02/10/2014 04:28 pm ET Updated Apr 12, 2014

Is Disliking Veggies in Your Kid's Genes?

Pediatricians and family members often tell parents that their kids' eating habits are for them to shape and mold. As a parent, so you're told, you have the enormous responsibility and opportunity to not only decide what's going into your baby's growing body -- but to influence his eating patterns for life.

But many parents are adamant that their child has a mind of her own, that although they raised several kids, results vary, and while one child is adventurous and loves his veggies, the other refuses all but bland, yellow, starchy foods.

There's no better way to settle a nature vs. nurture food fight than a twin study, and the U.K. has a very large cohort of those called Gemini: 2,400 families who had twins in 2007 are being studied for their food preference, activity level, appetite, weight gain and family feeding style.

Twins are special, but why are twins so valuable for studying weight gain and nutrition? In the Gemini cohort, about one-third of the twins are identical or monozygotic, which means that they share 100 percent of their genes. The rest of the twins are fraternal, or dizygotic, and share just 50 percent of their genes, like regular siblings do. All twins who grow up together share pretty much the same environment -- the same uterus, parenting style, socioeconomic background, etc. So when we compare a trait and see greater similarity in identical vs. fraternal twins we can deduct that for this trait, genes play a more important role.

Is it in the genes?

A new study published ahead of print online in the American Journal of Clinical Nutrition looked at the food preferences of about 2,700 3-year-olds from the Gemini study. Parents were asked for each of their kids if they liked or disliked a food on a sliding scale. 114 foods were included in the study.

There was a higher correlation of opinion on a whole lot of vegetables among the identical twins compared to the fraternal ones -- 89 percent compared to 62 percent. This was true for fruit as well, but when it came to starches, dairy and snacks, the difference between the twin pairs was less pronounced -- 88 percent agreement among identical twins compared to 76 percent among fraternal twins about the taste of snacks. Across all the foods tested, it seems like genes affect preferences to some degree (identical twins always came on top for agreement). But for foods like snacks and desserts, the shared environmental seems to affect preferences more prominently.

So parents are right to notice that their child is not a blank slate. It's perhaps a relief to know that our kids have a personality and innate tendencies before they were ever exposed to our influences (and the consolation -- there's also a limit to how much damage our inevitable shortcomings may do).

But when it comes to food, that doesn't put us of the hook.

Obesity, food preference and early childhood.

All babies prefer sweets, and to some degree fat and perhaps also salt.

One could argue that the universal natural tendency is sit on a couch and eat bonbons, to be selfish and to seek immediate pleasure.

This study shows that genetic influence goes further, and genes may predispose some toddlers to a better relationship with healthy foods such as veggies. But other studies have shown time and again that repeated exposure and parental modeling work, too, and continuing to serve healthy options in a non-pressured, pleasurable and calm atmosphere, eventually influences kids' preferences. Creating a home environment that doesn't train kids' taste buds on sugar fat and salt, and pushing aside the marketing messages of snack- and fast-food makers makes room for developing a fond relationship with real food. 

Another study published this week in the New England Journal of Medicine reemphasized just how important early childhood is to later healthy weight. This major study followed 7,700 kids for nine years, and found that a third of the kids who were overweight in kindergarten were obese by eighth grade; that almost all obese kids remained obese; and that most of the kids who became obese between the ages of 5 and 14 had signs of extra weight from the very beginning of the study. The conclusion: obesity is very often established very early in life.

So the time to prevent overweight and obesity -- which now afflicts a third of our kids -- is early in life, and even if your kid didn't win the genetic lottery jackpot of inherently liking healthy foods, they have an excellent chance of growing to prefer them, given a chance.

Dr. Ayala