Role of Proteins in Insulin Secretion and Glycemic Control - Advances in Food and Nutrition Research - page 30

responses are known to be major determinants of postprandial blood glucose
excursions ( Rayner, Samsom, Jones, & Horowitz, 2001 ). Therefore, it
appears that protein ingested with carbohydrates can reduce glycemic
response partly by slowing the rate of gastric emptying.
Moghaddam, Vogt, andWolever (2006) observed a dose-response effect
on glycemic response and insulin sensitivity in nondiabetic individuals when
fed soy protein (0, 5, 10, or 30 g) after intake of 50 g glucose. A dose of 30 g
soy protein caused a significant reduction in glycemic response. Other stud-
ies have investigated the impact of coingesting more than one protein
type with glucose on glycemia. Spiller et al. (1987) evaluated increasing
levels of two combined proteins (milk protein: soy protein 1: 2 ratio,
amount ranging between 0 and 50 g) along with 58 g carbohydrate
(maltodextrin þ fructose þ lactose) on serum glucose and insulin. Mean
AUC above fasting for glucose decreased with increasing protein dose. Pro-
tein appeared to exert a dose-dependant effect on glucose response in normal
fasted subjects fed test meals consisting primarily of carbohydrate.
In contrast, the serum insulin curves did not show a protein dose-dependent
effect ( Spiller et al., 1987 ) . But overall, protein increased the insulin response
compared to the meal with no protein. Increasing levels of protein and its
impact on postprandial blood glucose has also been studied in type 2 dia-
betics. A diet consisting of 30% protein was able to reduce postprandial
blood glucose and improve overall glucose control compared to the nation-
ally recommended 15% protein diet (control) in a sample of 12 adults with
type 2 diabetes ( Gannon et al., 2003 ) . Similar results were observed by
Nuttall et al. (1984) .
Other studies have observed no protein dose-response effects on blood
glucose. Various amounts of protein (10, 30, 50 g of lean hamburger) plus
glucose (50 g) ingested by healthy subjects did not alter serum glucose
response compared to that observed with 50 g glucose alone ( Westphal,
Gannon, &Nuttall, 1990 ). Interestingly, there was also no increase in insulin
concentration when proteins were ingested with glucose, except in the 50 g
protein treatment where a modest but prolonged increment was seen. The
sum of the insulin areas for the meals containing either 50 g protein or 50 g
glucose was 100% that of the combined protein and glucose treatment, indi-
cating that these insulin responses were additive ( Westphal et al., 1990 ) .
However, Nuttall et al. (1984) observed that subjects with type 2 diabetes
showed a linear relationship between the quantity of protein ingested and
the insulin response, suggesting that the insulin response is much more sen-
sitive to protein quantity in persons with noninsulin-dependent diabetes.