Carbohydrate digestion begins in the mouth with an enzyme called amylase. Saliva mixes with your food as you chew it, and the amylase in saliva begins breaking down carbohydrates into simple sugars. Amylase is also produced by the pancreas and used for further breaking down carbs in the small intestines.
Amylase isn’t the only enzyme involved in breaking down carbohydrates; it is just the first step. Amylase helps convert starches eventually into maltose or maltotriose, which are then converted by the enzymes maltase into glucose in the small intestines. Glucose then is utilized by the body for energy production. (Vampire bats are the only mammals not to produce maltase)
Amylase is coded for by the genes AMY1 in the saliva, and AMY2A and AMY2B in the pancreas. These genes vary widely in the number of copies of the gene that a person can have. For example, AMY1 can vary between 2 and 17 copies, thus giving a wide variation in the amount of amylase a person normally secretes in their saliva. [ref]
Several studies that have found that low AMY1 copy numbers are associated with higher BMI.[ref] [ref] [ref] In contrast, a large study published in Nature Genetics in 2015 found no association between amylase copy numbers and BMI. Part of the discrepancy may be differences in diet in the populations; perhaps it is a mismatch between the percentage of carbs in the diet and the ability to break down carbohydrates that causes an increase in BMI.
Other interesting studies:
23andMe and Ancestry data do not give copy number variation information, but several studies have linked specific SNPs to higher or lower amylase activity and copies of the gene.
A couple of studies note that rs11185098 is associated with amylase activity. The studies show that the A allele has higher amylase activity and the G/G genotype has the lowest amylase activity.[ref] [ref] [ref]
A study looking at the effects of different weight loss diets over a two year period found that those with higher amylase activity (carriers of the A allele for rs11185098) were less likely to regain the weight that they had lost. Those that carried the G allele tended to regain weight. This study was interesting because it showed that the type of diet (low carb, low fat, high protein, etc) did not have an effect on weight loss based on amylase activity.
Another study linked a tendency towards higher carbohydrate and starch intake to those with the A allele, but, at least in a Caucasian population, those with the minor (A) allele also had a lower overall caloric intake. [study]
Check your 23andMe results for rs11185098 (v.4 only):
There are many digestive enzyme supplements available that contain amylase. One brand that I like is Enzymetica, but there are other good brands as well.
Coming back to the study referenced above that found that cellulose inhibits the amylase enzyme… If you eat processed or packaged foods (like most everyone does), you are likely eating a lot more added cellulose that you think. Check out the labels, and take a look at my article on emulsifiers and your gut microbiome.
It may be worth experimenting with your diet based on your amylase production — perhaps reducing the proportion of carbs in a meal if you are a low amylase producer would make a difference in how you feel after the meal? Experiment and see if replacing some of the carbs with lower carb alternatives makes a difference.