- Women who ate the most ultra processed foods had about a forty five per cent higher risk of bowel growths that can turn into cancer
- A typical high ultra processed diet includes sweetened cereals, white bread, ready meals, processed meats, crisps and sugary drinks
- Cutting back on ultra processed foods is likely to benefit bowel health and is also important for managing weight and type 2 diabetes
A large study reported in JAMA Oncology looked at how ultra processed food intake related to early changes in the bowel.
Researchers followed 29,105 women, with an average age of forty five, and collected detailed diet information every four years from 1991 to 2015.
They focused on adenomas, a particular type of polyp in the bowel. Adenomas are not cancer, but most bowel cancers start from these growths over a long period of time.
Among the women in the study:
- 1,189 cases of early onset adenomas were identified
- Those who ate the highest amounts of ultra processed foods had a forty five per cent higher chance of having an adenoma compared with those who ate the least
- The highest group ate around 9 point 9 servings of ultra processed foods daily, compared with about 3 point 3 servings in the lowest group
The research was funded by Cancer Grand Challenges, a global initiative backed by Cancer Research United Kingdom and the United States National Cancer Institute.
The findings fit with wider concern that rising rates of bowel cancer in younger adults are linked partly to modern dietary patterns.
What counts as ultra processed food
Ultra processed foods are products that have gone through many industrial steps and contain ingredients you would not normally use in a home kitchen.
This includes many preservatives, artificial sweeteners, colourings, flavour enhancers and altered fats or starches.
Cancer Research United Kingdom gave a clear example of what almost ten daily servings of ultra processed food might look like:
- Breakfast of sweetened breakfast cereal and a slice of white toast with margarine or jam, plus a flavoured yoghurt cup or breakfast bar
- Lunch of a pre packed supermarket sandwich, a packet of crisps and a can of cola or flavoured drink
- Evening meal of frozen pizza or oven chips and chicken nuggets with ketchup and mayonnaise, followed by ice cream or biscuits as an evening snack
By contrast, the women who ate the fewest ultra processed foods averaged just over three servings a day.
It is worth stressing that it is the overall pattern that matters.
A single ready meal or snack will not cause cancer on its own. Problems arise when ultra processed choices crowd out more nutritious foods, day after day.
Why this matters for bowel cancer and diabetes
Bowel cancer rates in people aged 25 to 49 have risen by more than sixty per cent since the early nineteen nineties.
Scientists are trying to understand why, and diet is one of the main suspects alongside factors such as physical inactivity and changes in the gut microbiome.
Ultra processed foods tend to be high in sugar, salt and unhealthy fats and low in fibre. This combination can:
- Promote weight gain and abdominal fat
- Worsen insulin resistance and blood glucose control
- Alter gut bacteria in ways that may increase inflammation and cancer risk
For people living with type 2 diabetes or at high risk of it, a diet heavy in ultra processed foods is particularly unhelpful.
It makes blood sugar harder to manage, undermines weight loss efforts and may increase long term risk of bowel cancer on top of existing risks.
The authors of the study emphasised that more work is needed to confirm the link, including studies in more diverse groups and research into how the body responds to these foods at a biological level. Even so, the direction of travel is clear and consistent with other work on diet and cancer.
Practical steps you can take
You do not need a perfect diet, but shifting the balance away from ultra processed products is likely to help both bowel health and diabetes control. Practical ideas include:
- Base meals around minimally processed foods such as vegetables, fruit, beans, lentils, whole grains, nuts, seeds, fish, eggs and plain yoghurt
- Keep processed meats, crisps, biscuits, sweets, sugary drinks and ready meals as occasional choices rather than daily habits
- Read food labels and be wary of very long ingredient lists with many additives and little fibre
- Cook simple meals at home when possible, using frozen vegetables and tinned beans to save time and money
As Cancer Research United Kingdom points out, our food choices are shaped by cost, marketing and what is available locally. That means individual effort is only part of the story. Better food policies and public health measures are needed to make healthier options the easy default for everyone.
For now, doing what you can within your own circumstances will still make a difference. If you live with diabetes, speak to your diabetes team or a dietitian for support in building a pattern of eating that works for your blood glucose, weight and overall health.
