Higher Vitamin D blood levels associated with better fitness

Levels of vitamin D in the blood is associated with cardiorespiratory fitness (CRF), according to a new study published in the European Journal of Preventive Cardiology.

It is well established that vitamin D is important for healthy bones, but there is increasing evidence that it plays a role in other areas of the body including the heart and muscles.

Amr Marawan, assistant professor of internal medicine, Virginia Commonwealth University, Virginia, US, and colleagues conducted the study to investigate the association between Vit. D levels and CRF in a representative sample of the US population using data from the National Health and Nutrition Survey.

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"Our study shows that higher levels of Vit. D are associated with better exercise capacity," said Dr. Marawan. "We also know from previous research that Vit. D has positive effects on the heart and bones. Make sure your Vit. D levels are normal to high. You can do this with diet, supplements, and a sensible amount of sun exposure."

Cardiorespiratory fitness, a reliable surrogate for physical fitness, is the ability of the heart and lungs to supply oxygen to the muscles during exercise. It is best measured as the maximal oxygen consumption during exercise, referred to as VO2 max. People with higher cardiorespiratory fitness are healthier and live longer.

The study was conducted in a representative sample of the US population aged 20-49 years using the National Health and Nutrition Survey (NHANES) in 2001-2004. Data was collected on serum vitamin D and VO2 max. Participants were divided into quartiles of vitamin D levels.

Of 1,995 participants, 45% were women, 49% were white, 13% had hypertension, and 4% had diabetes. The mean ± SD age was 33 ± 8.6 years, with a mean ± SD vitamin D level of 58 ± 5.3 nmol/L and a mean ± SD VO₂ max of 40 ± 9.7 ml/kg/min.

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Key Findings:

• Participants in the highest quartile of vitamin D levels had a significantly higher CRF than participants in the lowest quartile.


• After adjustment for potential confounders, the difference between the highest and lowest vitamin D quartiles remained significant.


• Each 10 nmol/L increase in vitamin D was associated with a statistically significant 0.78 mL/kg/min increase in VO2 max.

Dr. Marawan said: "The relationship between higher vitamin D levels and better exercise capacity holds in men and women, across the young and middle age groups, across ethnicities, regardless of body mass index or smoking status, and whether or not participants have hypertension or diabetes."

Dr. Marawan noted that this was an observational study and it cannot be concluded that vitamin D improves exercise capacity. But he added: "The association was strong, incremental, and consistent across groups. This suggests that there is a robust connection and provides further impetus for having adequate vitamin D levels, which is particularly challenging in cold, cloudy places where people are less exposed to the sun."

On the other hand, Vitamin D toxicity can lead to excess calcium in the blood, which can cause nausea, vomiting, and weakness. "It is not the case that the more vitamin D, the better," said Dr. Marawan. "Toxicity is caused by megadoses of supplements rather than diet or sun exposure, so caution is needed when taking tablets."

Regarding further research, Dr. Marawan said: "We know the optimum vitamin D levels for healthy bones but studies are required to determine how much the heart needs to function at its best. Randomized controlled trials should be conducted to examine the impact of differing amounts of vitamin D supplements on cardiorespiratory fitness. From a public health perspective, research should look into whether supplementing food products with vitamin D provides additional benefits beyond bone health."

"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," concluded the authors.

For further reference follow the link: https://doi.org/10.1177/2047487318807279