Highest Potency, GMP Quality Assured

Chances are, you're at least a little deficient in vitamin D. Most people are. And deficiencies can cause a host of problems: low testosterone, reduced power, reduced muscular size and strength, poor endurance, and maybe even depression-like symptoms.

I like this brand because they're inexpensive, easy to swallow, and pack 5000 IU into every tiny capsule. I take one daily in the winter and then one about every other day during the sunnier months of the year. – Chris Shugart