One of the principal reasons why kidneys start to lose their functionality and can eventually start to fail is because of the consumption of excessive protein – animal protein. So, you’d think that a whole food plant-based diet would be the ideal assumption. But does the research back this up? And what are the opinions of the renowned medical experts in this field? Best find out…

We’ll look at some of the research in this area as we hear the opinions (some quotes and some summaries) of some eminent physicians who emphasise the importance of diet in the prevention and treatment of disease. In Part 1, we’ll take a look at what Dr John McDougall ¹ has to say on the matter.

Dr McDougall – starch-based diets for kidney health

“The kidneys are vital organs that filter the blood. One of the primary wastes is dietary protein. Excess protein increases the wear and tear on the kidneys’ filtering units. By following the high-protein Western diet over seventy years, people lose on average a third of their kidney function, although this is usually inconsequential due to the organ’s reserve capacity (people can function normally after removal of one entire kidney, after all). The damage from excess protein becomes critical when kidney tissues have been previously lost for other reasons, such as injury, donation, diabetes, atherosclerosis, and nephritis. With reduced kidney function, the amount of protein commonly consumed on the Western diet can result in progressive kidney failure, dialysis, and transplant. A simple, highly effective way to preserve kidney function is to reduce the workload on them by eating a diet with a minimal amount of excess protein, and this is best accomplished with a starch-based diet. Medications commonly recommended to “protect” the kidneys are of limited benefit with serious side effects and costs. They should only be prescribed as a medical treatment of last resort…”

“Typically a patient discovers his or her kidneys are failing by a routine laboratory blood test called a serum creatinine, which indirectly measures kidney function. (Normal creatinine depends on a person’s age and in older adults is 1.2 mg/dL or less.) Once a problem is discovered, the doctor will try to slow the progression of this disease with medications intended to treat high blood pressure, diabetes, high cholesterol, and/or the use of anti-angiotensin medications. Little or no attention is given to what the patient eats, because primary and ongoing medical training never covers profit-free diet therapy…

“Diet becomes a topic for discussion only after the kidneys have been almost completely lost, a condition called end-stage kidney disease —a stage of pre-dialysis. Now the powerful kidney-saving benefits from a healthy diet are of very limited value. At this time a referral is made to a kidney specialist, a nephrologist, and a renal dietitian. They will mention a low protein diet. But, because most of these professionals do not believe patients will follow such a diet, and because they themselves do not have real training and experience with this simple approach, no meaningful change is accomplished. After this cursory discussion of diet, the very sick patient is shuffled off on a tour of the dialysis ward – where he will soon be attached to machines for several hours a day, three or more days a week.” ²

Dr McDougall refers to a 1997 study ³ which found that patients with failing kidneys who opt for a low-protein diet would reduce the progression of their kidney disease and death on average by 33% to 50%. The researchers concluded that there is: “…a persuasive argument to restrict dietary protein intake in order to minimize complications of renal failure while preserving nutritional status.” And their research indicates that many individuals will thereby be saved having to ever go on dialysis. Additionally, this same diet will improve their overall health and feelings of well-being, eliminating uremic symptoms ⁴ as well as allow patients with kidney disease who are on multiple medications (e.g. for high blood pressure, diabetes) to reduce the number of medications they take.

Research even further back in time, namely Thomas Addis‘s landmark treatise in 1948 ⁵ , argued that protein-restriction (which happens pretty naturally in a wholefood plant-based diet) was effective in minimising further loss of kidney function in patients suffering from chronic kidney insufficiency.

But can kidney disease be reversed in some cases? A 2006 study⁶ is not only useful to read for those who wish to understand more about the mechanisms involved in the progression of kidney disease, but they refer to evidence that kidney disease (specifically glomerular sclerosis ⁷ can indeed be reversed, partly through the adoption of a low-protein and low-sodium diet.

Taking just the above research into account, Dr McDougall states: “… for the past sixty years doctors and patients should have known that the primary focus of attention for the preservation of the kidneys should be diet.” ²

We’ve already seen ⁸ that if we eat enough plant food, we will get enough protein – easily between 10% and 12% of calories. The human body actually needs no more than 5% ⁹ of the calories consumed to be from protein in order to build all cell structures, enzymes and hormones; once these needs are met then the excess must be excreted from the body, and that’s a problem for the kidneys. The typical Western diet, focused as it is on meat, poultry, eggs, dairy and highly processed foods is packed full of protein: 35% or even more protein content within the total calories consumed.

When all this excess protein is eliminated, the blood flow and filtration rates of the kidney tissues (called nephrons) increase, which in turn, causes a condition known as “intra-glomerular hypertension.” ¹⁰ . The progressive damage sustained hypertension in the glomeruli causes is most important and apparent in those people who have pre-existing kidney loss from conditions such as donation of a kidney, physical injury, diabetes, atherosclerosis, hypertension, and polycystic kidneys. The excess protein accelerates the loss of kidney tissue to the point of end stage kidney disease..

Even in individuals who have not been diagnosed with kidney disease, the kidneys are “overworked” by the burden of excess protein in the typical Western diet. Studies ^{11 12} have shown that as much as 25-50% of functional kidney capacity is destroyed after 7 to 8 decades of eating the typical protein-rich diet.

A 1998 analysis ¹³ of multiple studies using a low-protein diet for people with kidney disease has found that glomerular filtration rate (GFR) ¹⁴ , which will tend to decrease as time passes, decreases by 0.53 mL/min less each year for those on a low protein diet compared with those who follow the usual diet.

A 1989 study ¹⁵ looked at people with chronic glomerulonephritis¹⁶ and concluded that: “…a vegetarian diet seems to be superior to a meat-containing diet. Thus we conclude that there are sufficient data from the literature to suggest that a low protein diet delays the progression of chronic renal failure.”

People with other forms of kidney disease, including those with polycystic kidney disease ¹⁷ , have shown remarkable benefits from being on a low-protein diet. ¹⁵ The amount of protein in the urine (proteinuria), which is considered an important sign of kidney health, has also been shown ¹³ to be greatly reduced by this side-effect-free form of natural dietary “therapy”.

Animal vs plant protein for kidney health

For many years, studies ^{18 19 20} have clearly shown that proteins from plants are much healthier for the kidneys and can slow down the progression of kidney disease more effectively than animal proteins. Consuming wholefood plants provides the perfect balance of macro- and micro-nutrients. However, eating processed plant foods that contain unnaturally high levels of protein can still be damaging to anyone’s kidneys. The authors of the latter 2007 study ²⁰ concluded: “…long-term consumption of high protein diets composed of either predominately animal or vegetable protein, by persons with normal kidney function may cause kidney injury and both animal and vegetable protein accelerates the progression of chronic kidney disease.” But, to repeat, there’s no worry at all about eating too much protein if you eat a diet consisting of whole plant foods – not extracted protein in such things as protein powders or processed ready meals.

When Dr McDougall wrote the article (July 2007) on which the information thus far is largely based, there was already plenty of research ^{21 22 23 24 25} showing the benefits of a vegan diet (which, by merely removing all animal foods, can generally be far from the optimal WFPB diet) for preventing and treating failing kidneys.

Concentrated soy protein products and kidney disease

Following on from a gentle warning above about extracted plant proteins also being potentially harmful for the kidneys, Dr McDougall has very strong views on the “kidney toxic protein” contained in isolated soy proteins such as “Vegetarian” burgers, hot dogs, luncheon meats, sausages, candy bars, shakes, and cheeses. He calls these “fake foods“, partly because they are an “unbalanced hodge-podge of ingredients” and are usually deficient in natural dietary fibres, carbohydrates, vitamins, minerals and other phytochemicals. Isolated soy protein can cause large quantities of calcium to be lost from the body. The result of this has been shown ^{26 27} to be potential bone loss and kidney stones. In addition, and rather worryingly for those who think that eating these “fake foods” are doing them good, these isolated proteins also appear to dramatically increase the production of the growth hormone IGF-1 ²⁸ , something which is proven ²⁹ to promote cancer growth.

As is usual, the picture is not black and white in relation to soy protein, since studies have shown that soy proteins have some positive effects on kidney function. However, eaten regularly in relatively large amounts, they also provide this huge excess of protein which contributes to uremia and, therefore, has to be eliminated by the kidneys. Dr McDougall’s conclusion on this topic is that these isolated soy protein foods “…should be strictly avoided by anyone with failing kidneys.”

Dr McDougall on “How to Save the Kidneys”

A low-protein, starch-based diet, such as the McDougall Diet ³⁰ “…should be vigorously followed to reverse conditions of hypertension, type-2 diabetes, and atherosclerosis, all of which, in their own right, lead to kidney damage. Even people who believe they are in good health need to heed this advice.”

His advice for those with clear evidence of failing kidneys is that they should should restrict their diet even further: “…the avoidance of high protein vegetable foods, especially the legumes (beans, peas, and lentils). Green and yellow vegetables and mushrooms are also high in protein, but the absolute amount consumed is usually small, so their consequences are few. Fruits and fruit juices are low in protein and can be used more liberally, as plentiful sources of calories…The dietary protein intake can be further reduced by adding simple sugars like table sugars, honey and molasses—which are essentially protein-free.”

When a person is heading towards the final stages of kidney disease, he suggests that “…caution must be taken to avoid the buildup of potassium in the body, which can be fatal. Fruits and vegetables are high in potassium and contribute to this problem, especially when less than 10% of the kidney function remains. Careful monitoring and changes in diet to include lower potassium fruits and grain products (avoiding green and yellow vegetables and potatoes, for example) will be necessary. Effective dialysis also corrects potassium build-up.”

High Potassium Fruits and vegetables

High-potassium fruits:

• apricots
• bananas
• cantaloupe
• dried fruit
• honeydew melon
• kiwi
• mango
• nectarines
• oranges and orange juice
• papaya
• pomegranate and pomegranate juice
• prunes and prune juices
• pumpkin
• raisins

High Potassium vegetables:

• acorn squash, butternut squash, Hubbard squash
• avocado
• artichoke
• beets
• baked beans, black beans, refried beans
• broccoli (cooked)
• Brussels sprouts
• kohlrabi
• lentils
• okra
• onions (fried)
• parsnips
• potatoes (white and sweet)
• swede (rutabaga)
• spinach (cooked)
• tomatoes, tomato sauce, and tomato paste
• vegetable juice

Low potassium fruits and vegetables

Low-potassium fruits:

• apples (plus apple juice and apple sauce)
• blackberries
• blueberries
• cranberries
• fruit cocktail
• grapes and grape juice
• grapefruit
• mandarin oranges
• peaches
• pears
• pineapple and pineapple juice
• plums
• raspberries
• strawberries
• tangerine
• watermelon

Low-potassium vegetables:

• alfalfa sprouts
• asparagus (6 raw spears)
• broccoli (raw or cooked from frozen)
• cabbage
• carrots (cooked)
• cauliflower
• celery (1 stalk)
• corn (half an ear if it’s on the cob)
• cucumber
• aubergine/eggplant
• green beans or wax beans
• kale
• lettuce
• white mushrooms (raw)
• onions
• parsley
• peas (green)
• peppers
• radish
• water chestnuts
• watercress
• yellow squash and zucchini ³¹

Joe’s comments

The foregoing seems to suggest that it’s a good idea for all of us to cut out all animal foods in the first instance. Then, we would do well to cut out all the processed “fake foods”, like the soy burgers and tofu sausages. Next, eat a balanced wholefood plant-based diet. If, however, an individual is already diagnosed with kidney disease, Dr McDougall makes it clear that there are groups of plant foods that are best avoided or, perhaps at least, reduced in proportion compared with others (see lists above).

As with all diseases, there’s rarely just one system or organ within the body affected by poor diet. It’s often the case that those who succumb to chronic kidney disease (and it’s now reported ³² that one in three Americans is at at risk of CKD) have already experienced one or several other diseases – such as obesity, diabetes, atherosclerosis, CVD, hypertension, hypercholesterolemia, etc. But the great news is that a WFPB diet can benefit all these conditions at the same time – preventing, slowing and even reversing in many cases. And this would be dealing with the causes of the disease/s and not just the symptoms as is mostly the case with pharmaceutical or surgical alternatives.

In Part 2, we will look at Dr Greger’s views on the causes and treatments for kidney disease.

When is the best time to look after your kidneys?

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2. Dr John McDougall: Kidney Disease article [↩] [↩]
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