Transcript: 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. 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 are associated with increased blood pressure and uric acid levels that can both damage the kidney. The saturated fat, trans fat, and cholesterol found in animal fat and junk food negatively impact kidney function. The consumption of animal fat can actually alter kidney structure. And, 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 require 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. 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 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, we 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 protein, like soy, for animal protein is associated with less hyperfiltration and protein leakage, therefore, slowing deterioration of kidney function. However, the long-term effect had 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 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 that 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, then low sodium, then vegan, then low sodium, then 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 abolished 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, confirming the role of inflammation in the impact of animal protein on our kidneys.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.
Please consider volunteering to help out on the site.