March 20, 2014 posted by

Can High-Protein Diets Cause Cancer?

Can High-Protein Diets Cause Cancer?

A very interesting study was just published, showing a theoretical link between animal protein and cancer, though it was ruined by sensationalistic headlines stating things like “Meat, dairy may be as detrimental to your health as smoking.” This ludicrous assessment couldn’t be less true and belittles some good science. Let’s shed a little light on what actually happened and how this might affect you.

As you might know, I’m no proponent of Big Meat and Dairy. I’d love having stats showing we’d all be healthier if we ate less animal products. So the natural assumption is that I’d support this media spin. Instead, it makes the position weaker because it’s crying wolf, at best, and could even be called outright lying. Sensationalism generates “clicks”, the new be-all-end-all of “effective” journalism under the rationale “what good is it if nobody reads it?” These 2 + 2 = 10 leaps of illogic, however, don’t aid matters of health as much as they arm the opposition by allowing them to dismiss what otherwise is solid research that we can benefit from.

Rant aside, let’s have a look at what did happen, because even though eating meat is absolutely nothing like smoking, there is evidence that should might, at least, give your animal protein consumption some thought. I’m going to summarize, but if you want to delve deep into the science, Examine has done it. This fine and rationale assessment is sexy journalism in my world. Check it out if you want to logically debate your Paleo friends. Examine states:

 The individual pieces of data they found from dietary analysis were: – A positive correlation between moderate and high protein intakes and diabetes-related mortality, relative to the lowest intake. This persisted, albeit to a lesser degree, when looking at people over the age of 65. – No relation between higher protein intake with all-cause mortality, cancer-related mortality, or cardiovascular mortality overall. A small increase in risk was seen when looking only at people between the ages of 50-65. This risk was reversed for people above the age of 65, where dietary protein had a protective effect against all forms of mortality (excluding diabetes-related).

Hard to draw a cancer link from this, since things reversed once aged 65, and even more so when you consider that this was as lifestyle study over a number of years. Yes, there was a 2 – 4 fold increase in mortality (the smoking gun, so to speak) but the parameters make it impossible to chalk anything up to one element of nutrition. So the study took another step, doing some work on rats, where they found that protein intake increased tumor growth rates. Examine states,

 It demonstrated, perhaps via a correlation again, that tumor growth was associated with IGF-1 activity. This makes logical sense. IGF-1 is an anabolic agent to most cells, be they skeletal or tumor cells! While a GH inhibitor was not used, they did use a GH-deficient line which produces less IGF-1 and found significantly less effects of protein on tumor growth suggesting a causal role.

This makes a lot of sense to those of us in the training business, especially if we’ve spent some time researching supplements. Insulin growth factor (IGF) – 1 is sort of a Holy Grail for bodybuilders, as it promotes protein synthesis, which translates to muscle growth. Since both muscle and tumor growth are cell proliferation, whether or not you want this to happen depends upon whether or not you have tumors, particularly if the tumors happen to be cancerous.

In the performance nutrition and supplement world, we’re always looking at this. A typical bodybuilding diet (with associated supplementation) looks to maximize protein synthesis, which is exactly the opposite of the dietary advice you’ll get if you have cancer, where retarding protein synthesis is paramount.

While confusing, this is the balance of life we’re always addressing. Elements that sustain life in one amount become poisonous in another. Nutrient needs change by activity and environmental conditions. Just look at something as simple as salt, which is so essential for life that wars have been waged over it, yet (along with sugar) is the most maligned nutrient in the modern American diet due to its abuse.

This Ying-Yang of life is precisely why sensationalized headlines should be ignored or taking with a grain (not 12,000 milligrams) of salt.

The study further identifies this,

 Interestingly, both studies noted that carbohydrates had a protective effect on mortality (specifically cardiovascular mortality), leading to a hypothesis that perhaps increased protein seen in this study is merely a proxy measurement of reduced carbohydrate intake; plausible due to food sources nor carbohydrate intake in the protein groups being measured, but at this time that hypothesis cannot be addressed with the study in question. If true, however, it would pinpoint protein as accidentally being a red herring in the mortality issue.

This also makes sense, from a nutrition 101 perspective. CHO consumption should be direcly related to activity and/or hormone production (stimulated by exercise, thinking, or active things), since it’s the body’s primary (and most efficient) fuel source, for both physical and mental function.

 The bottom line

Like many studies, this one (two, really) leads to “more study is needed”. However, it draws a pretty straight line to macronutrient consumption in regards to performance. The cancer link is tenuous at best. In single study situations, almost anything can get linked to cancer. At this stage, making that kind of conclusion is irresponsible. Still, if I were one who got a massive amount of my caloric intake from animal products I’d consider toning it down. There is definitely a link between dietary overindulgence when it comes to protein, be it through excess protein or lack of carbohydrates or total nutrients, and overall health as we age.

My longtime adage, based on assessments of hundreds of individuals from professional athletes to morbidly obese, and mass experimentation,  has been “no one diet is right for everyone, or even for one person in all situations, so eat for what you do” is simplistic, yet these findings support it. High protein diets can serve a purpose, particularly for deconditioned people with a lot of excess body fat, but should be adjusted downward as fitness and health increases. Unfortunately, that stance is not dogmatic enough to make sexy headlines. In turn, as market research tells us, it’s not want to general public wants to hear.


  • This is one of the best articles you’ve put up on here in a long time; (not that the others aren’t good) Thanks for the rational perspective on nutrition:

    • Thanks, Seth. I had two full weeks away from the madness of the office and my brain began to function creatively again. I miss being a decent writer.

  • I presume you’ve read “The China Study” which is in general drawing a link between animal protein and a host of poor health issues such as diabetes, cancer and heart disease. It bears this out with solid science with both animal studies and multi-year multi-site populations. The community of researchers and followers are pretty much represented in both the movie and website, “Forks Over Knives”. After reading the book I find the research to be quite convincing. I say this not to sound like a know it all but to ask if you can comment on how the two notions of the article you mention above and China Study are either contradictory or similar. Steve I know you to be a thinking man from years of benefiting from your posts so I look forward to your response.

  • I’ve stayed away from reviewing both of those titles on purpose, even though I’m a fan, because both contain more conjecture than I’m comfortable with. I do not believe their general tone is wrong, and I hope they are correct as a person who is strongly against mistreatment of any animals, but feel they present their information in a way that’s a bit too full of themselves. If you’ve followed, well, any science over the years–and particularly nutrition science–it’s very hard to present information as 100% certain. And they absolutely, from a scientific perspective, do not have evidence to do so. They do, however, make a very compelling case and if you choose to follow this advice I would bet that you’ll live both a healthier and longer life. If it helps to define my position, I do not take risky bets.

    • Thanks for the response Steve. Good advice to be wary of anyone giving nutrition guidance with absolute certainty. (Same as it goes with parenting advice.)

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