Want to get fit? Check your vitamin D levels. Cardiorespiratory fitness (CRF) may well be linked to serum vitamin D levels. A study, published in the European Journal of Preventive Cardiology (October 2018), looked at data from nearly 2,000 participants in the National Health and Nutrition Survey. Subjects were between the ages of 20 and 49.
Researchers used VO2 max as an indicator of cardiorespiratory fitness. Used to establish the aerobic endurance of an athlete, VO2 max is the amount of oxygen a person can utilize during intense exercise. By putting a face mask on the subject, the volume and gas concentrations of inspired and expired air can be directly measured.
Of the 1995 participants, 45.2% were women, 49.1% were white, 13% were hypertensive and 4% had diabetes. Vitamin D levels did not vary between matched subjects with confounding variables like diabetes, high blood pressure, age, sex, race, CRP levels, BMI, etc. The one variable that did make a difference between matched subjects was serum vitamin D levels. The researchers found that serum vitamin D levels had a significant effect on cardiorespiratory fitness (VO2 max). Those in the highest quadrille had a VO2 max 2.9 higher on average than those in the lowest quadrille.
According to the authors, “We found a strong independent association between vitamin D levels and CRF, which was robust to potential confounding variables. Future studies are needed to explore the underlying biological mechanisms of the observed association. Clinical trials of vitamin D supplementation are required to validate the relationship.”
Vitamin D levels have been associated with other cardiovascular issues. Low levels are linked to a higher risk of hypertension, poor outcomes for congestive heart failure patients and overall cardiac mortality. Now we can add cardiorespiratory fitness to that list. Because CRP status may be an indicator of cardiovascular risk, the American Heart Association has recommended that CRP be measured in routine clinical practice.
I will be looking for a local facility that can measure CRP. In the meantime, you all should have your serum vitamin D levels checked. I recommend my patients have a vitamin D test as a part of their routine yearly blood test.
To review, the medical norm for serum vitamin D is 30-100 ng/mL. However, the ideal range is 42-80 ng/mL. If you look at my blogs from a year ago, I used 40-100 ng/mL as ideal. I raised the lower end slightly and dropped the upper end significantly based on a 20-year study of vitamin D published earlier this year.
The serum test for vitamin D measures the inactive, stable form 25-hydroxy vitamin D. The active form 1,25-hydroxy vitamin D is very unstable and varies from minute to minute in the blood stream. However, the level of 1,25-hydroxy vitamin D in each cell is what really matters. Unfortunately, we have yet to develop an economically feasible method for this measurement. Current research does indicate that there is pretty good correlation between the inactive form in the blood and the active form in the cells.
Research indicates 95% of Americans are deficient in vitamin D, even in sunny South Florida. Get your level checked and start supplementing vitamin D3. That’s the form that is supposed to be made in your skin via the conversion of cholesterol. It then travels to the liver to be converted to the 25-hydroxy form. The kidneys convert 25-hydroxy vitamin D to 1,25-hydroxy vitamin D as needed but every cell can also do this conversion for its’ own use.
Source: December 7,2018 Biotics Research Corporation