Tip of the day from the 'You Docs': There's something funny going on (and it's making you healthy)

Laugh, and you might keep your arteries healthy. Why? Cracking up relaxes blood vessels and increases blood flow — the exact opposite of what happens when you're tense. When people with normal blood pressure watch a funny movie, their blood flow increases by about 20 percent. But when they watch an intense, violent film, they get stressed out, their blood vessels constrict and their blood flow decreases by about 35 percent. (So much for last year's grim Oscar winner!)

Another reason to laugh all you can: Bum moods increase cortisol levels, the bad-boy stress hormone that increases fat accumulation in your belly and makes your kidneys retain salt and water, which boosts your blood pressure. So whether you're renting a comedy or catching a rerun of an old Lucy show, pay zero attention to anyone who says, "Get serious."

If you've seen all the humor flicks you can handle for the moment, a funny friend is at least as good — and might even help keep you slim: One study has found that a good chortle increases the number of calories you burn. The researchers estimate that if you spend 10 to 15 minutes a day laughing, you can burn up to 40 extra calories. Not a ton, but hey, every little waist-shrinking bit adds up.

All of which explains one of our favorite health factors: Frequent laughter can make your RealAge — that's your biological, not your birthday age — up to eight years younger. So TiVo Leno, Stewart or Letterman with wild abandon.

The YOU Docs, Mike Roizen and Mehmet Oz, are authors of the best-selling "YOU: The Owner's Manual" and "YOU: On a Diet." To submit questions and find ways to grow younger and healthier, go to www.RealAge.com, the docs' online home. Distributed by King Features Syndicate.