Serena Williams has had her share of health issues. Last summer Williams returned to tennis after battling a year-long series of problems, including cuts on her feet from glass at a restaurant and blood clots in her lungs. Earlier this year she cast doubt on the success of her 2012 season after spraining her ankle during the Australian Open in Brisbane. And last week she opened up to the Huffington Post about another health concern she's been trying to overcome -- insomnia.

"A lot of people underrate sleep. You need a certain amount of sleep to rejuvenate your body, to rejuvenate the cells and to perform, whether you're going to school or whether you're playing a professional sport," she said. "I'm not a sleeper. I'm kind of like my dad, never slept much. I can really go off of five hours of sleep, but obviously that's not healthy."

Williams is among some 50 to 70 million U.S. adults who have sleep or wakefulness disorder, according to the Centers for Disease Control and Prevention (CDC). And although Williams has achieved record-setting wins in tennis, the CDC warns that sleep insufficiency can have detrimental long-term effects, increasing the risk for chronic diseases such as hypertension, diabetes, depression, obesity and cancer, and can lead to increased mortality.

Williams blames her insomnia on the natural high she's been on in recent years. “[I'm] constantly on a natural high, high on life and happy, happy, happy and working,” she told the Washington Post. But it has affected her ability to stay fit, she says.

"When I don't get enough sleep I just can't get a good workout. It's low quality and I don't have enough rejuvenation in my cells to use the muscles that I need to use," Williams says. It even hindered her performance at the Australian Open one year, according to the Washington Post, when she was forced to take a prescription sleep aid, which she says slowed her down the following day.

These days Williams is tackling her insomnia with the help of a "natural" sleep aid called Sleep Sheets, which is, coincidentally, a new work project as well (in addition to a clothing and nail polish line and an acting stint on Lifetime network's "Drop Dead Diva" that's set to debut in June).

Williams joins fellow athletes Amar’e Stoudemire and Chris Paul as co-owners of the brand, along with LeBron James, who caught some flak last year for promoting the energy-boosting version of the product, which experts feared could lead to caffeine abuse among teens.

Earlier on HuffPost:

Serena Williams: Style Evolution (PHOTOS)