Monday, 17 August 2009

Porkie pies on ham sandwich risk?

Blimey, it's easy to get out of the habit of this blogging lark, isn't it?

But I've been prompted to get back into things by today's story about a cancer charity's call for ham sandwiches to be no longer part of kids' lunchboxes due to an apparent increased risk of bowel cancer from processed meats.

My first reaction on hearing this story this morning was to think it wasn't anything new - and indeed it isn't, as a quick Google search comes up with these items from March 2008, November 2007 and June 2005, amongst others.

But the evidence behind this claim is not quite what it seems. Yes, there almost certainly is a link between consumption of red meat and increased risk of bowel cancer, but it's not as hard and fast as the call to stop giving kids ham sandwiches might suggest.

For a start, the World Cancer Research Fund, which made the call, acknowledges that little research has been done on red meat consumption in kids. Many of the studies which make up the research are like this one, which focuses on elderly people in the USA. It's certainly plausible to speculate that elderly people might be more prone to developing cancers linked to red meat consumption or that there is something about the way food is processed in the USA which might lead to the results. This study also notes that increased red meat consumption was linked to colorectal cancer when adjusting for age and energy intake, but when additional factors such as obesity or smoking were taken into account, the link is less clear.

It's also important to put the increased risk, such as it is, in context. As the American Institute for Cancer Research notes, the increased risk of bowel cancer from eating red meat is somewhere in the region of 20-25 per cent, which compares with an increased risk of lung cancer from smoking of up to 2000%. The rate of colorectal cancer in the UK is 55 per 100,000 people for men and 34.1 for women. A 25% increase in the risk of getting bowel cancer from excessive consumption of red meat would therefore mean a rate of about 68 per 100,000 for men and 42 for women. It's also worth noting that mortality rates for bowel cancer are falling, although more young people are developing the condition.

Even putting these issues aside, it's not easy to isolate the exact impact which red and processed meat has when compared to other aspects of diet. For instance, it seems that a diet with plenty of fibre is associated with a reduced risk of bowel cancer. Would a diet which is high in both red meat and fibre be good or bad? The evidence is unclear.

There are also questions about exactly what the figures show. In this study of 500,000 elderly Americans, it appears that those in the top 20 per cent for red meat consumption had a 25 per cent greater likelihood of developing various cancers than those in the lowest 20 per cent (although their incidence of leukaemia and melanoma were reduced). That indicates that eating A LOT of red or processed may be bad for you. But it certainly doesn't indicate that moderate consumption of red meat will give you cancer - and I can't find any evidence that it does.

Indeed, some experts question to what extent diet generally is an important factor in combating or causing cancer. This article, for instance, claims that regular exercise and maintaining a healthy weight are most important and that eating fruit and veg to prevent cancer is more significant in preventing cancer than eating red meat is in causing it.

So, should you give your kids ham sandwiches for lunch? I don't see any great reason not to, especially if you also slip an apple and a cereal bar into their lunchboxes. If they then run around the playground a bit after having it, so much the better.

Anyone who tells you that ham sandwiches will give your kids cancer is being unduly alarmist and is not giving you all the facts.

Right, I'm off to get a bacon sandwich for my tea.

1 comment:

Stuart Winton said...

I'm inclined to agree - I can't do without my over a pint of day of milk, but excess calcium is (apparently!) linked to prostate cancer, but tomatoes - or even better, tomato ketchup - is claimed to be preventive, so it's a good excuse to smother things in tomato ketchup ;0)

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