Vitamin D may reduce inflammation during resistance training, tout experts

14 Dec 2022 --- Data on the effect of vitamin D supplementation on cardiorespiratory fitness (VO2 max) are conflicting. Researchers have found it has a negligible impact on cardiorespiratory fitness performance, while discovering that it may still help regulate inflammation in vitamin D-deficient young men conducting resistance training.

A possible reason for the discrepancies found in the academic literature investigating this topic is the differences in baseline vitamin D levels among participants in previous studies, the researchers of the current paper flag.

The main objectives of the present study were to assess the impact of Vit-D supplementation on VO2 max and inflammatory status in vitamin D deficient young, healthy men. The overall findings of the paper were published in the journal Nutrients.

Vitamin D is a fat‐soluble vitamin, the bioactive form of which – calcitriol – acts in the human body like a steroid hormone via specific nuclear receptors.Reasoning behind the hypothesis
Vitamin D is a fat‐soluble vitamin, the bioactive form of which – calcitriol – acts in the human body like a steroid hormone via specific nuclear receptors.

Calcitriol inhibits and stimulates the production of pro‐ and anti‐inflammatory cytokines, respectively. This regulates the body’s inflammatory system, as evidenced in previous analysis.

Biological receptors for vitamin D have been detected in most cells and tissues in the human body, including skeletal muscle, vascular smooth muscle, lungs, cardiac muscle and immune cells. Given the ubiquity of these receptors, the researchers argue that it was reasonable to assume that vitamin D may affect the function of these organs and thus improve VO2 max.

Furthermore, previous research has uncovered that vitamin D may promote erythropoiesis and hemoglobin synthesis, while affecting the binding affinity of oxygen to hemoglobin.

“It is therefore not surprising that [previous studies] reported an independent robust association between serum vitamin D levels and VO2 max in adults over a wide age range,” state the researchers.

“However, studies in adolescents did not show such an association, or showed that it occurred only in boys but not in girls.”

The researchers note it is well established that VO2 max is inversely associated with cardiovascular disease risk and all‐cause mortality. Chronic low-grade inflammation, on the other hand, plays a critical role in the pathogenesis of athero‐ sclerosis, the latter being the main cause of cardiovascular diseases.

Sunshine vitamin’s effect on sports
Participants were assigned to one of the two groups, which, in a double-blind manner, supplemented their diet daily with either vitamin D (8,000 IU) or a placebo. They were asked to simultaneously perform a 12-week supervised resistance training program.

During the 12-week intervention, serum vitamin D concentrations increased 3.9-fold in the group given vitamin D, while no changes occurred in the placebo group.During the 12-week intervention, serum vitamin D concentrations increased 3.9-fold in the group given vitamin D, while no changes occurred in the placebo group.

“Baseline VO2 max did not differ in the two groups and remained unchanged during the intervention,” the researchers write.

In conclusion, the 12-week vitamin D supplementation was found to improve the inflammatory status, while having no impact on VO2 max in vitamin D-deficient young men engaged in resistance training.

“One of the strengths of the present study is the inclusion of only vitamin D-deficient men,” state the researchers. “This excludes the possible influence of substantial individual differences in baseline vitamin D status on the results.”

“In addition, monitoring participants’ habitual diet three times during the supplementation and RT period enabled us to exclude the possibility that changes in dietary intake influenced the study results.”

However, the scientists flag that whey protein consumed during training may also possess a similar anti‐inflammatory effect. Therefore, the inclusion of a vitamin D-only supplemented group in the study would have been appropriate.

“However, we consider it improbable that post-training session whey supplement influenced the inflammatory status of participants in our experimental setting because both vitamin D and placebo groups administered whey,” they conclude.

During these winter months, when natural sunlight comes in shorter time frames, nutritional leaders have stepped up calls to supplement with vitamin D. A study published in October found that vitamin D deficiency may be causally linked to premature death.

In an unexpected finding, a “higher-than-expected” number of people with hypovitaminosis D was recently identified by researchers in some of the sunniest nations in Europe.

By Benjamin Ferrer