Infants have a higher risk of developing Type 1 diabetes later in life if they were started on solid food before the age of 4 months, researchers from the University of Colorado and the CU School of Medicine's Barbara Davis Center for Diabetes reported in the JAMA Pediatrics. The risk is also greater if solids are introduced after the baby is six months old.
The authors added that infants who are still being breastfed when starting on solid foods have a lower risk of developing Type 1 diabetes, especially if those foods contain wheat or barley.
Team leader, Jill Norris, MPH, PhD, said, "For children who are introduced to solid food before four months of age, the risk of developing Type 1 diabetes is almost two times higher than for children introduced to solid foods at 4 or 5 months of age."
These findings support the American Academy of Pediatrics' guidelines on when to start introducing solid foods.
Dr. Norris and team gathered and analyzed data on Colorado children with a greater genetic risk for Type 1 diabetes. The investigators focused on when solid foods were introduced, what foods were eaten, and whether the child went on to develop Type 1 diabetes.
Dr. Norris said "The data suggest that parents should wait to introduce any solid foods until after the 4-month birthday. And when baby is ready, solid foods should be introduced by the 6-month birthday or soon after, preferably while the mother is still breast-feeding the baby, which may reduce the risk of Type 1 diabetes."
Further studies need to be carried out on other types of foods to determine whether they might also impact on Type 1 diabetes risk when weaning an infant, Norris said, particularly fruits before four months of age and rice and oats after six months.
The number of people developing Type 1 diabetes has been steadily increasing each year over the last couple of decades, particularly among very young children.
A Swedish study published in The Lancet found that breastfeeding for longer protects the infant from developing Type 1 diabetes later on.
Low exposure to pathogens early in life linked to Type 1 diabetes risk
Why are Type 1 diabetes rates much higher in countries with low death rates from infectious diseases? According to scientists from the University of Malta, their study supports the hygiene hypothesis which suggests that humans are genetically designed to be exposed to micro-organisms. If infants and young children are kept too clean and over-protected from germs and dirt, their immune systems may not develop properly.
Type 1 diabetes is an autoimmune disease - the person's immune system destroys the insulin-producing beta cells in the pancreas as if they were harmful pathogens.
Study leader, Professor Stephen Fava, said "(the data in our study) provide support for the notion that the immune system can somehow become disordered and attack the body's own cells if it is not trained by regular exposure to micro-organisms - the so called hygiene hypothesis. More research is needed to try to identify other environmental factors that may be linked to the continuing conundrum of rising type 1 diabetes rates."
Some may wonder whether it is the vitamin D factor rather than an over-abundance of hygiene. Studies have suggested that infants and children with good vitamin D levels are much less likely to develop Type 1 diabetes compared to kids with low levels. Rich nations have the lowest death rates from infectious diseases. With the exception of Australia and the southern tips of the USA, all developed countries also have comparatively long-dark winters when people's vitamin D levels drop dramatically.