LONDON -- Having trouble persuading your child to eat broccoli or spinach? You may have only yourself to blame.
According to a study of twins, neophobia -- or the fear of new foods -- is mostly in the genes.
"Children could actually blame their mothers for this," said Jane Wardle, director of the Health Behavior Unit at University College London, one of the authors of the study in this month's American Journal of Clinical Nutrition.
Wardle and colleagues asked the parents of 5,390 pairs of identical and fraternal twins to complete a questionnaire on their children's willingness to try new foods.
Identical twins, who share all genes, were much more likely to respond the same way to new foods than fraternal twins, who like other siblings only share about half their genes. Researchers concluded that genetics played a greater role in determining eating preferences than environment, since the twins lived in the same household.
Wardle said food preferences appear to be "as inheritable a physical characteristic as height."
Unlike nearly every other phobia, neophobia is a normal stage of human development.
Scientists theorize that it was originally an evolutionary mechanism designed to protect children from accidentally eating dangerous things -- like poisonous berries or mushrooms.
Neophobia typically kicks in at age 2 or 3, when children are newly mobile and capable of disappearing from their parents' sight within seconds. Being unwilling to eat new things they stumble upon may turn out to be a lifesaver.
While most children grow out of the food fussiness by age 5, not all do. For parents of particularly picky eaters, experts encourage them not to cave in when their children throw food tantrums.
"Parents should not feel like they're doing something wrong if they keep trying but their child is not overjoyed to be eating Brussels sprouts," said Marlene Schwartz, deputy director of the Rudd Center for Food Policy and Obesity at Yale University, who is not connected to the study.
While most people will eventually like any food -- even one they initially disliked -- after trying it about 10 times, more persistence may be needed when trying to convert a neophobic child.
"It's like learning to ride a bike," Schwartz said. "Some children have a harder time learning and it takes longer, but it's still worthwhile to teach them."
Other taste-related traits -- like the ability to taste bitterness -- are also inherited. Scientists have already identified the gene responsible, and have found that approximately 30 percent of Caucasians lack the gene and cannot taste bitterness.
Some experts think that neophobia is essentially a reflection of personality. People known as "sensation seekers," or those in search of new and intense experiences, tend to be willing to eat anything. Conversely, shy people tend to be reluctant to experiment with their palate.
"Food is just one kind of stimulus in the environment that people either approach or avoid," said Patricia Pliner, a professor of psychology at the University of Toronto.
Still, experts say that the environment parents create is crucial to determining their children's eating habits.
"It can't all be genetics," said Marcy Goldsmith, a nutrition and behavior specialist at Tufts University. "Parents need to offer their children new foods so they at least have a chance to try it."