NEWSLETTER (£) The rise in early-onset bowel cancer has been happening at a faster rate in England than in many other countries
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The articles I write on cancer are usually about good news – better treatments or diagnostic tests, for instance.
But there’s one cancer story I have been following that is distinctly worrying. This is that cases of several different kinds of tumours are rising in people under 50 in many countries. This trend is especially pronounced for bowel cancer.
Cancer is overall more common as people get older, when our cells have had more time to accumulate genetic mutations. So, cases in under-fifties – known as early-onset cancer – are only a small proportion of the total cancer cases.
But the rise in young and middle-aged adults is alarming, partly because the trend is showing no signs of slowing.
This week, it emerged that the rise in early-onset bowel cancer has been happening at a faster rate in England than in many other countries**.**
A study found that the condition has been on the rise over the past decade in 27 out of 50 countries analysed. In England, there was a 3.6 per cent rise in the incidence per person, every year, with that annual rate being higher in only three other countries (New Zealand, Chile and Puerto Rico).
That equated to a roughly 50 per cent increase over the 10 years studied, from 2007 to 2017. “It’s a shocking trend,” said Dr Hyuna Sung of the American Cancer Society, who was involved in the research.
The big worry is that we don’t know its cause.
The main theory is that it is some aspect of the modern lifestyle, with the chief suspect being the typical unhealthy Western diet, as gut cells are so directly exposed to what we eat.
But what aspect of our diet? There is no shortage of possible culprits. But there’s no clinching proof for any of them.
One that might spring to mind is the current tendency to eat ready meals, takeaways and pre-prepared foods like pasta sauces and desserts rather than home-cooked meals.
There has certainly been an outpouring of concern in the media over highly processed food, also known as ultraprocessed food (UPF), in the past couple of years, although this has mainly been over studies linking it with being overweight and having heart disease.
But bodies such as the government’s Scientific Advisory Committee on Nutrition have said that the links with obesity and poor health could be because processed food tends to be higher in fat, salt and sugar, rather than it being uniquely harmful.
And anyway, the evidence linking UPF consumption with higher cancer risk is weak and suggests a very small increase in risk, if it really is there, according to Cancer Research UK (CRUK).
Long before the UPF health scare exploded, health officials have been advising us to reduce our bowel cancer risk by limiting our intake of red meat, and especially processed meat, such as bacon and ham. This is based on studies that see slightly higher rates of bowel cancer in people who eat more of such foods.
I’m not going to contradict NHS advice, but there is a bit of a problem with the processed meat idea, which is that we don’t know how it could cause bowel cancer.
The reasoning usually given is that the risk comes from substances called nitrates, added during manufacturing of bacon and so on. But nitrates are a natural substance also found in green vegetables – in fact most people eat far more of them from plants than from meat.
Rather than too much of something, could the problem actually be a lack of something – namely, fibre? Dietary fibre has also long been advised to help reduce bowel cancer risk.
Here there is at least a more plausible mechanism, as fibre has a clear effect on our bowel movements, making them more regular and ahem, “bulky”. One idea is that fibre binds to cancer-causing substances in food so they are excreted.
But neither trends in red meat consumption nor dietary fibre seem consistent with these foods being the cause of the rise in bowel cancer. Over the past couple of decades, UK fibre intake has stayed about the same, while red meat intake has fallen.
I predict that once the latest bowel cancer figures are released, the nation’s nutritional gurus will be quick to claim that they support their own favoured diet ideology.
Anti-UPF crusaders will blame a lack of home cooking, while vegetarians will put it down to red meat. It wouldn’t surprise me if fans of blood glucose arm monitors find a way to point the finger at sugar.
The truth is that we really don’t know. In fact, CRUK last year began a £20m, five-year research project to discover the cause of the rise in early-onset bowel cancer, using stored samples of blood, urine and faeces from millions of people from about 15 biobanks in Europe, North America and India.
The aim is to analyse if the rise in incidence correlates with any particular food, drink, pharmaceuticals or environmental chemicals, by measuring everything people are exposed to – known as their “exposome”. They wouldn’t have begun that project if we already knew the explanation.
In the meantime, people should continue to follow existing health advice on cancer prevention, which also includes avoiding smoking and excess alcohol and trying to stay a healthy weight, said Dr Yin Cao, a cancer specialist at Washington University School of Medicine in St Louis, who is co-team leader of the CRUK project.
We should keep the rise in perspective, said Dr Cao. Only about one in 20 bowel cancer cases in the UK are in people under 50. “People shouldn’t get scared,” she said. “But it’s important to raise awareness among the younger population, that when they have potential symptoms, they think about seeing their doctor.”
I’ve been watching
Cynthia Erivo as Elphaba and Ariana Grande as Galinda in ‘Wicked'(Photo: Universal Pictures/AP)
As a lifelong Wizard of Oz fan, I had to watch the film Wicked, based on the origin story for the Wicked Witch of the West. I had big expectations, having already seen the stage show of Wicked, and the film lived up to them. If you haven’t yet seen this musical on the stage, you may be surprised how well the concept works.
This is Everyday Science with Clare Wilson, a subscriber-only newsletter from i. If you’d like to get this direct to your inbox, every single week, you can sign up here.