Study links protein diet, kidney damage
Multi-year Heart Institute research to be published in leading journal; findings show danger for diabetics

By Megan Cooley
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The American Journal of Physiology, a Bethesda, Md.-based leading scientific journal, plans to publish a study conducted by a group of Heart Institute of Spokane researchers, who found that diets high in protein harm the kidneys, especially in diabetics.

The paper shows that amino acids, which are the organic compounds of protein, injure the small blood vessels of the kidney, says Dr. Katherine Tuttle, director of research at the Institute. High-protein diets, such as the Atkins and Zone diets, produce hypertension in the kidneys, and hypertension leads to progressive kidney disease, she claims. Study findings also show that people who suffer from diabetes, the most common cause of end-stage renal failure, are at greater risk of kidney damage from protein consumption than other people, Tuttle says.

“Our work is the first to demonstrate this novel mechanism of injury,” Tuttle asserts. She adds that the research will help the scientific community understand kidney and circulatory diseases in diabetics better.

The paper, titled “Amino Acids Induce Indicators of Response to Injury in Glomerular Mesangial Cells,” is expected to appear in the journal this summer and is posted on its Web site now. It’s authored by Tuttle, senior research scientist Rick Meek, and research technologist Sheryl Cooney, all of whom are with the Heart Institute. Also listed as authors are former institute graduate student researchers Stephanie Flynn and Maria Poczatek, research technician Dr. Robert Chouinard, and Joanne Murphy-Ulrich, a professor of pathology in Alabama, none of whom are with the Heart Institute now.

With knowledge from the research, Tuttle is developing and studying a Mediterranean-style diet, which she thinks offers better nutritional balance than other types of diets. Mediterranean diets emphasize grains, fruits, vegetables, legumes, fish, and so called “good” fat, such as olive oil. Red meat is eaten sparingly in a Mediterranean diet.

Tuttle also is eyeing the possibility of developing a low-protein meal-replacement drink for diabetics. The nutritional supplement would control blood sugar levels, prevent weight gain, and prevent injury to the circulatory system, with a focus on the kidneys, she says.

In recent years, many diabetics, as well as many Americans in general, have turned to high-protein diets and meal-replacement drinks that support those diets, as a quick way to lose weight, she says. The long-term effects, though, cast a shadow on short-term weight-loss results, Tuttle contends.

“Very few nutritional products have been subjected to any kind of study,” she claims. If a drink were developed for diabetics, “we’d have the credibility of some science behind the recommendation.”

A drink for diabetics could be compared with Gatorade, a popular drink developed by nephrologists at the University of Florida. Those kidney doctors designed the drink to replenish that school’s athletes with nutrients after they were weak from sweating in the hot Gainesville, Fla., sun during workouts, Tuttle says.

There are 20 million diabetics in the U.S., and 30 million to 40 million people with kidney disease, who could benefit from a meal-replacement drink geared toward them, she says.

Although development of such a product is a far-off goal, she says.

“We haven’t created anything yet, but we’re thinking of what that might be,” she says.

The kidneys remove waste, filter and clean the blood supply, and maintain chemical and fluid balances in the body. At all times, they hold about 25 percent of the body’s blood supply, Tuttle says.

People often overlook the importance of the kidneys, she says, bewildered that many people confuse them with the liver, which has an entirely different function.

Kidney disease “is one of the most important problems in the developed world” and diagnosis of it “is galloping away at exponential rates,” she adds.

The Heart Institute paper “fills a lot of gaps as to why high-protein diets are bad for kidneys,” Tuttle says. Because amino acids are doing vascular damage to the kidneys, the problems protein causes could extend to other organs and parts of the circulatory system, such as the brain and the heart, she says.

It’s possible for hypertension, in which the force of blood, or blood pressure, against the artery walls is too strong, to exist in the kidneys, but not in the rest of the body, Tuttle says.

Yet, although the only organ the study directly addresses is the kidney, “it certainly would be a strong hypothesis that the kidney is not the only target of vascular injury,” Tuttle says.

That's nice. Who eats a high-protein diet?

The abstract is concerned with what happens "When rat mesangial cells were cultured with an amino acid mixture designed to replicate the composition in plasma after protein feeding". Does that mean they're experimenting with a 100% protein diet? Let us know how that goes, guys! I'll continue with 70% fat...

Let's see what we've got here.

First...they weren't testing the effects of protein on kidneys in live humans or even in live rats. They were doing it by using cultures and simulating varying conditions (specifically high amino acid and high glucose).

When rat mesangial cells were cultured with an amino acid mixture designed to replicate the composition in plasma after protein feeding, production of mRNA (Northern blot) and/or protein (ELISA or Western blot) for transforming growth factor-1 (TGF-1), fibronectin, thrombospondin-1 (TSP-1), and collagen IV were enhanced in a manner comparable to culture with high glucose

an index of cellular proliferation, increased in response to amino acids and was further enhanced by culture with increased levels of both amino acids and glucose.

So why, I wonder, aren't they pointing their fingers at kidney damage in diabetics due to high concentrations of glucose in the blood instead? Bottom line is that researches have yet to produce a single healthy person whose kidneys have been harmed by eating more than 20% of their daily caloric intake from protein.

I could say that protein causes kidney damage in diabetics and technically, I'd be correct unless you knew the whole story.
Hemoglobin is a protein. When glucose is in excess in the bloodstream, it binds to the hemoglobin molecule creating glycosolated hemoglobin. The kidneys are designed to remove excess blood glucose from the body by filtering it through the kidneys. The whole function of the kidneys is to filter and normally it would not filter molecules such as proteins that are too large to fit through the filtering pores. The problem is that once the glucose binds to the hemoglobin molecule, it becomes too large to be filtered and gets "stuck" in the filtering pores when the kidneys try to get rid of the excess glucose. Pressure builds up behind the molecule and eventually forces it through creating damage. So...technically, its the protein hemoglobin molecule that causes the damage, but it wouldn't have had their not been an excess of blood glucose to bind to the hemoglobin. So what is the root cause of the problem? Not protein...excess blood glucose but if someone was trying to prove that it was the protein, they could report it as protein damage and noone would question it unless they had knowledge of how the whole system works. See how studies can get twisted to "prove" the results that the researcher was after?

Thanks for explaining that issue.

The fact that diabetics get kidney damage caused by out of control blood sugars seems to be too simplistic for these people.

No one seems to be interested in research about getting blood sugars under control. I guess the whole Atkins bashing agenda must pull in more funding than plain old common sense...

Seyont quipped: "That's nice. Who eats a high-protein diet?"

That was my response, exactly. And what do they call "high"? So they were able to blow up rat kidney tubules. What does that translate to in human quantities? Is it possible to even *eat* that much protein?

--
Kristine, who has trouble finishing a couple of eggs or a chicken breast, and forget about a steak.

Kinda like how drinking a whole tanker truck full of pure sacchrin will cause cancer in a lab rat.

It never ceases to amaze me how these people can call themselves "scientists" and actually sleep at night.

I just did a design review where I attempted to predict the production yield of an integrated circuit we are designing. My starting data was very limited and, hence, my conclusions have a significant margin of error in them. Yet my best estimate, based on that data, is that we will meet the production yield specifications if certain design changes are made. If I had the professional ethics that these "reasearchers" obviously have, I would have spent fifteen minutes showing five nifty graphs that say that we can meet yield requirements and been done. But that would have been highly misleading and so, instead, I spent about four hours and over thirty slides detailing the limitations of the data, the steps I took to overcome those limitations, the limitations of those same steps, the degree of uncertainty in my results, and the direction that I expect the actual results to end up relative to my predictions.

These people aren't seeking knowledge or truth - they are seeking funding and notoriety. The are contemptable.