A structured diet lowered calprotectin in relatives at risk of Crohn's disease

Design

Randomised two-period crossover trial

Population

29 first-degree relatives of people with Crohn's disease with raised calprotectin

Primary outcome

Faecal calprotectin response at 8 weeks

Effect

≥50% fall in 71% vs 27%; RR 2.68 (1.09–6.60)

PIONIR was a randomised crossover trial in 29 healthy first-degree relatives of people with Crohn's disease who had persistently raised faecal calprotectin (above 70 µg/g) but no more than minor non-specific changes on capsule endoscopy or colonoscopy. Each followed the Tasty and Healthy diet, a whole-food pattern that limits processed foods, or their habitual diet for 8 weeks, then crossed over.

At week 8, median calprotectin was 64 µg/g on the diet against 112 µg/g on habitual diet. Calprotectin fell by at least half in 71% on the diet against 27% (RR 2.68, 95% CI 1.09–6.60). Across both periods, the diet was associated with a 37% greater fall. Most participants found the diet acceptable and adhered to it.

This is a small trial using a surrogate marker, and it cannot show that the diet prevents Crohn's disease. It does show that low-grade gut inflammation in at-risk relatives can be modified, which makes longer prevention trials worthwhile.

• Treat a raised calprotectin in an asymptomatic relative as a research-stage finding, not a diagnosis.
• Consider general advice to limit ultra-processed food for relatives who ask what they can do.
• Do not tell relatives that diet will prevent Crohn's disease; that has not been shown.
• Refer relatives with symptoms such as persistent diarrhoea, blood or weight loss for investigation.

Why it matters

This is the first randomised evidence that preclinical gut inflammation in Crohn's relatives responds to diet.

Don't overread it

Calprotectin is a surrogate; the trial did not measure whether anyone developed Crohn's disease.

The statistics, in plain English

An RR of 2.68 means the diet made a halving of calprotectin about two and a half times as likely. The interval 1.09–6.60 is wide because only 29 people took part.

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