How Irish diets of the past affect the present
Coeliac disease is a digestive disorder of the small intestine and interferes with the absorption of nutrients from food. The disease is particularly common in Ireland and the reasons why are discussed in a recent paper by Cornelius Cronin and Fergus Shanahan, in Perspectives in Modern Medicine, Vol. 44, number three. Cornelius Cronin works in the department of medicine, Mallow General Hospital, and Fergus Shanahan is professor of medicine at UCC. Dr William Reville reports.
People with coeliac disease cannot tolerate a protein called gluten, which is found in wheat, rye, barley and, to a lesser extent, in oats. When they eat gluten their immune system responds by damaging the small intestine. The disease is therefore considered an auto-immune disorder.
Nutrients from food are absorbed in the small intestine through fingerlike projections called villi. These villi are lost or damaged when the person with coeliac disease eats gluten-containing food. Without villi a person becomes malnourished, regardless of the amount of food eaten.
coeliac disease is genetic and runs in families. Sometimes the disease is triggered after surgery, pregnancy, childbirth, viral infection or severe emotional distress. The disease can affect people differently. Some develop symptoms as children, others not until adulthood. Breastfeeding may protect somewhat against the disease. It is reported that the longer one was breast-fed the later the symptoms of coeliac disease appear, and the more atypical these symptoms present themselves. Symptoms of the disease may or may not occur in the digestive system. One person may display abdominal pain and diarrhoea, while another may not have these symptoms, instead suffering from irritability or depression. Irritability is a common symptom in children.
coeliac disease symptoms may include one or more of the following: abdominal bloating and pain; diarrhoea; weight loss; pale, foul stools; gas; bone pain; behaviour changes; tiredness; cramp; failure to thrive in infants; joint pain; seizures; sores in mouth; missed menstrual periods.
Some people with the disease may not show symptoms. The undamaged part of the intestine can absorb enough nutrients to prevent symptoms, but such people are still at risk of developing complications of coeliac disease. Some symptoms of coeliac disease resemble those of other diseases, such as irritable bowel syndrome, Crohn's disease, diverticulosis, chronic fatigue syndrome and depression.
ANTIBODIES are produced by the immune system in response to substances the body perceives to be threatening. People with coeliac disease have higher than normal blood levels of certain antibodies. To diagnose coeliac disease blood samples are tested to measure levels of antibody. If tests and symptoms suggest coeliac disease, the doctor may remove a piece of small intestine and check for damage to villi.
The only treatment for coeliac disease is to avoid foods that contain gluten. For most people this will stop symptoms, heal intestinal damage and prevent further damage. Improvements are seen within days of starting the gluten-free diet and the small intestine is usually healed in three to six months. Sticking with the gluten-free diet is a lifetime requirement. A small number of people with severely damaged intestines will not improve on the gluten-free diet and may have to receive intravenous nutrition supplements.
A gluten-free diet means avoiding foods that contain wheat, rye, barley and, possibly, oats. This means most grain, pasta and cereal, and many processed foods. Oats are less toxic in coeliac disease than other cereals and only substantial consumption over a long period of time is injurious to the intestine. People with coeliac disease can eat a balanced and varied diet, even including special bread and pasta. Instead of wheat flour, they can use potato, rice, soy or bean flour, or can buy gluten-free bread, pasta and other products from specialist suppliers. Fish, rice, plain meat, fruit and vegetables do not contain gluten and can be eaten freely by people with coeliac disease.
Ireland was first settled 9,000 years ago and the first farmers arrived 6,000 years ago. Irish agriculture became dominated by pasture. Milk products were central to the Irish diet. Although cereal was eaten, it was largely in the form of oats. Ireland's basic human genetic stock was established 5,000 years ago and has remained relatively homogenous and distinct ever since.
The diet of the planters of the 16th and 17th century was cereal-based. The planter farmers displaced the native Irish to poor land where tillage was difficult. Commercialisation also made dairy products and oats more expensive and these items were progressively lost from the diet of the poor. The potato became important. Oats were the only cereal and source of gluten consumed before the Famine. Wheaten bread became a staple of the Irish diet only with the dietary changes that followed the Famine and the Irish diet now differs little from elsewhere in the western world.
From prehistory until relatively recently, the Irish diet has been very low in gluten. This allowed gluten-intolerant genetic traits to persist. Our relatively high incidence of coeliac disease is explained by our dietary past.
William Reville is associate professor in biochemistry and director of Microscopy at UCC