It has long been a public health truism that limiting meat consumption is better for your body. The World Health Organizations International Agency for Research on Cancer and the World Cancer Research Fund both say red or processed meat can cause cancer, as Reuters noted. But a study published in the Annals of Internal Medicine Tuesday argued that this might not be the case.
Based on the research, we cannot say with any certainty that eating red or processed meat causes cancer, diabetes or heart disease, Bradley Johnson, an associate professor at Dalhousie University in Canada and a co-leader of the study, said, as Reuters reported. To reach this conclusion, a team of 14 researchers in seven countries spent three years reviewing studies of the link between the consumption of red or processed meat and heart disease or cancer, The New York Times explained.
Their three reviews of the evidence covered randomized trials of 54,000 people and observational studies covering millions, according to The New York Times and Reuters. They concluded that the randomized trials showed no statistically significant link between meat consumption and diabetes, heart disease or cancer.
The observational studies showed a very small reduction in risk for those who ate less red or processed meat, but observational studies are a weaker form of evidence than random trials, as The New York Times explained:At the heart of the debate is a dispute over nutritional research itself, and whether its possible to ascertain the effects of just one component of the diet.
The gold standard for medical evidence is the randomized clinical trial, in which one group of participants is assigned one drug or diet, and another is assigned a different intervention or a placebo.But asking people to stick to a diet assigned by a flip of a coin, and to stay with it long enough to know if it affects the risk for heart attack or cancer, is nearly impossible.
The alternative is an observational study: Investigators ask people what they eat and look for links to health. But it can be hard to know what people really are eating, and people who eat a lot of meat are different in many other ways from those who eat little or none.The researchers concluded that adults could continue to consume red and processed meat at their current levels.
Many public health experts pushed back against the new findings.From a public health point of view, it is irresponsible and unethical to issue dietary guidelines that are tantamount to promoting meat consumption, even if there is still some uncertainty about the strength of the evidence, Dr. Frank Hu and colleagues at the Harvard T.
H. Chan School of Public Health wrote on the schools website. Because of the difficulty of conducting randomized trials for a variety of public health issues, they argued in part that dismissing high-quality observational studies as weak evidence would make it difficult to support things like the benefits of exercise.