May 1, 2005 In the first study to link taste genes to behavior in children, researchers looked at how natural variations in a recently discovered taste gene affected sensitivity to bitter tastes and food preferences in a group of children and adults. Collecting genetic samples from 143 children and their mothers, the researchers showed moms and kids who had at least one bitter-sensitive region in the gene were generally able to detect even a hint of bitter flavor in a test drink. The same group of children, carrying one or two bitter-sensitive regions of a gene, also preferred higher concentrations of sucrose solutions and had stronger preferences for sweet-tasting food and beverages than did the bitter-insensitive kids.
PHILADELPHIA -- If you're a parent, chances are you've had a difficult time getting your child to eat certain veggies. The next time your child pushes away his spinach, it may not be that he's being difficult or picky. A new study finds some children may be extra sensitive to bitter tastes.
Abby Plummer is part of a tasting study that looks at the effect of a bitter-taste receptor gene on food preferences.
"We genotyped children and mothers -- and by genotyping, I mean we took cheek swabs and got DNA from mothers and children -- and looked for the presence of this bitter taste receptor gene," says Julie Mennella, a developmental Psychobiologist at Monell Chemical Senses Center in Philadelphia.
Psycho-biologists, who combine psychology and biology, grouped the 143 children and their mothers into three genotypes: PP, AP or AA. The P signifies the presence of the bitter gene. As expected, those with two bitter genes, PP, were the most sensitive to bitter taste. However, mothers and children with the same genotypes did not have the same taste experience.
Mennella says, "An interesting thing is that children who carried one of these bitter taste alleles were much more sensitive to the bitter taste than mothers."
Which could be why many children have an aversion to bitter foods like certain vegetables. "Childhood may represent a period of heightened bitter taste sensitivity in some children that lessens with age. That's not to say that as you get older you can't taste bitter anymore, it's just a dampening effect," Mennella says. She hopes her research leads to healthier diets for kids.
The study also found children who had the bitter taste gene preferred higher levels of the sucrose solution they were given in the study. Researchers point out that as we age, life experience begins to override genetic disposition for taste.
"Nature versus nurture" refers to an ongoing debate about how much genes are responsible for an individual's traits, compared to how much is due to the environment around the person.
There are some areas where genetics clearly dominate: certain hereditary diseases, for example, such as cystic fibrosis, or hair and eye color. And what language a child ends up speaking is entirely determined by his or her environment. But other traits appear to develop from a combination of both influences.
For example, a person's height as an adult is determined to some extent by his or her genes, but environmental factors such as diet can also impact height. The same is true for weight. Some women are genetically predisposed to store more body fat in particular areas of the body (around the abdomen versus the hips), but this propensity can be controlled through diet and exercise. The issue becomes even more complex when dealing with the brain. Hormones help build structures in the brain, so genetics clearly play a role in such matters as distinctly male or female behaviors. But the brain is also designed to be flexible, enabling it to adapt to environmental experiences.
In order to better determine genetic and environmental influences, scientists study sets of twins.
Non-identical twins have genes as different as any other sibling, but they share a very similar environment, so genetic differences can be more accurately studied.
Identical twins share the same genes, and often the same environment, but some are separated at a young age and raised in different homes. Since they share all the same genes but experience a very different home environment, the differences between them are likely to arise from environmental factors.
Recent twin studies have shown that shortsightedness is largely genetic, for example; only 15 percent of cases are caused by environmental factors like using computers or reading lots of small print.
Editor's Note: This article is not intended to provide medical advice, diagnosis or treatment.