Dennis’s Pet Menace

As it happened, I’d already agreed to appear on Jeremy Sallis’ Lunchtime Live Show on BBC Radio Cambridgeshire – the plan being just to chat about cancery topics that might be of interest to listeners. Which would have been fine – if only The World Health Organization had left us in peace. But of course they chose last Tuesday to publish their lengthy cogitations on the subject of whether meat is bad for us – i.e. causes cancer.

Cue Press extremism: prime example The Times, quite predictably – they really aren’t great on biomedical science – who chucked kerosene on the barbie with the headline ‘Processed meats blamed for thousands of cancer deaths a year’.

But – to precise facts – and strictly it’s The International Agency for Research on Cancer, the cancer agency of the World Health Organization (WHO), that has ‘evaluated the carcinogenicity of the consumption of red meat and processed meat.’

But hang on … haven’t we been here before?

Indeed we have. As long ago as January 2012 in these pages we commented on the evidence that processed meat can cause pancreatic cancer and in May of the same year we reviewed the cogitations of the Harvard School of Public Health’s 28 year study of 120,000 people that concluded eating red meat contributes to cardiovascular disease, cancer and diabetes. To be fair, that history partially reflects why the WHO Working Group of 22 experts from 10 countries have taken so long to go public: they reviewed no fewer than 800 epidemiological studies! However, as the most frequent target for study was colorectal (bowel) cancer, that was the focus of their report released on 26th October 2015.

So what are we talking about?

Red meat, which means any unprocessed mammalian muscle meat, e.g., beef, veal, pork, lamb, mutton, horse or goat meat, that we usually cook before eating.

Processed meat: any meat not eaten fresh that has been salted, cured, smoked or whatever and commonly treated with chemicals to enhance flavour and colour and to prevent the growth of bacteria.

What did they say?

Processed meat is now classified as carcinogenic to humans – that is it goes into the top group (Group 1) of agents that cause cancer.

Red meat is probably carcinogenic to humans (Group 2A). Group 2B is for things that are possibly carcinogenic to humans.

Why?

Because 12 of the 18 studies they reviewed showed a link between consumption of processed meat and bowel cancer and because it’s known that agents commonly added to processed meat (nitrates and nitrites) can, when we eat them, turn into chemicals that can directly damage DNA, i.e. cause mutations and hence promote cancers.

For red meat 7 out of 15 studies showed positive associations of high versus low consumption with bowel cancer and there is strong mechanistic evidence for a carcinogenic effect i.e. when meat is cooked genotoxic (i.e. DNA-damaging) chemicals can be generated. They put red meat in the probably group because several of the studies that the Working Group couldn’t fault – and therefore couldn’t leave out – showed no association.

Stop woffling

My laptop likes to turn ‘woffling’ into ‘wolfing’. Maybe it’s trying to tell me something.

But is The WHO trying to tell us something specific about wolfing? To be fair, they have a go by estimating that every 50 gram portion of processed meat (say a couple of slices of bacon) eaten daily increases the risk of bowel cancer by about 18%. For red meat the data ‘suggest’ that the risk of bowel cancer could increase by 17% for every 100 gram portion eaten daily.

And what might that mean?

In the UK about 6 people in 100 get bowel cancer: if you take The WHO maximum estimate and have everyone eat 50 grams of processed meat every day of their lives such that 18% more of them would get bowel cancer, the upshot would be 7 people in 100 rather than 6. So it’s a small rise in a relatively small risk.

As the report points out, the Global Burden of Disease Project reckons diets high in processed meat cause about 34,000 cancer deaths per year worldwide and, if the reported associations hold up, the figure for red meat would be 50,000. Compare those figures with smoking that increases the risk of lung cancer by 20-fold and The WHO’s estimate of up to 6 million cancer deaths per year globally caused by tobacco use and 600,000 per year by alcohol consumption.

All of which suggests that it isn’t very helpful to lump meat eating, tobacco and asbestos in the same cancer-causing category and that The WHO could do worse than come up with a new classification system.

And the message?

Unchanged. Remember mankind evolved into the most successful species on the planet as a meat eater. As the advert used to say: It looks good, it tastes good and by golly it does you good – not least as a source of protein, vitamins and other nutrients. Do some exercise and eat a balanced diet – just in case you’ve forgotten, that means limit the amount of red meat (The WHO suggests no more than 30 grams a day for men, 25 g for women) so try fish, poultry, etc. Stick with the ‘good carbs’ (vegetables, fruits, whole grains, etc.), cut out the ‘bad’ (sugar – see Biting the Bitter Bullet), eat fishy fats not saturated fats and, to end on a technical note, don’t pig out.

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‘The Divine Swine’ Castelnuovo Rangone, Italy

Meanwhile back on the Beeb

When the meat story broke I was a bit concerned that we might end up spending the whole of Lunchtime Live on how many bangers are lethal – especially as we were taking calls from listeners. Just in case things became a bit myopic I had Rasher up my sleeve. Rasher, you may recall, was Dennis the Menace‘s pet pig (in the The Beano‘s comic strip) who had a brother (Hamlet), a sister (Virginia Ham) and various other porky rellos. To bring it up to date we’d have introduced Sam Salami and Frank Furter and, of course, Rasher’s grandfather who was the model for the bronze statue named ‘The Divine Swine’ to be found in the little town of Castelnuovo Rangone in Pig Valley, Italy, the home of Parma ham.

But I shouldn’t have worried. All was well in the hands of Jeremy Sallis who, being a brilliant host, ensured that we mainly chatted about meatier matters than what to have for breakfast.

References

Press release: IARC Monographs evaluate consumption of red meat and processed meat.

Q&A on the carcinogenicity of the consumption of red meat and processed meat.

Carcinogenicity of consumption of red and processed meat. www.thelancet.com/oncology Published online October 26, 2015

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Fancy that?

Seeing as they started 28 years ago we can hardly blame members of the Harvard School of Public Health for publishing the results of their labours in tracking 120,000 people, asking them every few years what they’ve eaten and seeing what happened to them (a ‘prospective’ study). About one in five of the subjects died while this was going on but the message to emerge was that eating red meat contributes to cardiovascular disease, cancer and diabetes. The diabetes is non-insulin-dependent diabetes mellitus (NIDDM) or adult-onset diabetes – about 90% of diabetes cases. The cancers weren’t specified, although the evidence for a dietary link is generally strongest for colon carcinoma. The risk is a little higher for processed red meat than unprocessed.

How much?

Massive, if you mean the amount of data they accumulated from such a huge sample size followed over many years. If you mean on a plate, their standard serving size was 85 grams (3 ounces) for unprocessed beef, pork or lamb) and 2 slices of bacon or a hot dog for processed red meat. One of those a day and your risk of dying from heart disease is increased by about 20 per cent and from cancer by about 10 per cent – and the risks are similar for men and women. Just to be clear, that is a daily consumption – and the authors very honestly acknowledge that ‘measurement errors inherent in dietary assessments were inevitable’. They also mentioned that one or two things other than steak can contribute to our demise.

Are we any wiser?

If you recall from Rasher Than I Thought? the risk of pancreatic cancer is increased by just under 20 per cent if you eat 50 grams of processed meat every day. This report suggests that a limit of 1.5 ounces (42 grams) a day of red meat (one large steak a week) could prevent around one in 10 early deaths. So does it tell us anything new? Not really. Was it worth doing? Yes, because it adds more solid data to that summarized in Are You Ready To Order?

And the message?

Unchanged. Do some exercise and eat a balanced diet – just in case you’ve forgotten, that means limit the amount of red meat (try fish, poultry, etc.), stick with the ‘good carbs’ (vegetables, fruits, whole grains, etc.), cut out the ‘bad’ (sugar – see Biting the Bitter Bullet), eat fishy fats not sat. fats and, to end on a technical note, don’t pig out.

 References

Pan A, Sun Q, Bernstein AM; et al. Red meat consumption and mortality: results from 2 prospective cohort studies [published online March 12, 2012]. Arch Intern Med. doi:10.1001/archinternmed.2011.2287.

Pan A, Sun Q, Bernstein AM; et al. Red meat consumption and risk of type 2 diabetes: 3 cohorts of US adults and an updated meta-analysis. Am J Clin Nutr. 2011;94(4):1088-1096.

Are You Ready To Order?

Next time you’re grappling with menu selection you might wish to thumb through the latest bit of government advice on what to eat. It comes from The Scientific Advisory Committee on Nutrition (SACN) and, as it runs to 374 pages, you’re unlikely to have missed it. They’re trying to stop you getting bowel cancer and their advice is don’t eat more than 70 grams a week of red or processed meat. Processing meat means smoking, adding salt or otherwise curing to limit decay. There’s a lot of meat in this report: it tells you not only how much iron you get from different types of food but, perhaps more helpfully, what 70 grams looks like (it’s a lamb chop or two slices of beef). So, as a fact file it’s well worth the price (you can download from the web).

What’s the problem?

There are three potential sources of trouble in these foods. The first is that redness in meat comes from blood, specifically the iron-containing haem group in red blood cells that carries oxygen. When haem is broken down in our gut one product is a chemical group called nitroso compounds (that’s a nitrogen and oxygen atom (–N=O) that can attach to other groups to make a family). The second is that meat’s better eaten cooked than raw and cooking at high temperatures produces substances that can pass from the stomach to the circulation. There’s one report that shows how often you flip your burgers on the grill may affect this factor! The third problem is that suppliers often add chemicals to meats to give colour and flavour and to stop bugs growing.

What do these have in common?

Each of these trouble sources involve chemicals that can damage DNA – that is, either directly or after conversion to something else, they can cause mutations and thus help to promote cancer. The evidence that they can do this in rats is clear but it comes with the rider that, generally, far higher doses than humans would ever consume are required or they cooperate with other tumour-causing chemicals to make them more effective – the rats will get tumours from one treatment: the meat-related chemicals just make them grow faster.

So much for rats, what about humans?

Over the years a number of large and seemingly well-conducted studies have shown that you’re more likely to get bowel and stomach cancers if you eat lots of red or processed meat. The risk is not huge: the most recent review of the major studies concludes that the relative risk is 1.18 for those with a high haem iron intake – which the authors describe as ‘modest’. Remember that’s an 18% risk increase: a relative risk of 2.0 means your risk is doubled.

It should be added that the various bodies responsible for meat production have been quick to point out that there are also large and seemingly well-conducted studies showing no link between meat eating and cancers.

A masterpiece!

So this report is another look at a long-running controversy over a non-trivial matter, given that cancer of the colon or rectum is, world-wide, the third most common form. What it neither does nor pretends to do is tell us anything new. It simply reviews the data and presents its conclusions in a brilliantly detached, scientific assessment. It notes that green vegetables and potatoes are a much greater source than preserved meats of the chemicals used as meat additives and concludes that the data do not support a link between them and bowel cancer. On a link between iron-rich diets and bowel cancer in humans, it points out that The World Cancer Research Fund considers the evidence to be  ‘sparse, of poor quality and inconsistent’ and that it is not possible to quantify the association. Its delicate conclusion is that ‘It may be advisable for adults with relatively high intakes of red and processed meat (over 90 grams/day) to consider reducing their intakes.

Having digested all this, the next time the waiter appears at your elbow, don’t panic! Recall that mankind evolved eating meat because it’s a mighty good source of protein, vitamins and minerals. If the roast beef smells good, crack on and enjoy it!! Yes, it might add fractionally to your risk of getting bowel cancer in years to come. But when you finally stagger out of the restaurant (full but not satiated) remember that crossing the road will contribute fractionally to your risk of being squashed by a truck. Just do everything with your eyes open and don’t over-do anything!

References

Scientific Advisory Committee on Nutrition (SACN) Iron and Health Report – 25th February 2011.

Bastide, N.M., Pierre, F.H.F. and Corpet, D.E. (2011). Heme Iron from Meat and Risk of Colorectal Cancer: A Meta-analysis and a Review of the Mechanisms Involved. Cancer Prevention Research 4, 177-184.

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