CASES of Scots youngsters being diagnosed with inflammatory bowel disease have soared by 75% in little over a decade, according to new research that points to changes in diet and low levels of vitamin D for the trend.

The Edinburgh University study found that between 2003 and 2008, 436 under-16s in Scotland were diagnosed with the condition, up from 260 cases when it was last monitored between 1990 and 1995.

Inflammatory bowel disease (IBD) is the umbrella term for a group of incurable, chronic bowel disorders including Crohn's Disease and ulcerative colitis – the condition which forced Scotland captain Darren Fletcher to take indefinite sick leave from professional football last year. It also includes inflammatory bowel disease unclassified (IBDU), a colon disorder which emerges in childhood but lacks the distinguishing features for doctors to diagnose it as either Crohn's disease or ulcerative colitis.

All share similar symptoms, including abdominal pain, vomiting and diarrhoea, rectal bleeding, severe muscle spasms in the pelvic region and weight loss.

The researchers noted slightly more boys than girls were affected and the average age for diagnosis had fallen from 12 to 11 – with some children as young as two being diagnosed.

It is not known what causes IBD, although there appears to be an interplay between genes and environmental factors such as sunlight. Previous research has indicated rates increase in more northerly regions, suggesting a connection with declining levels of vitamin D. Rates in Scotland are lower than anywhere else in the UK.

David Wilson, professor of paediatric gastroenterology and nutrition at Edinburgh University, said: "The biggest risk factor clinically is if you have a first-degree relative – mother, father, etc – with Crohn's or ulcerative colitis, then you have a 10% to 15% chance of developing the condition in your lifetime. However, there are cases of one identical twins brought up together where one twin develops the condition and the other doesn't, so there's obviously an issue about environmental trigger factors and that's where our speculation about the northerly latitude comes in."

Most patients can manage the condition using immune-suppressant drugs, athough in severe cases the large bowel may have to be surgically removed.

Unusually for most diseases in Scotland, research has previously revealed the people living in more affluent areas are statistically more likely to develop IBD.

Dr Daniel Gaya, consultant gastroenterologist at Glasgow Royal Infirmary and Yorkhill Children's Hospital, said this pattern backs up the "hygiene hypothesis", a theory which links the escalating rates of IBD in the western world to the emergence of refrigeration and antibiotics and the tendency for wealthier households to have a cleaner, better-prepared diet.

"Since the 1950s, we've become a much cleaner society, our food is much more sterile, and we use antibiotics much more frequently, so we are just not exposed to the amount of microbial agents that we would normally have been exposed to during our childhood," said Dr Gaya. "As a result, our immune system doesn't have the chance to get primed to these so-called 'safe bugs'.

"So, as we've become a cleaner society, this is predisposing us to these diseases which are characterised by an overexaggerated immune response to your gut – your body begins attacking your gut. So in a way, your pie supper from the chippy which may be loaded with bacteria could actually protect you."

Meanwhile, a US study pub-lished today claims concentrated milk fat used in junk food may be behind soaring rates of IBD. Researchers in Chicago found genetically susceptible mice fed a diet high in milk fat tripled the rate at which they developed colitis.