an increase of 18% a day?!
A striking figure I saw earlier this week in a newspaper and confirmed by checking on the World Health Organisation (WHO) today:
…if the association of red meat and colorectal cancer were proven to be causal, data from the same studies suggest that the risk of colorectal cancer could increase by 17% for every 100 gram portion of red meat eaten daily…
The way I interpret this sentence and the every in it when I read it is that each time I eat a portion of 100g of red meat, my probability of getting a cancer increases by 17%. Actually the previous sentence in the report sounds even more dire:
An analysis of data from 10 studies estimated that every 50 gram portion of processed meat eaten daily increases the risk of colorectal cancer by about 18%.
Which means that eating a sausage a day would multiply the probability by about… 10²³! This cannot be: turning statistics into “plain” language can be so confusing! Or else pardon my French!!!
Xi'an's Og 
June 3, 2017 at 8:19 am
No, it cannot be. These are comparisons of risk by daily intake.
Per 50g difference in daily processed meat intake, there’s an 18% higher lifetime risk of colorectal cancer.
Or, later in the WHO Q&A, per 100g difference in daily red meat intake, there’s a 17% higher lifetime risk of colorectal cancer.
The WHO Q&A is quite clear about the intakes being “daily”, i.e. you’d need to eat 50g/100g extra processed/red meat per day to have the extra risk.
Even if one wants to quibble about whether these log-linear relationships hold at all levels of intake, the associations make sense as population averages.
June 3, 2017 at 2:54 pm
I am simply reflecting on my understanding of the sentence when I read it! I understand the 18% risk is meant to be associated with an extra daily dose of meat for one’s entire life, but to my French eyes it reads differently!!!