Study findings: Participants who received 4,000 IUs of vitamin D per day saw their arterial stiffness decrease 10.4 percent in the four months of a recent study. These participants’ blood levels of vitamin D increased the quickest—reaching a healthy level in eight weeks—but then plateaued.
In those who took 2,000 IUs, arterial stiffness dropped 2 percent during the study. Among participants who took 600 IUs, arterial stiffness increased 0.1 percent; however, those who received the placebo saw their stiffness increase 2.3 percent over the 16 weeks. (During the study, the RDA for most adults and children was 600 IUs of vitamin D.)
The study: Anas Raed, PhD, and Yanbin Dong,PhD, looked at arterial stiffness and vitamin D levels in 70 black people age 13 through 45 before and after a 16-week double-blind study in which some participants took placebos, while others took 600 IUs, 2,000 IUs or 4,000 IUs per day in a monthly dose to ensure compliance.
Arterial stiffness was measured from the carotid artery in the neck to the femoral artery using non-invasive pulse wave velocity.
Study conclusions: Arterial stiffness improves in young, overweight black people with vitamin D supplementation. The reduction in stiffness corresponds with the dose of vitamin D consumed. Participants taking the highest dose of vitamin D considered safe benefited the most from the supplement.
Why the research is interesting:
- Heart disease is the leading cause of death in the United States. Black people tend to acquire heart disease and die from it at a younger age than white people.
- Stiff arterial walls are a predictor of cardiovascular disease and death; vitamin D deficiency seems to contribute to these problems, as well. Blacks are at higher risk of vitamin D deficiency because dark skin does not absorb as much sunlight as lighter skin. Also, fat holds vitamin D, preventing the body from receiving its benefits.
- This study is the first of its kind, according to the researchers. Because of this research, the Institute of Medicine increased its highest limit of vitamin D to 4,000 IUs from 2,000 IUs.
Points to consider:
- This was a small, short study. The researchers say a larger study among high-risk populations that lasts a year would provide more information, such as whether higher levels of vitamin D would reduce the risk of cardiovascular disease.
- More than 80 percent of Americans have insufficient levels of vitamin D.
Current RDAs: For adults 19-70 years old, the National Institute of Health recommends a daily supplement of 600 IUs. For those older than 70, the RDA is 800 IUs. The upper limit of daily supplementation is 4,000 IUs for anyone 9 or older.
Authors: Dr. Anas Raed and Dr. Yanbin Dong
Published: PLOS One, Dec. 7, 2017