Several studies have suggested that semen quality and fertility in men have declined during the last decades. Deterioration in semen samples has been related to environmental pollution, occupational habits, lifestyle changes, exposure to toxins (tobacco, etc.), and dietary habits.
Oxidative stress is considered the main cause of sperm DNA damage. Reduced individual and total antioxidant capacity and high concentrations of seminal ROS (reactive oxygen species) have been detected in men with elevated DNA damage in numerous studies. As for dietary factors, a lower intake of some antioxidant nutrients, such as vitamins A, C and E, carnitine, folate, zinc or selenium, has been associated with male infertility.
Antioxidant therapy of vitamin administration has been tested in numerous trials. The general view is that antioxidant treatment may play a relevant role, although some results have been inconsistent. Among the most recommended preparations are vitamin E and C, zinc, selenium, coenzyme Q10 or L-carnitine.