A new controlled clinical trial published in the Iran Journal of Pediatrics found that daily vitamin D supplementation for one month increased HDL cholesterol levels among children.
Conventionally, cholesterol is divided into two categories, the “good” and the “bad.” The good cholesterol refers to high density lipoprotein (HDL) cholesterol, which helps remove low density lipoprotein (LDL) cholesterol from the arteries and carries it back to the liver, where it is flushed from the body. Research has shown that a higher HDL cholesterol levels protects against heart attack and stroke.
LDL cholesterol is traditionally known as the “bad” cholesterol, because it deposits plaque to the arteries, making them less flexible. When arteries become clogged and stiff, one is affected by atherosclerosis. Atherosclerosis puts one at an increased risk for heart attack, stroke and peripheral artery disease.
The consequences of high cholesterol on health has posed a large debate recently due to the publication of a review that aimed to determine whether LDL cholesterol was linked with mortality in elderly adults over the age of 60. The review concluded that there was no link between cholesterol and mortality. A total of 30 studies were included in the meta-analysis, with 12 finding no link between LDL and mortality and 16 determining that lower LDL was, surprisingly, linked with higher mortality risk.
This shocking new discovery has prompted much media coverage, along with scientific skepticism of the results. For instance, a recent review discussed the long list of limitations to the study. One of the authors stated, “Only LDL cholesterol was examined. Levels of total cholesterol, triglycerides, and the ratio of LDL to HDL “good” cholesterol could be having an effect and mediating the link between LDL and mortality.”
While the role of LDL cholesterol in heart health remains widely unknown, the role of HDL in heart health appears certain. In fact, some scientists and doctors believe that the medical community should be paying more attention to the ratio of HDL/total cholesterol levels, rather than only the total cholesterol levels or LDL levels.
Due to the known relationship between HDL and heart health, researchers have investigated ways to increase HDL levels.
Multiple studies have shown that vitamin D deficiency is associated with cardiovascular disease. Yet, a few studies have produced conflicting results. An observational study from 2015 suggested that both high and low vitamin D levels were associated with increased cardiovascular disease mortality. Therefore, researchers recently conducted a study to evaluate the effects of vitamin D supplementation on HDL levels, a known protector of cardiovascular disease.
A total of 47 children between the ages of 10-14 years old were included in the study. The children were randomly divided into two groups: the vitamin D group that received a daily 1,000 IU vitamin D supplement for one month and a control group that received placebo pills for the same duration.
Here is what the researchers found:
- Before the intervention, the average vitamin D status was 12.3 ng/ml and 4.9 ng/ml for boys and girls, respectively (p < 0.001).
- The vitamin D group’s average vitamin D status increased from 7.6 ng/ml at baseline to 11.5 ng/ml after the intervention (p < 0.001).
- The control group’s average vitamin D status remained nearly the same, starting with 9.7 ng/ml and ending with 9.3 ng/ml (p = 0.27).
- The vitamin D group’s average HDL levels significantly increased from an initial value of 45.6 mg/dl to 49.7 mg/dl (p = 0.007).
- The control group’s average HDL levels decreased slightly from 45.3 mg/dl to 43.7 mg/dl (p = 0.27).
The researchers concluded,
“The present study provides consistent support for a relationship between vitamin D and HDL-C, indicating that vitamin D supplementation results in increased blood levels of HDL and that it can be regarded as a protective factor to reduce the risk of cardiovascular disease.”
The study had a few minor limitations to consider. First, the sample size was relatively small. Second, the study duration was largely inadequate. Due to vitamin D’s half-life of 3-4 weeks, ideally, studies should last for two months or longer to produce the most profound effects.
Tovey, A. & Cannell, JJ. Clinical trial finds vitamin D supplementation increases “good” cholesterol in children. The Vitamin D Council Blog & Newsletter, 2016.