I Taste, Therefore I Reject

Science isn’t always about far-reaching ideas or solving major issues. Sometimes it’s just about trying to understand everyday problems like why don’t kids like vegetables, particularly those of genus Brassica. More commonly known as cruciferous vegetables, this group includes cabbage, cauliflower, broccoli, Brussel sprouts, radishes, and many others. Members of this group are low in calories, high in fiber, rich in minerals,  and an excellent source of vitamins such as vitamins A, C, and K. Additionally, these vegetables contain numerous compounds that fight inflammation and reduce cancer development. This highly favorable nutritional combination makes Brassica plants an important daily part of a healthy diet. Unfortunately, many parents can attest that getting children to eat any of these vegetables can be a difficult and frustrating task often met with whining and refusal. Even numerous adults (including me) don’t like some or all of the cruciferous group. Part of the issue is a compound possessed by these vegetables called glucosinolate (GLS). GLS is nutritionally beneficial but breaks down to pungent and bitter products. This smell and bitter taste combination contribute to why many children and some adults dislike these important foods. Furthermore, children are more sensitive to bitterness than are adults and this likely accounts for their greater aversion to these vegetables.

A recent study in the Journal of Agricultural and Food Chemistry revealed an additional wrinkle that influences an individual’s like or dislike of cruciferous vegetables. Along with GLS, these vegetables contain a molecule called S-methyl-L-cysteine sulfoxide (SMCSO). When chewed, disruption of the plant tissues releases the enzyme alliinase (also known as cysteine sulfoxide lyase) which breaks down SMCSO into pungent, sulfur-containing compounds that contribute to the taste. Some oral bacteria also express this enzyme, and the presence of such bacteria in saliva would increase the production of the unpleasant sulfur compounds while chewing. To assess differences in oral alliinase content, the authors of the study tested the saliva of 65 adults and 52 children (all of the children had a parent in the adult group). Saliva was mixed with a cauliflower powder and the generated sulfur compounds were quantitated by mass spectrometry. The levels of sulfur compounds produced varied widely in the tested subjects, but interestingly were comparable for parent/child pairs suggesting a familial similarity in saliva composition and oral bacteria. Test subjects were also asked to rate the taste of cauliflower on a scale of 1-9. Importantly, there was a strong correlation between high sulfur compound production by their saliva and a child’s dislike of cauliflower. Therefore, a child’s rejection of this class of vegetables may not just be a general disdain for these healthy foods. Instead, it may reflect the child’s innate oral environment causing the production of these foul-smelling and foul-tasting sulfur compounds that truly make these vegetables unpalatable while chewing. So your child may not be recalcitrant, but may actually be having a very unpleasant experience with these foods. As we age we generally become less sensitive to bitter tastes so that some children eventually become adults who learn to eat cauliflower and/or other cruciferous vegetables. Other individuals, including yours truly, still can’t stomach cauliflower, Brussel sprouts, or cabbage, though I do eat broccoli now. Lastly, the authors noted that steaming Brassica vegetables reduced the odor intensity of these foods, so that type of preparation may be your best choice for those cruciferous vegetable-adverse people in your life.

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