Unhealthy food habits are risk factors for developing type 2 diabetes. An important purpose with the study was to examine the role of the AMY1 gene in breaking down starchy foods after a meal. The study may lead to personalized nutrition recommendations that can reduce the risk for type 2 diabetes and obesity.

The researchers invited 19 participants to two meals of white wheat bread in order to gain a better understanding of how different genetic traits affect the ability to break down starch. After the meal intervention, blood sugar and insulin levels differed between groups, depending on the AMY1 copy number variation.

“People all over the world eat a lot of starchy foods, such as bread, pasta, rice and potatoes. Carbohydrates are an important source of energy, but we need to be careful with carbohydrates that lead to elevated blood sugar levels. High blood sugar levels are risk factors for developing type 2 diabetes. In our study, we are getting closer to an answer to the question of how our genes impact our ability to break down starchy foods,” says Emily Sonestedt, one of the lead authors of the study in Genes & Nutrition.

Copy number variation

Amylase is an enzyme that breaks down starch and AMY1 is the gene coding for salivary amylase. Out of the 19 participants in the meal study, nine had between two and four copies of the AMY1 gene, whereas the others had ten or more copies.

“Humans have between 2-17 copies of the gene. In average, Swedish people have around six copies of the gene. We wanted to invite participants with extremely few and very many copies to better understand if the gene variant affected blood sugar and insulin levels,” says Emily Sonestedt, a researcher in nutrition epidemiology at Lund University Diabetes Centre (LUDC).

The participants, who were recruited from the Malmö Offspring Study (MOS), did not have diabetes or problems with high blood sugar levels and had fasted before the meals. They were asked to eat two and a half slices of white wheat bread for the first meal and five slices during the second meal, over a period of 15 minutes. Blood samples were drawn before the meals and on several occasions up to two hours afterwards.

Quick process

Following the the meal of two and a half slices of bread, the group with many copies of the AMY1 gene had 83 percent higher blood sugar levels and 73 percent higher levels of insulin compared to the group with few copies of the gene. After the meal of five slices, the differences were smaller. The group with many copies of the gene then had 40 percent higher blood sugar and insulin levels, compared to the group with few copies of the gene. 

“Participants with a high number of copies will see an increase of blood sugar levels, as the process of breaking down starchy foods and distributing the energy into the body is quick. A positive thing is that this is a group that may benefit from healthy starchy foods, something we have seen in one of our previous studies. This is also a group that may need to be careful with fast carbohydrates leading to elevated blood sugar levels,” says Emily Sonestedt.

Personalized recommendations

The few similar studies that have been carried out in the field both verify and contradict the results from the study. The researchers are planning to carry out a larger study with more participants and additional values aside from blood sugar and insulin levels.

“The goal is that our research will lead to personalized nutrition recommendations that may reduce the risk of type 2 diabetes and obesity. We hope that the knowledge will result in a test that will measure salivary amylase. Such a test may be valuable for people who need to find starchy foods that will keep blood sugar levels within healthy limits,” says Emily Sonestedt, a research group leader in Nutrition epidemiology at Lund University Diabetes Centre.