Role of Proteins in Insulin Secretion and Glycemic Control - Advances in Food and Nutrition Research - page 2

1. INTRODUCTION
Proteins are a major dietary component essential for the survival of
animals and humans. It is the principle macronutrient involved in the struc-
ture, function, and biochemistry of the human body. They function as hor-
mones, enzymes, and transport factors, and are the major component in all
structural units of the body (muscle, tissue, organs, nails, etc.). Proteome
research has shown that the human body has the genetic capacity to synthe-
size around 21,000 different proteins ( Pearson, 2008 ). Proteins are contin-
ually synthesized and broken down in the body and its rate depends on
factors such as health, physiological status, and stage of life. The rate of pro-
tein turnover, in turn, affects body size, protein mass, and protein require-
ments ( Jeor et al., 2001 ). Consuming adequate proteins to maintain
optimum levels in circulating pools is therefore essential for proper growth,
reparation, and metabolism.
Both European and North American guidelines recommend that proteins
constitute 10-15% of total daily energy intake ( DH, 1991; Klein et al., 2004 ).
A similar amount is recommended in diabetic dietary guidelines ( Rodbard
et al., 2007 ). Higher amounts of proteins may be consumed depending on
age, body size, disease, pregnancy, lactation, fitness, and environment
( Henley, Taylor, Obukosia, & Steve, 2010; Jeor et al., 2001 ) . Protein intake
in high-income countries is typically above the recommended levels of 0.8 g/
kg body weight ( WHO, 2007 ). Data from Europe and North America show
that average protein intake in these countries are 109 g/person/day and 91 g/
person/day, respectively ( de Boer, Helms, & Aiking, 2006; Fulgoni, 2008 ).
Rising affluence is also raising protein consumption in developing countries
( Popkin, 2001 ) . Therefore, there is a change in the global dietary pattern
where a greater percentage of energy is obtained from proteins.
Proteins have a notable role in the prevention and management of
chronic noncommunicable diseases. High-protein diets have been shown
to beneficially affect blood glucose ( Gannon, Nuttall, Saeed, Jordan, &
Hoover, 2003 ), blood pressure, heart health and cardiovascular disease
( Appel, 2003; Erdman & Committee, 2000 ) , and cholesterol levels
( Forsythe, Green, & Anderson, 1986 ) . High-protein meals have also been
indicated to have a greater thermic effect and increase energy expenditure
( Acheson et al., 2011 ). Therefore, there is greater focus on proteins also from
a therapeutic perspective. Increased protein consumption has also been
shown to be beneficial in weight loss ( Halton & Hu, 2004 ) and has thus