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The Nutrition Examination Research Digest (NERD) aims to provide rigorous, unbiased analysis of the latest and most important nutrition and supplementation studies. Click here to subscribe or login if already a subscriber .

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Investigating vitamin D as a performance enhancer

Having sufficient vitamin D levels has been associated with better muscle recovery. This trial not only looks at the question of causality, but also addresses some potential mechanisms of vitamin D’s benefit for exercise.

Study under review: A Systems-Based Investigation into Vitamin D and Skeletal Muscle Repair, Regeneration and Hypertrophy

Introduction

Why is Vitamin D such a popular supplement, among both researchers and the general public? One reason is that it potentially acts on a broad spectrum of health and performance measurements. Researchers have examined the effects of this fat-soluble vitamin on chronic pain[1], cystic fibrosis[2], multiple sclerosis[3], and the risk of cardiovascular disease and mortality[4] (covered in NERD #7).

Many people are not getting enough of this vitamin. Recent estimates have indicated that 37.3% of the world’s population[5] may have an inadequate level of vitamin D. The Institute of Medicine has defined blood concentrations between 30 to 50 nmol/L of vitamin D to generally be considered inadequate. Although sometimes defined at different cutoff points, risk of deficiency can be characterized by levels lower than 30 nmol/L, while an adequate, healthy range is usually considered to be between 50 and 125 nmol/L.

We’ll be using units of nmol/L throughout this article, although many labs report vitamin D levels in ng/mL. You can see how these two units relate to each other in Figure 1. One possible downstream effect of these inadequacies may be a decrease in the body’s ability to regenerate muscle tissue. Researchers have known since 1985 that there are vitamin D3 receptors on muscle[6] cells, and in the past few years research on vitamin D in the context of boosting performance has become popular. One intervention trial in well-trained athletes showed an improvement in sprint times and vertical jump[7] with supplementation. Further studies have associated higher vitamin D status[8] with a more rapid recovery of skeletal muscle strength after an acute bout of intense exercise.

The growing body of data[9] showing that vitamin D plays an important part in the function of skeletal muscle[10] suggests this vitamin may be a potential ergogenic aid. The fact that vitamin D3 is a relatively inexpensive and widely-available supplement makes it all the more attractive to athletes. Around 56% of athletes have[11] vitamin D levels of 80 nmol/L or lower, so supplementation could help combat deficiency. Although previous research has indicated[12] vitamin D may help with improved muscle healing, a causal relationship has not yet been firmly established. The study under review looked further into this connection to determine if there is a potential cause-effect relationship between vitamin D and muscle repair, regeneration, and hypertrophy.

Figure 1: Converting nmol/L to ng/mL
Vitamin D plays diverse roles in maintaining health, and has been investigated for beneficial effects on a host of conditions. A developing line of research has looked into the roles this vitamin could play in the context of boosting physical performance. The present study investigated vitamin D to determine how it affects muscle repair, regeneration, and hypertrophy.

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The big picture

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Other Articles in Issue #14 (December 2015)

  • Trans fats: “natural” might not mean “healthy”
    In the nutrition community, a common message has been that artificial trans fats are bad, however natural trans fats are not only okay but beneficial. This trial on blood lipids puts that to the test.
  • High versus low fat diets for insulin sensitivity
    More body weight means more risk for metabolic syndrome. But the question of whether more fat (and especially saturated fat) impacts insulin sensitivity hasn’t been adequately addressed until now.
  • Exercise, with a (tart) cherry on top!
    Berries have burst onto the research scene in recent years. Tart cherries have shown some of the most promise in certain areas, leading to this study of powdered tart cherry on exercise recovery.
  • Interview: Dan Pardi MS PhD(c)
    Dan Pardi is an entrepreneur and researcher whose life’s work is centered on how to facilitate health behaviors in others.
  • Root rage: The impact of ashwagandha on muscle
    So called “adaptogens” like ashwagandha are typically studied for stress-easing potential. A randomized trial looked into this popular herb for a different purpose: bolstering adaptations to weight training.
  • Does the Food Guide make my butt get fat?
    By Francy Pillo-Blocka, RD
  • Antioxidants, anti-adaptations?
    We’ve covered antioxidants and strength training before. This study is a bit different — it investigates whether vitamin C and vitamin E might impact adaptations to endurance exercise.
  • I <3 green tea
    When it comes to curbing cardiovascular disease, it’s not all about reducing cholesterol. Green tea may help prevent oxidation of LDL, as is explored in this trial looking at green tea catechins both in vivo and in vitro.
  • Investigating slow carbs for metabolic rate
    Glycemic index, glycemic load, insulin index: only one of these is widely known by the public. But when it comes to keeping weight off, does glycemic index and total carb content actually have any impact?