To date the cause of type 1 diabetes is not known, however, there are a number of theories and possible factors that have been put forward.

Many researchers agree that genetics is an important factor in type 1 diabetes and that one or more environmental factors must then contribute to trigger the start of type 1 diabetes.

How type 1 diabetes develops

Type 1 diabetes is an autoimmune condition, which means that the body incorrectly mistakes cells within the body as an attacking organism.

In type 1 diabetes, the cells which are incorrectly targeted and killed off are the beta cells in the pancreas that produce insulin.


Research has shown that people with certain genetic markers are more likely to develop type 1 diabetes than people without these. One notable genetic region has been named IDDM1 because of its strong associations with insulin dependent diabetes mellitus.

Research indicates that having a parent or sibling with type 1 diabetes increases the statistical likelihood of developing diabetes. Type 1 diabetes also tends to be more common in families that have a history of autoimmune conditions including coeliac disease and rheumatoid arthritis.

It is known that some people with genetic predisposition to type 1 diabetes don’t develop the condition and this is a key reason why researchers feel that an environmental trigger must also be involved.


Viral infections have long been suspected as being a potential trigger for type 1 diabetes. Research has identified one specific type of enterovirus, known as Coxsackie B virus, as being particularly closely associated with type 1 diabetes.

Vitamin D

Research has shown a strong association between type 1 diabetes and exposure to vitamin D from the sun. Supporting this assertion is that countries with some of the highest rates of type 1 diabetes, including Finland, Canada and Scotland are those that are furthest from the equator and therefore get a smaller amount of sunshine.

Cow’s milk

Cow’s milk has been researched as a possible trigger for type 1 diabetes. Some researchers have found associations between an early introduction of cow’s milk with a higher incidence of type 1 diabetes.

Researchers believe that small amounts of cow’s insulin within cow’s milk may trigger antibodies to act against insulin producing cells in humans with a genetic susceptibility to type 1 diabetes.


Vaccinations have been mooted as a possible cause of type 1 diabetes. Whilst some associations have been found between vaccinations and incidence of type 1 diabetes, these links have not been strong enough (statistically significant enough) to warrant large scale investigation.