“The Protein and the Kidney Monologue
Credit: CharlesPolquin.com and Jose Antonia, Ph.D.
By Jose Antonio, Ph.D.
One of my close friends is a professor at a fairly high profile Midwestern university (he’ll remain anonymous so as to avoid the wrath of his fellow protein-hating colleagues) and we were talking recently about how grossly misinformed many in academia are regarding dietary protein intake.
This is what you’ll often hear in the ivory towers.
“High protein diets are bad for your kidneys.”
“Protein dehydrates you.”
“Athletes get plenty of protein in their normal diets.”
“Protein is evil.”
Okay, maybe the last one is an exaggeration; albeit a slight one.
For whatever odd reason, some of the most educated individuals are also some of the most misinformed when it comes to dietary protein. First, let me set the record straight.
There is no evidence that high protein diets (which I’ll operationally define as 2-3 times greater than the ridiculously low RDA) is harmful to otherwise healthy individuals.(1)
There is evidence that in individuals with renal dysfunction may need to consume protein that even exceeds the RDA.(2)
The addition of protein to a sports drink does not dehydrate you and may in fact improve performance and recovery.(3)
Athletes do need more protein than couch potatoes.
Protein is not evil. (Sorry, no references).
What the heck is protein anyway?
Just as glucose serves as the building block of glycogen, so are amino acids, which are the building blocks of proteins. Proteins are arguably the most important component of your cells.
They’re involved in formation of contractile tissue or muscle, they make up a large part of the structural component of cells, they are a part of enzymes, antibodies, blood, etc. You name it, protein is part of it.
The main function of protein is to provide the needed amino acids for maintaining an anabolic (growth) or weight-stable state. However, recent data shows that additional protein promotes recovery and performance during exercise. (3, 4)
How much protein should you consume?
The easiest way to remember how much protein to consume is via the formula – 1 gram of protein per pound of body weight. Hence, a 200 pound individual needs about 200 grams of protein. And don’t be misled by the “carb-Nazis” who pontificate on the impending doom of your kidneys if you consume this much protein. If that were the case, gyms would be littered with strength-power athletes with failing kidneys.
In fact, according to Darryn Willoughby, Ph.D., of the International Society of Sports Nutrition and member of AXL’s Advisory Board, “the hazards of eating a high protein diet are as overblown as a big Texas hairdo. Now if you have damaged kidneys then the work that your kidneys need to perform to eliminate excess nitrogen would make it wise to avoid excess protein. Otherwise, enjoy that Porterhouse.”
Suffice it to say that the RDA of 0.8 grams per kilogram body weight per day is grossly inadequate for anyone whose activity levels exceed that of a La-Z-Boy recliner. Even though muscle protein degradation or breakdown increases during exercise, there is a significant increase in muscle protein synthesis for at least 24 hours after either resistance or endurance exercise. If you are not getting adequate protein during this time, then it would make sense that you probably will not gain lean body mass.
How much protein can I consume at one sitting?
Great question! Unfortunately, the scientific answer isn’t known. But I’ll give you the Midwestern common sense answer. Would your 75 year old grandma and the 250 lb, 25 year old martial arts fighter have the same limitations when it comes to digesting and absorbing protein? Obviously, the fighter needs more protein to assist with recovery and repair of muscles.
In all fairness, there are studies in which levels of 30 grams of protein are fed to subjects; and this amount produces a tremendous rise in blood amino acid levels. I’d imagine that 30 grams of protein per meal is a good starting point. If you eat 30 grams a sitting and you eat 6 times daily, that’s about 180 grams of protein.
For most “normal-weight” individuals, that should suffice. But imagine if you’re a 300 lb football player or bodybuilder? You’d either have to eat more protein per sitting or just eat more meals. The answer to this problem? Consume meal replacement powders as a protein supplement.
Protein and those with real kidney problems – the other viewpoint
A recent paper discussed two of the National Kidney Foundation Kidney Disease Outcomes Quality Initiative (K/DOQI) clinical practice guidelines for nutrition in chronic renal failure.
These guidelines recommended a dietary protein intake of 1.2 g protein/kg body weight/day for clinically stable maintenance hemodialysis (MHD) patients (Guideline 15) and 1.2 to 1.3 g protein/kg/day for clinically stable chronic peritoneal dialysis (CPD) patients (Guideline 16).
If you do the math, that is roughly 50% to 63% greater than the regular RDA or recommended daily allowance. But I thought eating protein was evil, evil, evil? Maybe not.
Scientists suggest that the possible mechanisms that require these increased protein needs include (a) the substantial quantity of amino acids, peptides, and proteins removed by the dialysis procedure and (b) the protein catabolic or anti-anabolic state caused by the uremic milieu, the inflammatory state, the oxidative and carbonyl stress, and the bio-incompatible dialysis materials to which MHD and CPD patients are exposed. In English, that means these individuals tend to be very catabolic and need to somehow replace the lost amino acids or protein. (2)
Protein types – the slow and the fast!
Cool work from France delineated the concepts of “slow” and “fast” proteins. In fact, this may play a greater role in muscle protein metabolism than the older concepts of biological value.
In essence, there are two proteins that many of us consume, which are digested at different rates (hence, slow and fast). In comparing whey to casein protein, whey is a faster protein, meaning it’s absorbed quickly into the bloodstream and remains elevated for about 3 to 4 hours. On the other hand, casein tends to clot in your stomach and in essence is “timed-released” such that you have significant elevation of blood or plasma amino acids for up to 7 hours.
Why are these distinctions important? First of all, whey is a very anabolic protein. However, inasmuch as you get a quick rise in plasma aminos, you also get quite a bit of oxidation of the protein (i.e. it is used for fuel). Casein however does not promote as much anabolism but is very anti-catabolic (i.e. inhibits protein breakdown). The “net” effect is that if you do a head to head comparison, casein beats whey over the long haul. Does that mean you should dump that bucket of whey into the trash bin? Hell no.
In fact, take advantage of whey’s easy and quick digestion/absorption qualities and consume it as part of your post-workout meal. Casein may be best if consumed as a single meal prior to bed (to sustain plasma aminos throughout the day).(5-9)
Protein and bone health
According to one study, protein intakes do not contribute to the wide variability in calcium absorption efficiency. (10) Or put another way, eating protein probably has no effect on bone mineral content.
Another investigation stated verbatim that “several recent epidemiological studies demonstrate reduced bone density and increased rates of bone loss in individuals habitually consuming low protein diets.” (10-12) So, one might argue that low protein intakes is the culprit. Either way, it would be wise to consume both adequate protein and calcium to maintain lean body mass and reduce body fat.
Adding protein to sports drinks
In a recent study that compared a traditional sports drink (water, carbs, and electrolytes) versus a sports drink that contained added protein, they found that cyclists rode 29% to 40% longer when they consumed the sports drink with protein than the one without.
Also, peak post-exercise plasma CPK (creatine phosphokinase) levels, an indirect measure of muscle damage, was 83% lower after consuming the sports drink plus protein. So don’t believe the baloney about protein dehydrating you (’cause if it did, these cyclists would not have performed better) or being unimportant during exercise. Even a small amount (~3-6 grams) during exercise might do wonders for you!(3)
The Moral of the Story
Consume 1 gram of protein per pound of body weight daily.
Spread it out over 6 meals.
Protein intake 2-3 times over the RDA is not harmful to your kidneys, bones, or anything else for that matter.
Adding a touch of protein to a sports drink may improve performance and speed up recovery.
Consume “fast” proteins after you exercise and “slow” proteins at the end of the day.
Listen to the Performance Nutrition Show at www.pnshow.com ; download the podcast and keep updated on the newest findings in sports nutrition!
Poortmans JR, Dellalieux O. Do regular high protein diets have potential health risks on kidney function in athletes? Int J Sport Nutr Exerc Metab 2000;10:28-38.
Kopple JD. The National Kidney Foundation K/DOQI clinical practice guidelines for dietary protein intake for chronic dialysis patients. Am J Kidney Dis 2001;38:S68-73.
Saunders MJ, Kane MD, Todd MK. Effects of a carbohydrate-protein beverage on cycling endurance and muscle damage. Med Sci Sports Exerc 2004;36:1233-8.
Flakoll PJ, Judy T, Flinn K, Carr C, Flinn S. Postexercise protein supplementation improves health and muscle soreness during basic military training in marine recruits. J Appl Physiol 2004;96:951-6.
Dangin M, Boirie Y, Garcia-Rodenas C, et al. The digestion rate of protein is an independent regulating factor of postprandial protein retention. Am J Physiol Endocrinol Metab 2001;280:E340-8.
Beaufrere B, Dangin M, Boirie Y. The ‘fast’ and ‘slow’ protein concept. Nestle Nutr Workshop Ser Clin Perform Programme 2000;3:121-31; discussion 131-3.
Boirie Y, Beaufrere B, Ritz P. Energetic cost of protein turnover in healthy elderly humans. Int J Obes Relat Metab Disord 2001;25:601-5.
Boirie Y, Broyer M, Gagnadoux MF, Niaudet P, Bresson JL. Alterations of protein metabolism by metabolic acidosis in children with chronic renal failure. Kidney Int 2000;58:236-41.
Boirie Y, Dangin M, Gachon P, Vasson MP, Maubois JL, Beaufrere B. Slow and fast dietary proteins differently modulate postprandial protein accretion. Proc Natl Acad Sci U S A 1997;94:14930-5.
Heaney RP. Dietary protein and phosphorus do not affect calcium absorption. Am J Clin Nutr 2000;72:758-61.
Kerstetter JE, O’Brien KO, Insogna KL. Low protein intake: the impact on calcium and bone homeostasis in humans. J Nutr 2003;133:855S-861S.
Kerstetter JE, O’Brien KO, Insogna KL. Dietary protein, calcium metabolism, and skeletal homeostasis revisited. Am J Clin Nutr 2003;78:584S-592S.”