There is no safe amount of processed meat to eat, according to new research

RNZ News

2 days ago

The equivalent of one medium-size hot dog was associated with an increased risk of colorectal cancer and type 2 diabetes in a new study.
Photo:
SCIENCE PHOTO LIBRARY
By
Madeline Holcombe,
CNN
There is strong evidence that there is "no safe amount" of processed meat to eat, nutrition experts say in response to a new study on the connection between diet and the risk of major diseases, including cancer, type 2 diabetes and heart disease.
The researchers also found elevated risks from the consumption of sugar-sweetened beverages and trans fatty acids.
Researchers analysed data from more than 60 previous studies on the relationship between processed meats, sugar-sweetened beverages and trans fatty acids in a person's diet and their risk of type 2 diabetes, colorectal cancer and ischemic heart disease, which reduces blood supply to the heart and cuts off oxygen and nutrients, according to the study published on Monday in the journal Nature Medicine.
"Habitual consumption of even small amounts of processed meat, sugary drinks, and trans fatty acids is linked to increased risk of developing type 2 diabetes, ischemic heart disease and colorectal cancer," said lead author of the study, Dr Demewoz Haile, a research scientist at the Institute for Health Metrics and Evaluation in Seattle.
The data showed that people who ate as little as one hot dog a day when it comes to processed meats had an 11 percent greater risk of type 2 diabetes and a seven percent increased risk of colorectal cancer than those who didn't eat any.
And drinking the equivalent of about a 12-ounce (350 millilitres) soda per day was associated with an eight percent increase in type 2 diabetes risk and a two percent increased risk of ischemic heart disease.
"This current research has shown, yet again and consistent with prior research - that to achieve health gains it is best to avoid or minimise the habitual consumption of each of processed meat, sugar-sweetened beverages (SSBs) and industrially produced trans fatty acids (TFAs)," said Dr Nita Forouhi, head of nutritional epidemiology at the University of Cambridge in the United Kingdom. She was not involved in the research.
The risk increased as consumption increased; and for processed meat consumption, the data showed that there was no "safe amount", she added in an email.
At first glance, the increase in risk seems modest and might look like the association is weak, said Dr Mingyang Song, associate professor of clinical epidemiology and nutrition at the Harvard TH Chan School of Public Health. He was not involved in the research.
"When we look at the actual data there, it's really remarkably consistent and remarkably strong, and even in the lower dose of consumption, we can still see an increased risk of disease," he said.
The researchers examined dozens of earlier findings on diet and disease using a burden-of-proof method: a newer form of meta-analysis that not only tries to quantify an association across multiple studies but also accounts for the quality of each, Song said.
"One caveat is it tends to give very conservative results," he added.
It's also important to note that the studies included in the analysis were observational, meaning that the data can only show an association between eating habits and disease - not prove that what people ate caused the disease.
They also relied on people recalling their dietary patterns, which can leave room for misremembering or misreporting, said Dr Gunter Kuhnle, professor of nutrition and food science at the University of Reading in the United Kingdom. He was not involved in the study.
Utilising even "the most sophisticated techniques does not really solve the problem that the information about diet is rather limited - which is obviously a big problem in nutritional epidemiology in general", he said.
There are many reasons why such foods could be associated with health problems.
Sugar-sweetened beverages and processed meat - such as sausages, bacon, salami and burgers - can increase inflammation, which plays a big part in a variety of chronic diseases, Song said.
Processed meats are also often cured with nitrite, which is converted to carcinogenic nitrosamines in the stomach, Kuhnle said.
The problem with sugary drinks is that they are a quick way to consume large amounts of sugar, he added.
Not only can that cause weight gain, but it also influences metabolic pathways that affect heart disease and diabetes risk, Kuhnle said.
Trans fatty acids reduce levels of good cholesterol and increase the bad, which is known to increase the risk of plaque build-up in arteries and heart disease, he added.
Other potential connections to consider are that people who are more likely to eat processed meats, sugar-sweetened beverages and trans-fats are often also at a higher risk of diseases because of "lifestyle factors (smoking, lack of exercise), but also social factors such as education and income, chronic stress and limited access to health care", Kuhnle said.
"It is very difficult to take these apart."
Although the data can't say reducing your consumption of these foods and drinks will cause a lower risk of the diseases, it does suggest that a reduction is a good idea, Song said.
A sensible approach is to follow a varied and balanced diet that avoids excess, Kuhnle said.
That means people who drink a lot of sugary drinks should cut back, he said.
It can also be helpful to avoid excess amounts of processed meats and avoid hydrogenated fats where possible - although they are no longer as common as they used to be, he said.
"The goal shouldn't be perfection but rather a healthy and sensible dietary pattern that allows room for enjoyment," Kuhnle said.
A good diet isn't just about what to avoid. It's also important to get good nutrients, Forouhi said.
"Wider research has shown us that overall dietary patterns that include higher consumption of fruit and vegetables, whole grains, legumes, nuts and fermented dairy products like yogurt are good for health and longevity," she said.
"My general advice: don't panic," Kuhnle said in an email.
"Food is not just (a) source of nutrients - it plays a central role in culture, pleasure, family life, and social connection. Reducing it solely to a list of health risks misses the bigger picture."
- CNN