“I ate everything except for tomatoes,” Britt van Belkom remembers; “I refused to eat those until high school. I really disliked the structure, the consistency…” That glitch in her dietary development can be glossed over. Eating vegetables in general though, especially from an early age, is crucial.

While only 3% of Dutch children are obese and 15% overweight, that grows to half of all Dutch adults who are overweight. “Overweight increases your risk of diabetes and a host of other diseases including several cancers. Since it’s difficult to treat in adulthood, early childhood interventions are crucial because that’s the time when you establish eating habits and tastes.”

For 3 months, she ran an experiment across 26 day-care centres, involving a total of 598 children aged 1-4 across North Limburg. Beyond the obligatory control group, one group would see children exposed to different vegetables, which they were also free to eat, and a third group, which, in addition to exposure, had a reward system to incentivise the children to try the vegetables. “We used stickers to reward them. It’s a system not dissimilar from the one many parents use for toilet training.”

Natural aversion to bitterness

The second group already performed significantly better at recognising different vegetables but only the third group showed an increased willingness to try new vegetables. “It makes sense. Evolutionarily, we are drawn to sweet tastes because they indicate calorie-dense foods and that’s crucial in times of scarcity. At the same time, we are naturally averse to bitterness, which characterise many healthy veggies – we need to acquire a taste for those.”

Making someone acquire this taste against their explicit wishes, however, might cause a little bitterness in turn. “Children will instinctively reject bitter tasting foods the first 8-10 times. That is normal, but obviously very frustrating for parents and most just give up after a couple of attempts.” Effectively, the children condition the parents out of persisting with vegetables before the parents can condition the children into accepting them.

Van Belkom urges parents to be patient and persistent though. “Just try it ten times – they will usually accept it after that. And reward them in any way that works for you – just not with food.” She realises that it’s a sensitive subject – telling people how their children should eat – but the endgame of current trends is a public health crisis. “Some parents might lack awareness of how important a healthy diet is – but I think this is a minority. In our questionnaire, 78% said that they considered the promotion of healthy eating in the day-care centres important.”