Wednesday, November 20, 2019

Does Protein Damage Kidneys?

When I was diagnosed with type 2 diabetes more than 20 years ago, the accepted dogma was that protein damaged kidneys, and because people with diabetes are at high risk of kidney damage, they were told to eat more carbohydrate and less protein. Fat of all types was considered bad.

Of course, it's eating carbohydrate that makes blood glucose levels go up, and high blood glucose levels cause all kinds of complications.

In the ensuing years, studies have shown that protein does not damage healthy kidneys. If you already have kidney damage, then protein can make the damage worse. But not if you have healthy kidneys.

Now, a headline in a press release implies that protein can harm kidneys ("High-protein diets may harm your kidneys"). To be fair, it doesn't say "will harm" but "may harm," but how many readers will pick up on that?

What I found odd were some of the statements in the press release. For example, "Avoiding carbohydrates and substituting them with proteins has become a leading dogma for all those who care for their looks and health."


When did a low-carbohydrate high-protein diet become mainstream? A low-carb high-fat diet is currently popular, but the protein in such a diet is not especially high. So I went to the article cited in the press release.

It begins, "How often have you been told to eat more protein and less carbohydrates to stay healthy?" Actually, never. "This is not an emerging food culture but rather a prevailing dogma in our society. Physicians, dietitians and other health care professionals tell us constantly about the advantages of a high-protein diet."

 Again, huh? Maybe I've been living under a rock, but I've never been told this. 

"We feel compelled to eat only the meat patty of the sandwich and leave behind the bun when eating in front of others, otherwise we may lose credibility among friends and peers."

That's odd. Most of my friends and peers are still into bread and pasta. Maybe I need different friends and peers.

Since the dawn of agriculture, the authors write, the total protein intake of our ancestors was <1 g/kg body weight/day, most likely in the 0.6–0.8 g/kg/dayrange." But 0.8 g/kg is what most medical people recommend, a little more for older people who are at risk of sarcopenia, or muscle loss.

Before recent times, "obesity was never a problem," they write. That's odd. I guess they never heard of William Banting, who was obese and died in 1878. He found that it was starchy foods that made him gain weight and proposed a low-carb diet. In fact, some people call going on a low-carb diet "banting."

The next issue is what constitutes a high protein diet. If you used to have a burger, fries, and a soda for lunch and you give up the bun, the fries, and the soda and substitute salad or low-carb vegetables, your percentage of protein goes way up, but the amount is the same. And it's the amount that makes a difference for kidney function.

The standard recommendation is about 0.8 grams of protein per kilogram of body weight, or 0.36 grams per pound. This means 56 grams per day for the average sedentary man or 46 grams per day for the average sedentary woman. But this is the minimum you need. If you get a lot of exercise, or if you're elderly, you need more.

Then you need to know if you do, in fact, have some kidney damage. Keep track of your blood creatinine levels when you get bloodwork done, and make sure your doctor also tests urine for protein. If your kidneys are healthy, you shouldn't have protein in your urine. And if your kidneys are healthy, you shouldn't worry about getting too much protein in your diet.

We should all understand that too much protein is not good for compromised kidneys, but we should also understand that low-carb diets aren't usually superhigh in protein, and calling all low-carb diets high-protein diets is misleading and may scare people into reverting to the  high-carb diets that make diabetes so difficult to control. 


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