A SHORTAGE OF VITAMIN D

What are the health benefits of vitamin D? How do we get vitamin D and how much do we need? Why are so many doctors and dieticians worrying about vitamin D deficiency?

Vitamin D is a substance that is stored in the body’s fat. It is naturally found in many fish – including mackerel, sardines, salmon and cod liver oil. It is added to milk, breakfast cereals, multivitamins and other dietary supplements. Finally, vitamin D is synthesized in the skin through sun exposure.

Vitamin D is crucial for healthy bones because it aids in the body’s absorption of calcium in the small intestine. People with severe vitamin D deficiency have very low levels of calcium and may develop rickets (in children) or osteomalacia (in adults) – diseases in which bone is deformed or softened. Chronic vitamin D deficiency is linked to osteoporosis which can lead to an increased risk of fractures.

It has been assumed that the fortification of milk since the 1930s had essentially wiped out vitamin D deficiency but recent studies have shown that vitamin D deficiencies are far more widespread than previously suspected – extending to as many as 40 percent of American adults. Those at greatest risk of vitamin D deficiency include the elderly who often have limited sun exposure and African-Americans and other dark-skinned people (skin pigmentation interferes with vitamin D production). Surprisingly, women of child-bearing age and healthy children and adolescents are also at risk – comprising what has come to be known as a “hidden epidemic.” Vitamin D deficiency is also common in people who are housebound, those who are living in northern climates including Pittsburgh in the winter, and people with certain stomach or intestinal disorders. In a study of hospitalized patients with general medical problems, vitamin D deficiency was detected in 57 percent.

While vitamin D has long been known to benefit bones, other organs are protected as well. In a study of people with chronic pain in their bones and joints, 93 percent of them were deficient in vitamin D – perhaps due to undetected osteomalacia. Research into other benefits of vitamin D is just beginning but suggests that vitamin D may also protect against prostate, colon, and breast cancers by as much as 30 percent. Other studies suggest that vitamin D may protect against some autoimmune diseases including multiple sclerosis, Type I diabetes, and rheumatoid arthritis. Finally, many scientists believe that vitamin D can help lower blood pressure.

If current sources of vitamin D are inadequate, how should we meet our bodies’ needs? Existing national guidelines recommend that adults receive 200-600 IU, depending on age. However, most current researchers believe that adults should receive at least 800-1000 IU per day to obtain maximum benefits. This quantity is the equivalent of 8 glasses of milk or 2 vitamin D supplement tablets. Although dermatologists are concerned about a growing risk of skin cancers, vitamin D experts recommend that people increase their UVB sun exposure – without sunscreen – to 10-15 minutes per day a few times per week.

Your doctor can easily check your vitamin D levels to determine whether you would benefit from additional supplementation. Levels of 25-hydroxyvitamin D of less than 20 ng/ml represent vitamin D deficiency while levels between 20-30 are evidence of vitamin D insufficiency. People with a mild-moderate deficiency can take 50,000 IU once a week for 6-8 weeks. Those with a more severe deficiency may require 50,000 IU twice a week for 6-8 weeks. After achieving a normal blood level, you can usually be switched to a maintenance therapy of 800-1,000 IU per day. It is important to avoid over-supplementation and vitamin D toxicity which can cause such symptoms as kidney stones, nausea, vomiting, poor appetite, constipation, and weight loss.

Dr. McMahon, a graduate of Yale University and the University of Pittsburgh School of Medicine, is board certified in Internal Medicine. She is a member of the American College of Physicians and the Allegheny County and Pennsylvania Medical Societies. She is in solo practice in the North Hills of Pittsburgh.