In the struggle against childhood obesity, many parents have adopted covert tactics – adding pureed cauliflower to macaroni and cheese or kale to meatballs, as Jessica Seinfeld advocates in her “Deceptively Delicious” cookbook.

But at some point, encouraging a child to develop a sustainably healthy diet for life has to involve confronting the horror of an exposed vegetable.

“Hiding broccoli in brownies might add fiber, but if the goal is to get someone to like broccoli, you gotta taste it,” says Julie Mennella, a taste researcher at the Monell Chemical Senses Center in Philadelphia.

Mennella was one of several researchers presenting the latest research that makes the case for using a little bit of sugar to get kids to eat their vegetables at the AAAS Annual Meeting in Boston.

A kid's dislike of vegetables is a product of biology, it turns out. Sugar is pure energy, and also acts as a pain-reliever – Mennella has found that children can hold their hands in a bucket of ice water longer with a mouthful of sugar versus a mouthful of water.

Children naturally prefer a more intense sweetness, and there's evidence that they also are more sensitive to bitter flavors. Taste does tend to develop over time – one study compared adults and children with similar gene variants for taste receptors, and found that the child will still prefer a food with a higher concentration of sugar than the adult with virtually the same genes.

The ideal concentration of sugar that the average kid prefers is .6 molar, according to Mennella. For comparison, the sugar concentration in a can of Coca-Cola is .3 molar.

While sugar-seeking behaviors may have served children well in the prehistoric days when sweetness was harder to come by, in an age of processed and sugary foods it's a recipe for poor health and child obesity.

“There's a mismatch between the environment and our biology,” Minella said.

The problem isn't confined to childhood – a natural dislike of vegetables can often lead to an adult that avoids anything green like the plague. So how can parents, schools and nutritionists make vegetables more palatable and establish a taste for veggies early in life?

Valerie Duffy, a dietician at the University of Connecticut, says that adding just a bit of sweetness to vegetables can balance out the bitter flavors that turn kids off.

“It could be as little as throwing a bit of sugar in the cooking water,” Duffy says.

Duffy's research bears that out. In small pilot studies with elementary and preschoolers, she's found that even just misting a little sweetness over bitter vegetables like asparagus and kale makes them palatable to adults and children that are avowed vegetable haters.

There are only 16 calories in a teaspoon of sugar, and the vegetables are getting a tiny fraction of that – Duffy found that just three-fourths of a teaspoon of sugar, added to a half a cup of vegetables, can do the trick -- so the added caloric value is nearly negligible.

Plus, introducing kids to vegetables with the helping hand of sugar doesn't mean encouraging them to eat sweetened vegetables for life. The ultimate goal is to wean kids off of sweeteners – Mennella drew a comparison to the Argentinian practice of sweetening the bitter mate tea for children, and then gradually decreasing the amount of sugar over time.

Other research suggests this strategy is successful. A 2008 paper in the journal Appetite from a pair of University of Arizona researchers found that just three exposures to a sweetened vegetable was enough to get children and young adults to like the taste of the unsweetened vegetable later on.

A little bit of sugar is enough “just to establish the liking” for vegetables, Duffy said.

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