Biology Reference
In-Depth Information
only 28% of the insulin response seen when glucose was given. Although
they observed an effect of protein on glucagon, there was no impact on
C-peptide.
Lang et al. (1998)
fed 12 healthy participants egg albumin, casein,
gelatin, soy protein, pea protein, and wheat gluten (22.4% of total energy)
and found that all the proteins increased insulin secretion to the same degree.
Unlike the previously discussed studies, proteins were provided as part of a
mixed meal in this study and the lack of differences may have been due to
the influence of other macronutrients. Indeed, studies looking at the effects
of combined protein and carbohydrate meals have shown weaker effects
of protein quality on insulin (
Claessens, Calame, Siemensma, van Baak, &
Saris, 2007
)
.
A few studies have also looked at the effect of proteins in type 2 diabetics.
A meal with glucose and cottage cheese resulted in a higher insulin response
than a meal with other proteins such as fish or soy
(
Gannon, Nuttall, Neil, &
Westphal, 1988
)
. The major stimulus for insulin secretion was the increase in
incretins that were stimulated in response to proteins (or its digestion prod-
ucts) in the intestine. This implies that the insulin response was related to the
protein digestion rate.
Gannon, Nuttall, Damberg, Gupta, and Nuttall
(2001)
fed 10 untreated type 2 diabetics either 50 g of lean beef or water
and measured insulin for the subsequent 8 h. They found that beef showed
a threefold increase in insulin compared to water and that these levels
remained for up to 7 h. An increase in C-peptide and glucagon was also
observed. Another study investigated the effect of 50 g of protein from lean
hamburger on insulin in type 2 diabetics and reported similar effects (
Nuttall,
Mooradian, Gannon, Billington, & Krezowski, 1984
). The same group
compared the insulin response to 25 g of protein from cottage cheese and
egg white in type 2 diabetics in another study (
Gannon, Nuttall, Lane, &
Burmeister, 1992
)
. While both proteins stimulated insulin secretion, the
response for cottage cheese was 3.6 times greater compared to that of egg
white. This was also the same for C-peptide concentrations. Again, cottage
cheese was metabolized more (81%) than egg white (52%) and elicited a
serum amino acid N content twice that of egg white and this may explain
the greater hormonal responses. The data therefore suggest that insulin
secretion in response to proteins is hyperstimulated in type 2 diabetics.
However, more data are required before firm conclusions can be made.
A very limited number of studies have looked at the effect of proteins on
insulin in diabetics and there are no studies looking at effects of combined
proteins on insulinemia. These are areas worthy of further study.
