Macronutrients - I love that we're still arguing about them! Truly it gives us more room to tinker with so-called absolutes when we realize that nutritional guidelines are sometimes as accurate as our daily horoscope. Keep in mind that 'qualified professionals' are developing both.
As if nutritional science isn't already an intricate weave of twisted statistics we have no choice but to factor in the influence of food lobbyists when guidelines are finally agreed upon. The book by Marion Nestle 'Food Politics: How the Food Industry Influences Nutrition and Health (California Studies in Food and Culture, 3)' will unsettle you when you realize how little our health factors into decisions regarding food labeling. That said, it didn't surprise me that protein intakes were not only still up for debate, they're the topic of a science smack-down by two very formidable foes.
Loren Cordain, Ph.D., Department of Health and Exercise Science Professor at Colorado State University and T. Colin Campbell, Ph.D., a Jacob Gould Shurman Professor Emeritus of Nutritional Biochemistry at Cornell University present hugely contrasting viewpoints in a dueling debate presented by Performance Menu. I was excited by the opportunity to read dovetailed arguments, as both scientists provide a rebuttal, and make a decision for myself. I wanted to be unbiased and I tried to leave my own opinions and experience out of the reading but, alas, Campbell made that next to impossible.
Campbell, co-author of 'The China Study: The Most Comprehensive Study of Nutrition Ever Conducted and the Startling Implications for Diet, Weight Loss and Long-term Health' seems to be a big fan of backward engineering in which he takes some of the healthiest people he can find and asks them what they eat. This would be great if we weren't bothered by factor such as variances in food quality, food sources, genetics, environments, stressors, etc. I suspect the book covers these issues far better than his essay 'How much protein is needed?' which seems happy to stick to the parental justification "because I said so!" as his most compelling argument. Like the child on the other end of that statement, I wanted to cross my arms and stamp my foot in frustration.
Cordain, author of 'The Paleo Diet' and 'The Paleo Diet for Athletes' on the other hand has three pages of references to back up his conclusion that "The evolutionary evidence indicates that so called "high protein diets" (20-30% total energy) and "very high protein diets" (30-40% of total energy) actually represent the norm which conditioned the present day human genome over more than 2 million years of evolutionary experience". The references made me cozy up to his argument even if I hadn't already done so. He made a compelling case that evolution isn't an overnight phenomenon and we need to look at our past, as it predates many modern ailments, in order to understand our dietary design.
Campbell's manifesto suggests many-times over in a writing style not too dissimilar from the Unabomber that protein intake from plant sources should only be 10% of total calories and it's primary purpose is the replacement of nitrogen. Footloose and footnote free, he'll assert his recommendation over and over again in case you were too slow to catch it. Did I mention it was 10%? He seems to find it laughable that anyone would study evolution for clues to nutrition and his assessment of Cordain's work borders on a personal attack. His desire to study only present day nutrition, however, makes me wonder how strong a role luncheon meat could play in spoiling his outcomes (never mind his sandwich). I think I could get cancer looking at Bologna so I doubt I'd trust any data that counts its composition as a protein source. I'm not sure if that's the case in his research but I bet I'd know if I had access to his references.
Robb Wolf alluded to further comments from Campbell. Until and unless that's forthcoming, the debate will be the last word on protein. Well, until someone else has a last word.
Note: Folks on p-menu's message board clamored for science heavyweights to brawl over fats next. Having read most of Weston A. Price's information about saturated fats, it would be a juicy read. It's clear saturated fat has gotten a bad wrap. Between the data and the creepy font, I was so skeptical I fact-checked all of Price's footnotes because I thought I'd find fictional sources but everything was solid at room temperature. I guarantee you'll go to the food isle, personally apologize to the butter and demand the government do so officially. For the government end, you might want to hire a lobbyist.