
Diet and Kidney Health
Typically a
patient discovers his or her kidneys are failing
by a routine laboratory blood test called a
serum creatinine, which indirectly measures
kidney function. (Normal creatinine depends on a
person’s age and in older adults is 1.2 mg/dL or
less.) Once a problem is discovered, the doctor
will try to slow the progression of this disease
with medications intended to treat high blood
pressure, diabetes, high cholesterol, and/or the
use of anti-angiotensin medications (as
discussed in my June 2007 newsletter). Little
or no attention is given to what the patient
eats, because primary and ongoing medical
training never covers profit-free diet therapy.
Diet becomes a
topic for discussion only after the kidneys have
been almost completely lost, a condition called
end-stage kidney disease—a stage of
pre-dialysis. Now the powerful kidney-saving
benefits from a healthy diet are of very limited
value. At this time a referral is made to a
kidney specialist, a nephrologist, and a renal
dietitian. They will mention a low protein
diet. But, because most of these professionals
do not believe patients will follow such a diet,
and because they themselves do not have real
training and experience with this simple
approach, no meaningful change is accomplished.
After this cursory discussion of diet, the very
sick patient is shuffled off on a tour of the
dialysis ward—where he will soon be attached to
machines for several hours a day, three or more
days a week (at an annual cost of $50,000 to
$75,000 per patient; most paid by taxpayers in
the USA).
Lack of financial
incentives is the reason for no meaningful diet
therapy training for your doctors. However,
patients with failing kidneys would be very
interested in a low-protein diet that would
reduce the progression of their kidney disease
and death on average by 33% to 50%.1
In many cases this is a diet that will keep them
from ever having to be on dialysis.1
Moreover, this same diet will improve their
overall health and feelings of well-being,
eliminating uremic symptoms*. The multiple
medications that are being used by patients with
kidney disease for high blood pressure, diabetes
and kidney disease can also be reduced and
eliminated by adopting this sensible diet.1
*Uremia is a
condition resulting from advanced stages of
kidney failure in which urea and other wastes
build up in the body. Early signs of uremia are
lethargy, mental depression, loss of appetite,
and edema; later, diarrhea, anemia, convulsions,
and coma.
The
Kidneys
Your two
kidneys are located in both sides of
your posterior abdomen below the rib
cage. These sophisticated processing
machines filter 200 quarts of your blood
daily and remove on average 2 quarts of
waste products and extra water. The rate
of filtration is reported as a
glomerular filtration rate (GFR),
which is
calculated from the blood (serum)
creatinine level using the patient’s
age, weight, gender, and body size.
The actual filtering occurs within
millions of tiny units inside the
kidneys called nephrons. The waste from
the breakdown of body tissues and from
food, and extra water, becomes urine.
Dietary protein is the most common waste
(other than water) removed by the
kidneys. The kidneys have many other
functions including acid-base and fluid
balancing, hormone production, and
regulation of blood pressure. |
Diet Therapy
In his milestone
treatise in 1946, Thomas Addis
argued from personal clinical experience that
reduction in renal "work" by judicious dietary
protein restriction was effective in minimizing
further loss of kidney function in patients with
chronic kidney insufficiency from a variety of
causes.2,3 Thus, for the past sixty
years doctors and patients should have known
that the primary focus of attention for the
preservation of the kidneys should be diet.
The kidneys filter
and eliminate most of the nutrients that we do
not use, as well as many non-nutrients. (The
liver, skin and lungs are also organs that
eliminate waste.) Dietary excesses, protein
being the primary one, can easily become a
burden. (You can actually observe the effects of
eating excess protein with the formation of
frothy bubbles in the toilet bowl after
urinating following a single high protein meal.
You (or at least some people) can also smell
asparagine, an amino acid, found in high
concentration in the protein of the vegetable
asparagus when you urinate.)
The human body
needs no more than 5% of the calories consumed
to be from protein in order to build all cell
structures, enzymes and hormones; once these
needs are met then the excess must be excreted
from the body. The typical Western diet, focused
as it is on meat, poultry, eggs, and dairy
products, is loaded with protein; as a result,
many people consume a diet with 30% or more of
the calories from protein.
In the process of
eliminating the protein excesses, the blood flow
and filtration rates of the kidney tissues (nephrons)
increase, which in turn, causes a condition
known as “intra-glomerular hypertension.”4
Sustained hypertension in the glomeruli leads to
progressive damage. This damage is most
important and apparent when people have
pre-existing kidney loss from conditions such as
donation of a kidney, physical injury, diabetes,
atherosclerosis, hypertension, and polycystic
kidneys. The excess protein accelerates the
loss of kidney tissue to the point of end stage
kidney disease all too soon in these people.
Even under
“normal” conditions, the burden of excess
protein from the typical Western diet
“overworks” the kidneys, causing the loss of
kidney tissue.4
In an otherwise
healthy person, 25-50% of his functional kidney
capacity will be destroyed after seven to eight
decades of eating typical foods.4-6
Even so, we have so much reserve tissue that
with only 30% of kidney function remaining all
of the wastes are still removed; and the damaged
and failing kidneys go unnoticed.
The Scientific
Research Says Diet Therapy Is Fundamental
Treatment of
chronic kidney failure with a low-protein diet
is effective in reducing uremic intoxication,
slowing the progression of the disease, and
preventing secondary hyperparathyroidism. An
analysis of multiple studies using a low-protein
diet for people with kidney disease has found
the measurement of glomerular filtration rate (GFR)
decreases by 0.53 mL/min/year less for those on
a low protein diet compared with those who
follow a usual diet.7 Furthermore,
this analysis found people with diabetic kidney
disease received more benefit from diet than
those who had kidney disease of other origins.
However, people with other forms of kidney
disease, including those with polycystic kidney
disease have shown remarkable benefits.8
The amount of protein in the urine (proteinuria),
which is considered an important sign of kidney
health, is also greatly reduced by this therapy.7
Animal vs.
Vegetable Protein
The kinds of diets
fed to patients vary from those with an emphasis
on animal proteins to those of all vegetable
proteins (with and without supplementation of
essential amino acids and other nutrients).
There is substantial evidence that proteins from
plants are much healthier for the kidneys and
slow the progression of kidney disease more
effectively than animal proteins.11-13
For the past
twenty years many investigations have focused on
the benefits of a vegan diet (no animal foods)
for failing kidneys.13-19 After
studying people on diets of various amounts of
vegetable protein one group of researchers
concluded, “The vegan diet is associated with
glomerular and systemic haemodynamic changes
which may be beneficial in the prevention of
glomerular sclerotic changes in health and
disease.”19
In one research
project the investigators pointed out that
traditional low protein diets were of poor
palatability, costly for protein-free
substitutes, and hard to follow away from home,
resulting in poor compliance. To overcome these
drawbacks they used a diet of natural foods of
plant origin. Results of the vegan diet were
similar to those obtained with the conventional,
unpalatable, low-protein diet.15
In addition,
kidney patients have a very high incidence of
developing atherosclerosis, heart disease, and
strokes20–conditions all accelerated
by eating high-fat, high-cholesterol animal
foods. Substituting vegetable for animal
protein decreases cholesterol which can be
expected to translate into better heart health.12
Too Much
Vegetable Protein Is Harmful Too
A 2007 review
published in the Journal of the American
Dietetic Association concluded: “long-term
consumption of high protein diets composed of
either predominately animal or vegetable
protein, by persons with normal kidney function
may cause kidney injury and both animal and
vegetable protein accelerates the progression of
chronic kidney disease.”13
This advice to
limit vegetable protein, too, was once a matter
of avoiding beans, peas and lentils, including
soy beans. However, today’s markets are filled
with “kidney toxic protein” made of
predominately isolated soy proteins.
“Vegetarian” burgers, hot dogs, luncheon meats,
sausages, candy bars, shakes, and cheeses are
foods gravitated to by people looking into a
healthier diet. But, these “fake” foods are in
fact unhealthy; made of an unbalanced
hodge-podge of ingredients. They are usually
deficient in natural dietary fibers,
carbohydrates, vitamins, minerals and other
phytochemicals. The isolated soy protein causes
large quantities of calcium to be lost from the
body; resulting in bone loss and kidney stones.21,22
These proteins also dramatically increase the
production of growth hormone (IGF-1), which is
known to promote cancer growth.23
Even though soy
proteins have shown some positive effects on
kidney function,24 they will also
provide a huge excess of protein that
contributes to uremia and must be eliminated by
the kidneys. In conclusion, these
“soy-vegetarian-foods” should be strictly
avoided by anyone with failing kidneys.13
Diabetic Kidney
Disease and Glomerulonephritis
Two common forms of
kidney disease deserve a little more attention.
Approximately 40% of people with diabetes severe
enough to require insulin will eventually
develop kidney damage.25 In patients
with diabetic kidney disease there is a 40-fold
difference in the rate of progression of
disease.1 The important and
controllable difference is due to the patient’s
diet. Once kidney disease begins there is a
relentless decline in kidney function and a
decline in overall health. The median survival
time once kidney disease is established (as seen
by the presence of persistent proteinuria) is
only 5 to 10 years.25 These grim
statistics can all be changed with a healthy
diet and lifestyle.1,25-28
Chronic
glomerulonephritis, also
called
nephritis, is a disease of
the kidneys in which the glomeruli, the tiny
filters in the kidneys, become inflamed or
damaged. This chronic inflammation will slowly
destroy the kidneys unless the cause is removed.
An allergic-type of reaction to animal proteins
is the most common correctable cause of
nephritis. Many children and adults with
glomerulonephritis have been cured by changing
to a diet of low-allergy vegetable foods.29-34
How to Save the
Kidneys
Life without your
kidneys, which means you are tied to a dialysis
machine, is “hell on earth.” I have found over
the years that a tour through the dialysis ward
is one good way to motivate people to learn to
enjoy a low-protein, starch-based diet, such as
the McDougall Diet. That same diet should be
vigorously followed to reverse conditions of
hypertension, type-2 diabetes, and
atherosclerosis, all of which, in their own
right, lead to kidney damage. Even people who
believe they are in good health need to heed
this advice.
Evidence of
failing kidneys should cause further dietary
restrictions; such as the avoidance of high
protein vegetable foods, especially the legumes
(beans, peas, and lentils). Green and yellow
vegetables and mushrooms are also high in
protein, but the absolute amount consumed is
usually small, so their consequences are few.
Fruits and fruit juices are low in protein and
can be used more liberally, as plentiful sources
of calories. Specially processed low-protein
flour products (flours, breads, pastas) can be
purchased. (Search the Internet for sources.)
The dietary protein intake can be further
reduced by adding simple sugars like table
sugars, honey and molasses—which are essentially
protein-free.
Towards the end of
kidney disease caution must be taken to avoid
the buildup of potassium in the body, which can
be fatal. Fruits and vegetables are high in
potassium and contribute to this problem,
especially when less than 10% of the kidney
function remains. Careful monitoring and
changes in diet to include lower potassium
fruits and grain products (avoiding green and
yellow vegetables and potatoes, for example)
will be necessary. Effective dialysis also
corrects potassium build-up.
When indicated,
medications, such as chlorthalidone, a diuretic,
should be used to reduce blood pressure. Most
doctors will more aggressively treat high blood
pressure than I do when there is evidence of
kidney disease (indicated by more than 1 gram of
protein in the urine daily). However, reduction
of blood pressure below 140/90 mmHg carries risk
of an increase of stroke and heart attacks.
Anti-angiotensin medications in the form of ACE
inhibitors should be used when significant
proteinuria is present (See the June 2007
McDougall Newsletter). Diabetics, when
necessary, should use insulin, rather than
pills, to control blood sugars.
At all stages of
kidney health, from perfectly normal to end
stage, diet should be a fundamental part of the
program. In reality, you are going to have to
take the lead in order to incorporate this
lifesaving therapy.
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