Diet is well known to impact the risk of developing type 2 diabetes, but a new study has found that eating lots of processed meats carries a particularly high risk of causing the disease.
Eating the equivalent of just two slices of ham a day was associated with a 15% greater chance of developing the disease, according to a study published in Lancet Diabetes and Endocrinology.
The studyof nearly 2 million people across 20 countries investigated diabetes risks associated with eating unprocessed red meat, processed meat and poultry.
When age, sex and body mass were accounted for, the research found 50g of processed meat a day was enough to increase the risk of type 2 diabetes by 15%.
The equivalent of eating a 100g steak daily raised risk by 10%, but associations with poultry consumption and the disease were less clear, according to the researchers from Cambridge University who conducted the study.
What causes type 2 diabetes?
Type 2 diabetes is a condition in which the level of sugar (glucose) in the blood becomes too high. It's caused by the body developing a resistance to a hormone called insulin, which normally lowers blood sugar.
Type 2 diabetes often develops due to being overweight or inactive, but can also be related to genetics.
Health authorities around the world recommend healthy diet and exercise, avoiding smoking and controlling blood pressure and fat levels to reduce the chances of develop type 2 diabetes.
Nick Wareham, Cambridge of University, UK, a senior author on the study, said their study shows that meat consumption has a particularly large impact on diabetes risks which is independent from obesity or body mass index.
Reducing consumption of processed meats could reduce risk of developing type 2 diabetes, he said.
"Maybe the way to think about it is also to flip it around and say how much you need to reduce your meat intake to reduce your risk by 10%," he said.
That's to say: reducing one's consumption of processed meat by at least two slices of ham per day in turn reduces the chance of getting type 2 diabetes.
"If everybody ate a little bit less, risk would go down, and obviously there are planetary benefits to that as well," said Wareham.
Meaty data from some places, not others
537 million people around the world have been diagnosed with diabetes, according to data from the International Diabetes Federation (IDF). Around 90% of diabetics have type 2 diabetes.
Estimates by the IDF and other health monitors show the prevalence of type 2 diabetes is on the rise globally. Three times more people now have diabetes compared to 25 years ago.
Fast developing regions like Africa are projected to have sizeable increases in type 2 diabetes, however the quality of data available to understand how this change is taking place is patchy.
"We already had strong evidence of this relationship, but this study adds another layer with additional studies and geographic coverage," says one of the study's co-authors and a leading metabolic disease researcher from Harvard University, US, Walter Willet.
"This is most important for the higher income countries that are consuming the most meat, but it is also important for most low-income countries because they are currently increasing their intakes of red meat," he said.
Sabrina Schlesinger at the German Diabetes Centre, who was not involved in the study, noted the use of 20 countries in the data improved the "generalizability" of the research.
"The findings of this study provide convincing evidence that supports the need for a shift in dietary patterns, especially in modern Western diets, which are characterized by high intake of processed and red meat," Schlesinger said.
"Remarkably, the study suggests that simply replacing processed meats with other types of meat (like unprocessed red meat or poultry) may not be sufficient. A broader shift towards plant-based diets could be more beneficial for health outcomes," she said.
Metabolic mechanisms linked to fatty diet
Processed and red meats are usually high in saturated fats. While consumption of these fats are known to cause a range of health issues, scientists haven't been entirely sure why.
A separate study has identified a new role of molecules called ceramides acting in the gut which could be contributing to type 2 diabetes risks.
Diets high in saturated fats provide the material needed to create a metabolically toxic variant known as C16.
These toxic C16 molecules were known to be made by the liver. But the new study shows the gastrointestinal tract (the gut) also makes them.
"We've identified a second organ that can make it, and actually makes it in response to what's coming in with the fat consumption," said the study's lead researcher Sarah Turpin-Nolan, from Monash University in Australia.
"If drug companies are trying to make something to treat metabolic disease and type 2 diabetes, if their drug can hit the liver and the gut, they will have a better effect overall," added Turpin-Nolan.
Scientists are yet to establish how C16 and metabolic processes lead to type 2 diabetes. Knowing more could help understand why diets rich in processed meats carry a particularly high risk of causing type 2 diabetes.