Multiple factors contribute to your overall level of fitness. Gender, age, diet, the amount of stress you have and the kind of drugs you take, even the environment in which you live, are just a few of the obvious things that influence the way your heart, lungs and mind work together to energize and sustain your muscles during a workout. But did you know that the amount of vitamin D in your blood can also play a part in how well you perform on any given day? A study published in the European Journal of Preventive Cardiology at the end of last year reports that higher levels of serum vitamin D seem to be associated with better physical fitness. It’s an interesting finding that is prompting a lot of discussion. Take a look:
What is Vitamin D?
Vitamin D is a fat-soluble vitamin that is produced in our bodies as a result of sun exposure. It naturally occurs in only a limited number of foods: Mushrooms, eggs and certain types of fish and other seafood are the best edible sources other than those that have been fortified artificially. Because it enables our bones to absorb calcium, vitamin D has long been linked to higher bone density, but it also helps regulate cell growth and immune responses, as well as reduce inflammation.
What the Study Found
Previous research has shown that people who exercise regularly usually have higher levels of vitamin D than those people who don’t. This has often been attributed to the fact that many fit people tend to exercise outside in the sun, boosting their levels of vitamin D in the process. The most recent study by Virginia Commonwealth University, however, notes that athletes with higher levels of vitamin D have corresponding higher levels of cardiorespiratory fitness (CRF) as measured by maximal oxygen uptake (VO2 max), as well. (According to the online health resource Verywell Fit, “VO2 max…is the measurement of the maximum amount of oxygen a person can utilize during intense exercise.”) A higher VO2 max number means more oxygen is getting to the skeletal muscles, indicating better heart and lung health.
Using data from 2,000 subjects aged 20-49 from the National Health and Nutrition Survey (2001–2004), researchers at Virginia Commonwealth University’s School of Medicine created four separate groups based on participant vitamin D levels. The people in the top quartile (with the highest levels of vitamin D) had a 4.3 times greater level of cardiorespiratory fitness than those in the lowest quartile (P < 0.001). And when researchers adjusted the numbers to account for potential confounders (such as “age, sex, race, body mass index, hypertension, diabetes, smoking, C-reactive protein, hemoglobin and glomerular filtration rate”), the difference was still highly significant at P < 0.001. Indeed, they noted that every 10-point increase in serum vitamin D levels was associated with a .78-point increase in VO2 max across all the quartile groups, leading them to conclude that a person’s vitamin D level and his or her cardiorespiratory fitness are somehow related. The researchers do warn that this study is not necessarily indicative of a causal relationship between vitamin D and CFR. However, they still believe there is enough evidence to recommend that athletes who want to maximize their exercise capabilities monitor their serum vitamin D levels and maintain a sufficient amount. Just as marketing professionals use various types of market research to garner insight, the medical and sports communities can take this information and use it to further their own understanding of how vitamin D plays a multifaceted role in a person’s overall health.