Does ultra-processed food raise your risk of IBD? What a 116,000-person study found
There's a link, but not proof. The PURE study followed 116,087 adults in 21 countries for almost 10 years. People eating 5 or more servings of ultra-processed food a day were 82% more likely to develop inflammatory bowel disease than those eating less than 1. It's an observational study, so it can't prove cause, and the absolute risk was small. But swapping some ultra-processed foods for whole foods is low-risk, and a randomised trial shows ultra-processed diets lead people to eat more without noticing.
Ultra-processed foods are everywhere: fizzy drinks, packaged snacks, sweetened cereals, processed meats, many ready meals. They're cheap, convenient and often designed to be hard to stop eating.
At the same time, inflammatory bowel disease (IBD), the umbrella term for Crohn's disease and ulcerative colitis, has become more common in many countries as diets have changed. Researchers wanted to know whether the two are connected. Here's what one of the biggest studies found, how much weight it can carry, and what has good evidence for your gut.
What the PURE study did
The Prospective Urban Rural Epidemiology (PURE) study, published in the BMJ in 2021, followed people across a wide range of countries and incomes.
- Who: 116,087 adults aged 35 to 70 in 21 countries, in Europe, the Americas, Asia, Africa and the Middle East.
- What: diet recorded once at the start with a food questionnaire, then everyone followed for a median of 9.7 years.
- What was counted: new diagnoses of IBD. There were 467 in total: 90 Crohn's disease and 377 ulcerative colitis.
What it found
| Compared with less than 1 serving a day | Risk of IBD | 95% range | Strength |
|---|---|---|---|
| 5 or more servings of ultra-processed food a day | 82% higher (HR 1.82) | 1.22 to 2.72 | Observational |
| 1 to 4 servings a day | 67% higher (HR 1.67) | 1.18 to 2.37 | Observational |
| Unprocessed red meat, white meat, dairy, starchy foods, fruit, vegetables and legumes | No clear link | n/a | Observational |
Within ultra-processed foods, the strongest links were with soft drinks, refined sweetened foods, salty snacks and processed meat. Notice what wasn't linked: unprocessed meat, dairy and starchy foods. That points at processing rather than at any one food group.
Keep the absolute numbers in mind too. 467 cases among 116,087 people over about 10 years means IBD was rare in every group. An 82% higher risk of something rare is still a small risk for any one person.
How robust is this?
PURE has real strengths: it's very large, it covers many countries (so it isn't just a Western finding), and it followed people for a long time. But there are important limits:
- Observational. People who eat lots of ultra-processed food may differ in other ways, like income, smoking or stress. The researchers adjusted for many of these, but can't rule out everything.
- Diet measured once. A single questionnaire at the start can't capture how eating changes over 10 years.
- Diagnoses partly self-reported. Only around a fifth of cases could be checked against medical records.
- Few Crohn's cases. With only 90, the results for Crohn's alone are less certain.
- Many comparisons. Testing lots of food groups raises the chance that some links are flukes.
What has good evidence for your gut
You don't need a perfect diet. These are the changes with the best support, and none of them involves cutting out whole food groups.
| Change | What the research shows | Evidence |
|---|---|---|
| Swapping some ultra-processed foods for minimally processed ones | In a tightly controlled US trial, 20 adults lived on an ultra-processed diet for 2 weeks and a minimally processed diet for 2 weeks. On the ultra-processed diet they ate about 500 more calories a day and gained weight, even though both diets were matched for sugar, fat, fibre and salt on offer. Small and short, but randomised. | Good |
| Regular meals, taken slowly | For IBS, NICE and the British Society of Gastroenterology recommend regular meals, taking time over eating, and limiting caffeine, alcohol and fizzy drinks as first steps. | UK guidance |
| Moving regularly | Regular physical activity is recommended for everyone with IBS in the British Society of Gastroenterology guideline. | UK guidance |
| More variety of plants | In the American Gut Project, people eating 30 or more different plants a week had more varied gut bacteria than those eating fewer than 10. It's observational, but variety is easy and low-risk. | Emerging |
| Fermented foods | In a 10-week trial, 18 healthy adults who ate more fermented foods like yoghurt, kefir and kimchi ended up with more varied gut bacteria and lower levels of some inflammation markers. Promising, but small. | Emerging |
The pattern is clear: more whole and varied foods, eaten regularly, with a bit less of the most processed stuff. Simple to say, harder to do every week, which is where I come in.
One swap at a time, not a new diet
Most people know they "should" eat less processed food. What gets in the way is time, cost, habit and the fear of getting it wrong. Here's how we'd tackle it together.
Your swap list
We look at what you actually eat in a normal week and pick the swaps that are easiest for you, starting with one, not ten.
Quick meals for busy days
We build a small set of simple, mostly whole-food meals you can make on autopilot, so ready meals stop being the default.
Gentle variety
We add plants, and fermented foods if they suit you, gradually, at a pace your gut can handle.
Food without fear
Gut symptoms can make eating stressful. We keep food enjoyable and flexible, and avoid unnecessary restriction.
My take
I'm not anti-convenience. Real life includes busy weeks, tight budgets and nights when cooking isn't happening. What the evidence supports isn't perfection, it's a gradual shift: a few more whole foods, a bit more variety, a little less of the most processed stuff, kept up over months.
That kind of slow, steady change is exactly what coaching is good at. It's how I work with my clients: one swap at a time, built around the life they actually have.
Frequently asked questions
Does ultra-processed food cause IBD?
It hasn't been proven. The PURE study found that people eating 5 or more servings a day were 82% more likely to develop IBD, but it's observational, so it shows a link rather than cause.
Which ultra-processed foods were most linked to IBD?
In PURE, the strongest links were with soft drinks, refined sweetened foods, salty snacks and processed meat.
Was red meat linked to IBD in the PURE study?
No. Unprocessed white meat, red meat, dairy, starchy foods, and fruit, vegetables and legumes were not linked to IBD in the adjusted analysis.
What is an easy first step to eat less ultra-processed food?
Pick one food you eat most days, like a sugary drink, a packet snack or a processed meat, and swap it for a less processed option. One swap a week is plenty.
Are fermented foods good for gut health?
They look promising. In a 10-week trial, eating more fermented foods increased the variety of gut bacteria and lowered some inflammation markers, but the trial was small and in healthy adults.
Sources
- Narula N, Wong ECL, Dehghan M, et al. Association of ultra-processed food intake with risk of inflammatory bowel disease: prospective cohort study. BMJ 2021;374:n1554. Read it
- Hall KD, Ayuketah A, Brychta R, et al. Ultra-processed diets cause excess calorie intake and weight gain: an inpatient randomized controlled trial of ad libitum food intake. Cell Metab 2019;30:67-77.
- Vasant DH, Paine PA, Black CJ, et al. British Society of Gastroenterology guidelines on the management of irritable bowel syndrome. Gut 2021;70:1214-1240.
- McDonald D, Hyde E, Debelius JW, et al. American Gut: an open platform for citizen science microbiome research. mSystems 2018;3:e00031-18.
- Wastyk HC, Fragiadakis GK, Perelman D, et al. Gut-microbiota-targeted diets modulate human immune status. Cell 2021;184:4137-4153.
Follow @habitiahealth on Instagram for a new evidence check most days.
I'm Shivy, a certified Integrative Nutrition Health Coach (Institute for Integrative Nutrition, 2020). I have a degree in biology and a master's in environmental science, and I've lived with psoriasis since 2019. I read the research on food, sleep, stress and movement and turn it into small, realistic habits. More about me.
This article is education, not medical advice. Always follow the advice of your GP or medical team, and check with them before changing your diet or supplements.
