Sweet Tooth Gene

El-Sohemy and his colleagues studied two large groups of volunteers, who completed detailed records of their daily diet. Analyzing blood samples, they found that people with a different form of a gene called GLUT 2 had consistently higher daily sugar intakes.

“Initially what we were interested in finding is why some people show a more dramatic rise in blood sugar after a meal,” El-Sohemy explains.

“The reason we focused on this particular gene is because it’s known to function primarily in the pancreas. That’s the organ that’s responsible for sensing changes in blood sugar and producing insulin in response to clear it. We found there was no difference in how quickly individuals with the two versions of the gene cleared glucose from their blood, but surprisingly, those who had a particular version of this gene just consumed more sugar... the fat intake was the same, protein was the same, other types of carbohydrates was the same. So it seemed to be very specific to sugar.”

The first group the researchers studied were people with type 2 diabetes. Then they went on to study a separate group of people without diabetes. In large studies that look at peoples’ diets over time, the only practical way for scientists to collect dietary information is to rely on people’s own records of their daily food intake.

Since some peoples’ self-reports about their diets are not reliable, the researchers were careful to take steps to validate their findings.

“Any variations or error in reporting in self-reports of food consumption are not likely to explain this phenomenon, because it’s not likely that one version of the gene leads you to be less accurate in your reporting,” El-Sohemy says. But to make sure that’s not a problem. we repeated our experiment on another visit, and then looked at a separate population using a different method of dietary assessment to ensure that this observation is not likely due to chance.”

As they wrote in the journal Physiological Genomics, this gene was known to work in the pancreas, but other researchers also studied it in the brains of mice.

“It turns out this gene is also turned on in regions of the brain that control appetite,” says El-Sohemy. "The individuals who have that version of the gene might have an impaired ability to detect changes in blood sugar that ultimately signal the brain to stop eating."

People with the GLUT 2 variation consumed “between 20 and 30 grams of sugar extra... every day,” he says.

"It was about the equivalent amount of sugar that you would find in a regular sweetened can of soda."

Sugar & Diabetes

We’ve all heard the tale that eating too much sugar causes diabetes, and we’ve also heard that described as a myth.

El-Sohemy says this research indicates that really answering question is much more complicated, While some previous studies have linked GLUT 2 with the risk of type 2 diabetes, he says the findings have been inconsistent, possibly because previous studies didn’t “account for different dietary habits of those with and without the gene variant,” or other gene variations that may influence dietary choices, such as those that affect sweet taste.

“If we’re suggesting that individuals who consume high or low levels of sugar as part of their regular diet are, in fact, genetically different, and the variation in that gene affects other biological processes in the body, then how do we disentangle the affect of the diet versus the effect of the gene?” he asks. “That really is the next step.”

But he suggests that your grandmother may have been right after all, but indirectly, because extra energy intake caused by extra sugar consumption increases your risk of obesity, which increases your risk of diabetes.

This study didn’t look at whether this gene variation plays a role in diabetes because the group with diabetes was older than and had other health differences from the group without diabetes.

And following the younger group long-term wasn’t possible this time around. “That would certainly be worth doing, but the study wasn't designed to be prospective/longitudinal because that would've made it much more costly.” El-Sohemy explains. We will, however, try to raise funds to do that.”

He hopes the work will ultimately lead to diets tailored to our genetic makeup, but in the meantime, he doesn’t see it as an excuse to indulge.

“The factors that affect sugar constumption are fairly complex, it involves not only genetic factors, but also environmental,” he says. “Food availability is known to influence consumption. If you’re at a birthday party and there’s a cake, you’re likely to have a slice, whereas you won’t go out of your way, necessarily to go and buy a piece of cake.”

“So just minimizing the availability of high sugar foods is probably the best strategy for an individual who has this gene to ensure that they’re not over-consuming calories in the form of sugar,” El-Sohemy says.

This research was published in Physiological Genomics, May 2008, and funded by: Advanced Foods and Materials Network (AFMNet), Canadian Institutes of Health Research, Natural Sciences and Engineering Research Council of Canada, and the Canada Research Chairs Program.