As many as 50 percent of conceptions fail and about 20 percent of clinical pregnancies end in miscarriage, the researchers noted in their report. Both male and female reproductive dysfunction is believed to contribute to this high level of reproductive failure, they said, but few real causes have been identified. 

"Some people and physicians are already using antioxidants to help with fertility problems, but we don't have the real scientific evidence yet to prove its efficacy," Hagen said. "It's time to change that." 

Some commonly used antioxidants, such as vitamins C and E, could help, Hagen said. But others, such as lipoic acid, are a little more cutting-edge and set up a biological chain reaction that has a more sustained impact on vasomotor function and health. 

Polyphenols, the phytochemicals that often give vegetables their intense color and are also found in chocolate and tea, are also of considerable interest. But many claims are being made and products marketed, the researchers said, before the appropriate science is completed - actions that have actually delayed doing the proper studies.