A Swedish study, published in the journal "Archives of Disease in Childhood," has found that children who develop gluten intolerance -- known as celiac disease -- are mostly girls, born in springtime and in the south of the country.
Swedish researchers followed two million children born in Sweden between 1991 and 2009 up to the age of 15. Among them, 6,569, or almost 0.4 % -- most of whom were girls -- were diagnosed with celiac disease before the age of 15.
Celiac disease is characterized by intolerance to gluten, a protein found in wheat, rye and barley. This causes the destruction of the small intestine walls, making nutrients and vitamins less effectively absorbed. To prevent symptoms such as stomach aches, diarrhea and abdominal pain, sufferers must follow a strict diet.
The study identified two factors influencing the development of celiac disease: season and region of birth.
Children born in winter (December to February) were less likely to be diagnosed with celiac disease, whereas those born in spring (March to May), summer (June to August) and fall (September to November) had a ten percent higher risk of developing the disease. Children under two were found to be at greater risk if born in springtime, whereas children diagnosed after this age tended to be born in the fall.
The researchers also found that children born in southern regions of Sweden were at greater risk of developing the disease.
Could vitamin D have a role to play?
In an attempt to explain their findings, the researchers suggest that children born in spring or summer could be more widely affected by the disease since they are more likely to be weaned and exposed to gluten for the first time during the autumn and winter months. At these times of year, seasonal viral infections are rife and can affect gut flora, making it more fragile.
Another factor could be the mother's vitamin D levels during pregnancy. Vitamin D levels are usually lower in mothers who give birth in spring due to reduced exposure to sunlight during their pregnancy.
Symptoms of celiac disease vary with age. In young children, it can lead to chronic diarrhea, as well as tiredness, listlessness and sadness. Young children may also have a swollen abdomen and slender limbs, and growth in weight and height can slow. In older children, the disease has fewer symptoms, limited to isolated indications such as small size, late onset of puberty, chronic anemia, tooth enamel defects and joint pain.
The findings were published in the journal "Archives of Disease in Childhood."