Venus Williams drinks Jamba Juice in Santa Monica

Tennis star Venus Williams was in Santa Monica on Thursday, doing fitness demonstrations, leading regular, less-in-shape folks in some exercise and promoting Jamba Juice because she likes to be able to add wheatgrass shots to her juice.

Since announcing at the 2011 U.S. Open that she suffered from Sjogren’s syndrome, an autoimmune disease that affects her energy levels and can leave her eyes and mouth exceptionally dry, Williams has taken the lead in learning about nutrition, diet and just about everything else about her body.

“My trouble is,” she said Thursday, “I love sugar but it’s important I have lots of greens and less fruit. In my time I could destroy a candy aisle.”

Every day Williams evaluates how she feels on the tennis court, whether her energy level is good enough for an intense practice or whether it’s better to take it easy.

But Williams is not backing away from the game yet even though she will be 33 next month. She would love to win one more Wimbledon (she has won five) and she would love to move back into the top 10 (she’s ranked 20^th).

Up next, though, is her less favorite part of the season, the European clay courts. Her next tournament is in Rome. Williams actually did well on an American clay court in Charleston last month, winning two matches in one day because of rain delays before losing in the semifinals to her No. 1-ranked sister Serena.

“I’m getting better every day,” Williams said. “Definitely, absolutely, if I didn’t think I could win, I would stop playing.”

But stop drinking Jamba Juice? “Never,” she said.