INTRODUCTION
Diabetes Mellitus is a disease identified by the body’s
impaired ability to produce (or respond to) the pancreatic hormone insulin,
which results in abnormal carbohydrate metabolism elevating sugar levels in the
blood and urine. Greater than 90% of all cases of diabetes is classified as
Type II (T2D) which will be the primary focus of this white paper.
Currently, 9.4% of the U.S. population, or 30.3 million
people have T2D1. Some characterizations of T2D patients and risk
factors leading to the diagnosis include:
There are many pharmacotherapy treatments that help manage
T2D including oral medications and insulin. However, the last 15 years of
clinical research has also shown promising dietary strategies as adjunct
therapies when managing diabetes, most notably therapies aiming to manage
postprandial glycemia, or after meal blood sugar levels.
One particular nutrient, whey, once viewed as a waste
product, has garnered particular interest as demonstrated by its ability to
diminish postprandial glycemia through many interrelated pathways. For every
nine pounds of cheese that is produced there is about 9 pounds of liquid whey.
This liquid contains approximately 0.8% protein by weight, and it’s been rapidly
gaining recognition as a critical functional food2-3. With respect
to T2D, there is tremendous clinical evidence that demonstrates that:
Due to the current cost of T2D, whey protein can be used as an adjunct dietary therapy in the managements of type 2 diabetes.
AVAILABLE FORMS OF WHEY PROTIEN
There are currently three main forms of whey protein
available: whey protein concentrate (WPC), whey protein isolate (WPI) and whey
protein hydrolysate (WPH). WPC is defined as containing 35% - 89% protein with
fat, lactose and minerals comprising the balance. WPI is defined as containing
at least 90% protein with very low levels of both fat and lactose. WPH can be
either a concentrate or isolate (depending on level of protein), but contain a
percentage of the whole proteins that’s been hydrolyzed by proteolytic enzymes3-6.
In the presented studies, WPC and WPI were the primary forms of whey unless
mentioned otherwise.
WHEY PROTIEN AND POSTPRANDIAL GLYCEMIA
There is clear clinical evidence that whey has an
insulinotropic effect, meaning that it stimulates the release of insulin
following food intake. However, it is less clear as to whether this effect is
meaningful when evaluating postprandial glycemia in patients with T2D, often
whom are severely insulin resistant and present with hyperinsulinaemia7-10.
Data presented by Frid et al looked at the effects of adding whey protein into
both high glycemic meals (breakfast and lunch) in patients with T2D. Plasma
insulin levels were higher after both meals, especially when compared to
controls that included lean ham protein or lactose11. In other
studies evaluating dietary interventions for T2D there have been reports of up
to 4 fold increase in insulin response to meals that contain both protein and
carbohydrates, when compared to carbohydrates alone12-13. Lastly, in
a study of male subjects (Nuttall et al) with diet controlled T2D, demonstrated
that when adding protein to a mixed meal that glucose response as measured by
blood glucose response (AUC) was 1/3 lower than no protein14-16.
WHEY PROTEIN AND GASTRIC EMPTYING
The term “preload” refers to small doses of a given
macronutrient at a specified time before a main meal. The concept here is that
a “preload” would be administered at some specified time before the actual meal
in an attempt to encourage the small intestine to release the hormones glucagon
like peptide 1 (GLP-1), gastroinhibitory peptide (GIP), cholecystokinin (CCK)
and peptide YY (PYY) – all of which play roles in delaying gastric emptying and
stimulating the release of insulin. In general, whey protein has been given as
preloads (in healthy non T2D subjects) and shown to delay gastric emptying. In
one study by Akhavan et al, blood measurements of oral paracetamol absorption (a
common analgesic) were delayed, along with elevated postprandial GLP-1 levels17.
In another instance where whey protein
was given just prior to a meal, blood glucose measurements via AUC was
decreased by over one third with accompanying elevated insulin and GLP-1 levels18.
When looking at specifically those patients with T2D, it’s
well established that whey protein stimulates incretin hormones. Researchers Ma
et al reported that in patients with T2D a preload given 30 minutes before a
meal slowed gastric emptying. In this particular study gastric emptying was
quantified by the accepted gold standard method scintigraphy, where radioactive
tracers are used to track internal movement. Whey protein significantly reduced
what’s known as postprandial glucose excursion, as well as stimulated hormones
insulin, CCK, GIP and GLP-1. These findings have been confirmed in other
studies as well19-20.
WHEY PROTEIN AND APPETITE REGULATION
It’s well studied that manipulating dietary macronutrient
composition plays a significant role in energy expenditure and appetite reduction21.
Also, it’s been demonstrated that protein has a more satiating effect than
either dietary carbohydrates or fat22-26. Looking at the effects of
whey protein specifically it has been shown to not only enhance satiety, but
also reduce caloric intakes at subsequent meals. This effect is attributed to
whey’s effect on appetite and regulatory hormones. More specifically, it’s
purported that whey stimulates the secretion of PPY, GLP-1 and CCK by
suppressing a different appetite hormone, ghrelin, one of our body’s orexigenic
hormones. In one particular study by Bowen et al the intake of whey protein had
actually suppressed ghrelin and elevation of both GLP-1 and CCK. This effect
was associated with a reduction in energy intake for ad libitum meals. In one
last study where an indexed hunger score was evaluated looking at the effects
of whey versus casein, both GLP-1 and CCK levels were significantly higher
following whey, contributing to a greater satiating effect. There is also other
evidence that reports higher PPY after whey protein intake (compared to other
proteins), that demonstrate comparable ghrelin and CCK responses27-31.
LONG TERM WHEY CONSUMPTION
A main outcome in the successful management of T2D is the
measurement of glycated hemoglobin, or HbA1c; this is the body’s long-term
response to carbohydrate metabolism. While it’s well known that higher protein
diets positively affect weight loss (i.e. lose weight) and preserve lean body
mass, there is still question as to long term HbA1c outcomes in patients with
T2D. In a five week study conducted by Gannon et al, men with T2D were given
diets with either 15% or 30% energy from protein. The group at 30% protein had
a more significant reduction in HbA1c. Another area of concern in the long-term
use of whey protein for the adjunct management of T2D are effects on both bone
and renal health. One recent two year-long study of postmenopausal women found
no difference in bone densities for those in the high protein diet; in a
separate study that evaluated patients with T2D and microalbuminuria, there was
no negative effects on renal function in the one-year weight loss trial32-35.
CONCLUSION
There’s a massive body of peer-reviewed evidence that’s
accumulated over the years that shows the promising effect of whey protein to
be used as an adjunct therapy in the management of TD2. Patients that add whey
protein to their dietary intake (and subsequently reduce other nutrients like
carbs) experience benefits in three main ways: 1) reduced postprandial glycemia,
2) delayed gastric emptying and 3) appetite regulation via increntin hormone
stimulation. When it comes to supporting patients with T2D the clinical
evidence is clear that including whey protein in meals and supplements that:
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