"Which Type of Protein is Better for Our Kidneys?"
Between 1990 and 2010 some of our leading causes
of death and disability haven't changed.
Heart disease was the leading cause of loss of life
and health then and remains the leading cause today.
Some things got better, like HIV/AIDS,
but others got worse, like chronic kidney disease,
a doubling in the tens of thousands of deaths
and the hundreds of thousands whose kidneys fail completely,
requiring kidney transplants or lifelong dialysis. And about one in
eight of us now have chronic kidney disease whether we know it or not.
And most of those with kidney disease don't know it.
About three-quarters of the millions affected are unaware their kidneys
are starting to fail, which is particularly worrisome
given that early identification provides an opportunity to slow
the progression and alter the course of disease.
So what can we do about it?
The Western-style diet is a major risk factor
for impaired kidney function and chronic kidney disease,
also known as the meat-sweet diet, or standard American diet,
causing an impairment of kidney blood flow, inflammation,
and subsequent leakage of protein in the urine,
and a rapid decrease in kidney function. Table sugar and
high-fructose corn syrup is associated with increased blood pressure
and uric acid levels that can both damage the kidney.
And saturated fat, trans fat, and cholesterol found
in animal fat and junk food negatively impact kidney function as well.
The consumption of animal fat can actually alter the structure of the kidney.
And the animal protein can deliver an acid load to the kidneys,
increase ammonia production, and damage the sensitive kidney cells.
That's why restricting protein intake is recommended for preventing
kidney function decline, though it may be animal protein in particular,
not just protein in general.
So the source of the protein, plant versus animal, may be more important
than the amount regarding adverse health consequences.
Animal protein intake has a profound effect
on normal human kidney function, inducing what's called hyperfiltration,
increasing the workload of the kidney.
This may help explain why our kidneys fail so often.
Unlimited intake of protein-rich foods, now generally regarded as "normal,"
may be responsible for dramatic differences in kidney function
between modern human beings and their remote predecessors
who hunted and scavenged for meat here and there.
Sustained rather than intermittent excesses of protein
requires us to call on our kidney reserves continuously,
causing a kind of unrelenting stress on our kidneys
that can predispose even healthy people
to progressive kidney scarring and deterioration of kidney function.
It's like always revving our engine into the red.
On the other hand, administration of an equal quantity of vegetable protein
does not appear to have the same effects. Eating meat, for example,
increases the workload on the kidneys within hours of consumption,
but, apparently, taking care of plant protein appears to be a cinch.
This was done with beef, but any animal protein will do.
Eat a meal of tuna fish, and you can see the increased pressure
on the kidneys go up again within just hours, for both non-diabetics
with normal kidneys, and diabetics with normal kidneys.
If instead of having a tuna salad sandwich you had a tofu salad
sandwich with the same amount of protein, no effect.
And same thing happens with eggs and dairy protein,
both in people with normal and diseased kidneys.
Short-term studies have indicated that substituting plant proteins
like soy for animal protein is associated with less hyperfiltration
and protein leakage, therefore slowing deterioration of kidney function.
However, the long-term effect has not been adequately studied
until this study was published in 2014.
A 6-month double-blind, randomized, placebo-controlled trial,
soy versus dairy protein, and the consumption of whole soy
tended to preserve renal function, kidney function, compared with milk
in individuals with lowered renal function.
Similar results were reported in diabetics.
Even just giving isolated soy protein appeared to make things better,
compared to dairy protein, which made things worse.
Once one's kidneys have deteriorated to the point where they're actively
losing protein in the urine, a plant-based diet may help
turn it off and on like a light switch.
Here's protein leakage on a standard low sodium diet,
switched to a supplemented vegan diet,
low sodium, vegan,
low sodium, vegan.
What is going on?
Why does animal protein cause that overload reaction, but not plant protein?
It appears to be an inflammatory response triggered by the animal protein.
We know this because administration of a powerful anti-inflammatory drug
abolishes the hyperfiltration, protein leakage response to meat ingestion.
Here's the typical kidney stress response to a meat meal,
but here's with the anti-inflammatory drug on board, confirming the role
of inflammation in the impact of animal protein on our kidneys.