Does vitamin D help for muscle growth?

Geschatte leestijd: 6 minuten What is the added value of vitamin D supplements if muscle growth, muscle mass, and muscle strength are your goals?

Vitamin D and muscle growth

If there’s one thing that has a lot of publications, it’s vitamin D. However, the majority of these publications consist of epidemiological research. In short, this only yields associations between vitamin D concentrations and certain diseases, as I previously discussed in the article addressing how realistic a vitamin D deficiency is. Answer: very realistic. Double-blind placebo-controlled research, the gold standard for determining whether vitamin D actually does something, is a bit scarcer. Unfortunately, there is only one such study that looked at vitamin D supplementation and muscle growth in young people. In this study, young and old participants were divided into a vitamin D group (daily 1920 IU vitamin D and 800 mg calcium) and a placebo group [6]. The supplementation period lasted sixteen weeks in total. In the last 12 weeks, the subjects also trained (strength training). To determine the effect on muscle hypertrophy, measurements of the cross-sectional area of the quadriceps were taken. Unfortunately, no significant effect of vitamin D supplementation on muscle hypertrophy was found. You could place some caveats on this study. One important one is that the 25(OH)D concentration in the blood in the group of young people who supplemented with vitamin D only increased from 41.3 nmol/l to 71.6 nmol/l. According to the guidelines of the Endocrine Society, 71.6 nmol/l is still an insufficient level [7]. It has also been suggested before that an optimal level for sports performance could be around 125 nmol/l [8]. In short: the amount of vitamin D supplementation may have been inadequate in this study to achieve a potential effect on muscle hypertrophy. Fortunately, we have more research material available than just Wilson’s results. However, a considerable number of studies involve funding from MTI or employees (especially Steven Nissen himself) as co-authors of the publications. Especially these studies show positive results on strength or body composition. However, most independent studies do not show any effect. This suggests that if HMB does work, the effect is likely to be small. These studies also have a limited number of subjects, making it difficult to detect a small effect.

Vitamin D supplementation may help with muscle strength

If you have a severe deficiency, vitamin D supplementation certainly helps with muscle strength. Whether it helps with minor deficiencies is another question. A recently published systematic review titled “Effects of Vitamin D Supplementation on Muscle Strength in Athletes: A Systematic Review” attempted to answer this question. This systematic review considered the results of six studies. The authors found that vitamin D2 (the ‘plant-based’ form of vitamin D), used in two of the studies, had no effect on muscle strength. Vitamin D3 (the ‘animal-based’ form of vitamin D), on the other hand, showed a significant effect on muscle strength in two of the studies, and a trend for a significant effect in the remaining two. The increase in muscle strength between the studies ranged from only 1.37% to as much as 18.75%. Personally, I think the lack of effect in the vitamin D2 studies didn’t come because it was vitamin D2 instead of D3. In one of the studies, a very low dosage was used (600 IU per day). In the other study, the dosage was adequate (3800 IU per day), but the 25(OH)D concentration at baseline was already high (about 100 nmol/l). In that case, it’s quite likely that supplementation will do little to nothing. It seems, in any case, that if you are vitamin D insufficient and you supplement enough vitamin D, it may promote your muscle strength. The dosages used in the four studies with vitamin D3 ranged from 2000 to 5000 IU per day. The acceptable upper intake level used by the Health Council for adults is 4000 IU per day. This amount also seems necessary for most people to achieve a serum 25(OH)D concentration of more than 100 nmol/l [10, 11]. With winter approaching, vitamin D becomes interesting again. We can indeed produce vitamin D when we sit in the sun, but not in the winter. To be precise, we can hardly produce any vitamin D under the Dutch sun from October to March [1].

Vitamin D needed?

As a result, we depend on vitamin D from our healthy diet. However, there isn’t much vitamin D in our diet. Naturally, it’s not found in many foods. Exceptions to this are fatty fish such as salmon, mackerel, and herring [2]. These contain about 400-500 IU of vitamin D per 100 grams. And that’s not much actually. Despite the low concentration, vitamin D in fat and meat, due to the low fish consumption here in the Netherlands, is still our main source of vitamin D [3]. A deficiency is therefore quite common in the Netherlands. A high percentage of non-native Dutch people appear to be vitamin D deficient, and the majority (50-80%) of the Dutch elderly population has been found to be vitamin D deficient [4]. A similar picture was recently found among Dutch athletes [5]. Of these, 34% were found to be deficient and 36% insufficient.

Vitamin D status	serum 25(OH)D concentration
Deficient	< 50 nmol/l
Insufficient	52.5 – 72.5 nmol/l
Adequate	> 75 nmol/l

Interpretation of vitamin D status. Based on guidelines from the Endocrine Society [7]. Between 72.5 nmol/l and 75 nmol/l, you’re in a bit of a bind because they don’t have a word for that.

A vitamin D deficiency can be serious: these are the consequences

So there’s a good chance that your vitamin D level could use a boost. Especially if you spend as little time outside as I do. With a (severe) deficiency, you risk several serious skeletal abnormalities, namely osteomalacia, rickets, and osteoporosis. In addition to the skeleton, your muscles can also be affected. A vitamin D deficiency can be associated with muscle weakness (proximal myopathy) and muscle pain (myalgia). Which, undoubtedly, is detrimental to your athletic performance and muscle growth. There are also many epidemiological studies that demonstrate a negative correlation between vitamin D status and cardiovascular diseases or cancers. A negative correlation means that the higher the serum 25(OH)D concentration, the lower the occurrence of cardiovascular diseases or cancers. This has led to the suggestion that vitamin D supplementation could reduce the risk of cardiovascular diseases and cancer. In many other articles on the internet, vitamin D is praised to the skies for this reason. Epidemiological studies can find associations. That’s nice, but you still don’t know if it’s because of vitamin D or not. What do the randomized intervention studies say that can actually establish a causal relationship? In this article, I have to disappoint you a little based on those studies. Randomized studies (which have a greater burden of proof than the aforementioned epidemiological studies) have so far been unable to find a causal relationship [12,13]. So it’s premature to say that it works protectively against cardiovascular diseases and cancers. On the other hand: it doesn’t seem to hurt either…

Conclusion: Vitamin D and muscle growth

With winter approaching, it’s wise for many people to supplement with vitamin D. You can easily become deficient in the Netherlands, and recent research suggests that most athletes are also vitamin D deficient or insufficient. It’s still unclear whether vitamin D supplementation has an effect on muscle growth, as there is simply too little research on this. However, it seems that it may promote your muscle strength. A dosage of 4000 IU per day is high enough for most people and is also safe.

References

1. Webb, Ann R., L. Kline, and Michael F. Holick. “Influence of season and latitude on the cutaneous synthesis of vitamin D3: exposure to winter sunlight in Boston and Edmonton will not promote vitamin D3 synthesis in human skin.” The journal of clinical endocrinology & metabolism 67.2 (1988): 373-378.
2. Holick, Michael F. “Vitamin D in Health and Disease: Vitamin D for Health and in Chronic Kidney Disease.” Seminars in dialysis. Vol. 18. No. 4. Blackwell Science Inc, 2005.
3. Van Rossum, C. T. M., et al. “Dutch National Food Consumption Survey 2007-2010: Diet of children and adults aged 7 to 69 years.” RIVM rapport 350050006 (2011).
4. Wielders, Jos PM, Frits AJ Muskiet, and Albert van de Wiel. “Nieuw licht op vitamine D: herwaardering van een essentieel prohormoon.” Nederlands tijdschrift voor geneeskunde 154.49 (2010): 2271-2276.
5. Backx, E. M. P., et al. “The impact of 1-year vitamin D supplementation on vitamin D status in athletes: a dose–response study.” European journal of clinical nutrition 70.9 (2016): 1009-1014.
6. Agergaard, Jakob, et al. “Does vitamin-D intake during resistance training improve the skeletal muscle hypertrophic and strength response in young and elderly men?–a randomized controlled trial.” Nutrition & metabolism 12.1 (2015): 32.
7. Holick, Michael F., et al. “Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline.” The Journal of Clinical Endocrinology & Metabolism 96.7 (2011): 1911-1930.
8. Shuler, Franklin D., et al. “Sports health benefits of vitamin D.” Sports Health4.6 (2012): 496-501.
9. Chiang, Chien-ming, et al. “Effects of Vitamin D Supplementation on Muscle Strength in Athletes: A Systematic Review.” The Journal of Strength & Conditioning Research 31.2 (2017): 566-574.
10. Vieth, Reinhold. “Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety.” The American journal of clinical nutrition 69.5 (1999): 842-856.
11. Vieth, Reinhold, Pak-Cheung R. Chan, and Gordon D. MacFarlane. “Efficacy and safety of vitamin D3 intake exceeding the lowest observed adverse effect level.” The American Journal of Clinical Nutrition 73.2 (2001): 288-294.
12. Bjelakovic G, Gluud L, Nikolova D, Whitfield K, Krstic G, Wetterslev J, Gluud C. Vitamin D supplementation for prevention of cancer in adults. Cochrane Database of Systematic Reviews 2014, Issue 6.
13. Pilz, Stefan, et al. “Vitamin D and cardiovascular disease prevention.” Nature Reviews Cardiology 13.7 (2016): 404-417.