European Journal of Preventive Cardiology (EJPC)



The small number of studies that have investigated the relationship between serum vitamin D levels and cardiorespiratory fitness (CRF) have reported conflicting results. We investigated the association between vitamin D levels and CRF in a representative sample of the US population using data from the National Health and Nutrition Survey (2001–2004).
We included participants between the ages of 20 and 49 years and excluded those with vitamin D levels at the 5% extremes of the distribution. We used survey-weighted linear regression without and with adjustment for age, sex, race, body mass index, hypertension, diabetes, smoking, C-reactive protein, hemoglobin, and glomerular filtration rate to examine the relationship between the maximal oxygen consumption (VO2 max) (as a surrogate for CRF) and vitamin D levels.
We found an independent and robust association between serum vitamin D levels and CRF, but our results need to be validated with clinical trials examining the effect of vitamin D supplementation on CRF.
Low serum vitamin D levels have been associated with a high risk of hypertension, poor outcomes in patients with heart failure, and increased all-cause and cardiovascular mortality.1,2 Receptors for vitamin D are found in at least 30 different types of cell, including skeletal muscle cells.3,4 Therefore vitamin D may have several effects in addition to its role in bone homeostasis.4,5 The American Heart Association recommended in 2016 that cardiorespiratory fitness (CRF) should be measured in routine clinical practice for high-risk patients because there is unequivocal evidence that CRF significantly improves cardiovascular risk prediction.6 CRF refers to the ability of the circulatory and respiratory systems to supply oxygen to skeletal muscles during sustained physical activity. It is best measured as the maximal oxygen consumption (VO2 max) during exercise.6 It is well established that a higher CRF is associated with better outcomes in all-cause and cardiovascular mortality.6–8 Some studies have investigated the association between vitamin D and CRF, but the reported results are contradictory. These studies had several limitations. Some enrolled only adolescents and others were not representative of the general population in other ways.9–13 The objective of our study was therefore to investigate the association between serum vitamin D levels and CRF in a representative sample of the US population using the National Health and Nutrition Examination Survey (NHANES) database.