Will more (animal) protein kill you? Well something is eventually going to get you right? The data from two recent papers http://www.cell.com/cell-metabolism/abstract/S1550-4131(14)00062-X and http://www.cell.com/cell-metabolism/fulltext/S1550-4131(14)00065-5. At first glance it seems like damming evidence against a high(er) protein diet, at least if you’re a mouse. However, there are some human data – collected from 24h food recall – in this paper http://www.cell.com/cell-metabolism/abstract/S1550-4131(14)00062-X that seems to indicate an association between higher protein intake and mortality/cancer if you’re between the ages of 50-64, but not if you’re over age 65. I had to ask myself, based on a ridiculously small sample on which to based mortality and cancer outcomes and the crummiest way of estimating food intake (by the way these folks were apparently eating ~1800kcal/d – really?), what happens at age 65 that protein becomes a good thing, whereas between 50 and 64 it’s so bad for you? The answer lies in the authors’ own admission that, “We underline that our hazard ratios and confidence intervals may be inflated due to our sample size…” I’ll admit that they state this in respect to their diabetes mortality, but if you dig in their data the number of cancer deaths would be subject to the same comment! It might seem like a lot of people (more than 3000 per cohort) but when 10 people died in the low protein cohort and 17 in the high protein cohort, then there’s the ~70% difference! Note there were only 113 causes of death determinable, but they don’t tell you how many died due to each disease process, but in a sample of 6381 that’s less than 2% of your sample! A dietary reality of high protein or a statistical ‘blip’? The researchers say they ‘controlled’ for other factors but that’s a mathematical ‘control’ not a real biological control. In other words, they mathematically tried to ‘factor out’ other influences (like plant versus animal protein). It’s not a true control, but largely mathematical hand-waving and statistical modelling.
One question to ask is whether the mouse, as an animal that generally eats and survives on grains and high (very high) carbohydrate, is the right animal model to determine what might happen in humans? The same question should have been asked when people first started looking at atherogenic processes and high fat diets in rabbits. So it’s definitely bad to be a mouse on a high protein diet!
Take away: relax, breath, thank the blessed creator you’re not a mouse and: eat real food, cut down on processed carbohydrates, enjoy what you eat, and don’t eat too much of any one thing least that be the next thing that gives you cancer or kills you! Oh, and you’d better be active because I’ve yet to see the study where’s that’s bad!