Vitamin D is a nutrient that is needed to maintain good health for every part of the body – from keeping bones strong and helping the body absorb calcium to working with parathyroid function and the immune system. It is also a nutrient in which most adults are deficient. Atlanta Medicine recently spoke with two Atlanta rheumatologists, who shared their knowledge of current research involving vitamin D.
Research Finds Deficiencies in Most Adults, Genetic Predisposition
According to Gary E Myerson, M.D., a founding fellow of the American College of Rheumatology and practicing rheumatologist with Arthritis and Rheumatology of Georgia, the majority of adults in the U.S. have a vitamin D. deficiency.
“I’d say at least 80% of the adult population has a vitamin D deficiency,” he says. “A level of 30-100 ng/mL is in the normal range, but it’s shocking to see how many people have labs that show their level is in the teens.”
Raising the vitamin D level can be accomplished in one of two ways – either by prescription or with an over-the-counter supplement. A prescription dose is 50,000 IU taken once a week, and the over-the-counter dose can range from 1000-5,000 IU daily. Either way, success depends on compliance in taking the supplement.
Myerson adds that absorption of vitamin D appears to be somewhat determined by genetics. Recent research done on a pediatric population that included African Americans, Hispanics and Caucasians showed that ethnicity is a definite factor in the ability to absorb vitamin D.
“There are three alleles associated with absorption, and allelic variations in the vitamin D receptor were found in different races,” he says. “The study found that African Americans are at a much higher risk for deficiency, with a 95% genetic predisposition toward inability to bind vitamin D. Hispanics had a 48% predisposition, and Caucasians were at lowest risk at 27 percent.” Myerson again stresses the importance of supplementation for low vitamin D levels.
“To some degree, we’re all genetically predisposed in our ability to absorb vitamin D. You cannot change it by what you eat, because if you have a problem with absorption, you won’t be able to get vitamins through food,” he says. “Supplements are proven to work better because they are concentrated doses and the volume is controlled. It’s important for patients with a number of diagnoses – osteoporosis, chronic congestive heart failure, diabetes, kidney disease – to have their vitamin D level tested and see if it’s low enough to need supplementation.”
Vitamin D and Autoimmunity
Vitamin D deficiency is present in many autoimmune disorders and is likely a factor for people at risk of autoimmunologic diseases, according to John A. Goldman, M.D., MACR, FACP, CCD.
“There are vitamin D receptors everywhere in the human body,” he says. “Studies have shown that people who develop Type I diabetes have a lower vitamin D level; the same is true for rheumatoid arthritis and for lupus. The importance of the receptors on immune regulatory cells makes me wonder if there is more to it. But because these are observational studies, I can’t say with certainty that vitamin D is shown to improve these diseases. We need clarification.”
However, Goldman cites another study of people with vitiligo and psoriasis who definitely experienced improvement of their symptoms with vitamin D supplementation.
“These study participants were given 35,000 units of vitamin D a day. To put that in perspective, I prescribe 4,000 IU a day for my own patients and the Institute of Medicine’s RDA is 800 IU a day,” he says. “In this study, the treatment was shown to benefit both diseases. This is promising research because it surely would be cheaper to treat disorders like vitiligo and psoriasis simply with increased doses of vitamin D.”
Goldman suggests that supplementation may be more effective in prevention of some autoimmune diseases, rather than treatment.
“For example, you can use vitamin D to help prevent rheumatoid arthritis, but once someone has the disease, they’re not as responsive to a regular supplement,” he says. “When researchers looked at paired blood and synovial fluid T-cells in people with rheumatoid arthritis, they found the cells were less responsive to regular vitamin D supplements, but did become slightly more responsive at much higher levels.”
In addition, researchers are questioning whether vitamin D2 or D3 is more effective in the prevention and treatment of disease or whether the type of vitamin D matters.
“The results of recent clinical trials have been varied. But analysis primarily shows that D3 is more effective in raising levels,” he says. “I prescribe over-the-counter vitamin D3 for my own patients, but I encourage them to order it from a specific company that ensures purity of the product.”
Study Finds Vitamin D Doesn’t Prevent Type 2 Diabetes in People at High Risk
Taking a daily vitamin D supplement does not prevent type 2 diabetes in adults at high risk, according to results from a study funded by National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. The Vitamin D and Type 2 Diabetes (D2d) study enrolled 2,423 adults and was conducted at 22 sites across the United States. These findings were published in The New England Journal of Medicine and presented at the 79th Annual Scientific Sessions of the American Diabetes Association in San Francisco.
D2d is the largest study to directly examine if daily vitamin D supplementation helps keep people at high risk for type 2 diabetes from developing the disease. The study included adults aged 30 or older and assigned participants randomly to either take 4,000 International Units (IU) of the D3 (cholecalciferol) form of vitamin D or a placebo pill daily. All study participants had their vitamin D levels measured at the start of the study. At that time, about 80% of participants had vitamin D levels considered sufficient by U.S. nutritional standards.
The study screened participants every three to six months for an average of 2.5 years to determine if diabetes had developed. Researchers then compared the number of people in each of the two study groups that had progressed to type 2 diabetes. At the end of the study, 293 out of 1,211 participants (24.2%) in the vitamin D group developed diabetes compared to 323 out of 1,212 (26.7%) in the placebo group – a difference that did not reach statistical significance. The study was designed to detect a risk reduction of 25% or more.
D2d enrolled a diverse group of participants with a range of physical characteristics, including sex, age and body mass index, as well as racial and ethnic diversity. This representation helps ensure that the study findings could be widely applicable to people at high risk for developing type 2 diabetes.
“In addition to the study’s size, one of its major strengths is the diversity of its participants, which enabled us to examine the effect of vitamin D across a large variety of people,” says lead author Anastassios G. Pittas, M.D., principal investigator from Tufts Medical Center in Boston. “When the study ended, we found no meaningful difference between the two groups regardless of age, sex, race or ethnicity.”
More than 50% of adults in the United States take nutritional supplements, and use of vitamin D has increased substantially over the last 20 years. Because of these trends, the study also evaluated the safety of taking 4,000 units of vitamin D daily – greater than the average daily recommended dose of 600-800 IUs a day, but within limits deemed appropriate for clinical research by the Institute of Medicine. The researchers saw no difference in the number and frequency of predicted side effects such as high blood calcium levels and kidney stones when they compared the vitamin D and placebo groups.