VOLUME 11 NUMBER 1 • MARCH 2014
19
SA JOURNAL OF DIABETES & VASCULAR DISEASE
REVIEW
High-protein diets and renal disease: is there a
relationship in people with type 2 diabetes?
Amber Parry-Strong, Murray Leikis, Jeremy D Krebs
Abstract
Diabetic kidney disease is the greatest cause of kidney
disease worldwide and a cause of significant morbidity and
mortality
– in New Zealand it accounts for more than 50% of
patients receiving renal dialysis. Diet and lifestyle modification
are recognised as the cornerstones of management of type 2
diabetes. Dietary interventions to aid weight loss and improve
glycaemic control typically increase total energy intake from
protein by about 10%. The effects of increased protein intake
on kidney function and progression of kidney disease in
type 2 diabetes has not been established. Evaluation of the
literature reviewed here suggests that there is some evidence
for the benefit of treating existing nephropathy with protein
restriction, but no evidence that increasing protein intake
in patients with microalbuminuria accelerates diabetic
nephropathy, or causes it in those with normal renal function.
Substituting chicken, fish and vegetable protein sources for
red meat may be helpful, while retaining a focus on other
aspects of a healthy diet, such as high fibre, will ensure that
potential risks are minimised.
Keywords:
albuminuria, chronic kidney disease, high-protein
diets, nephropathy, type 2 diabetes
Introduction
Type 2 diabetes causes significant morbidity, leading to both
microvascular (retinopathy, nephropathy and neuropathy) and
macrovascular (cardiovascular and cerebrovascular) complications.
1
Diabetic kidney disease (DKD) is the greatest cause of kidney
disease worldwide, with 36% of those with diabetes in the US also
having DKD in 2008.
2
In New Zealand, diabetic nephropathy was
the aetiology of chronic kidney disease (CKD) in 51% of patients
requiring initiation of dialysis in 2010.
3
As overweight and obesity
are most often factors in the development of type 2 diabetes,
weight loss is a primary management goal. While diet and lifestyle
Correspondence to: Dr Jeremy Krebs
Endocrine, Diabetes and Research Centre, Capital and Coast District Health
Board, Wellington, New Zealand.
Department of Medicine, University of Otago Wellington, Wellington,
New Zealand
e-mail:
Amber Parry-Strong
Department of Endocrinology, Diabetes and Research, Capital and
Coast District Health Board, Wellington, New Zealand
Murray Leikis
Department of Renal Medicine, Capital and Coast District Health Board,
Wellington, New Zealand
Previously published in:
Br J Diabetes Vasc Dis
2013;
13
(5–6): 238–243.
S Afr J Diabetes Vasc Dis
2014;
11
: 19–22
modification are recognised as the cornerstones of management
of type 2 diabetes, an enormous amount of research has as yet
failed to define the optimal approach. This is reflected in the dietary
recommendations from the European Association for the Study of
Diabetes (EASD) and American Diabetes Association (ADA) which
have both recently adopted a more flexible approach toward dietary
composition, while maintaining a focus on reduced energy, reduced
saturated fat and increased dietary fibre.
4,5
One approach which
has proved effective for both weight loss and glycaemic control
is a high-protein, moderate-carbohydrate diet.
6
Typically such diets
increase protein intake from the usual level of 15–20% of total
energy (TE) to 25–30% of TE.
7
In a recent study of 419 people with
type 2 diabetes in New Zealand, baseline protein intakes were 19%
of TE (88 g per day).
8
Dieticians and health practitioners have been reticent to
recommend high-protein diets for people with type 2 diabetes due
to the unknown effect on renal function. A low-protein diet has
been the standard recommendation for the treatment of diabetes
with impaired renal function and albuminuria for more than 20
years, and is currently the recommendation of the National Kidney
Foundation.
9
A modest benefit of slowing disease progression has
been demonstrated by reducing urinary protein excretion.
10
The
suggestion then follows that a high-protein diet might accelerate
renal disease in susceptible individuals, for example, those with
type 2 diabetes. While an earlier meta-analysis concluded that
a low-protein diet was not associated with improvements in
nephropathy in type 2 diabetes,
11
the present review aimed to
include recent literature and to query the relationship between
protein and renal function in the context of high-protein weight-
loss diets. To achieve this, Medline and PubMed searches were
undertaken to locate articles relating to type 2 diabetes, low-
and high-protein diets, diabetic nephropathy, renal function and
weight loss. All clinical trials that specified type 2 diabetics as the
study population were reviewed.
Protein restriction to treat nephropathy in type 2
diabetes
Dietary protein restriction has been the standard recommendation
for those with end-stage renal failure for many years. This is
based on evidence from trials dating as far back as the 1970s and
summarised in several
Cochrane Reviews
, most recently in 2009.
12
A
Cochrane Review
in 2007 specifically considering diabetes
concluded that reducing protein intake slowed progression of
renal failure slightly but not statistically significantly.
13
Diabetic
nephropathy is characterised by early glomerular hyperfiltration and
later by evolving proteinuria and progressive decline in glomerular
filtration.
14
Therefore the potential for dietary protein to influence
the pathogenesis and/or the progression of diabetic nephropathy
is clear. Despite this, few studies have tested the effect of a low-
protein diet on diabetic nephropathy solely in those with type 2
diabetes. Furthermore it is difficult to compare studies with different
