Experts have urged caution over a series of reviews which claimed to find there is no need for humans to reduce their meat intake.
While the World Health Organisation refers to red meat as “probably carcinogenic” and dietary guidelines around the world recommend reducing meat in our diets, four new systematic reviews have questioned the need to limit meat consumption.
The reviews, published in Annals of Internal Medicine on Tuesday, looked at existing studies on how eating different amounts of red and processed meats affects a person's risk of heart disease, diabetes and cancer.
Bacon is not killing you, but what you eat it with matters.Credit:Getty
Researchers concluded the evidence for adverse health effects is weak and, at best, risk reduction from eating three serves or less of meat a week was “very small”. Eleven of the 14 researchers concluded that people do not need to eat less fresh or processed meat for their health.
The controversial study has elicited a strong response from experts around the world. Criticisms include concern about conflict of interest among the researchers, the omission of certain studies from the review, and the inclusion of inherently flawed ones.
Studies looking at specific foods or nutrients are notoriously “messy” explains Rod Jackson, a professor of epidemiology at the University of Auckland.
This is because few people can accurately remember what and how much they have eaten, it is difficult to distinguish the effect of one food or nutrient from the rest of a person’s diet and lifestyle, and it is “impossible” to keep people on a specific diet – as needed in randomised controlled trials (RCTs) i.e. the “gold standard” of studies – for more than a couple of months, which makes long-term conclusions difficult to draw.
For these reasons, Jackson says he doesn't "think these new studies reported in this journal are meaningful".
Nutritionist and visiting fellow at the University of New South Wales' School of Medical Sciences Dr Rosemary Stanton adds: “It's not really possible to 'prove' anything by looking at a single food in diets– at least not the way you can prove if a drug versus placebo works in an RCT.”
This is because it is “unethical” to put people on a test diet for 10 or 20 years just “to see” what diseases they got and what they died from, explains Clare Collins, a professor in nutrition and dietetics at the University of Newcastle.
“However, the evidence doesn't show that red meat should be cut from the diet,” Dr Stanton says. “Having personally examined studies on red meat consumption a few years ago, I couldn't find any evidence of problems from modest intake. But, as with all foods, more is not better.”
Accredited practising dietitian Dr Joanna McMillan adds that dietary patterns are better predictors of outcomes than individual foods.
“Someone who consumes meat along with lots of vegetables, whole grains, legumes, nuts, seeds and fruits is entirely different from another who consumes lots of bacon, burgers and sausages with few plant foods and a high intake of refined grain foods such as burger buns and fried chips,” Dr McMillan says.
“The best advice is to ensure you consume a plant-rich diet and you can choose, based on ethical and other beliefs, likes and dislikes, as to whether you also include meat.”
If Australians followed the Australian Dietary Guidelines, the burden of disease would drop by 62 per cent for heart disease, 41 per cent for type 2 diabetes, 34 per cent for stroke, and 22 per cent for bowel cancer, Professor Collins says.
“Poor eating habits are the leading cause of death worldwide … People need more support to adopt the healthiest eating patterns they can.”
Still, the findings of the new reviews are helpful in debunking certain myths about meat, says Dr Ian Johnson, nutrition researcher and emeritus fellow at the UK’s Quadram Institute of Bioscience.
“In my opinion, people who choose to do so can still reasonably believe that they will experience modest reductions in their risks of cardiovascular diseases and cancers over a lifetime,” Dr Johnson says.
“On the other hand, this study will, I hope, help to eliminate the incorrect impression sometimes given that some meat products are as carcinogenic as cigarette smoke, and to discourage dramatic media headlines claiming that ‘bacon is killing us’.”
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