There is new research out of Italy that suggests a lack of vitamin D may increase his risk of erectile dysfunction. After testing 143 men with varying degrees of erectile dysfunction, the researchers discovered that close to half of them were showing a vitamin D deficiency with only one in five showing optimum levels of the nutrient. Get this, men with severe ED were found to have vitamin D levels 24 percent lower than those who had only a mild form. Study author, Alessandra Barassi, M.D., says that insufficient levels of vitamin D spur the production of the free radicals called superoxide ions. These free radicals deplete nitric oxide which is a molecule that helps blood vessels function properly. Without proper blood vessel function, erections can be difficult to come by. Larry Lipshultz, M.D., a Men’s Health urology advisor, explains, "Nitric oxide causes the blood vessels to relax, which increases the blood flow and causes an erection under normal circumstances." Without the right amount of nitric oxide, his blood vessels may not relax enough to allow an erection. If your man suffers from ED, recommend he have his doctor check his vitamin D levels. If his levels prove low, the study suggests taking supplements to get back to the optimal level of 30 ng/mL or higher. If your man has normal penis function, stay tuned. Dr. Barassi is now studying whether or not vitamin D supplementation can act as a preventative to delay ED.