of crusts & cancer

When I was little, I remember, my mother was forever trying to get me to eat all of my sandwiches: "if you eat your crusts, your hair will curl." (It didn’t. If that particular tale was true, I’d have a massive afro. It must date back to a time when curly hair was particularly desirable, & perhaps also when people were less inclined to leave things on their plates.)

After the headlines on Friday, I suspect some children will be hearing a different refrain. "Eating crusts ‘protects against bowel cancer,’" said the Telegraph. "Bread crusts key to bowel cancer fight," said The Grocer.

Perhaps my mother was onto something? The news stories are based on research done by a group of Indian scientist, who looked at the effect of feeding rats an antioxidant chemical – pronyl-lysine – found in bread crusts. Pronyl-lysine is produced during baking, & is more concentrated in the crust than in the main part of a loaf of bread. Rats given a daily dose of pronyl-lysine & exposed to a known carcinogen were less likely than those denied the antioxidant to develop aberrant cells in the lining of their colons, a condition that can lead to bowel cancer.

Media reports have certainly picked this one up & run with it. The article in The Grocer begins: "Eating bread crusts could protect people from bowel cancer because of a chemical released during the baking process, scientists have claimed."

Except I’m not sure that they did. I can’t read the whole article because the uni doesn’t subscribe to that particular journal, but the abstract is freely available. From that I can see that the researchers tested the effects of pronyl-lysine on 7 groups of male rats: one group – the control animals – received no antioxidant & weren’t exposed to the carcinogen. A second group received pronyl-lysine every day for the duration of the experiment. The remaining 5 groups were given a weekly dose of a carcinogen: one of these groups received that chemical only, while rats in the other 4 groups were also given pronyl-lysine at various times (before the experiment started; at the time when it began; once they’d started getting the carcinogen; & throughout the experiment). The researchers reported that the antioxidant reduced the incidence of pre-cancerous changes in the rats’ bowels, particularly if the animals were receiving a daily dose. Sample size? – I can’t answer that, as these data weren’t included in the abstract.

While these are interesting results, they do need to be treated with caution. It’s a preliminary study – on male rats (shades of the saccharin story). We do not know whether these findings will also apply to humans, & it’ll probably be a while until things move to the point of testing in humans. The best-protected rats received 2mg/kg of pronyl-lysine each day – without an indication of the amounts found in the crust of an average slice of bread, it’s impossible to say how much crust you’d have to eat to gain any protective effect. In other words, there are a lot of unknowns in this one.

But I bet bakers are happy 🙂

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