If You Can’t Taste the Sugar, Will You Stop Craving It?

Do our taste buds make us crave sweet foods? If the results of a study with a chewing gum that temporarily prevents taste buds from responding to a sweet food are to be believed, the answer is yes. Two Israeli researchers have formulated a chewing gum containing an extract from the leaves of the Gymnema Sylvestre plant, a botanical that is found in India. They found that chemicals in the leaves alter the taste buds, so that sweet foods taste sour. Indeed, the taste is so unpleasant people don’t want to put anything sweet in their mouths for a few hours after chewing the gum. Gitit Lahav, a psychologist, and Shimrit Lev, a self-described Chinese herbalist, tested the gum on women who claimed to have a constant craving for sweets. They reported that their subjects stopped wanting to eat anything sweet for a few hours after chewing the gum.

Studies have to be done to confirm these results but if they are confirmed, chewing this gum might be helpful in controlling the eating of sweet foods, especially the kind of eating we term mindless. For example, these days in which we are still pretty much confined to our homes, we may take frequent breaks from whatever we are doing to snack even though we are not hungry. If the snacks we want to eat are sweet, such as cookies, candy, and ice cream, but now they taste sour because the gum we have just chewed is blocking our sweet taste receptors, we may stop snacking. One can imagine the potential a gum or a mouthwash might have on blocking our eating of other foods that are not good for us: we might eat less salt if salty foods don’t taste good. Or perhaps a chewing gum that makes fatty foods taste greasy or slimy would decrease our desire for bacon or chocolate. We would be left with the desire to eat only healthy low-fat, high-nutrient foods. Maybe.

But what the inventors of this chewing gum have not taken into account is that a craving for sweets is generated not only by our taste buds. Consuming a sweet carbohydrate or a starchy one has a significant neurochemical effect that goes far beyond the transient enjoyment of a sweet taste. Serotonin, the neurotransmitter that regulates behavior such as depression and anxiety, is made only after carbohydrates, either sweet or starchy, are consumed. When about 25 grams of sucrose or starch or a combination of both are eaten, e.g., jam on toast, insulin is released. The effect of this pancreatic hormone is to allow an amino acid, tryptophan, to enter the brain where it is immediately converted into serotonin.

Often changes in serotonin activity, for example the changes that occur during the premenstrual days of the menstrual cycle, cause a substantial change in a woman’s need to eat carbohydrates. Cravings for sugary carbohydrates like chocolate or salty crunchy items like chips are common during this time and usually are accompanied by deterioration in mood, attentiveness, and sleep. Women experiencing PMS may want to eat a chocolate bar or a bag of tortilla chips, but the taste of the carbohydrate food is not what their brains are craving. Rather, it is the carbohydrate itself. We showed this to be the case by measuring changes in affect, cognition, and fatigue in women with severe PMS after they consumed beverages containing carbohydrates or protein. The women did not know what they were drinking, as the beverages tasted equally sweet because of the addition of non-nutritive sweeteners. Significant improvement in premenstrual symptoms occurred only after ingesting the carbohydrate beverage.

Many people experience a subtle but real change in their mood, fatigue, and ability to concentrate in the late afternoon. These changes are particularly noticeable when sunset occurs by 4 or 5 p.m. Carbohydrate craving and the subsequent consumption of a sweet or starchy carbohydrate snack often accompany the changes. As with premenstrual women, the sweet craving is related to alterations in brain serotonin activity, not sweet perceiving taste buds.

If the late afternoon carbohydrate cravers used the chewing gum to block their receptors for sweet taste, they might turn to alternative carbohydrate foods such as crackers or popcorn. This change in choice of carbohydrate foods is best understood if we view their cravings not for a sweet food, but for a sweet beverage when they are thirsty. The sweet juice or soda would be rejected after chewing the special gum because it would taste sour. However, the need to satisfy their thirst would remain, and presumably they would reach for a neutral-tasting beverage like water. In this hypothetical situation, the gum’s effect would be only on the choice of beverage, not on whether they would drink to satisfy their thirst or not.

Some simple studies would determine whether sweet cravings of the women described by the inventors of the gum are simply for a sugary taste, or because sucrose is a carbohydrate. If it were only the taste, then the women who chewed the sour-tasting gum would not seek any alternative carbohydrate. But if the need to eat a sweet food were driven by changes in brain serotonin, just as the need to consume liquid is driven by thirst, then the women would seek some other form of carbohydrate.

It is important to resist the temptation to use taste to explain why people overeat. I have had many weight-loss clients explain their overeating as, “I like the taste of food, so I eat.” However, this explanation does not explain why they eat too much. We all know that the first bite of the fudge cake or cheese pizza is going to taste better than that last forkful of frosting or last slice in the box. Yes, taste is involved but other factors, often emotional, are at play as well.

Chewing gum that obliterates a sweet taste may prevent mindless nibbling on the Valentine’s Day candy already for sale in the supermarket, but it will not obliterate the many complex reasons we overeat.