A comprehensive new study finds eating more meat is associated with a higher risk of developing type 2 diabetes, with processed meat and unprocessed red meat highlighted as being particularly significant for overall risk.

An international team of researchers analyzed data on almost 1.97 million people, covering 20 countries across Europe, Asia, the Americas, and the Western Pacific.

Consuming the equivalent of about two slices of ham each day – 50 grams (1.8 ounces) of processed meat – was associated with a 15 per cent higher risk over 10 years, the study found. For the equivalent of a small steak (100 grams of unprocessed red meat) a day, the risk increase was 10 per cent.

"Our research provides the most comprehensive evidence to date of an association between eating processed meat and unprocessed red meat and a higher future risk of type 2 diabetes," says epidemiologist Nita Forouhi from the University of Cambridge in the UK.

The research takes advantage of the InterConnect project, where raw data from studies is made available alongside the published results. This means further analysis can take place using the collected data, going beyond the original study's aims and objectives.

Here, the team was able to use the data from 31 previous studies that had collected information on meat consumption and the development of type 2 diabetes. They could also account for factors such as age, body mass index, and health-related behaviours in their calculations.

The study also found a link between regularly eating 100 grams of poultry a day and an 8 per cent higher risk of developing diabetes across a 10-year period, but here the relationship was less clear, and it was only significant in Europe.

"While our findings provide more comprehensive evidence on the association between poultry consumption and type 2 diabetes than was previously available, the link remains uncertain and needs to be investigated further," says Forouhi.

Like many studies of this type, these results don't mean there's any definitive proof that eating meat increases the likelihood of developing diabetes. What it does show is a strong correlation, meaning a relationship is probable, and it matches findings from earlier studies.

Quite why processed meat and unprocessed red meat might push up type 2 diabetes risk isn't yet clear, though the researchers have some ideas: red meat is high in saturated fatty acids, for example, that have previously been found to affect insulin resistance.

It's most likely that a number of different mechanisms are at play, but pending further research, the study authors suggest we now have another reason to cut down on meat consumption – besides its links to other mental and physical health issues.

"[The study] supports recommendations to limit the consumption of processed meat and unprocessed red meat to reduce type 2 diabetes cases in the population," says Forouhi.