Biology Reference
In-Depth Information
become the basis of popular weight loss regimes (
Malik & Hu, 2007
)
which
are followed by many
(
Blackburn, Phillips, & Morreale, 2001
).
The global trend toward increased protein consumption combined with
its suggested positive impact on health and weight control implies that
higher protein diets are and will become commonplace in most societies.
Protein consumption is directly correlated with affluence, and incidentally
it is in the same affluent demographic that the greatest incidence of diabetes,
obesity, and related diseases can be typically seen (
Fall, 2001
). Therefore,
gauging the impact of proteins on glucose metabolism is of paramount
importance. Proteins affect glucose regulation primarily through their effects
on insulin. Likewise, a large volume of research has shown that consuming
proteins in combination with carbohydrates significantly alters glucose
homeostasis mechanisms. This chapter reviews studies that have looked at
the effects of proteins on glycemia and insulin secretion. This chapter col-
lates research so far and provides an overview of the current state of the art.
2. BLOOD GLUCOSE HOMEOSTASIS AND
THE ROLE OF INSULIN
The blood glucose concentration is a dynamic but finely regulated
entity in the human body. In healthy individuals, the postabsorptive/fasting
concentration is precisely maintained between 4 and 6 mM/L (
van den
Berghe et al., 2009
)
. Postprandial blood glucose levels may go up to around
10 mM/L after consumption of a carbohydrate-rich meal. Glucose is the
principle fuel for the brain and red blood cells and a constant supply in
the blood is therefore critically important.
Both hypo- and hyperglycemia have been shown to adversely affect
health and well-being (
Davidson, 2004
)
. Hyperglycemia over time may
induce toxic effects on
b
-cells and produce reactive oxygen species. Abnor-
mally high blood glucose concentrations desensitize
b
-cells to glucose which
later results in apoptosis and cessation of insulin secretion. Prolonged expo-
sure to abnormally high blood glucose levels may also initiate cellular dam-
age through lipotoxic effects. Hyperglycemia has also been shown to
accelerate the onset of cardiovascular complications in type 2 diabetes due
to oxidative stress (
Ceriello, 2006
)
. Therefore, optimum glycemic control
is important toward avoiding a cascade of events leading to increased
morbidity and mortality (
Ceriello et al., 2004; Ohkubo et al., 1995
).
The blood glucose concentration is regulated by balancing the rate of
digestion and intestinal absorption of dietary carbohydrates, rate of removal
