n addition to enhancing
protein synthesis,
high protein diets have other beneficial effects.
Several lines of evidence have pointed to better
weight loss with higher protein diets due to increased thermogenesis and higher satiation associated with protein ingestion.
Casein
is one type of protein that has unique qualities. Casein is the most
abundant protein in milk, the other main protein being whey. Unlike
whey and most other protein sources, casein has a much slower digestion
rate that make it unique for potentially promoting thermogenesis for
extended periods of time. The thermogenic properties and ability of
protein to reduce hunger have not been tested under rigorously
controlled conditions in large number of subjects because of the
difficulties in making sensitive measures of energy expenditure. A
recent study however sheds some very important light on the benefits of
a high casein diet. Researchers tested the effects of a high protein
diet (25% of total energy) to a low protein diet (10% of total energy).
Casein was the sole source of protein in both diets
that were provided at weight maintenance levels. Subjects consumed the
diets for 36 hours (3 days) while staying in a tightly sealed
respiratory chamber that allowed precise measurements of total energy
expenditure while subjects were in the room. The respiratory chamber
was the size of a very small efficient apartment and only a few
laboratories in the world have the capabilities to do this type of
testing. The results were therefore extremely accurate and reflect the
true level of thermogenesis possible with increasing protein intake in
the form of casein. The results showed an increase of 2.6% in 24-hour
energy expenditure. That amounted to an increase of 55 kcal per day.
The majority of the increase in metabolic rate was seen while sleeping
suggesting that a high casein diet promotes an extended thermogenesis.
There was casein diet also reduced hunger and increased satiety
compared to the low casein diet. These findings provide strong evidence
for the thermogenic effects of protein, and in particular show that
casein is an effective protein source to promote increased metabolic
while sleeping.
Hochstenbach-Waelen
A, Veldhorst MA, Nieuwenhuizen AG, Westerterp-Plantenga MS, Westerterp
KR. Comparison of 2 diets with either 25% or 10% of energy as casein on
energy expenditure, substrate balance, and appetite profile. Am J Clin
Nutr. 2009 Mar;89(3):831-8. Epub 2009 Jan 28.
