Eating Two Slices of Ham a Day Can Raise Type 2 Diabetes Risk by 15%

Eating any kind of processed or red meat may increase a person's risk of type 2 diabetes, according to a new review.

After trawling through data from 31 prior study groups – which accounted for 1,966,444 adults across 20 countries – the researchers from the University of Cambridge found that those who regularly ate meat were significantly more likely to develop type 2 diabetes.

Individuals who replaced their red and processed meat with poultry tended to have lower incidences of diabetes.

Given the unprecedented scale of data used in the study, the researchers say their findings are the most comprehensive yet to link red and processed meat consumption with diabetes, which is rapidly becoming one of the most prevalent diseases across the world.

The findings were published in the Lancet Diabetes and Endocrinology.

More ham, less insulin

Type 2 diabetes currently affects more than 500 million people worldwide and is estimated to affect 1 billion by 2050.

Previous research linking the disease to meat intake has occasionally drawn conflicting conclusions.

To better establish whether red and processed meat can increase the risk of type 2 diabetes, the researchers from the University of Cambridge and the InterConnect project reviewed pre-existing meat-diabetes studies.

The 21 individual cohort studies and 9 meta-analysis studies chosen were conducted between 1970 and 2023.

After taking into account factors such as age, gender, health-related behaviors, energy intake and body mass index, the researchers found that habitual consumption of 50 grams of processed meat a day – equivalent to 2 slices of ham – was associated with a 15% higher risk of developing type 2 diabetes in the next 10 years.

The consumption of 100 grams of unprocessed red meat a day – equivalent to a small steak – was associated with a 10% higher risk of type 2 diabetes.

These associations were observed across North America, Europe and the Western Pacific.

“Our research provides the most comprehensive evidence to date of an association between eating unprocessed red meat and processed meat and a higher future risk of type 2 diabetes,” said Nita Forouhi, a professor of population health and nutrition at the University of Cambridge’s  MRC Epidemiology Unit and senior author of the paper.

“It supports recommendations to limit the consumption of processed meat and unprocessed red meat to reduce type 2 diabetes cases in the population.”

Regular consumption of 100 grams of poultry each day was initially associated with an 8% higher risk of type 2 diabetes. But when Forouhi and her colleagues looked again after further analyses under different scenarios, this association became weaker. Under the same scrutiny, the associations between diabetes and processed/red meat persisted.

“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,” Forouhi clarified.

Missing links

While the Cambridge researchers may not have proven a causational connection between meat and diabetes – only demonstrated an observational connection – they’re confident enough in their findings to support a reduction in meat consumption for public health.

Other researchers, however, have highlighted the study’s flaws.

“The authors did try to control for other risk factors associated with increased risk of developing type 2 diabetes, including having a higher body weight, smoking, alcohol, low vegetable intake,” Dr. Duane Mellor, a dietitian and spokesperson for the British Dietetic Association, told the UK’s Science Media Centre.

“However, due to missing data in the studies the authors were not able to account for the effect of family history, insulin resistance or waist circumference which are more strongly associated with the risk of developing diabetes than many of the risk factors which were accounted for. So, it is possible that the increased risk associated with processed and red meat intake could be a result of these other confounding factors the analysis was not able to take account of.”

Ultimately, though, Mellor agreed with the researchers’ assertion that a reduction in red and processed meat consumption could help alleviate the health costs of diabetes.

“The overall message to moderate meat intake is in line with national healthy eating guidelines and advice to reduce risk of developing type 2 diabetes, which include eating a diet which is based on vegetables, fruit, nuts, seeds, beans, peas and lentils along with some wholegrain and moderate amounts of meat and dairy with limited amounts of added fat, salt and sugar,” they said.

“This should be accompanied by regular physical activity to minimise risk of developing type 2 diabetes. If people are considering reducing their meat intake, it is important that the nutrients found in meat are obtained from other foods, these include iron, vitamin B12 and protein. It is important when considering reducing or taking a type of food out of the diet, that any replacement foods provide the same nutrients to maintain a healthy diet overall.”

Reference: Li C, Bishop TRP, Imamura F, et al. Meat consumption and incident type 2 diabetes: an individual-participant federated meta-analysis of 1·97 million adults with 100 000 incident cases from 31 cohorts in 20 countries. The Lanc Diabet & Endocrin. 2024. doi: https://doi.org/10.1016/S2213-8587(24)00179-7