Testing Vitamin D for Heart Health in Type 2 Diabetes
Researcher Carlos Bernal-Mizrachi, MD, investigates whether large doses of Vitamin D improve heart health in African Americans
Carlos Bernal-Mizrachi, MD
Professor of Medicine, Washington University School of Medicine in St. Louis
Clinical Treatment of Diabetes
ADA Research Funding
Clinical Translational Award
There are many reasons to be grateful for the invention of sunscreen and office jobs, but vitamin D deficiency is not one of them. Produced in the body in response to sunlight, vitamin D is crucial for everything from strong bones to heart health.
These days many people aren’t getting enough of the stuff. Modern life has made vitamin D deficiency more common, as people simply spend less time outdoors. Sunscreen, generally a good idea, can also reduce exposure.
And people living north of the 42nd parallel, which passes through Chicago and includes most of the northern United States, are at a disadvantage thanks to shorter days in the winter. “When you’re living farther north, there are less months of vitamin D production in your body,” says Carlos Bernal-Mizrachi, MD, a researcher at Washington University in St. Louis. “At 42 degrees latitude, you’re not producing vitamin D between September and April.”
Lots of skin pigment can also make vitamin D harder to come by. Many African Americans, for example, have difficulty producing enough vitamin D. “Because of their skin color, African Americans require longer exposure to sunlight to produce the same amount of vitamin D as Caucasians,” Bernal-Mizrachi says. Making things worse, type 2 diabetes, an epidemic among African Americans, also makes it harder for the body to produce vitamin D.
Lots of people think—mistakenly—that the vitamin D added to milk takes care of their needs. “The common food people eat doesn’t include enough vitamin D to replace what you don’t produce in the winter and fall,” says Bernal-Mizrachi. “Milk does very little—you’d require huge amounts of milk every day to achieve the daily allowances of vitamin D.” Better sources include shiitake mushrooms and Alaskan salmon or mackerel, none of which are part of the average American’s everyday diet.
Bernal-Mizrachi says that in recent years researchers have connected vitamin D deficiency to the higher rates of heart disease in African Americans, whose risk of developing cardiovascular disease is double that of whites. To understand why, researchers combed through large-scale studies that ask thousands of people with diabetes about their lifestyle and health.
After correcting for other possible explanations, such as hypertension, smoking, and income levels, one factor still stood out: vitamin D. “Vitamin D explains 50 percent of the increased risk, suggesting that vitamin D could be a factor that needs to be studied to prevent cardiovascular disease in African Americans,” says Bernal-Mizrachi.
The connection came as a surprise to many. Vitamin D deficiency has long been known to cause diseases such as rickets, a softening of the bones that affects growing children, but heart health was a new link. “Vitamin D deficiency has been linked to osteoporosis for years,” Bernal-Mizrachi says. “What is new is non-bone illnesses.”
With the help of a grant from the American Diabetes Association, Bernal-Mizrachi is conducting an experiment to see if correcting the vitamin D deficiency can slow or halt the progression of cardiovascular disease. He’s put together a randomized controlled trial, the most rigorous type of research study, to see if large doses of vitamin D—nearly seven times the standard dose used to treat vitamin D deficiency—might reduce the risk of heart attacks and strokes.
Here’s how it works. Bernal-Mizrachi is recruiting nearly 100 older African Americans with type 2 diabetes. Half of the patients in the study get 600 IU of vitamin D a day for a year; the other half get a whopping 4,000 IU (100 mg).
Neither the patients nor the doctors know who’s getting which dose until after the trial. Bernal-Mizrachi then uses ultrasound to measure the thickness of the inner walls of the carotid artery, the big blood vessel that pulses in your neck. The measurements are done before the vitamin D treatment, after six months, and after a year.
The carotid artery, Bernal-Mizrachi says, is a good indicator of overall cardiovascular health and, in combination with blood tests, gives the researcher a way to gauge whether patients’ heart and circulatory health is improving. He’s hoping that when all the data are collected and analyzed, the patients getting the megadose will show more signs of improvement than patients on the smaller dosage. That would show vitamin D has promise as a low-cost treatment for cardiovascular disease. “If this works, it could really change policies,” Bernal-Mizrachi says. “Vitamin D could be a medication that will decrease cardiovascular disease.” Until the results are in, though, Bernal-Mizrachi urges people to avoid self-medicating: “It’s important for physicians to determine the level appropriate for you.”
If the experiment is a success, the next step would be to do a larger trial for public health policy purposes, to see if African Americans should supplement their vitamin D intake to promote heart health. An affordable, easy fix, vitamin D could be just what the doctor ordered.