Flavours experienced in the womb and, later, in mothers' milk may have a significant influence on what children are willing to eat.
Research shows that the experience of food eaten by pregnant women and mothers can be transmitted to their foetuses and infants, according to a nutritionist, Julie Mennella.
Those first flavours can play a major role in determining a child's later food preferences. The research suggests that one way to help persuade children to eat their greens might be for mothers to eat vegetables themselves during and just after pregnancy.
"Although there are a lot of different factors involved, it might be sensible for mothers to think about what they're eating," said Ms Mennella, of the Monell Institute in Philadelphia.
She told a nutrition conference in Barcelona that research around the world had demonstrated the transmission of flavours through amniotic fluid in the womb and breast milk. One French study had shown the children of mothers exposed to anise-flavoured drinks while breastfeeding were less likely to be put off by the taste of aniseed than other babies. Similar research in Ireland found the same kind of results using garlic.
Other work involving vanilla, onions and carrots had shown that foods could flavour amniotic fluid as well as breast milk and they also influenced children's tastes.
The effect is already well known in animals. A European study showed that newly weaned rabbits will make juniper berries their food of choice if the berries had previously been fed to their mothers.
Ms Mennella repeated the rabbit experiment with 45 human mothers, substituting carrot juice for juniper. The women were split into three groups. One was given carrot juice over several weeks during the last three months of pregnancy while another had carrot juice as the women were breastfeeding. "When the babies were at weaning we tested their acceptance of carrot-flavoured cereal," said Ms Mennella. "Not only did they eat more but when we looked at videotapes, the babies made less negative faces while eating."
The same effect was not seen in babies of the third group of mothers who had not been exposed to carrot juice. They tended to turn their noses up when presented with the carrot-flavoured cereal.
Taste and smell are primitive senses developed according to evolutionary pressure to help guide us towards the most beneficial food sources, Ms Mennella told the meeting, organised by a baby food manufacturer, Nutricia. In times of scarcity, this means seeking out sweet tastes which act as "labels" for high calorie foods. Unpleasant, bitter tastes, on the other hand, offer a warning of potentially harmful foods such as poisonous vegetables.
Mothers, Ms Menella suggested, could help "programme" their new-borns into knowing what is good for them through their own food choices.