Researchers at the University of Washington School of Medicine have devised and published a star rating system to help people assess the health risks and benefits of various foods including red meat and vegetables.
Recent headlines interpreted the research in a simplistic way which may be misleading and give the wrong message about what to eat for health.
This article delves into the study and explores what it means, why nutrition research is complicated, and why you shouldn’t take headlines at face value. In addition, it looks at the evidence for the health benefits of more plant-based food and less meat in the diet.
What did the headlines say?
Some headlines told steak-lovers the “good news” – that unprocessed red meat will not raise their risk of stroke. They pointed out that for decades there have been fears that consuming lots of steak and pork can increase the risk of heart disease due to their high fat levels. But the new study found no evidence of this link. Other news sources interpreted the research with the headline “red meat is good for you after all.”
However, these articles completely miss the point. The study team is eager to explain that their findings serve as a basis for future research, having identified areas where scientists need to know more.
In addition, some experts expressed concern with the over-simplification of a star rating system and how people may interpret it.
What did the research say?
The Institute for Health Metrics and Evaluation at the University of Washington School of Medicine published the findings in Nature Medicine. They used Burden of Proof Studies as a new way of reviewing and evaluating evidence about the risks that certain lifestyles or dietary aspects pose to health.
The burden of proof risk function (BPRF) complements existing systems such as GRADE, which researchers use to rate the quality of evidence. The BPRF converts risks into a star rating, with one star reflecting no true association. Five stars supports a very strong association of harmful or protective factors.
Using the BPRF tool, the researchers indicated very strong associations between lung cancer and smoking. They also found strong links between high blood pressure and ischemic heart disease. However, one study found that the association between unprocessed red meat and increased risk of ischemic stroke was only one star (suggesting no evidence). Furthermore, the evidence for vegetable consumption and ischemic heart disease and stroke was classified as two and three-star pairings, respectively.
What does this mean?
So does this mean people should carry on eating red meat and not be so worried about including plenty of vegetables if they want to look after their cardiovascular health?
In a nutshell, no.
Firstly, while nutrition evidence has the potential to improve the populations’ health and lower their risk of diseases, it is well-accepted that it’s a complicated area of research. Studies have methodological limitations, including bias, confounding variables, and study design. People are also complex and may react differently to food based on their health status, genes, or other factors. In addition, many studies use self-report data. This means they rely on participants to remember what, how much, and what type of food they ate. And, how they cooked it, which can change the food’s nutrient profile.
A review of the burden of proof studies notes that scientists should know what people who reduce red meat replace it with. For example, if study participants replaced red meat with processed foods high in sugar or fat, this may not lead to a decreased risk of chronic disease.
Alice H. Lichtenstein D.Sc., FAHA, is a senior scientist and director of the Cardiovascular Nutrition Team at Tufts University in Boston. She is also the chair of the scientific statement writing group for the recent American Heart Association (AHA) dietary statement. Speaking about the new research, Lichtenstein said to Plant Based News: “Focusing on changing a single food or category of foods without taking the replacement item into consideration is not consistent with the concept of dietary patterns and can lead to misleading conclusions.”
A misleading approach
Kevin McConway, Emeritus Professor of Applied Statistics at The Open University, spoke to Science Media Centre about the BPRF studies. He expressed concern about what’s being lost in the process of boiling down the complexity of all the original studies to a five-star system.
Importantly, the goal of the Burden of Proof Studies was to help the public understand which relationships might stay as they are and which may change with future research. The link between smoking and lung cancer is well-researched and is unlikely to change from a five-star rating.
However, researcher Dr. Christopher Murray, author of the papers, said in a press briefing, “for one-star and two-star relationships, the public and scientific community should not at all be surprised if future work changes our understanding because the evidence for those is comparatively weak.”
Thus, just because the current evidence does not support a strong link between unprocessed red meat and stroke, it doesn’t mean that there isn’t one. “We should not be at all surprised if future studies change our understanding of the risks associated with red meat,” said Dr. Murray.
So is red meat healthy or not?
The reason the new Burden of Proof studies made misleading headlines is because, for many years, experts have advised that saturated fat from red meat may cause high cholesterol and narrowing of the arteries. This, in turn, can cause ischemic heart disease and stroke.
Previous research, including extensive studies, has indicated the severe health risks of red meat.
For example, a 2017 systematic review and meta-analysis examined the relative risk of meat consumption and stroke using 23 studies. The researchers found that the risk of developing stroke was 1.18 for total meat. And, 1.11 for red meat, and 1.17 for processed meat. Risk ratio figures over one mean that there is an increased risk compared to the control group.
Another 2021 study linked dietary saturated fat from red meat and butter to a higher incidence of coronary heart disease.
The AHA cites a 26-year observational study that suggests that replacing animal protein with plant protein could influence longevity. In fact, it found that swapping just five percent of daily calories from animal protein with equivalent calories from plant protein was linked to a nearly 50 percent decrease in the risk of dying of any cause. This includes coronary heart disease.
The study design had limitations, as many studies do. Nevertheless, the AHA recommends limiting saturated fat from meat and dairy to lower the risk of heart disease. In addition, the British Heart Foundation advises people to eat less red meat to avoid heart disease and bowel cancer.
Can you be healthy without eating meat?
Red meat contains nutrients such as protein, iron, and vitamin B12. And some cardiologists and nutritionists advise that eating organic grass-fed red meat in moderation is healthy. However, vegans can obtain the same nutrients from plant-based food and supplementation.
Established mechanisms suggest that meat raises the risk of heart disease and high cholesterol. And, that vegetables lower blood pressure and protect against stroke and heart disease. Healthy plant-based diets are associated with a lower risk of dying from any cause, including heart disease.
Considering the abuse of animals and the effects on the environment of meat and dairy production, plus the health risks, why would you choose to eat meat other than purely for taste? And is this a good enough reason to counterbalance the negative effects?
In a review of the Proof of Burden Studies, author Tammy Y. N. Tong said the potential environmental benefits of reducing meat and increasing plant food consumption are substantial. And, that future evaluations of dietary guidelines should consider environmental and societal impacts, as well as health.
She told Plant Based News: “The main take-home message is that we should still maintain our current dietary guidelines to limit red meat and increase vegetable intake.”
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