High protein diet causes cancer? Nonsense!

My previous post looked at the WHO’s claim that bacon causes cancer. Now it seems that we are faced with a study that claims to have proven that a high protein diet causes cancer. Before you give it all up and opt for a vegan lifestyle, we need to examine this study in more detail.

The claim: a high protein diet causes cancer.

This study was based on the theory that a high protein diet causes cancer because the protein increases IGF-1. This substance has been linked to potentially increasing the growth rate of already-present tumours, in mice.

The study: flaws and all.

  • The participants were asked to recall what they had eaten. This is known to be highly inaccurate.
  • Details about the IGH-1 testing were absent in the report.
  • This study was observational in nature. This means that they can note an association between two factors (in this case, a high protein diet and cancer) but they cannot prove causation (i.e. they can’t state that a high protein diet causes cancer).
  • What is meant by a ‘high protein diet’ varies considerably between individuals. Someone eating lots of steamed fish and grilled chicken, for example, can hardly be considered to be following a similar diet to someone who’s wolfing down greasy hamburgers.
  • There are many other lifestyle factors that would interact with the participants’ diets and affect their chances of getting cancer. Some of these factors include levels of physical activity, consumption of fresh fruits and vegetables, smoking, alcohol, exposure to chemicals, etc.
  • This study doesn’t address the fact that a diet too low in protein is linked to poor weight maintenance and an increase in frailty.
  • The statistics that caused a media frenzy (a claim that a high protein diet causes cancer as it increases in incidence of cancer by 70%) are not present in the findings.
  • Some argue that the author of this study had a noted vested interest in the findings.

The bottom line? A healthy balanced diet is best: lean protein (as much as your body needs), fresh fruits and vegetables, dairy, and unprocessed carbs.