Can a lemon ever taste sweet?

You’re probably well aware that the flavour of what you’ve just eaten can change the flavour of what you eat next. So, if you do what dentists recommend and brush your teeth first thing in the morning, then following the application of toothpaste have a glass of orange juice, you will likely find that the normal sweet taste of the orange juice is quite bitter. Why? According to Linda Bartoshuk, a taste scientist at the University of Florida, the culprit is sodium lauryl sulphate, a detergent that foams when you brush your teeth. Detergent molecules like sodium lauryl sulphate have the capacity to disperse fat and the theory is that sodium lauryl sulphate can in some way interfere with the fat containing membranes of the taste cells on our tongues and reduce the capacity to taste sweet replacing the sweet taste with a bitter taste.

A more direct way to knock out a sweet taste is to chew on Gymnema sylvestre, a herb native to India and Sri Lanka. Chewing the leaves suppresses the sensation of sweet. This effect is attributed to the gymnemic acids. G. sylvestre has been used in herbal medicine as a treatment for diabetes for nearly two thousand years and though there is insufficient scientific evidence to draw definitive conclusions about its efficacy two small clinical trials have shown gymnema to reduce glycosylated haemoglobin levels.

But can any substances have the opposite effect – ie make a sour taste sweet? Bartoshuk’s studies have shown that a substance called miraculin can allow lime and for some people, lemon, to taste sweet. Miraculin is a natural sugar substitute, a glycoprotein extracted from the fruit of Synsepalum dulcificum. Miraculin itself is not sweet. However, after the taste buds are exposed to miraculin, which binds to sweet receptors on the tongue, acidic foods which are ordinarily sour, such as citrus fruits are perceived as sweet. This effect lasts up to an hour. This effect does not work for everyone tasting very strongly sour foods, such as lemon, because some people, described by Bartoshuk as super tasters, taste things very intensely, so a lemon will taste so sour that miraculin has little impact.

Not surprisingly, Bartoshuk has applied her expertise in taste to examine dietary choice. How does taste affect diet and weight? Are supertasters more likely to be obese? The answer is actually the opposite. Because supertasters taste everything more intensely, much food is too sweet, salty, sour, or bitter. So, supertasters are actually more likely to be slim than regular tasters. But, the effect is very small. This is because so many factors play a role in weight and being a supertaster, which is one genetic difference, is not enough to have a wide effect on weight across the population.

Last updated
The Pharmaceutical Journal, PJ, 14 February 2015, Vol 294, No 7849;294(7849):DOI:10.1211/PJ.2015.20067669

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