Child won’t eat their greens? Blame biology

Researchers found that a chemical in brassica crops makes children much more likely to shun sprouts

GETTING children to eat their greens is a battle as old as time, and every parent has their own way of getting vegetables into a protesting child. But a study has found that the vocal objections to vegetables from children are not merely petulant behaviour, but a natural consequence of biology.

A chemical in brassica crops – which includes broccoli, kale, cauliflower, cabbage, turnip and Brussels sprouts – mixes with enzymes in a person’s saliva and this produces sulphurous compounds which taste deeply unpleasant.

The chemical in question is S-methyll-cysteine sulfoxide which, on its own, is nondescript. It only becomes unpleasant when broken down by naturally-occurring enzymes found in our oral microbiome – the “good” bacteria that exists in our mouths. However, not everyone possesses the same concentration or recipe of enzymes, with some people naturally making a lot, and others producing very little.

For people who naturally have lots of these sulphur-producing enzymes, the pungent taste of brassica crops is more intense, and these individuals are therefore far more likely to shun Brussels sprouts at the Christmas table and avoid kale smoothies.

This relationship has long been known, but researchers at CSIRO in Australia investigated if there was any hereditary aspect to enzyme production, and therefore, if a dislike of vegetables is passed on from parent to child.

To do this, researchers took raw and steamed broccoli and cauliflower and ran it through an analytical process called gas chromatography-olfactometry-mass spectrometry.

This process captures vapour given off by the vegetables and pulls it apart into its component parts to determine what compounds are present and how much of them there are.

Then, 98 parent-child pairs were asked to smell the specific compounds and rate them on how much they liked or disliked them.

Researchers then collected saliva samples from the children, aged between six and eight, and their parents and mixed this with raw cauliflower powder. These concoctions were designed to mimic the reactions of when a person chews their food and the produced compounds and scents were then also run through the same analytical technique.

Children were found to have similar levels of sulphur to their parents, indicating the palate for vegetables, positive or negative, is passed down from one generation to the next.

Yet, only in the children did high sulphur compound concentration lead to a noticeable dislike of brassica vegetables.

Parents of these children, although they had the same oral microbiome makeup as their offspring and the same high sulphur levels, did not report a strong dislike of the vegetables.

Researchers say this may be due to them learning to tolerate the scent over time, and growing to accept and embrace the potent flavour.