Reproduced by Caroline Peyton from an article published online by Alliance for Natural Health 12 March 2014
The mainstream media has been awash with headlines along the lines of “Eating protein may be as bad as smoking”. As we know protein is essential to human life and that smoking is the number one cause of preventable death we thought this deserved a deeper look!
Protein: The new killer?
Many will have seen the headlines accompanying the recent publication of a study by Cell Metabolism  of the health consequences of high intakes of animal protein; such as “Diets high in meat, eggs and dairy could be as harmful to health as smoking,” (UK Guardian) and “Meat and cheese may be as bad as smoking,” (Science Daily).
So should we be dropping our eggs and meat into the same rubbish bin as our cigarettes?
The findings, minus the hype
The study was authored by a mix of US and Italian authors. They found that middle-aged people who ate a high-protein diet faced a 74% increase in the relative risk of death from all causes, compared with those of the same age eating a low-protein diet. Worse still, cancer deaths shot up dramatically among those on a high-protein diet, although this effect was only evident when the protein was from animal sources. A separate analysis revealed that “high levels of animal proteins promote mortality and not that plant-based proteins have a protective effect”.
But interestingly they found these results were reversed among the elderly – or those aged 66 years and older. Among this group, those on a high-protein diet experienced a 28% relative risk reduction in all-cause mortality and a 60% relative risk reduction in cancer mortality, compared with those on a low-protein diet.
To test their hypothesis that high levels of animal protein increased cancer and all-cause mortality, they performed a series of parallel experiments on mice. In a nutshell, they showed a similar effect and they related it to the protein insulin-like growth factor-1 (IGF-1). It has been previously shown that low levels of IGF-1 are linked to reduced cancer and diabetes mortality in humans. So the study now provides supporting evidence for this same effect in a mouse model.
Consider these findings carefully in light of all the available evidence before deciding to cut animal protein from your diet. Looking at some of the limitations of the study:
- The authors used data on 6,381 adult subjects, representative of the US population, taken from the National Health and Nutrition Examination Survey (NHANES) III. As an observational, epidemiological study, NHANES III cannot demonstrate cause and effect – only correlations
- Data was gathered using a single, 24-hour dietary recall questionnaire performed between 1988 and 1994 – relying on individuals’ often faulty recall of what they ate. Also, the data cannot account for changes that may have occurred in the subjects’ dietary patterns or food composition in the intervening two decades
- The meat and dairy consumed by the subjects would overwhelmingly have been derived from large-scale farming operations, including grain-fed animals raised in concentrated animal feeding operations (CAFOs) – (injected with antibiotics and growth hormones and fed genetically modified (GM) feed. Particularly in the context of an epidemiological study, to blame animal protein per se for the observed mortality associations is scientifically unsupportable with all of these other factors in play
- One of the key authors is the founder of a company promoting “an all-natural plant-based 5 five-day Fasting Mimicking & Enhancing™ Diet (FMED) program”. Could there be an interest in casting animal protein in a bad light? This potential conflict of interest is mentioned in the Acknowledgements at the end of the paper.
- The authors’ use of relative, rather than absolute, risk, and what we’re really looking at is “7.84 deaths per 1,000 person years vs 2.18 deaths per 1,000 person years”
- The high-protein mice in the supplementary study were fed something called “AIN-93G standard chow”. This includes a long list of processed ingredients – including casein and wheat starch – artificial vitamins and calculated levels of amino acids and minerals. Could such a “food” be cancer promoting in itself?
The paper also states: “High and moderate protein consumption were…not associated with all-cause, CVD [cardiovascular disease], or cancer mortality when subjects at all the ages above 50 were considered.”
Bearing all this in mind, we think it’s safe to say that this study is being given undue prominence in the media. At best, it appears the authors have applied the statistical thumbscrews until they got an ‘interesting’ result. Low Protein Intake Is Associated with a Major Reduction in IGF-1, Cancer, and Overall Mortality in the 65 and Younger but Not Older Population http://download.cell.com/cell-metabolism/pdf/PIIS155041311400062X.pdf?intermediate=true