5th October 2026
Bowel cancer has traditionally been thought of as a disease mainly affecting older people.
That is still broadly true. More than nine out of ten bowel cancers occur in people over 50.
But something has changed.
Bowel cancer is increasingly being diagnosed in younger adults, and scientists are trying to understand why.
Cancer Research UK says that bowel-cancer incidence among 25 to 49-year-olds in the UK has risen by more than 50% since the early 1990s. International research has found similar increases in many countries.
So what is happening?
Is it our diet?
Is it obesity?
Is it the enormous increase in highly processed food?
Could chemicals used to preserve meat be involved?
Or are we looking in the wrong place?
The uncomfortable answer at the moment is that we don't know.
But there are some important clues.
Our diets have changed dramatically
One of the obvious differences between today's younger generations and those of their grandparents is the food we eat.
Modern diets contain large quantities of processed and highly processed foods.
Cancer Research UK's new PROSPECT-UK study is recruiting 250,000 people aged 18 to 50 to investigate precisely this question. Researchers will collect detailed information about people's diets, including information about the actual brands and foods they consume.
That is significant because "ultra-processed food" covers an enormous range of products.
A packet of food described as processed may have very different nutritional characteristics from another.
Scientists therefore want to understand whether particular foods, ingredients or dietary patterns are associated with bowel cancer rather than simply blaming everything that comes out of a factory.
What about bacon, ham and sausages?
This is where the question about nitrates becomes interesting.
Processed meat includes bacon, ham, corned beef, salami, chorizo and some sausages.
Many processed meats are preserved using chemicals including nitrates or nitrites.
There are plausible biological reasons why some compounds associated with processed meat could contribute to cancer development.
But it would be wrong to say:
"Nitrates cause bowel cancer."
The evidence doesn't allow us to make that simple claim.
Processed meat itself is associated with an increased risk of bowel cancer, but it contains several potentially relevant components and the way meat is processed and cooked may also matter.
Cancer Research UK estimates that around 13% of bowel cancers in the UK are linked to eating processed meat.
So there is a genuine reason to limit processed meat.
But that does not mean that switching from ordinary bacon to "nitrite-free" bacon has solved the problem.
The science is considerably more complicated.
Perhaps the biggest missed opportunity is fibre
There is another dietary factor which receives rather less attention.
Fibre.
Cancer Research UK estimates that around 28% of bowel cancers in the UK are linked to eating too little fibre.
That is a remarkably large proportion.
The NHS recommends that adults should aim for around 30 grams of fibre a day, yet the average adult is eating only about 20 grams.
Fibre is found in foods such as:
wholemeal and wholegrain bread
porridge and wholegrain cereals
brown rice and wholegrain pasta
beans and lentils
peas and chickpeas
vegetables
fruit
nuts and seeds
potatoes eaten with their skins
This isn't an exotic diet.
It is largely the sort of food our grandparents would recognise.
So perhaps we should eat more of the foods our grandparents ate
There is an interesting irony here.
For much of the 20th century, ordinary British families often ate relatively simple meals.
Porridge.
Vegetables.
Potatoes.
Peas.
Beans.
Homemade soups.
Wholemeal bread.
Fruit when available.
Meat, but not necessarily at every meal.
Modern food technology has given us enormous choice and convenience.
But convenience has also made it remarkably easy to consume large quantities of calories while getting relatively little fibre.
A breakfast can contain very little fibre.
Lunch can be a sandwich made with white bread and processed meat.
An evening meal can contain processed meat, refined carbohydrates and relatively few vegetables.
Snacks and drinks can add large amounts of calories without contributing much fibre.
None of these foods is necessarily dangerous on its own.
It is the overall pattern that matters.
What should we actually eat more of?
The encouraging part of the research is that the advice isn't particularly complicated.
The World Cancer Research Fund recommends aiming for about 30g of fibre a day, with wholegrains, vegetables, fruit, pulses, nuts and seeds forming an important part of the diet.
So instead of asking:
"Which superfood prevents bowel cancer?"
perhaps the better question is:
"How can I make my ordinary diet contain more fibre and less processed meat?"
A bowl of porridge for breakfast is one possibility.
Wholemeal toast instead of white bread is another.
Adding beans or lentils to soups, stews and casseroles can increase fibre without requiring a completely different diet.
Peas and other vegetables are easy additions.
Leaving the skin on potatoes where appropriate also adds fibre.
Fruit makes a useful snack.
Nuts and seeds can also contribute.
And if someone normally eats bacon or sausages several times a week, replacing some of those meals with eggs, fish, beans, lentils or other foods can reduce processed-meat consumption.
What about red meat?
The evidence does not say that everyone needs to become vegetarian.
But eating large quantities of red meat is associated with increased bowel-cancer risk.
Government advice is that people eating more than 90g of red and processed meat a day should reduce this to 70g or less. Cancer Research UK notes that swapping some red meat for chicken or fish, or using beans and pulses instead, can help.
The World Cancer Research Fund recommends eating little or no processed meat and limiting red meat to around 350–500g cooked weight per week.
That gives people a practical target without suggesting that a Sunday roast has suddenly become a dangerous food.
What about calcium?
There is another interesting piece of evidence.
Cancer Research UK says that a recent study found that an additional 300mg of calcium a day, roughly the amount in a large glass of milk, was associated with a lower risk of bowel cancer.
However, more research is needed to establish whether calcium itself prevents bowel cancer, particularly whether taking calcium supplements provides the same benefit.
So this isn't a recommendation to start swallowing calcium tablets.
Milk, yoghurt and other calcium-containing foods already form part of a normal balanced diet.
And then there is body weight
Diet isn't just about individual foods.
Obesity and being overweight are increasingly being investigated as possible contributors to rising cancer rates among younger people.
A major 2026 study from Imperial College London found evidence that excess weight is an important contributor to rising rates of several cancers among younger adults.
That doesn't mean that being overweight inevitably leads to cancer.
It means that maintaining a healthy weight is another potentially important part of reducing risk.
Physical activity matters too.
The World Cancer Research Fund says there is strong evidence that regular physical activity reduces bowel-cancer risk.
Don't forget alcohol and smoking
It would be easy to make this entirely about food.
That would be a mistake.
Alcohol increases bowel-cancer risk, while smoking is also associated with bowel cancer.
Cancer Research UK estimates that around 6% of bowel cancers in the UK are linked to alcohol and 7% to smoking.
So the overall message is much broader than simply:
"Don't eat bacon."
It is closer to:
Eat more fibre-rich foods, eat less processed meat, stay active, maintain a healthy weight, don't smoke and limit alcohol.
But why are younger people getting bowel cancer?
This remains the big unanswered question.
The rise among younger people cannot simply be explained by ageing.
Scientists are now looking at diet, obesity, physical activity, the gut microbiome, metabolic changes, environmental exposures, genetics and other biological factors.
It may eventually turn out that there isn't one culprit.
Perhaps several relatively small changes in the way we eat and live have combined to produce a measurable increase in risk.
That is why the new PROSPECT-UK study is so interesting.
Rather than starting with an assumption that bacon, sugar, chemicals or ultra-processed food must be responsible, researchers are attempting to collect detailed information and find out what actually distinguishes people who develop early-onset bowel cancer from those who don't.
The practical message is surprisingly simple
We don't yet know exactly why bowel cancer is becoming more common among younger people.
But we don't need to wait for scientists to solve every part of the puzzle before making sensible changes.
There is already strong evidence that a fibre-rich diet is associated with a lower risk of bowel cancer.
There is good evidence that eating large amounts of processed meat increases risk.
There is evidence supporting physical activity and maintaining a healthy weight.
And there are established links with alcohol and smoking.
So perhaps the most useful dietary advice is not a complicated list of foods to avoid.
It is to put more plants and fibre onto the plate.
More porridge.
More wholegrain bread.
More vegetables.
More fruit.
More peas, beans and lentils.
More nuts and seeds.
And fewer bacon sandwiches, sausages, ham and other processed meats.
That doesn't guarantee anyone will avoid bowel cancer.
Genes, age, family history and factors we don't yet understand also matter.
But if scientists are right that some part of the modern rise is connected to the way we live and eat, then changing the balance of our diet could be one of the simplest things we can do.
And perhaps the most surprising lesson is that the answer may not involve some expensive new "superfood" at all.
It may simply be eating more of the ordinary, fibre-rich foods that have been around for generations.
Sausages
It is also worth making a distinction between sausages made by a family butcher and the processed meats often discussed in studies of bowel cancer.
A traditional fresh sausage does not necessarily contain added nitrates or nitrites. Fresh sausages are normally sold raw and are not cured, whereas nitrates or nitrites are more commonly used in cured, dried or fermented products such as salami and some speciality sausages.
The best approach is therefore not to assume that every sausage contains nitrates, but to ask the butcher whether E250 (sodium nitrite) or E251 (sodium nitrate) has been added. There is still a wider health question around processed meat, however, because the cancer evidence does not depend solely on the presence of nitrates or nitrites.