in the Golden Age of Bodybuilding, Arnold and Franco Columbo would be seen sunbathing on the beaches in Venice. Today’s bodybuilders rely on Pro-Tan and artificial methods of tanning to color the skin, but bodybuilder’s maybe be missing out on getting adequate Vitamin D. Vitamin D deficiency is a global health problem. With all the medical advances of the century, vitamin D deficiency is still epidemic. Over a billion people worldwide are vitamin D deficient or insufficient. Vitamin D, also described, as “the Sun Vitamin” is a steroid with hormone like activity. It regulates the functions of over 200 genes and is essential for growth and development.
A recent study conducted at The Westmead Institute for Medical Research has shed light on the role of vitamin D in muscle cells. The study looked at the role of vitamin D in muscles in mice, and showed that vitamin D signaling (how cells communicate with one another) is needed for normal muscle size and strength.
Researchers found that mice missing the vitamin D receptor only in myocytes (muscle cells) had smaller muscles, and they were less strong. They also had significantly decreased running speed and didn’t run as far as mice with normal vitamin D action.
Lead researcher, Professor Jenny Gunton says, “For a long time, we have known that vitamin D deficiency is associated with muscle weakness and greater risk of falls and fractures. However, whether vitamin D played a direct role in muscle wasn’t known.
“We show that vitamin D receptor is present in low levels in normal muscle, and our study found that deleting muscle cell vitamin D receptors had important effects on muscle function.”
Professor Gunton says that, compared to a previous study she conducted that looked at mice missing vitamin D receptors across their whole body, this new study has highlighted some important differences.
“We found that mice missing muscle cell vitamin D receptors had normal body size but less muscle mass and more fat mass.
“In terms of choosing to run on a wheel in their cage, the mice had shorter running distance and slower speed. These might contribute to the lower muscle mass and increase in fat.
In terms of muscle strength, these mice also had a significantly decreased grip strength from a very early age.”
While more research is needed, Professor Gunton says that these results suggest that maintaining normal vitamin D signaling in muscle is important for preserving muscle bulk and function.
“These findings also have the potential to open up avenues to pursue new therapies that target muscle cell vitamin D receptors. These therapies could help to address or prevent age-related sarcopenia (degenerative loss of skeletal muscle mass) and other disorders related to muscle function.”
The research paper was published in the Journal of Cachexia, Sarcopenia and Muscle.
There are two forms of vitamin D. Vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Vitamin D status depends on the production of vitamin D 3 in the skin under the influence of ultraviolet radiation from sun and vitamin D intake through diet or vitamin D supplements. Usually 50% to 90% of vitamin D is produced by sunshine exposure of skin and the remainder comes from the diet. Natural diets most humans consume contain little vitamin D. Traditionally the human vitamin D system begins in the skin, not in the mouth. However, important sources of vitamin D are egg yolk, fatty fish, fortified dairy products and beef liver. In addition to vitamin D’s well-known role in bone and calcium metabolism, vitamin D deficiency has been linked to a long-list of health conditions including atherosclerosis. Vitamin D is critical to the proper functioning of the endothelial cells that line blood vessels. Without sufficient levels of vitamin D, these endothelial cells become more susceptible to damage and dysfunction that ultimately can lead to the development of atherosclerosis as well as arterial calcification.
Vitamin D Keeps Lead in Your Pencil
Given the link between vitamin D and atherosclerosis, Italian researchers conducted a study in 143 men with erectile dysfunction (ED). The men were evaluated for penile atherosclerosis by ultrasound along with blood levels for vitamin D3. Fifty men were classified as suffering from atherosclerotic ED, 28 borderline ED and 65 non- atherosclerotic ED. The average vitamin D level was 21.3?ng/mL and 45.9% of the men had vitamin D deficiency (<20?ng/ml). Only 20.2% had vitamin D levels greater than 30 ng/ml. The results showed that most men with ED have low vitamin D levels and those with more severe ED had significantly lower vitamin D levels than those with mild ED. Vitamin D deficiency was also worse in those with ED due to penile atherosclerosis than in those men with ED due to other factors. These results indicate that low levels of vitamin D3 are linked to ED and indicate that vitamin D3 levels should be measured in men with ED. Establishing optimal blood levels of D3 may lead to better endothelial function and reduce/prevent ED. In addition to ED, low vitamin D levels have been associated with reduced testosterone levels and anabolic genes.
Vitamin D’s Role in Muscle Building
Vitamin D is not technically a vitamin or essential dietary factor. Vitamin D is actually a pro-hormone produced phytochemically in the skin. And unlike traditional vitamins, Vitamin D has its own hormone receptor (VDR). VDRs are found in at least 36 different organs in the body. To further establish this fact and to see if Vitamin D3 may actually have an anabolic effect, researchers carried out an in-vitro study using muscle cells, insulin, leucine, and Vitamin D. The focus of this study was on the mTOR anabolic signaling pathway in muscle cells. It is well known that insulin facilitates the activation of the mTOR pathway, particularly high insulin levels. Leucine is a direct activator of the mTOR pathway and in this way can “switch on” protein synthesis in muscle cells. These researchers took muscle cells and exposed them to leucine and insulin, or leucine, insulin, and Vitamin D. Results demonstrated that the addition of Vitamin D to insulin and leucine significantly enhanced the activity of the mTOR pathway and protein synthesis. The authors conclude that Vitamin D has the potential to directly alter protein synthesis in muscle cells. Additionally, several studies have found that low vitamin D is associated with low testosterone levels. One study found out that men with sufficient vitamin D levels had significantly higher testosterone levels and lower SHBG count, than men who had insufficient amounts of the vitamin (or hormone) in their blood serum. Another study found out that when healthy male participants take 3332 IU’s of vitamin D daily for a year, they end up having 25,2% more testosterone on average when compared to placebo. Getting out in the sun maybe be more than just relaxing, it may be anabolic for bodybuilders!
References:
Barassi A, Pezzilli R, Colpi GM, Corsi Romanelli MM, Melzi d’Eril GV. Vitamin D and erectile dysfunction. J Sex Med. 2014 Nov;11(11):2792-800.
Salles J, Chanet A, Giraudet C, Patrac V, Pierre P, Jourdan M, Luiking YC, Verlaan S, Migné C, Boirie Y, Walrand S. 1,25(OH)2-vitamin D3 enhances the stimulating effect of leucine and insulin on protein synthesis rate through Akt/PKB and mTOR mediated pathways in murine C2C12 skeletal myotubes.Mol Nutr Food Res. 2013 Dec;57(12):2137-46.
Wehr E, Pilz S, Boehm BO, März W, Obermayer-Pietsch B. Association of vitamin D status with serum androgen levels in men. Clin Endocrinol (Oxf). 2010 Aug;73(2):243-8.
Pilz S, Frisch S, Koertke H, Kuhn J, Dreier J, Obermayer-Pietsch B, Wehr E, Zittermann A. Effect of vitamin D supplementation on testosterone levels in men. Horm Metab Res. 2011 Mar;43(3):223-5.
Christian M. Girgis, Kuan Minn Cha, Benjamin So, Michael Tsang, Jennifer Chen, Peter J. Houweling, Aaron Schindeler, Rebecca Stokes, Michael M. Swarbrick, Frances J. Evesson, Sandra T. Cooper, Jenny E. Gunton. Mice with myocyte deletion of vitamin D receptor have sarcopenia and impaired muscle function. Journal of Cachexia, Sarcopenia and Muscle, 2019;
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