The first rule of nutrition for maintaining good retina health is, for some people, the most difficult to swallow. Consuming a diet rich in leafy green vegetables for their high antioxidant values is highly recommended by professional nutritionists and eye care specialists, and no one argues about its preventative value. So why is this rule so often broken?
The list of high-antioxidant vegetables includes kale, spinach, Brussels sprouts, alfalfa sprouts, broccoli, beets, red bell pepper, cauliflower, and eggplant. Opinions about the taste of these foods have been the cause of many dinner table arguments among family members, often ending in hurt feelings and unfortunate children going to bed without supper. Well, research now suggests that it may be the fault of a “bitterness gene”.
Researchers from the University of Kentucky School of Medicine report that 50% of consumers are normally sensitive to bitter foods. Another 25% are “non-tasters” who aren’t at all sensitive to bitterness, and 25% have extreme sensitivity to the bitterness some plants develop to keep animals from eating them.
It appears that a specific gene makes certain compounds taste bitter, which may make it harder for some people to include healthy vegetables in their diet. Everyone inherits two copies of a taste gene called TAS2R38, which has two variants (mutations) called AVI and PAV. People who inherit two copies of AVI aren’t sensitive to bitter tastes from certain chemicals. Those with one copy of AVI and one copy of PAV perceive bitter tastes of these chemicals. And then there are individuals with two copies of PAV, who find the same foods exceptionally and unpleasantly bitter.
Researchers analyzed food-frequency questionnaires from 175 people (average age 52, more than 70% female) and found that people with the PAV form of the gene were more than 2.5 times as likely to rank in the bottom half of participants on the number of vegetables eaten. These are people who are likely to be noncompliant with their nutritionists’ advice, not because they are being recalcitrant or childish, but, due to their genetic makeup, they simply cannot bear the taste.
So what can be done? One might use various cooking methods to mask the bitterness, such as including them in a casserole. Equally-nutritious substitute foods also may be found. Eggs, for example, are a rich source of the carotenoids lutein and zeaxanthin, which, like dark green leafy vegetables, are recommended for their high antioxidant value. Another example is collard greens, which are a less potent substitute for kale.
Thanks to empathetic food scientists, less bitter varieties of vegetables are being developed through cross-pollination, so even better options may be available in the future. All in hopes of keeping more people eye-healthy and keeping more children from being injudiciously sent to bed hungry.
- “Rare haplotypes of the gene TAS2R38 confer bitter taste sensitivity in humans” by Emma E. Boxer and Nicole L. Garneau (Published online 2015 Sep 17. doi: 10.1186/s40064-015-1277-z PMCID: PMC4574037PMID: 26405625
- Oral presentation to the American Heart Association’s Scientific Sessions 2019 by Jennifer Smith, RN (University of Kentucky School of Medicine), Nov 2019