For millennia, populations in Greenland enjoyed a relatively sugar-free diet. Without the need to rapidly process certain carbohydrates, many lost the function of a key sucrose-processing enzyme.
To learn what this loss means for the health of today’s populations, a team of researchers led by scientists from the University of Copenhagen analyzed the health of thousands of Greenlandic people.
The gene at the center of the study produces the enzyme sucrase-isomaltase. At some point in Greenland’s history it mutated to the extent it no longer works. Just over a third of its descendents now carry at least one of these broken variants.
For the rest of us, working versions of the enzyme sit in our intestinal wall, where they digest dietary carbohydrates such as sucrose (the kind of sugar you might sprinkle into your coffee) and isomaltose (a component of caramelized glucose).
Based on the results of past studies on children, this sugar-absorbing enzyme is necessary for good health. Without it, the consumption of any significant amount of sugary food results in diarrhea, gut irritability, and vomiting. Whether this applies to adults, however, remains an open question.
An assessment of blood chemistry, diet, and history of diabetes was carried out on more than 6,000 Greenlandic volunteers, along with a study of their genes. All were over 18 years of age.
Surprisingly, where children reportedly suffered severe reactions to sugar consumption to the point it could affect their development, adults more or less thrived.
The results associated possession of two copies of the defunct gene with a lower body mass index and reduced percentages of fat, as well as a healthy lipid profile.
A group within the study population also showed intriguing levels of a chemical called acetate. Circulation of this short-chain fatty acid has been linked with lower appetites, further indicating the loss of this key enzyme might have certain benefits in a world where overindulgence in high-energy foods is hard to avoid.
The researchers suspect the surplus of simple carbohydrates in the gut could favor microflora that transform it into acetate, turning it from a potential irritant into a tool for a healthier diet.
Experimental results based on mice engineered to resist absorption of sucrose also showed they stored less fat when fed energy-rich diets.
Whether this knowledge might inform future generations of fat-fighting therapies is hard to say. Further studies are needed to fully explore the consequences of inhibiting otherwise functional forms of sucrase-isomaltase in the guts of individuals who might need a helping hand in managing their sugar digestion.
This research was published in Gastroenterology.