Obviously not, although some news outlets thought so recently…
From TMZ: “High protein diets ‘nearly as bad as smoking'”
From LiveScience: “High protein diets raise cancer risk as much as smoking”
From the LA Times: “High protein diets: bad in middle age, good for the elderly”
Let me start out by saying that I’m not going to tell you to eat less animal protein. But I saw this headline earlier and felt like having a rant.
I read the Washington Post iteration of this story first but couldn’t find the study cited. I then searched in Google News and found 66 articles. I read 10 of them, and none cited the actual source of the article. I also searched on PubMed but lost my patience after a page or two. So I haven’t actually read the original study or abstract, just the mainstream media reports.
What We Know
The study followed 6,000 people over age 50 for 18 years and found that people age 50-65 who ate a “high protein diet” (over 20% of calories from protein) were almost 4 times more likely to die of cancer during the 18 year study period than people who ate a low protein diet (less than 10% of calories from protein). The link between cancer and protein was only noted in people whose diets were high in animal protein (milk, eggs, cheese, and meat), but people whose protein was mostly from plant sources were not at high risk. On the other hand, people over 65 were less likely to die of cancer if they ate more protein. The higher protein diet in that age group was thought to be beneficial because it helped older participants maintain a healthy weight and avoid frailty.
There was a concurrent study in mice looking at IGF-1 (a growth factor) and showing that the higher protein diet promoted tumor growth by increasing the IGF-1. The researchers also measured IGF-1 in 2,000 of the study participants and found that increasing IGF-1 levels were linked to increasing risk of cancer death.
A Few Thoughts
- What kind of “animal protein” were participants eating? Was it grass-fed steak and grilled chicken? Or was it dollar value hamburgers and fried chicken?
- Was there any health bias? Comparing vegetarians to meat eaters can be tricky, because vegetarians have already made a conscious effort to do something healthy, whereas “everyone else who eats meat” may not have. A better comparison might be comparing vegetarians to people who are following a healthy diet that includes meat.
- Did they account for physical activity and other health behaviors? Often the health bias works both ways – people who make one choice in the name of health improvement tend to make others (like exercising, not smoking, etc). It’s likely they did, as most studies do now, but worth asking.
It’s also important to remember that this is a long term, cohort study. These types of studies are good for identifying associations, but they can’t prove cause and effect.
So What’s The Point?
Don’t listen to mainstream news when you want nutrition information. Keep eating plenty of fruits and vegetables, healthy protein and fat, avoiding processed crap and staying active. And join me in praying for a study that FINALLY compares plant based diets to healthier diets that include animal proteins. Until then, pass the bison burger…