In the ever-evolving and confusing world of nutrition science, a new study has linked eating meat to an increased risk of type 2 diabetes.
and in particular have been linked to type 2 diabetes before, . To get a better understanding of the situation, at the University of Cambridge and her colleagues have analysed a massive set of data, gauging the meat consumption of 1.97 million adults, mainly aged 40 to 60, who participated in research projects around the world. They then linked this to any new diagnoses of type 2 diabetes over the next 10 years or so.
The results suggest that for every 50 grams of processed meat eaten per day, the risk of developing type 2 diabetes goes up 15 per cent, on average, while an extra 100g of unprocessed red meat per day was linked to a 10 per cent higher risk.
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鈥淭here鈥檚 a lot of plausible biology here,鈥� says at Tufts University in Massachusetts, who particularly points the finger at heme iron in red meat. in the body called reactive oxygen species that , the hormone that helps control blood sugar. Eating high amounts of salt, which is often found in processed cured meats like salami, .
While Forouhi and her colleagues鈥� analysis was large, the studies it consisted of weren鈥檛 randomised controlled trials, the best quality evidence, so it can鈥檛 prove cause and effect. The studies were also based on people self-reporting their meat consumption, which is always prone to errors, says at Stanford University in California. Despite these shortcomings, the analysis has helped convince some experts.
Though the evidence is observational, it has been shown 鈥渞epeatedly and pretty consistently鈥�, says at Harvard University. 鈥淚 would say the evidence is strong. This new study did a great job strengthening the evidence base.鈥�
The time it takes conditions like type 2 diabetes to develop means randomised controlled trials would probably need decades-long follow-up periods. Although impractical, Ioannidis says these are needed before health officials can make 鈥渟olid recommendations鈥� as to a healthy level of red and processed meat consumption, but adds that the latest results are still 鈥渘otable鈥�.
鈥淎t this point, there鈥檚 an association,鈥� says at Aston University in Birmingham, UK. 鈥淭he size of the effect is not big enough to suggest causality.鈥�
Forouhi and her colleagues also linked poultry to an increased risk of type 2 diabetes. Like with red meat, the results suggest that for every 100g of poultry eaten per day, the risk rises by 10 per cent.
Mozaffarian, Gu and Mellor all say that the link to poultry is less convincing. It wasn鈥檛 consistent across the various groups included in the analysis and , says Mozaffarian.
The researchers attempted to account for other factors that could affect the results, including age, sex, ethnicity and the consumption of other foods. They also considered physical activity levels and body mass index, as inactivity and being overweight are key risk factors for type 2 diabetes. Still, there will probably be other relevant factors that the team hasn鈥檛 accounted for, says Ioannidis.
England鈥檚 National Health Service already recommends that people . The latest study 鈥渒ind of confirms that dietary guidelines are already are on the right track鈥�, says Mellor. Red meat can be a key source of nutrients, such as vitamin B12 and iron, he says.
鈥淢eat is not necessary for a healthful diet, but for those who enjoy intake, the science supports modest intake of unprocessed red meat 鈥� up to one serving per week 鈥� and minimising intake of processed meat, less than one serving per week,鈥� says Mozaffarian.
The Lancet Diabetes and Endocrinology
