Adopting and maintaining a healthy lifestyle might prevent up to 60% of inflammatory bowel disease (IBD) cases, making it a feasible option for future preventive strategies, according to US researchers.

The findings, published in the journal Gut, are based on analysis of two large studies looking at the health of thousands of nurses and other healthcare professionals.

“We confirmed that a substantial proportion of Crohn’s disease and ulcerative colitis risk may be preventable through modification of lifestyle risk factors” Study authors

Diagnoses of IBD – comprising Crohn’s disease and ulcerative colitis – have been increasing globally, the study authors noted, with the condition currently affecting around 1.3 million adults in Europe.

Previous research has linked IBD risk with several lifestyle factors, they said, but it was not clear if adopting and maintaining a healthy lifestyle might lower the risk of developing it in the first place.

To investigate further, they looked at data on on participants from the Nurses’ Health Study, Nurses’ Health Study II, and the Health Professionals Follow-up Study.

The Nurses’ Health Study enrolled 121,700 female nurses, aged 30-55, from 11 US states in 1976, while the Nurses’ Health Study II monitored 116,429, aged 25-42, from 15 states in 1989.

Meanwhile, the Health Professionals Follow-up Study included 51,529 male doctors, aged 40-75, from across the US in 1986.

The researchers created modifiable risk scores (MRS) for each participant based on established modifiable risk factors for IBD, to estimate the proportion of cases that could have been avoided.

Risk factors included body mass index (BMI); smoking; non-steroidal anti-inflammatory drugs; physical activity; and daily intake of fruit, fibre, vegetables, polyunsaturated fatty acids and red meat.

The researchers then estimated the proportion of avoidable cases if an overall healthy lifestyle were adopted and maintained.

A healthy lifestyle comprised a BMI of between 18.5 and 25, never smoking, and a maximum of one alcoholic drink a day for women or two for men.

In addition, it included at least eight daily servings of fruit and veg, less than half a serving of red meat, at least 25g a day of fibre, two weekly servings of fish and half a daily serving of nuts or seeds.

During the monitoring period of the three trials, 346 cases of Crohn’s disease and 456 cases of ulcerative colitis were reported.

“Lifestyle modification may be an attractive target for future prevention strategies in IBD” Study authors

Based on the MRS scores, the researchers estimated that a low MRS could have prevented 43% and 44.5%, respectively, of Crohn’s disease and ulcerative colitis cases.

Similarly, maintaining a healthy lifestyle could have prevented 61% of Crohn’s disease cases and 42% of ulcerative colitis cases.

The researchers then applied their scoring systems to data from three large European studies to validate their findings.

This suggested a low MRS and maintaining a healthy lifestyle could have, respectively, prevented 44%-51% and 49%-60.5% of Crohn’s cases, and 21%-28% and 47%-56.5% of ulcerative colitis cases.

The study authors said: “Across six US and European cohorts, we confirmed that a substantial proportion of Crohn’s disease and ulcerative colitis risk may be preventable through modification of lifestyle risk factors or adherence to a healthy lifestyle.

“Further prospective interventional studies are needed to determine whether lifestyle modification is effective for the primary prevention of IBD, particularly in a high-risk population and younger-onset disease,” they said.

However, the researchers acknowledged that their study was observational and, therefore, could not establish causes.

“A key assumption of our findings is that the relationship between lifestyle factors and IBD development is causal,” they said.

“Though this has yet to be established, several lines of evidence support the critical role of environmental and lifestyle factors in the development of IBD,” they stated.

“Lifestyle modification may be an attractive target for future prevention strategies in IBD,” added the researchers from Massachusetts General Hospital in Boston.

“This may be of particular relevance to high-risk groups, such as first-degree relatives of IBD patients, who have an estimated 2%–17% risk of developing the disease over their lifetime.”