recommends adults take 5,000 international units a day; the Endocrine Society recommends 1,500 to 2,000 international units a day; and the Food and Nutrition Board recommends 600 international units a day. These discrepancies reflect the need for more research in this area, scientists say.


What problems can arise from a vitamin D deficiency?

A severe deficiency of the vitamin can cause the disease rickets in children and a condition known as osteomalacia in adults, both of which result in soft, thin, and fragile bones. A lack of vitamin D has also been linked to other conditions, including cancer, asthma, type II diabetes, high blood pressure, depression, Alzheimer’s disease and autoimmune diseases such as multiple sclerosis and type I diabetes, although more research is needed to better understand these links.


What does the latest research on vitamin D deficiency and cancer show?

Some early-stage studies have suggested that flaxseed and vitamin D may help reduce the risk of breast cancer. Judy Garber, MD, MPH, the director of the Center for Cancer Genetics and Prevention at the Susan F. Smith Center for Women’s Cancers at Dana-Farber, is helping lead two studies exploring the effectiveness of these substances.

A study by Kimmie Ng, MD, MPH, of the Dana-Farber/Brigham and Women’s Cancer Center showed that African-Americans of have lower levels of vitamin D in the blood and may need higher doses of vitamin D supplements to meet nationally-established goals.

Another study led by Ng showed that high levels of vitamin D increased survival for patients with metastatic colorectal cancer.

Learn more about vitamin D in the video below: