Is burnt toast *really* a cancer threat? (News)

toastNew “go for gold” advice from the Food Standards Agency is warning people not to overcook foods such as roast potatoes, chips and toast, as it increases their risk of cancer. The story was widely reported in the press on 23rd January 2017 (e.g. Browned toast and potatoes are ‘potential cancer risk’, say food scientists).

Useful broadcast media coverage includes:

BBC News at One: Is burnt toast a cancer risk?
(2 mins 40)

Channel 4 News: Feeling the burn URL:
(3 mins)

Today (BBC Radio 4): Can overdone toast be a cancer risk?
(4 mins 30)

Concern focuses on acrylamide, a chemical that is naturally produced when starchy foods (particularly those rich the amino acid asparagine, such as potatoes and cereals) are cooked at high temperatures (see Mottram et al and Stadler et al for underlying science, which actually dates from 2002).

Professor Guy Poppy, chief scientific adviser to the Food Standards Agency, argues that in animal experiments, the way acrylamide causes genes to mutate and trigger cancer is well established (although he admits that in it is difficult to conduct trials in humans regarding the lifetime effects in a diet).

However, statistician Sir David Spiegelhalter, Professor of the Public Understanding of Risk at the University of Cambridge, is amongst a number of critics skeptical about the FSA’s warnings. His concern is that evidence to show an association between acrylamide consumption and cancer is relatively weak (certainly in comparison against other known cancer risks, such as smoking, drinking alcohol and being obese). Of the 16 studies trying to find an association, none have shown anything consistent, with the data being unclear about what level of exposure would constitute “high risk”. It is suggested that even people taking in a ‘high’ amount of acrylamide in their diets could consume 160 times more than usual and still be below the exposure level shown to cause tumours in mice.

Cancer Research UK shared Spiegelhalter’s concern that warnings based on such weak correlation evidence might confuse the public about the importance of more established risk factors.

The FSA went on to suggest changes in both the way that we cook foods, and the way that we store them, might reduce the acrylamide risk. In addition to not cooking things at high temperatures for so long, the FSA also recommend that potatoes and parsnips are not stored in the fridge, as they will undergo ‘cold sweetening’  which increases the acrylamide formation when they are roasted.

The WHO and other organisations say that acrylamide is a cause for concern, and that people should be acting to try and reduce the amount in their diets.

For more on the concerns of David Spiegelhalter, see How dangerous is burnt toast?

Review by June Adams


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