Archive for June, 2011
A recent New York Times article took to task the all-too-often-expressed claim that high protein diets are bad for the kidneys. After citing some of the relevant research on the topic, the article goes on to conclude: “…studies show that in healthy adults, increased protein intake does not put excess strain on the kidneys.” Hooray for the New York Times for finally acknowledging what those of us who keep abreast of research have known for years! The real question is, What took so long?
The problem with the Brenner Hypothesis is that it was based almost entirely on data from animal subjects and those with existing kidney disease. Extrapolating results from such populations to healthy humans is a classic case of improperly generalizing findings. Research 101 dictates that external validity (i.e. generalizability) is limited to the population studied. That’s certainly the case here.
As noted in the New York Times article, research on healthy individuals has continually failed to find any negative correlation between protein intake and kidney problems. While a higher protein consumption does lead to changes in renal size and GFR, these have proven to be normal adaptations with no adverse effects on kidney health (2). And this is not a case of cherry picking studies; results have held true in multiple research trials across a wide variety of demographic groups including athletes, the elderly, and the obese.
In fairness, it should be noted that studies on the topic have been limited to examining an intake of under 3 grams/kg of protein a day. Thus, it is not known if intakes above this amount might cause detrimental effects. However, 3 grams/kg/day is a substantial amount of protein, equating to a daily intake of about 250 grams of protein for a 180 pound guy. What’s more, there’s a large body of anecdotal evidence from athletes who consume extremely high protein diets (sometimes in excess of two times body weight) without displaying associated kidney issues. This would seem to indicate that higher intakes are not an issue but further research is needed for confirmation.
In sum, it’s about time to put to rest the myth that a high protein intake will harm your kidneys. Given that higher protein diets have been shown to be metabolically advantageous for those who are trying to lose weight and/or maintain a healthy body weight, we should be encouraging people to adopt such nutritional practices, not scaring them off with baseless claims.
1) Brenner BM, Meyer TW, Hostetter TH. Dietary protein intake and the progressive nature of kidney disease: the role of hemodynamically mediated glomerular injury in the pathogenesis of progressive glomerular sclerosis in aging, renal ablation, and intrinsic renal disease. N Engl J Med. 1982 Sep 9;307(11):652-9
2) Skov AR, Toubro S, Bülow J, Krabbe K, Parving HH, Astrup A. Changes in renal function during weight loss induced by high vs low-protein low-fat diets in overweight subjects. Int J Obes Relat Metab Disord. 1999 Nov;23(11):1170-7
On July 9th and 10th, my friend and colleague Joe Dowdell will host the first annual Peak Performance Training and Diet Design Seminar. This a two-day intensive seminar covering a wealth of material. I’ve gotten a sneak peak at the content and I can say without hesitation you won’t be disappointed. It’s an excellent blend of theory and practice, extremely thorough and well-researched, that is sure to enhance your knowledge base.
Joe is covering the training material. As I’ve mentioned in a previous interview, Joe is one of the most astute trainers around. I’ve gotten to know him quite well, and have been extremely impressed with his ability to harness the science of exercise and apply it to training program design. In short, the guy knows his stuff!
The nutrition component of the seminar is being handled by Dr. Mike Roussell. Although I don’t know Mike personally, his credentials are outstanding and, based on the articles I’ve seen from him (he is a writer for many popular websites), he shows keen insight into the complexities of nutrition with respect to body composition.
The seminar will conclude with an expert panel of fitness professionals who will share their knowledge in a question and answer session. It is a rare opportunity to interact and learn from some of the leaders in the industry. The event is being held at Joe’s facility, Peak Performance, in New York City. You can check out specifics at the link below:
The NSCA National Conference will take place from Wednesday July 6 to Saturday July 9, 2011 at the Paris Hotel in Las Vegas. The national conference is always a terrific event and this year should be no exception. There are a host of great speakers lined up, including Stu McGill, JC Santana, and many others. My good friend and colleague Jay Dawes is doing a pre-con presentation on athletic assessment that’s sure to be highly informative.
For those who have attended the national conference in the past, you know what a great time it is. If you’ve never been to the event before, you owe it to yourself to check it out. Here’s a link to check out the schedule of events:
Hope to see you there!
One of the most widely held exercise beliefs is that you should never let your knees go past your toes when squatting. You’ll hear this “rule” echoed like a mantra over and over by the majority of personal trainers: “Keep the knees behind the toes!”
Fact is, though, there’s little evidence to back up such a claim. It is true that as the knees move anteriorly (i.e. forward) during the squat, the forces acting on the knee joint increase. However, there is no “magic point” where these forces suddenly become dangerous. The plane of the toes has been misguidedly used as a line of demarcation despite a complete lack supporting research. What’s more, intentionally preventing the knees from going past the toes can create additional problems at other joints that are potentially more injuries.
Restricted squats resulted in significantly greater torque at the hip joint compared to unrestricted squatting, with the differences here much greater than those seen at the knee joint (302 vs. 28 newton-meters). Perhaps even more problematic is that results were attributed to a greater forward lean when performing restricted squats. Why is this an issue? Well, in order to squat while keeping knees behind toes, lifters tend to compensate by increasing their forward lean. Studies have shown that an increased forward lean is associated with greater lumbar shear forces. And since the lower back is more susceptible to injury than other joints, this would seem to be a poor tradeoff.
So what’s the take home message? I’ll quote directly from the Fry et al. study as they sum things up very nicely: “While it is critical to protect the knees from unnecessary forces, it is also important to avoid unnecessary forces acting at the hips. These hip forces will ultimately be transferred through the lower back and therefore must be carefully applied. The net result is that proper lifting technique must create the most optimal kinetic environment for all the joints involved. Exercise technique guidelines should not be based primarily on force characteristics for only one involved joint (e.g., knees) while ignoring other anatomical areas (e.g., hips and low back).”
I would note that the same rules do not apply for lunges. Since the lunge involves stepping forward, there is no issue with maintaining an erect posture during performance. The biggest mistake I see is that people tend to push forward on their front leg, which significantly increases shear at the knee joint. Instead, your focus should be centered on dropping the rear leg. In doing so, your front leg will stay perpendicular to the ground, minimizing stresses to the knee joint without negatively impacting the hip or the spine.
Fry AC, Smith JC, Schilling BK. (2003). Effect of knee position on hip and knee torques during the barbell squat. J Strength Cond Res. 17(4):629-33.