Most people on this planet have too little 25-hydroxy vitamin D in their blood, and as a result their muscle quality is below optimum. Radiologists at the University of Southern California in Los Angeles discovered that the muscles of young women contain up to 20 percent more fat if their vitamin D levels are too low.
Countless people have less vitamin D in their blood than is good for them. Initially researchers recorded this vitamin deficiency in people living in northern countries, where the sun hardly shines, and where much of the population works indoors. Well, that used to be the story.
More recently research has shown that, even in sun-drenched countries like Turkey, Lebanon, the United Arab Emirates, India and Australia, 30-50 percent of the population is low on vitamin D. [N Engl J Med. 2007 Jul 19; 357(3): 266-81.] In Brazil the figure is 60 percent among young adults. [Ann Nutr Metab. 2009; 54(1): 15-21.]
Vitamin D & muscles
Sufficient vitamin D is necessary for strong muscles. One theory is that vitamin D is responsible for getting nutrients like calcium and phosphorus into the muscles. As a result muscles can contract better, and growth and fuel burning processes are also enhanced.
Animal studies have shown that rats put on a fattening diet develop more muscle and less fat when given extra vitamin D. In human studies, test subjects burn more calories after eating a breakfast that contains 0.5 g calcium and 9 mcg vitamin D. Elderly people who take vitamin D supplements are physically stronger, as are athletes who have high levels of vitamin D in their blood.
The researchers in this study made scans of the muscle and body composition of 90 young women aged between 16 and 22. Of these, 37 had sufficient vitamin D in their blood and 53 had too little. The more vitamin D the women had in their blood, the less fat they had in their muscles. Fatty muscle tissue is less strong and less sensitive to insulin. By the way, none of the women complained of having weak muscles.
Low levels of vitamin D in the blood were also associated with more subcutaneous fat [SF] and more abdominal [or visceral] fat [VF] Women with high levels of vitamin D also had more leg muscle, although the difference was not statistically significant.
Vitamin D is not the most exciting nutritional supplement in the world. Pills containing vitamin D don’t sound as interesting as exotic plant extracts or high-dose amino acids. But it looks as though lots of athletes could be that little bit stronger, muscular and slimmer if they increased their vitamin D intake.
Vitamin D status and its relation to muscle mass and muscle fat in young women.
Vitamin D insufficiency has now reached epidemic proportions and has been linked to increased body fat and decreased muscle strength. Whether vitamin D insufficiency is also related to adipose tissue infiltration in muscle is not known.
The objective of the study was to examine the relationship between serum 25-hydroxyvitamin D (25OHD) and the degree of fat infiltration in muscle.
This was a cross-sectional study. OUTCOME MEASURES AND SUBJECTS: Measures were anthropometric measures, serum 25OHD radioimmunoassay values, and computed tomography (CT) values of fat, muscle mass, and percent muscle fat in 90 postpubertal females, aged 16-22 yr, residing in California.
Approximately 59% of subjects were 25OHD insufficient (< or = 29 ng/ml), of which 24% were deficient (< or = 20 ng/ml), whereas 41% were sufficient (> or = 30 ng/ml). A strong negative relationship was present between serum 25OHD and CT measures of percent muscle fat (r = -0.37; P < 0.001). In contrast, no relationship was observed between circulating 25OHD concentrations and CT measures of thigh muscle area (r = 0.16; P = 0.14). Multiple regression analysis indicated that the relation between 25OHD and muscle adiposity was independent of body mass or CT measures of sc and visceral fat. Percent muscle fat was significantly lower in women with normal serum 25OHD concentrations than in women with insufficient levels and deficient levels (3.15 +/- 1.4 vs. 3.90 +/- 1.9; P = 0.038). CONCLUSIONS: We found that vitamin D insufficiency is associated with increased fat infiltration in muscle in healthy young women. PMID: 20164290 [PubMed - indexed for MEDLINE] PMCID: PMC2853984 Source: http://www.ncbi.nlm.nih.gov/pubmed/20164290