(Newser) – Scientists in California believe they have a tip for those with weakened immune systems: Fast for three days. The brief period "flips a regenerative switch" in the body, the University of Southern California researchers say, via the Telegraph: "It gives the 'OK' for stem cells to go ahead and begin proliferating and rebuild the entire system," creating new white blood cells. "If you start with a system heavily damaged by chemotherapy or aging, fasting cycles can generate, literally, a new immune system."

Research involved asking subjects to fast for two- to four-day periods over six months. If you're not ready to go entirely without food, eating just 750 to 1050 calories daily for four or five days should do the trick, researcher Valter Longo tells the Daily Beast. But nutritionists, the Telegraph notes, have warned against fasting diets, which they call unhealthy. Some outside researchers raise doubts, too. "There is some interesting data here," notes one. "But I think the most sensible way forward would be to synthesize this effect with drugs. … People are better eating on a regular basis." (Not that we're encouraging it, but drinking alcohol may also boost your immune system.)

