Eating red meat is probably healthier than many studies suggest

Canadian psychologist Jordan Peterson only eats meat. In several interviews, he claimed that he eliminated all other foods from his diet, eating only steaks, salt and water. You may be wondering if this is sensible, and you may be wondering how strictly he follows this, or if he sneaks vegetables from time to time.

Most of us would probably agree that Peterson’s all-meat diet, which is unfortunately gaining popularity online, is a bit extreme. But many would go much further, arguing that almost all of the carnivores among us should cut back on meat, especially red meat and processed meat, for health reasons.

The NHS website advises readers to reduce their red meat intake to 70 grams or less per day. The UK government’s healthy eating guidelines agree. And recommendations from a committee set up by the medical journal in 2019. Lancet – which take into account the ecological footprint of foods and their health consequences – recommend eating less than 98 g of red meat weekly.

These recommendations are based on a large body of research: Large studies, sometimes involving millions of people, have looked at links between red and processed meat consumption and various health conditions. Over time, the results of these studies were summarized in the form of a meta-analysis – a type of review study that collects available data on a specific scientific question – and a consensus emerged: eating red meat is bad for your health.

However, this consensus has been shaken in recent years. Studies have emerged that have questioned the quality of the entire series of studies and the nutritional advice derived from them.

In 2019, a series of review articles appeared in a well-known medical journal Annals of Internal Medicine this raised big questions about the link between red meat and health. Three studies reviewed all available data on the association between red meat and cancer, heart disease, and death, and concluded that despite a large number of studies, the evidence was very weak.

This is mostly due to “confusion”, the biggest scientific problem that makes nutritional research difficult. In an observational study, when you ask people about their diet and then monitor their health, it’s easy to assume that the disease must be caused by the diet. But there may be a third factor causing both. For example, if living in poverty affects the amount of meat people eat (as we know it) and their health (perhaps due to more dangerous jobs or living in more polluted parts of the city), then poverty could be the cause. and not food. relevant factor.

Nearly every study ever done on red meat and health has been observational. Reviews have shown that many of them don’t even try to account for confounding factors such as poverty (or other illnesses people may have or smoking). And these were far from the only research problems (see sidebar).

Why nutrition research is so difficult

Beyond the problem of “confusion” (when the diseases in your study could be caused by something other than eating red meat), there are many other pitfalls for nutritional scientists. Here are some of them:

Think bias. Can you remember exactly what you ate for lunch yesterday or last Tuesday? Can you remember exactly what else you ate during the day? Can you remember the exact amount of meat in each meal? Probably not – or at least not with perfect accuracy. Asking people to fill out food questionnaires from memory is always fraught with uncertainty.

Social Desirability Distortion. Even in an anonymous diet questionnaire, it’s embarrassing to admit that you’ve been to McDonald’s five times in the last week. It is “socially undesirable” to tell researchers that you have eaten very unhealthy food, and this may affect responses on the form.

replace. Even if you run an intervention that successfully gets people to eat less meat, what would you replace it with? If they eat more green vegetables than meat, you may see health benefits. But if they replace meat with high-carb snacks, they could be in an even worse position. It’s also a problem with observational studies where you have to ask what other foods people eat when they don’t eat meat.

survival bias. Suppose you find that older people tend to eat a lot of red meat. Does this mean eating red meat will help you live longer? Not necessarily: the survivors you find for your research may be a rare exception to the general rule, like the legendary centenarian who smokes 100 cigarettes a day.

The most controversial of all, in the final Annals of Internal Medicine In the paper, a team of researchers made these assessments and made their own recommendations. After reviewing the quality of the evidence, they said the only advice they could give is that people should continue to eat as much red meat as they used to. All of these studies have produced a body of evidence that is worth shrugging off.

This led to fireworks. The scientists urged the journal not to publish the recommendations because they could pose a risk to public health. Harvard University posted a response on its website, calling the recommendations an “irresponsible” interference in the debate by a “self-proclaimed organization tantamount to promoting meat consumption.” Even when reviewers criticized earlier studies, Harvard’s response stated that they had made their own scientific mistakes and failures. Despite their best efforts, they failed to reach a scientific consensus.

After several years of a pandemic in which infectious disease epidemiology, not diet, took center stage, the red meat debate is back. The study was published in a journal at the end of 2022. naturopathy researchers at the University of Washington, who again question previous red meat research.

Their main innovation was a complex statistical method that takes into account differences between studies. The studies come in all shapes and sizes: some are not only larger than others, but span different age groups, located in different parts of the world, where “red meat” could mean pork, beef, or something else; and they sometimes use different criteria to diagnose diseases.

As we have seen, studies also vary greatly in quality. Working with all of these variations is tricky, but the Washington researchers say it should make us all less confident about the overall results. In their analysis, they found that red meat was associated with a slight increase in colorectal cancer (a 6 percent increase) between those who ate no meat and those who ate up to 98 grams per day), breast cancer (a 3 percent increase). ). and percent), heart disease (1 percent) and diabetes (also 1 percent), but the added uncertainty prevented them from drawing more convincing conclusions.

Frank Hu, professor of nutrition and epidemiology at Harvard, disagrees. He argues that the new method unfairly “inflates” the uncertainty surrounding research. He points to another study done by Washington scientists that used the same smoking methods. Even there, some very well-established causal relationships (such as the fact that smoking causes heart disease) have only been described as “moderate” evidence. “A lot of the analysis in their articles,” he says, “is seriously misleading,” and we need to make it clear to people that the evidence suggests that more red meat is bad.

You may be wondering how we got to this point. We have thousands of nutritional studies with millions of people sharing their dietary habits and medical records. How can honest researchers still have such fundamental disagreements about what all this data shows?

One reason is that nutritional research is complex: we’ve seen some of the problems we’ve encountered in trying to determine the causal effect of a given food. It’s easy to find a dataset and publish another low-quality observational study. It’s extremely difficult to do a randomized controlled trial—the sort of gold standard study that’s commonly used in medicine—on people’s diets (at first, it’s hard to get them to make changes that last long enough to keep the diet going).

No specific studies have ever been done on reducing red meat, but some studies that inadvertently reduce red meat as part of a low-fat diet usually don’t have much of an effect on health.

Another source of confusion is that the interpretation of this study is associated with an uncomfortably high degree of subjectivity. In many cases, scientists on opposite sides look at the same results and come to opposite conclusions. In addition to disagreeing with the statistics, they voice their personal views on what they would like to eat (perhaps they love meat enough to justify the risk), their moral views on killing animals, and their ecological views on the impact of livestock. agriculture on the planet.

Scientists’ uncertainty about nutrition leaves the door wide open for potentially health-threatening trends such as Jordan Peterson’s 100 percent meat diet. Although such quirks at least give us something that both camps can agree on in Red Meat Wars. Eating 100 percent meat is clearly a bad idea. And eating 0% meat is probably the most beneficial for the diseases studied. But where you personally should draw the line—given your own taste, health, and long-term tolerance for small risks—science may not be able to tell us.