A cactus-based sugary syrup has become the latest darling of the alternative sweetener world.

Once mostly unheard of outside natural food stores, agave syrup -- made from the same Mexican cactus that yields tequila -- suddenly is getting celebrity endorsements, competing for shelf space at mainstream grocers and is a must-have cocktail ingredient.

"If I'm going to be making a premium margarita, agave nectar's got to be riding shotgun," says Food Network star Guy Fieri, who is better known for his greasy spoon affection than his natural foods know-how.

"It's not overly cloying. It's delicious. Put it over pineapple, strawberries," he says. "Don't worry, it doesn't taste like tequila syrup!"

The growth of agave has been strong, part of an overall trend in the natural and organic sweeteners market, which went from $85 million in 1998 to $200 million last year, according to Nutrition Business Journal, which follows the natural foods industry.

And last year, 304 products included agave syrup; in 2003 it was 60, according to market research firm DataMonitor.

Fans of the syrup praise its mild, fruity flavor, its ease in baking and its relative healthfulness. While it has the same number of calories per teaspoon as table sugar, it is sweeter, so you can use less of it.

Much of its popularity also stems from heavy marketing of its low glycemic effect, meaning agave syrup is believed to have a less dramatic effect on blood sugar levels than refined sugars such as white sugar and corn syrup.

It also is popular among vegans, who don't eat animal products and consider agave an ethically better choice than honey.

Agave syrup is generally available in three varieties -- raw, which has a maple syrup-like color and moderate caramel flavor; light, which has a light caramel flavor and color; and amber, which is similar in color and flavor to raw.

Ania Catalano, author of "Baking with Agave Nectar," says light agave is best for light, fruity desserts that call for a gentle sweetness without a distinct agave flavor. She suggests amber for heavily seasoned pies, such as pumpkin, or as a topping for pancakes or waffles.

Pastry chef Mani Niall, author of the cookbook "Sweet! From Agave to Turbinado," says agave nectar works well in everything from rich desserts to elegant cocktails. "It doesn't have to be some brown health food-y thing," he says.

One reason agave syrup has caught on is its versatility. Food manufacturers are using it as a sweetener in ketchup, coffee sweeteners, even tonic waters. Niall says it's easy to work with because it won't overwhelm a recipe.

In addition to baked goods and drinks, agave nectar can be used in marinades and barbecue sauces. But like sugar and honey, agave can burn under high temperatures, so grill with care.

When substituting agave syrup for white sugar in a recipe, use about 25 percent less than the amount called for. You also will need to adjust other ingredients to compensate for using a liquid, rather than a dry sweetener.

That extra moisture can be a boon if you like soft, chewy cookies. But don't try it for shortbread or a crispy chocolate chip cookie. "Agave doesn't like to get crispy," Catalano says.

And because agave tends to produce browning in baked goods faster than conventional sugar, reduce the oven temperature by about 25 degrees, Catalano says.