Is a High Protein Intake Bad for Bones?

Tl;dr Read the very short version of this here.  For the juicy details, stay here!

Let’s start with an enticing tidbit from a paper in no less than the Journal of the American College of Nutrition, with the wonderful title, “Dietary protein: an essential nutrient for bone health.”

“In agreement with both experimental and clinical intervention studies, large prospective epidemiologic observations indicate that relatively high protein intakes, including those from animal sources are associated with increased bone mineral mass and reduced incidence of osteoporotic fractures.”

Let’s not be guilty of the same sloppy epidemiological science we accuse other nutrition camps of, though. Epidemiology can generate hypotheses, and give us ideas to think about that then need to actually be tested.  Epidemiology can’t prove cause and effect, but it can generally disprove it.  For example, in the case of dietary protein, if epidemiological findings suggest that higher protein intakes—including animal protein—are “associated with” better bone health, we can’t conclude that the protein itself is directly responsible for the stronger bones, but we can safely assume that protein isn’t harmful for bones.  And in the case of protein and bone mass, we do have pretty good clinical and experimental evidence showing that indeed, higher protein intakes do induce positive changes in bone tissue.  Not in cultured bone cells. Not in mice. In actual living, breathing humans.

It’s hard to believe that in certain circles, protein has gotten a reputation as being harmful for bone health.  After all, Paleolithic hunter-gatherer diets typically contained a large amount of meat, yet anthropologists can sometimes distinguish the remains of hunter-gatherers from those of agriculturalists solely by examining the bones: the high-protein eating hunter-gatherers typically had bones that were larger, stronger and denser, and showed fewer signs of chronic disease. 

Scientists believe the differences in physical activity between the two civilizations played a bigger role than any dietary changes, and sure, hunting and gathering no doubt required a lot of time on one’s feet, but ask any farmer: farming isn’t exactly sedentary work!  Even if a heavy physical workload was responsible for Paleolithic peoples’ stronger bones, we can still conclude that a high intake of animal protein didn’t work against building bone mass.    

So how did some people come to think that protein—animal protein, in particular—is harmful for bones?

The Dietetics Organization Joins the 21st Century (Kind Of...)

If you’ve been living under a rock for the past few weeks, or, unlike me, you have an actual life, which precludes you from reading as many nutrition articles, blogs, and papers as I do, you might have missed the comments from the Academy of Nutrition and Dietetics (AND) in response to the Scientific Report of the 2015 Dietary Guidelines Advisory Committee. (The AND was formerly the ADA—the American Dietetic Association—the body that oversees the registered dietitian credential [RD].)

This thing has been making the rounds in the low-carb, Paleo, Primal and real food circles, mostly because it is a refreshing—and we might even say downright shocking—reversal of course by this supremely mainstream organization regarding some of the nutrients that have been public outlaws for the past few decades. While the AND has certainly not come out and directly endorsed higher-fat, low-carbohydrate diets, here a few general points they made about the recommendations by the 2015 Dietary Guidelines Advisory Committee (DGAC), some of which agree with the committee’s findings, and some of which don’t: 

• Very low sodium diets are not appropriate for everyone, and may, in fact, be harmful for some populations. 
• There is no correlation between dietary cholesterol intake and serum cholesterol levels.
• Since the studies on saturated fat, cholesterol, and heart disease over the years have been so terribly conducted and interpreted, “the Academy suggests that HHS and USDA support a similar revision [for that of cholesterol] deemphasizing saturated fat as a nutrient of concern.”
• Carbohydrate intake is a much stronger predictor for cardiovascular disease risk than is saturated fat, and it might not be such a bad idea to replace some amount of dietary carbohydrate with fat. 

As you can see, these points mark a huge step forward for this organization, which in the past, has been tepid, conventional, and by-the-book all the way. It’s a gutsy move, and I’m thrilled to see it happen. I applaud the AND for joining the rest of us in the 21^st Century with regard to basic science about food and human health. Since I have ragged pretty hard on the AND in the past, I’m happy to be able to give credit where credit is due.

That being said, this wouldn’t be all that interesting a post if all I did was sing the praises of this document. Naturally, there are a few points of contention. So let’s look at things little more closely, celebrate the good stuff, and bring to light the not-so-good stuff. We’ll start with the not-so-good stuff and then move to the good stuff, so that we end on a positive note.