The topic of vitamin D supplementation is a vast minefield of purported benefits - and lack thereof. Now, a new study suggests taking vitamin D supplements improves exercise performance and lowers the risk of heart disease.
The study, conducted by researchers from Queen Margaret University in Edinburgh, UK, is presented today at the Society for Endocrinology annual conference in the Scottish capital.
Vitamin D is produced in the body with ultraviolet B rays from sun exposure, and it can also be consumed through diet or supplements. Sources of the vitamin include oily fish and eggs, but it can be difficult to get enough through diet alone.
In the body, vitamin D helps control calcium and phosphate levels in the blood, and it plays an essential role in bone and teeth formation.
In geographical areas where the sun is not abundant, many populations turn to vitamin D supplementation for health benefits.
Researchers from this latest study, led by Dr. Emad Al-Dujaili, say previous studies have suggested that vitamin D can block the action of an enzyme called 11-βHSD1, which assists in making the stress hormone cortisol.
High levels of this stress hormone can increase blood pressure by restricting the arteries, narrowing blood vessels and encouraging the kidneys to retain water, say the researchers.
Because vitamin D may reduce levels of cortisol in the body, the researchers theorized that it could improve exercise performance and lower risk factors for cardiovascular issues.
Vitamin D deficiency: a 'silent syndrome'
To test their hypothesis, the researchers gave 13 healthy adults either 50 μg of vitamin D per day or a placebo during a 2-week period.
After the 2 weeks, results showed that the study subjects who received vitamin D supplements had lower blood pressure and lower cortisol levels - as measured in urine tests - compared with the subjects who were given a placebo.
Additionally, a fitness test revealed that the adults taking vitamin D were able to cycle 6.5 km in 20 minutes, compared with only 5 km at study baseline, and they also showed lower signs of physical exertion after supplementation - as revealed by systolic and diastolic blood pressure.
In the placebo group, there were no significant improvements on cardiovascular disease risk factors or exercise performance.
According to a National Health and Nutrition Examination Survey, the overall vitamin D deficiency rate for adults in the US is at 41.6%. Furthermore, people with darker skin are not as efficient at using sunlight to make vitamin D, so they are more likely to need a vitamin D supplement, particularly in the winter.
Commenting on their study, coauthor Dr. Raquel Revuelta Iniesta says:
"Our pilot study suggests that taking vitamin D supplements can improve fitness levels and lower cardiovascular risk factors such as blood pressure. Our next step is to perform a larger clinical trial for a longer period of time in both healthy individuals and large groups of athletes such as cyclists or long-distance runners."
Dr. Al-Dujaili adds that their findings add to previous evidence showing the importance of tackling vitamin D deficiency, which he refers to as "a silent syndrome linked to insulin resistance, diabetes, rheumatoid arthritis and a higher risk for certain cancers."
In August of this year, Medical News Today reported on a study that suggested vitamin D supplements offer no benefits to obese teens, in terms of lowering diabetes risk or bettering heart health.