Impact of Amylase on Dietary Starch and Obesity

Role of Amylase in Starch Digestion

Dietary starch undergoes digestion through the action of amylase, an enzyme present in saliva. Recent research has revealed a significant relationship among the genes responsible for amylase production, dietary starch intake, and obesity.

Genetic Factors Influencing Obesity

Obesity is influenced by various genetic factors. One noteworthy factor is the variation in copy number of the salivary amylase gene, AMY1, which may affect the heritability of body mass index (BMI). Previous investigations into the copy number variation (CNV) of AMY1 have yielded mixed results regarding its impact on BMI. Individuals typically have between 2 and 17 copies of the AMY1 gene, which correlates directly with the amount of amylase found in saliva. Consequently, individuals with a lower AMY1 copy number may have reduced capacity to digest starch due to decreased amylase levels.

Study Overview

A study published in the American Journal of Clinical Nutrition explored the connection between AMY1 copy number and obesity. The research analyzed data from 4,800 participants involved in the Malmö Diet and Cancer Study (MDCS), which took place between 1991 and 1996. The cohort included men born between 1923 and 1945, and women born between 1923 and 1950, all residing in Malmö, Sweden. The MDCS gathered extensive information on participants’ lifestyles, health, socioeconomic status, and dietary habits. Dietary starch intake was determined by subtracting sugars from total carbohydrate consumption, and participants were categorized into high, medium, and low starch intake groups. AMY1 CNV was assessed through digital droplet polymerase chain reaction of DNA samples from participants.

Key Findings

The study revealed no significant differences in AMY1 copy number concerning age, physical activity, or education levels across the different starch intake groups. Furthermore, overall AMY1 copy number did not show a link to BMI (p = 0.80) or body fat percentage (p = 0.38). However, a notable interaction was found between AMY1 copy number and starch intake concerning BMI (p-interaction = 0.007) and body fat percentage (p-interaction = 0.003).

Conclusion

These findings suggest that the interplay between starch consumption and AMY1 copy number may influence the risk of obesity. Specifically, individuals with high starch intake but low genetic capacity to digest starch may experience lower BMI due to a reduced caloric absorption from starch consumption.

Written By: Cindi A. Hoover, Ph.D.