6. Foods rich in vitamin D . If you’ve been thinking of increasing your testosterone levels, you better stock up on those mushrooms, salmon and milk. Clinical Endocrinology’s August 2010 issue published a study that was conducted by Austria’s Medical University Graz. According to the researchers, mushroom, salmon and dairy products are examples of food that are rich in Vitamin D. These researchers also found a relationship between Vitamin D and testosterone. Their study has shown that individuals with high levels of Vitamin D also had high testosterone levels. The obvious inverse relationship was true as well. Click here for a convincing study on HUMAN BEINGS to back this up.