What causes diabetes?

Diabetes is a disease of metabolism, which is the way the body uses food for energy and growth.¹ In particular, it's related to one of the food nutrients that supply energy, called carbohydrates.² Normally, the stomach and intestines digest the carbohydrates in food into a sugar called glucose. Glucose is the body's main source of energy. After digestion, the glucose moves into the blood to give the body energy.

To get the glucose out of blood and into the body's cells, the pancreas makes a hormone called insulin. In diabetes, either the body doesn't make enough insulin, or the cells can't use it the way they should. Instead, the glucose builds up in the blood, causing diabetes, otherwise known as high blood sugar.

The exact causes of diabetes are not fully understood and typically involve multiple factors, such as genetics and interactions with the environment.

The majority of cases of type 1 diabetes are "sporadic" meaning there is no family history of the condition. Likewise, the rates of type 1 diabetes in both members of set of identical twins is lower than would be expected if the condition was caused by genetics alone. The environmental component is strong and could result from a combination of factors, such as exposure to viruses in the small intestine or to foreign proteins from foods at a time when the immune system of the digestive tract is too immature to process them.

Researchers leading the Trial to Reduce the Incidence of Type 1 Diabetes Mellitus in the Genetically at Risk (TRIGR), which is supported in part by the NICHD, are examining whether exposure to foreign proteins from cow's milk or cow milk-based infant formula can cause type 1 diabetes, especially in children who are at high risk for the condition based on their family history and genetic profile. The Trial aims to determine whether a nutritional intervention—feeding cow milk-based formulas that have been specially processed to remove the foreign proteins—during infancy can delay or prevent the onset of type 1 diabetes in children at high risk for the condition.

Obesity is a major factor in developing type 2 diabetes. Most Americans with type 2 diabetes are affected by obesity or overweight. Obesity reduces the body's ability to control blood sugar, so the body overproduces insulin to compensate—and a cycle develops.³

Pregnancy causes many different changes to the body, including changes to metabolism that result in gestational diabetes. These changes are usually the result of hormones produced during pregnancy that keep insulin from doing its job.