Between 2% and 3% of Greenlanders have a genetic variant that prevents them from absorbing glucose into their blood. Instead, gut bacteria convert the sugar into substances that benefit their health. According to the researchers, Greenlandic adults with the variant can get almost as many health benefits from drinking cola as they can get from eating broccoli.
For most people, eating sugar is not very healthy. Once eaten, the glucose is quickly absorbed into the bloodstream, and eating too much can eventually lead to the development of type 2 diabetes, cardiovascular disease, elevated cholesterol, obesity and other conditions.
However, this does not apply to a small group of Greenlanders. They cannot absorb the glucose into their blood because they have a specific genetic variant, and their gut bacteria convert the glucose into beneficial health-promoting molecules.
They therefore find that eating sugar actually keeps them slim, lowers their cholesterol levels and protects them from developing cardiovascular disease and obesity.
According to a researcher behind a new study, the concept that more people could achieve health benefits from sugar is enticing.
“It would be fun if we could all have this variant. Then we could eat as much sugar as we wanted without it being unhealthy, as it is for the vast majority of us. In fact, making a substance that achieves the same effect as the one experienced by the people with this variant should be possible,” explains Anders Albrechtsen, Department of Biology, University of Copenhagen.
The research, published in Gastroenterology, was carried out in collaboration between researchers from the University of Copenhagen, Ilisimatusarfik (the University of Greenland) and the University of Southern Denmark.
Sugar gives Greenlandic children a stomach ache
The research is based on the fact that many Greenlandic children cannot tolerate sugar, and it causes diarrhoea and stomach ache.
However, for most children, this intolerance disappears for life when they start school.
The reason for this somewhat special condition is a mutation in the gene for an enzyme called sucrase-isomaltase that ensures the uptake of glucose through the intestinal wall.
People with this genetic variant on both chromosomes are therefore unable to absorb glucose, and the Greenlandic children with this genetic variant therefore have a stomach ache.
Like taking cholesterol-lowering medicine
In the study, the researchers wanted to determine how losing sucrase-isomaltase function affects the health of Greenlandic adults.
The researchers examined data for 6,551 individuals who had responded to health surveys.
The data included the serum cholesterol, blood pressure, serum triglycerides and weight of the participants and the responses to various questionnaires.
The researchers compared individuals with mutations in the sucrase-isomaltase gene with the others and found that those with the mutation had a lower body-mass index, lower weight, lower fat percentage and lower serum cholesterol and were generally healthier.
“Amazing that such a genetic variant can benefit health so much. The effect on unhealthy cholesterol in the blood is like taking cholesterol-lowering medicine. This is really remarkable,” says Anders Albrechtsen.
Fed mice with Happy Meals
To examine in greater depth why sugar seems healthy for some Greenlanders, the researchers carried out various experiments on mice.
Mimicking the 2–3% of Greenlandic adults with the variant, the researchers used sucrase-isomaltase knockout mice (Sis-KO), feeding one group of the mice a Happy Meal diet including a sugary drink and feeding the non-sugar-containing part of the Happy Meal to the other group of mice.
The researchers found that the mice fed the sugary diet were much healthier than those not fed sugar.
“The fascinating aspect is that this mutation not only seems to lead to fewer negative effects of eating sugar but definitely promotes health. This is like eating broccoli or other fibre-rich food,” explains Anders Albrechtsen.
Gut bacteria convert sugar into health-promoting substances
The researchers also took blood samples from Greenlanders to determine whether there were differences in various biomarkers for health and found that the people with the variant had concentrations of plasma acetate that were twice as high as those Greenlanders without the variant.
Acetate, which is mostly produced by gut bacteria, is a short-chain fatty acid that promotes health by reducing appetite, increasing metabolism and boosting the immune system.
The study therefore concludes that the gut bacteria of people with a variant of the sucrase-isomaltase gene who cannot absorb sugar across the gut wall convert the sugar to acetate, which is then absorbed into their bloodstream.
People with the genetic variant therefore have high concentrations of health-promoting acetate instead of harmful sugar. This may also explain why some Greenlandic children become ill when they eat sugar, with the researchers speculating that the composition of the children’s gut bacteria are not initially geared to convert the sugar as they are later in life.
A historically sugar-free diet
The history of Greenlanders probably shows why many of them have this special and seemingly healthy genetic variant in a modern society in which sugar is ubiquitous.
Greenlanders have traditionally eaten fish, whales and seals, and only very rarely have they had access to sugary foods such as berries.
Not being able to absorb sugar by having a functional sucrase-isomaltase gene has therefore not been a huge disadvantage.
“Today, we can see that this has resulted in improved defence against the sugar content of a modern diet, which is unhealthy for most people but can promote the health of some Greenlanders,” says Anders Albrechtsen.
A promising drug target?
Anders Albrechtsen thinks that the discovery may have useful pharmaceutical perspectives.
He says that making drugs that block the function of sucrase-isomaltase or inhibit its production is probably not very difficult, so that people with elevated cholesterol, diabetes or incipient cardiovascular disease do not absorb sugar across the intestinal wall, which will tend to promote their health.
However, attaining the full benefit of the lack of sugar uptake and not just diarrhoea requires the right gut bacteria to convert the sugar into acetate.
“This may mean that people need a transplant of gut bacteria from a person with the right acetate-producing bacteria. There are some interesting studies ahead that I would very much like to participate in,” concludes Anders Albrechtsen.
