Why do some of us have the «sweet tooth»

A new study explains why some of us can have a harder time resisting this delicious cupcake.

The Centers for Disease Control and Prevention (CDC) warns that large numbers of people in the United States are consuming significant amounts of sugar through their diet, leading to serious health problems such as heart disease, type 2 diabetes and obesity.

However, while for some it is relatively easy to abstain from eating sweets for others it can be particularly complicated. Is it a matter of will or is there a biological explanation for it?

An earlier study in rodents found that a hormone secreted by the liver, FGF21, “suppresses the mood for sweets.” Similarly, another study in primates came to the same conclusion about the action of this hormone.

In the same issue, new research – recently published in the Journal Cell Metabolism – examines whether FGF21 (Fibroblast growth factor 21) has the same effect in humans and whether fluctuations in this hormone may explain the increased desire for sugar.

People with mutations in the gene that encodes the hormone FGF21 are 20% more likely to have a “sweet tooth”.

The research was led by Matthew Gillum (Assistant Professor of Biological Sciences) and Niels Grarup (Associate Professor of Metabolism and Genetics) both from the University of Copenhagen in Denmark.

The study, called Inter 99, looked at data from an existing study of more than 6,500 Danish participants. Using the information

given by the participants themselves, Inter 99, studied their metabolism, lifestyle as well as their dietary behavior.

The researchers simultaneously measured the cholesterol and glucose levels in the participants’ blood and then sequenced the FGF21 gene, which encodes the hormone synthesis, in an attempt to identify possible mutations.

Genotypic research looked more closely at two mutations in the gene that had previously been linked to increased carbohydrate intake – rs838133 and rs838145. The study found that people who carried one of the two mutations were 20% more likely to regularly consume a large amount of sweets than those who did not carry either of the mutations.

“These mutations are very strongly associated with increased intake of sweets,” says Gillum.

In addition, the study found that these mutations may be associated with higher alcohol consumption and increased smoking, which will require further studies to confirm.

Fasting FGF21 levels are 50% higher among those who are not “excited” about sweets.

The researchers then conducted a second clinical trial to confirm the findings of the first cycle.

They examined the relationship between fasting FGF21 levels and the preference for sweet foods among 86 “young, healthy and non-obese” participants.

Participants completed a questionnaire asking them about their preferences for sweet, savory and fatty foods. The researchers measured the levels of FGF21 in the blood, after the participants had previously fasted for 12 hours. They were then asked to consume equal amounts of sugar and their serum hormone levels were measured 5 hours after ingestion.

During the first measurement (12 hours of fasting) the levels of FGF21 were 50% higher among those who are not “excited” by sweets compared to those who want them. During the next measurement (after consuming sugar) FGF21 increased approximately the same in both groups. In the near future, Gillum and Grarup hope to conduct similar research on a much larger scale in order to better understand the effects of increasing and decreasing blood FGF21 levels in relation to increased sweets and its “involvement” in various metabolic diseases such as obesity and diabetes.