It is very likely that your pediatrician has ordered a blood test in recent years to check your child’s vitamin D level. It is also likely that you have been told that the level is low and your child needs to take vitamin D. The number of people taking a vitamin D supplement regularly increased by 60 times between 1999 and 2014, and the role of vitamin D in health became one of the most talked-about issues in medicine.
Was this surge of vitamin D supplementation a reasonable recommendation or just another health scare?
Vitamin D has an important role in maintaining normal levels of calcium in the blood and in supporting bone health. Cod liver oil was used in the past to cure a bone disease in children called rickets, in which the bones become weak and the children develop bowed legs. It was not until much later that scientists discovered that the main component of cod liver oil that healed rickets is actually vitamin D.
Many types of food, such as dairy products, wild salmon and mushrooms, contain high amounts of vitamin D. Our body can also produce vitamin D naturally when we are exposed to sunlight.
Severe vitamin D deficiency in adults results in weaker bones and an increased risk of fracture. People at higher risk include seniors and women after menopause. Researchers are also studying the link between vitamin D deficiency and certain diseases such as cancer, but more studies are needed before we can reach conclusions.
Breast milk contains very low amounts of vitamin D, so vitamin D supplementation is needed for babies who are fed only breast milk. Several medical conditions such as liver and intestinal disease affect the absorption of vitamin D, and this also causes vitamin D deficiency. People with disabilities and the chronically ill may have limited exposure to sunlight and can also have vitamin D deficiency.
In recent years, blood tests to check vitamin D level have become more common. These tests have indicated that many children and adults have vitamin D levels that are less than optimal. This can result from insufficient vitamin D intake or limited exposure to sunlight. Before our body can use vitamin D, it has to be processed first in the liver and then in the kidney. There is also evidence that some people have a low level of vitamin D in their blood because they do not process vitamin D at the same rate as others.
In 2010, the Institute of Medicine released recommendations on vitamin D supplements calling for a daily intake of 600 international units for all ages up to 70, and 800 units from age 71 on. Most of the vitamin D supplements on the market have 800, 1,000 or 2,000 international units per pill. So if you are taking one vitamin D pill a day, it is likely that you are receiving between 800 and 2,000 units a day. There has been debate since the release of the recommendation on whether this amount is enough to improve bone health and prevent fracture. Patients with medical conditions that affect vitamin D absorption need a higher dose to maintain a normal level.
However, abnormally high levels of vitamin D in the body can also create problems. For example, the calcium level in the blood may increase, causing the body to lower the calcium by excreting it through the kidney. This can eventually cause a kidney stone.
While a vitamin D supplement is recommended for everyone, the optimal dose may be different from person to person. Taking a higher dose of vitamin D does not necessarily mean more benefits. If your child has a medical condition that requires him or her to take a higher dose of vitamin D, it should be done under the supervision of your pediatrician.
Supamit Ukarapong, M.D., is assistant professor of pediatric endocrinology at UHealth — the University of Miami Health System. For more information, visit UHealthSystem.com/patients/pediatrics.