Biology Reference
In-Depth Information
than the cod protein meal. The insulin/C-peptide ratio was higher after the
milk protein meal compared to the cod and soy protein meals at 120 min.
The insulin/glucose ratio was lower after the cod protein meal compared to
milk and soy protein meals at 120 min. This study showed that three differ-
ent protein meals with similar protein content had different metabolic
responses. The authors attributed these differences to the effects of different
kinds of proteins on insulin secretion and/or to the insulin extraction rates in
the liver (
Von Post-Skagegard et al., 2006
). Also, the specific amino acid
composition in the meal may have played an important role in these differ-
ences. An earlier study by
Soucy and Leblanc (1998)
showed that healthy
subjects had plasma insulin levels increased significantly, with a higher
insulin/glucagon ratio, when fed with a beef rather than cod meal. The rea-
son for different insulin levels was speculated to be due to the predominant
amino acids present. Beef increased the plasma histidine levels while cod fish
gave higher levels of arginine and lysine
(
Soucy & Leblanc, 1998
) and this is
consistent with the amino acid profiles of these proteins (
Table 1.1
). How-
ever, histidine alone has been shown to have little impact on insulin
(
Gannon & Nuttall, 2010
)
and the effects seen probably may have been
due to synergistic effects. Differences in absorption, digestion, and gut fac-
tors were also proposed to be factors contributing to different insulin levels
(
Soucy & Leblanc, 1998
)
. The plasma concentrations of histidine after a fish
meal was lower compared with a beef meal in another study on healthy
males although these differences were not significant (
Uhe, Collier, &
O'Dea, 1992
). Plasma glucose response also declined significantly and insu-
lin secretion increased significantly for both types of proteins. However, this
study used a different type of fish (Gummy shark) compared to the study by
Soucy and Leblanc (1998)
(cod) and this may explain the different outcomes.
The ratio of animal-to-plant (A/P) protein has also shown to be a poten-
tial factor affecting insulin secretion. A population-based study collected die-
tary data using validated semiquantitative food frequency questionnaires,
and associations were made between intakes of total protein as well as the
A/P protein ratio and with cardiometabolic risk factors (
Mirmiran,
Hajifaraji, Bahadoran, Sarvghadi, & Azizi, 2012
). The findings showed that
a higher ratio of A/P protein ratio was related with lower serum fasting
glucose.
In summary, protein source and content seem to significantly affect
their capacity to decrease postprandial glycemia. The different glucose
and insulin responses in healthy individuals after ingesting different protein
sources could be caused by their unique effects on insulin secretion,
