Functional Training Zones


by Dr. Spencer Nadolsky,

"Eating meat is as bad as smoking cigarettes!" This was the headline in the media for the past few weeks. That makes meat sound pretty bad, but does the headline fit with the actual data?

The first thing to note is that the study was actually two studies combined into one. One study was looking at about 6000 adults over the age of 50 and what they ate in the past. The other was an experimental mouse study where the researches injected the poor little guys with cancer cells and then fed them different amounts of protein and watched how fast the cancer grew.

Key Points in the Human Study

• A survey of around 6000 subjects over the age of 50 along with their dietary recalls (what they remembered eating).
• They were broken up into age groups – two groups aged 50-65 and over 65.
• Those two groups were then divided into 3 categories based on the amount of protein in their diets (low protein less then 10% total calories, high protein over 20%, and moderate protein, which was between 10-20%).
• The folks in the 50-65 age group had a higher mortality if they ate higher amounts of protein.
• On the other hand, those over 65 had lower mortality when eating higher amounts  of protein.
• The researchers then looked at IGF-1 (Insulin-like Growth Factor 1) in about a third of the subjects. They found that those aged 50-65 who ate higher protein had higher IGF-1 levels and also died more of cancer.
• It was epidemiological, which means no experiment was done and only correlations can be made. Not causation. But this won’t stop the media from making scary headlines. This doesn’t mean that epidemiological studies are worthless, it just means we have to look at them for what they are.

Key Points in the Mouse Study

• Researchers injected the rodents with cancer cells.
• They then fed them different amounts of protein and watched the cancer cell grow.
• Those fed higher amounts of protein had higher amounts of IGF-1 and also faster growing cancer.
• The mice did not start off with cancer.
• We can not say that the protein caused the cancer, but could make the conclusion that the higher protein could have sped up the growth.

It is important to note IGF-1 is a hormone in our body that makes all cells grow. Both muscle, which is great, and even tumor cells, which is obviously bad. So you see these two studies combined made the headlines. We cannot say that high protein causes cancer and is as lethal as cigarettes. We don’t know how many fruits and vegetables the human subjects were eating and we don’t know if they exercised. We don’t know what kind of "meats" they ate – as far as the researchers were concerned, pepperoni was equivalent to chicken breast was equivalent to salmon. What we can say is that higher protein in those aged 50-65 may have ill effects, but even that is a bit generalized.

If you want a full breakdown, check out our complete analysis.