A Recent study uncovered that men deficient in vitamin D have lower free testosterone in their bodies and higher estrogen levels. That would seem to indicate that optimizing your vitamin D level should be a priority for you.
The men who participated in the above-referenced study who had low vitamin D also had higher body fat content, less lean muscle mass, were at risk for a greater chance of depression, had higher rates of cardiovascular disease, and poorer fertility than the men with higher vitamin D levels. Conversely, the men in the study with higher vitamin D levels had leaner body composition, higher testosterone levels, and were generally healthier.
Subsequently, another study was done that tested the effect of giving some of the men with vitamin D deficiency and low testosterone dosages of 3,332 IUs of vitamin D and the others in the same control group a placebo for a year.
The individuals receiving the daily vitamin D supplement increased their free testosterone by 20 percent and achieved an adequate vitamin D level. The placebo group failed to increase their testosterone and vitamin D levels.
Vitamin D can be found in small amounts in some foods, including fatty fish like herring, mackerel, sardines and tuna. To make vitamin D more available to the general public, food manufacturers commonly add it to dairy products, juices, and cereals that are then labeled “fortified with vitamin D.” But most vitamin D (80 to 90 percent of what the body absorbs) is usually obtained by exposure to sunlight.
You can get your vitamin D and testosterone levels checked by visiting your doctor or a reputable lab that offers those tests. If they come back low you should discuss how to best address this with your doctor or another qualified health practitioner.