The impact of low carbohydrate consumption on glucose tolerance, insulin concentration and insulin response to glucose challenge in Dogrib Indians

Abstract

The NDDG and the WHO recommend that individuals undergoing an oral glucose tolerance test (OGTT) consume a minimum of 150 gm of carbohydrate on each of three days preceding the OGTT. Carbohydrate restriction affects the diagnostic accuracy of the OGTT. This is a problem for the diagnosis of diabetes among northern peoples, but may also have relevance for other Amerindians. Dogrib Indians of the Canadian NWT still rely on the traditional dietary, based on caribou-hunting and fishing. The impact of low carbohydrate consumption on oral glucose tolerance, insulin concentration (IC), and insulin response (IR) to oral glucose challenge can thus be examined in this population. Carbohydrate Intake (CI) on the day preceding the OGTT was assessed by a 24-hour dietary recall, and was correlated with another indicator of dietary intake, consumption on "a usual winter day." CI was categorized three ways, and two ways (less than 150 gm; greater than or equal to 150 gm). Covariance analysis of the best indicator of glucose tolerance, the hour-2 plasma glucose concentration, found that there were no differences in glucose levels among the consumers of different amounts of carbohydrate. Regression analysis showed that in the Dogrib fasting insulin (FI) is the best predictor of total IC, measured as insulin area. The impact of CI on FI, total IC and IR to a glucose load was assessed. The only significant effect was on FI in the total sample. Among normoglycemics (hr-2 glucose less than 11.1 mmol/L) no effect was seen. IC and IR were not influenced by the previous day's CI in either the total or normoglycemic samples. Nevertheless, the pattern of IR, including normal basal insulin levels with hour-1 IR 10 times higher than baseline occur in all Dogrib. This response pattern is normal for Dogrib, and should not be seen as a portender of glucose intolerance in them.