I used to get SADS in the winter and my doc wanted me to take 2000 IBU's everyday but I don't need in but I don't need it much anymore. It depends on how sunny or overcast the winter is. I live in lover Ontario so we have pretty big winters here.
During winters in your area the sun doesn't show at all or its just that you don't like going out in the cold to get some sun. Kind of a stupid question right? You will be all covered up when its cold so you can't get the sun anyway.
Girls with high level of vitamin D have stronger muscles. Girls are stronger with higher levels of vitamin D, but the association was not found in boys. These are the results from a new large study from the Odense Child Cohort. According to the study's first author, girls with low vitamin D have a 70 percent increased risk of being among the lowest 10 percent in a test for muscle strength. Source 1e.