Reduce Acid-Forming Proteins to Protect Kidney Function

Chronic kidney disease is a major public health problem affecting about one in eight Americans, increasing the risks of disease and death even among those with only mild decreases in kidney function. Low-cost, low-risk preventive strategies that anyone can do are needed to address the epidemic of kidney disease. I discuss some of these in my video Protein Source: An Acid Test for Kidney Function.

Diet plays a role in kidney function decline. “Specifically, diets higher in animal protein, animal fat, and cholesterol” may be associated with protein leakage into the urine, which is a sign of kidney damage, and, generally, “diets higher in fruits, vegetables, and whole grains, but lower in meat and sweets, may be protective” against kidney function decline.

In comparison to the diet eaten by our ancient ancestors, not only are we eating more saturated fat, sugar, and salt, we now also eat an acid-producing diet, as opposed to a base-producing, or alkaline, diet. Ancestral human diets were largely plant based and, as such, produced more base than acid.

“Dietary acid load (DAL) is determined by the balance of acid-inducing foods which is rich in animal proteins (such as meats, eggs, and cheese)” and offset by base-inducing foods, such as fruits and vegetables. In a national survey of 12,000 American adults, DAL was associated with kidney damage among U.S. adults.

Acid-inducing diets are believed to affect the kidney through tubular toxicity, damage to the tiny, delicate, urine-making tubes in the kidney via increased ammonia production. Ammonia is a base, so the kidney creates it to buffer the acid from the food we eat. This is beneficial in the short term to get rid of the acid; however, in the long term, all that extra ammonia in our kidneys day in and day out seems to exert toxic effects.

Our kidney function tends to decline progressively after our 30s, and, by our 80s, our kidney capacity may be down to half. “Perhaps, the so-called age-related decline in renal function is a result of damage induced by ammonia overproduction.” That’s just one theory, though. The acidic pH may increase the production of free radicals and damage the kidney that way, or add to scarring.

Not only is protein derived from plant foods accompanied by antioxidants that can fight the free radicals, but plant protein is also less acid-forming in the first place because it tends to have fewer sulfur-containing amino acids. One of the reasons plant foods tend to be less acid-forming than animal foods is because acid is produced by the sulfur in the protein, and there’s less in plant proteins.

“[T]he more important determinant of the effect of dietary protein on nephropathy [kidney disease] progression is the quality of the ingested protein (i.e., whether it induces acid-production like most animal protein or base production like most fruit and vegetable protein) when ingested rather than the quantity of protein ingested.”

American diets “are largely acid-producing because they are deficient in fruits and vegetables and contain large amounts of animal products,” so changing from a standard American diet to a vegan diet may improve acidosis in patients with chronic kidney disease. Under normal circumstances, a vegetarian diet is alkalinizing, whereas a nonvegetarian diet leads to an acid load. This was true even of vegetarians who consumed processed meat replacements such as veggie burgers.

Plant-based diets have been prescribed for decades for those with chronic kidney failure. They contain no animal fat, no cholesterol, and less acid formation, and help to lower blood pressure. Indeed, if you compare the kidney function of vegans with vegetarians and omnivores, the most plant-based diet was most associated with improved parameters for the prevention of degenerative kidney decline.


I was surprised to learn how powerfully diet can affect kidney function and structure. My kidney videos include:

And be sure to check out my overview video, How Not to Die from Kidney Disease.

Aren’t some plant foods acidic, though? Check out the chart in my video, How to Treat Kidney Stones With Diet.

Is there any way to test to see how acid-forming your diet is? Yes—and it’s fun! See Testing Your Diet With Pee and Purple Cabbage.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

White Meat May Be as Cholesterol-Raising as Red

White Meat May Be as Cholesterol-Raising as Red2

In light of recommendations for heart healthy eating from national professional organizations encouraging Americans to limit their intake of meat, the beef industry commissioned and co-wrote a review of randomized controlled trials comparing the effects of beef versus chicken and fish on cholesterol levels published over the last 60 years. They found that the impact of beef consumption on the cholesterol profile of humans is similar to that of fish and/or poultry—meaning that switching from red meat to white meat likely wouldn’t make any difference. And that’s really no surprise, given how fat we’ve genetically manipulated chickens to be these days, up to ten times more fat than they had a century ago (see Does Eating Obesity Cause Obesity?).

There are a number of cuts of beef that have less cholesterol-raising saturated fat than chicken (see BOLD Indeed: Beef Lowers Cholesterol?); so, it’s not so surprising that white meat was found to be no better than red, but the beef industry researchers’ conclusion was that “therefore you can eat beef as part of a balanced diet to manage your cholesterol.”

Think of the Coke versus Pepsi analogy. Coke has less sugar than Pepsi: 15 spoonfuls of sugar per bottle instead of 16. If studies on blood sugar found no difference between drinking Coke versus Pepsi, you wouldn’t conclude that “Pepsi may be considered when recommending diets for the management of blood sugars;” you’d say they’re both equally as bad so we should ideally consume neither.

That’s a standard drug industry trick. You don’t compare your fancy new drug to the best out there, but to some miserable drug to make yours look better. Note they didn’t compare beef to plant proteins, like in this study published in the American Journal of Clinical Nutrition. As I started reading it, though, I was surprised that they found no benefit of switching to a plant protein diet either. What were they eating? You can see the comparison in Switching from Beef to Chicken & Fish May Not Lower Cholesterol.  

For breakfast, the plant group got a kidney bean and tomato casserole and a salad, instead of a burger. And for dinner, instead of another burger, the plant protein group just got some boring vegetables. So, why was the cholesterol of the plant group as bad as the animal group? They had the plant protein group eating three tablespoons of beef tallow every day—three tablespoons of straight beef fat!

This was part of a series of studies that tried to figure out what was so cholesterol-raising about meat—was it the animal protein or was it the animal fat? So, researchers created fake meat products made to have the same amount of saturated fat and cholesterol by adding extracted animal fats and cholesterol. Who could they get to make such strange concoctions? The Ralston Purina dog food company.

But what’s crazy is that even when keeping the saturated animal fat and cholesterol the same (by adding meat fats to the veggie burgers and making the plant group swallow cholesterol pills to equal it out), sometimes they still saw a cholesterol lowering advantage in the plant protein group.

If you switch people from meat to tofu, their cholesterol goes down, but what if you switch them from meat to tofu plus lard? Then, their cholesterol may stay the same, though tofu and lard may indeed actually be better than meat, since it may result in less oxidized cholesterol. More on the role of oxidized cholesterol can be found in my videos Does Cholesterol Size Matter? and Arterial Acne.

Just swapping plant protein for animal protein may have advantages, but if you really want to maximize the power of diet to lower cholesterol, you may have to move entirely toward plants. The standard dietary advice to cut down on fatty meat, dairy, and eggs may lower cholesterol 5-10%, but flexitarian or vegetarian diets may drop our levels 10 to 15%, vegan diets 15 to 25%, and healthier vegan diets can cut up to 35%, as seen in this study out of Canada showing a whopping 61 point drop in LDL cholesterol within a matter of weeks.


You thought chicken was a low-fat food? It used to be a century ago, but not anymore. It may even be one of the reasons we’re getting fatter as well: Chicken Big: Poultry and Obesity and Infectobesity: Adenovirus 36 and Childhood Obesity.

Isn’t protein just protein? How does our body know if it’s coming from a plant or an animal? How could it have different effects on cardiovascular risk? See Protein and Heart Disease, another reason why Plant Protein [is] Preferable.

Lowering cholesterol in your blood is as simple as reducing one’s intake of three things: Trans Fat, Saturated Fat, and Cholesterol: Tolerable Upper Intake of Zero.

What about those news stories on the “vindication” of saturated fat? See the sneaky science in The Saturated Fat Studies: Buttering Up the Public and The Saturated Fat Studies: Set Up to Fail.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations: