Best Face Forward.(skin care products)

Byline: Judith Newman PHOTOGRAPHED BY MICHAEL THOMPSON

Pop quiz: Where do you find the words "sirtuins," "peptides," and "nanotechnology"? No, not in an MIT thesisbut on the jars of the newest anti-agers. allure translates.

Women like change. We always want to know: What's new? What's new now? How about now ?

Here's the problem: For the most part, medicine doesn't change nearly fast enough to suit us. It's not like this year's heart transplant is hot and last year's is, well, so last year. But there is one area of medicine so market-driven that change really does happen quicklyand that area is dermatology.

Skin care will be a $44 billion business by 2010, according to Global Industry Analystsquite a pile, when you consider that we spent only about $5 billion on cancer research last year. That much money demands merch that freshens, tightens, and moistens like never beforeso every year, skin-care companies obligingly come up with ever-niftier and more-high-tech-sounding ingredients and claims.

But which ones mean something, and which are merely marketing hoo-ha? The answer isn't always definitive, but we selected the buzzwords you really need to know and asked some of the most respected dermatologists to weigh in on them. What's true? What's half-true? Here, all the "new" that's fit to print.

SIRTUINS

THE CLAIM: They ramp up collagen growth to produce firmer skin with fewer lines and wrinkles.

THE PRODUCTS: Avon Anew Ultimate Age Repair Day SPF 25, Night Cream, and Ultimate Elixir Premium (out in January); EstA[c]e Lauder Time Zone Line and Wrinkle Reducing CrA[umlaut]me; Orlane Anti-Fatigue Night Repairing CrA[umlaut]me

THE SCIENCE: This is what we know about sirtuins: They are protein enzymes in our bodies that help repair cell damage and make cells live longer; without them, cells self-destruct.

This is what we don't know about sirtuins: everything else. How do they work? And can we control them? A great deal of money is being spent to find answers: GlaxoSmithKline just ponied up $720 million to buy Sirtris Pharmaceuticals, a company that studies sirtuinsbecause, so far, sirtuins are the only substances we know of that seem to make cells live longer in the lab. In an article in The Washington Post, lead researcher David Sinclair of Harvard Medical School reported that sirtuins appear to "serve as guardians of the cell," allowing cells "to survive damage and delay cell death.... What we think is that if a cell is at a point of deciding whether to live or die, these sirtuins push toward the survival mode and let the cell try a little harder and longer to fix itself." And that's not the only way sirtuins may be the fountain of youth. They also seem to keep you looking young by increasing collagen production.

THE VERDICT: There's no question we want sirtuins …