Do Genetics Affect Carb Tolerance?
Carbohydrates are sometimes universally condemned, but the fact is that many people have differences in their carbohydrate tolerance levels, and not all carbohydrates are the same. Basically, carbohydrates are not as negative for some people because they have genetic differences that help them metabolize carbohydrates better.
The differences come down to how the human gene pool separated. Hunter gatherer groups settled down in both cold and warm climates and adapted to each type of climate. Research suggests that the groups in colder climates likely relied more heavily on meat for food, while those in the warmer climates relied more on plant food.
There is a gene called AMY1 that breaks down carbohydrates, and it is an enzyme that breaks down starch in the mouth. It is this enzyme that causes starch to taste sweet, and there are differences between genetic groups in how much of this enzyme is produced. This is thought to be one of the main differences of how carbohydrates metabolize between people.
Studies have shown that different AMY1 groups have different carbohydrate metabolism levels. Healthy non obese people were divided into two groups: those with low amylase production and those with high amylase production. They both ingested starch, and the group with low amylase production had a higher blood glucose level compared to the group with high amylase production. The low amylase group had an increase of blood glucose that lasted almost two hours, while the group with high amylase production did not have as high an increase in blood sugar.
The research suggests that those with low levels of amylase production should not be eating high levels of starch. The US Department of Agriculture (USDA) has nutritional guidelines that suggest that anywhere from 40 to 60% of a person’s diet should come from starches. This is clearly questionable advice when a large amount of the population may have potential difficulties with starch metabolism. By advising this level of starch consumption, this group is at risk of developing diabetes and insulin resistance due to consistently high levels of starch consumption.
The safest bet for those who are not sure whether starch is causing weight gain or potential insulin resistance is to avoid starch consumption for a period of time and see whether there is a reduction in weight. If there is, a person may have low amylase production, and should avoid eating starch as much as possible. Blood tests can also indicate a person’s tolerance levels.