Transcript: Protein Source: An Acid Test for 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. So, low cost, low risk preventive strategies that anyone can do are needed to address the epidemic of kidney disease.
Diet plays a role in kidney function decline. Specifically, diets higher in animal protein, animal fat, and cholesterol may be associated with protein leakage in the urine (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 diets eaten by our ancestors, not only are we eating more saturated fat, sugar, and salt, we now 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 food, which is rich in animal proteins (such as meats, eggs, and cheeses) offset by base-inducing foods, such as fruits and vegetables. And, in this national survey of 12,000 American adults, dietary acid load was associated with kidney damage among U.S. adults.
Acid-inducing diets are believed to impact the kidneys via tubular toxicity, damage to the tiny delicate urine-making tubes in the kidneys via increased ammonia production. See, ammonia is a base; so, the kidneys create ammonia 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 can exert toxic effects.
Our kidney function tends to decline progressively after our 30’s, and by our 80’s, our kidney capacity may be down to half. Perhaps, this so-called age-related decline in kidney function is a result of damage induced by a lifetime of ammonia overproduction. That’s just one theory, though. The acidic pH may increase the production of free radicals and damage the kidneys that way or add to scarring.
Not only is protein derived from plant foods accompanied by antioxidants that can fight the free radicals, plant protein is less acid forming in the first place, because it tends to have less 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.
So, the more important determinant of the effect of dietary protein on kidney disease progression is the quality of the ingested protein (in other words, whether it induces acid production like most animal protein, or base production like most fruit and vegetables), rather than the quantity of protein ingested.
Since American diets are largely acid-producing, because they are deficient in fruits and vegetables and contain large amounts of animal products, 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 non-vegetarian diet leads to an acid load. This was true even of vegetarians that consumed processed meat replacements like veggie burgers.
Plant-based diets have been prescribed for decades for those with chronic kidney failure. No animal fat, no cholesterol, less acid load, and helps lower blood pressure. And, indeed, if you compare the kidney function of vegans to vegetarians to omnivores, the most plant-based diet was most associated with improved parameters for the prevention of kidney decline.
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.
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