Red meat has previously been blamed for causing health problems including cardiovascular disease and diabetes but according to researchers, processed meats could be to blame.
A full English breakfast including sausage and a couple of slices of bacon increases the risk of developing heart disease by two-fifths and diabetes by a fifth, they found.
But eating unprocessed red meats such as a steak, roast pork or lamb chop does not increase the risk as suggested by earlier research.
In the first research of its kind, a team from Harvard University systematically reviewed 20 studies involving 1.2 million people from 10 countries around the world into the effects on health of eating process and unprocessed meats.
Unprocessed red meat was defined as any meat preserved by smoking, curing or salting, or with the addition of chemical preservatives, and included bacon, salami, sausages, hot dogs or processed deli or luncheon meats.
The results, published in published in the journal Circulation, revealed that an average daily serving of 50 grammes of processed meat – equivalent to two slices of deli meat or one hotdog – increased the risk of heart disease and diabetes.
Dr Renata Micha, the lead author of the study and a research fellow in the university’s department of epidemiology, said most dietary guidelines still recommend reducing meat consumption despite prior studies into showing mixed results about the harm it causes.
“Most prior studies also did not separately consider the health effects of eating unprocessed red versus processed meats,” she said.
She said that while both types of meat have similar levels of saturated fat and cholesterol, processed meats tested in the United States had on average four times more salt and 50 per cent more nitrate preservatives.
Red meats 'may not be bad for the health'
“This suggests that differences in salt and preservatives, rather than fats, might explain the higher risk of heart disease and diabetes seen with processed meats, but not with unprocessed red meats,” she said.
Salt in food has also been linked to higher blood pressure – a strong risk factor for heart disease.
In animal experiments, nitrate preservatives can promote atherosclerosis and reduce glucose tolerance, effects which could also increase risk of heart disease and diabetes.
“To lower risk of heart attacks and diabetes, people should consider which types of meats they are eating,” Dr Micha said.
“Processed meats such as bacon, salami, sausages, hot dogs and processed deli meats may be the most important to avoid. Based on our findings, eating one serving per week or less would be associated with relatively small risk.”
Eating processed meat such as sausages increases the likelihood of heart disease, while red meat does not seem to be as harmful, a study suggests.
A Harvard University team which looked at studies involving over one million people found just 50g of processed meat a day also raised the risk of diabetes.
But there was no such risk from eating even twice as much unprocessed meat, such as beef, lamb or pork.
This was despite the fact the two forms of meat have a similar fat content.
Writing in the journal Circulation, the researchers speculated that given the similar quantities of cholesterol and saturated fats, the difference may be explained by the salt and preservatives added to processed meats.
This is defined as any meat preserved by smoking, curing or salting and includes bacon, sausages, salami and other luncheon meats.
Salt can increase blood pressure in some people, a key risk factor for heart disease.
In animal experiments, nitrate preservatives can promote atherosclerosis and reduce glucose tolerance, which can in
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If you think saturated fat is responsible for cardiovascular disease (CVD), you need a reality check-new evidence has shown that saturated fat intake has a very limited impact on CVD risk.
World-renowned scientists specializing in fat research analysed the evidence between saturated fat intake and health, and overall agreed upon the need to reduce over-simplification when it came to saturated fat dietary advice.
“Diets inordinately high in fat and saturated fat are associated with increased cardiovascular disease risk in some individuals, assuming that saturated fat at any intake level is harmful is an over-simplification and not supported by scientific evidence,” said J. Bruce German of the University of California.
Results from a research review conducted by Dariush Mozaffarian of the Harvard University found that the effects of saturated fat intake on CVD risk depend upon simultaneous changes in other nutrients.
For example, replacing saturated fat with mono-unsaturated fat yielded uncertain effects on CVD risk, while replacing saturated fat with carbohydrates was found to be ineffective and even harmful especially when refined carbohydrates such as starches or sugars were used in place of fat.
Replacing saturated fat with polyunsaturated fat gave a small reduction in CVD risk, but even with optimal replacement the magnitude of the benefit was very small.
”Carbohydrate intake has been intimately linked to metabolic syndrome, which is a combination of risk factors that can increase CVD risk,” said Jeff Volek of the University of Connecticut.
His research showed that very low carbohydrate diets could favourably impact a broad spectrum of metabolic syndrome and cardiovascular risk factors, even in the presence of high saturated fat intake and in the absence of weight loss.
Kiran Musunuru of the Massachusetts General Hospital showed that low-carbohydrate diets appear to have beneficial lipoprotein effects in individuals with atherogenic dyslipidemia, compared to high-carbohydrate diets, whereas the content of saturated fat in the diet has no significant effect.
As long as saturated fat targets remain firmly rooted in dietary advice, nutrient-rich foods that contribute saturated fat to the diet, like full-fat dairy products, will continue to be unduly criticized regardless of their health benefits.
The findings were published in Lipids.