Does the global meat trade lead to poor health?
A recent study published in BMJ Global Health, “Global red and processed meat trade and non-communicable diseases” is attributing three major diseases, colorectal cancer, type 2 diabetes and coronary heart disease, to the increase in global trade of 20 meat-based items.
Unfortunately, many leaps were taken in the “findings” from the paper – that we must reduce the global meat trade for the good of human health and the planet – which simply cannot be proven from the data that was accessed. As an example, the front page of the paper states that “increased intake of red and processed meat products via trade caused the abrupt increase of diet-related NCDs, and the attributable burden of diet-related NCDs had large geographical variations among countries.”
The use of the word “cause” in the above sentence is inappropriate, misleading, and could even be considered irresponsible. To prove a food causes a specific outcome, you must conduct an experimental study. Observational research, which is what was used in this study, can only show associations. What the researchers noticed was that in many cases when more meat was available, disease rates increased. But was this directly related to meat trade? This is impossible to determine through observational research.
Other factors to consider include possible increases in fast food consumption in these countries, sugar intake, alcohol intake and smoking. Was there a decrease in fresh fruit and vegetable consumption, cooking at home, exercise, visits to the doctor, or an increase in overall caloric intake? Maybe there was an increase in environmental pollution.
None of these confounding factors were considered in the study when they concluded that global meat trade is causing increases in non-communicable diseases. A more scientifically responsible conclusion would have been that more access to meat “was associated with” disease outcomes. There was no proven cause and effect – something that can only be proven with an experimental study.
Let’s look more closely at the relationship between meat intake and disease. Do red and processed meat even cause these diseases in the first place?
In the beginning of the paper, the researchers are working on the assumption that three diseases, colorectal cancer, diabetes type 2, and coronary heart disease, are caused by an increase in meat consumption.
First - Does meat cause cancer?
The idea that meat may play a role in cancer has been a feature of both research and mysticism for over a hundred years. The source most often cited is the World Health Organization (WHO), which leans heavily on the work of the International Agency for Research on Cancer (IARC), which categorizes different substances or “agents” into the following groups:
The most often-cited material places meat, particularly processed meats, among the group 1 carcinogens, along with a host of substances including tobacco, various viral infections, alcohol, and plutonium. News reports and documentary films such as What the Health have concluded that meat is “as bad” as smoking or exposure to radiation.
But let’s not be so hasty. In an interview for Cancer Research UK, Professor Phillips explains the IARC process: “IARC does ‘hazard identification’, not ‘risk assessment’. That sounds quite technical, but what it means is that IARC isn’t in the business of telling us how potent something is in causing cancer - only whether it does so or not.” To make an analogy, think of banana peels. They definitely can cause accidents, explains Phillips, but in practice this doesn’t happen very often (unless you work on a banana farm). And the sort of harm you can come to from slipping on a banana peel isn’t generally as severe as, say, being in a car accident. But under a hazard identification system like IARC’s, banana peels and cars would come under the same category—they both definitely do cause accidents.
So, let’s look at what IARC is actually saying about meat. Processed meat—meaning bacon, ham, sausages and cured meats, canned meat, and meat-based sauces—is classified as group 1, “carcinogenic to humans.” Also in the class 1 category, we can find “air,” wine, and sitting near a sunny window. The research seems to suggest that with every daily fifty-gram increase in processed meats, there is an 18 percent increase in the risk of colorectal cancer (this is the case we made previously about relative versus absolute risk). An 18 percent increase sounds scary, right? But does that mean we need to stop eating bacon?
One slice of bacon is approximately eight grams. So, if an individual ate five strips of bacon every single day, that person’s risk would go up 18 percent. Now, let’s also look at what an 18 percent increase in cancer risk really means. The risk of getting cancer is 1,500 to 3,000 percent (or fifty to thirty times) higher for smokers as opposed to nonsmokers. An 18 percent increase in cancer from eating processed meat isn’t even twice the risk. In the US the average rate of colon cancer is 5 percent. An 18 percent increase in this risk would move you to almost 6 percent, if you ate five slices of bacon every single day. Now, if eating five slices of bacon daily doubled your chance of contracting colon cancer, then that could be a cause for concern, but the risk is only slightly elevated (and based entirely on observational studies, which we explained previously are built from food frequency surveys—the actual risk is incredibly debatable given the potential error of these types of studies).
Yet with a bit of statistical massaging, the difference between 5 percent and 6 percent (18 percent but let’s round that up to 20 percent in this case just to be consistent with media clickbait, which is called the “relative risk”) is what is reported and what snags the pithy news headlines. To classify processed meats and cigarettes in the same category is clearly misleading. Additionally, smoking causes more different types of cancer, including lung, mouth, throat, esophagus, liver, bladder, kidney, cervix, stomach, bone marrow, and blood.
Fresh red meat was classified as group 2, or “probably” cancer causing. By the way, so is any food that’s grilled. Yet there is no strong evidence at all that fresh red meat causes cancer. None. Interestingly, a group of researchers analyzed the research that the IARC used to link red meat and processed meat to cancer. It turns out, most of the studies (about 80 percent) were in Western populations. Of the 15 percent of the studies on red or processed meat and cancer that were conducted in Asian countries, most of them showed no link between fresh or processed meat and cancer. If red meat and processed meat causes cancer, wouldn’t it also cause cancer in Asians? The researchers stated, “The incidence of colorectal cancer may be related to causative factors other than meat consumption, such as ethnicity, dietary habits, alcohol consumption, smoking, stress, exercise, medical check-up frequency, or environmental pollution.” If there was a mechanism for meat to cause cancer, we would expect to see some evidence of a mechanism in randomized controlled trials, but this is just not the case.
Does Meat Cause Heart Disease?
The claims that meat causes heart disease come largely from the fear that saturated fat increases cholesterol, and that high cholesterol causes heart disease. A very large meta-analysis and systematic review of both observational and randomized controlled trials involving over six hundred thousand participants concluded that “current evidence does not clearly support cardiovascular guidelines that encourage high consumption of polyunsaturated fatty acids and low consumption of total saturated fats.” Again, the studies that link dietary saturated fat and cholesterol to heart disease are based on epidemiology, which can reveal associations but not causes. Dietary cholesterol has been vindicated and is no longer “a nutrient of concern”
by the Academy of Nutrition and Dietetics. Once gospel, the diet-heart hypothesis has been proven wrong in many books and papers. There is no connection between dietary cholesterol and saturated fat intake and heart disease.
What about Type 2 Diabetes and meat consumption?
The country with the highest rate of red meat consumption is Argentina, and their prevalence of type 2 diabetes is less than 6%. Over 120 countries have higher rates than Argentina.
What DO we know about red meat consumption?
The truth is, lots of things are “associated” with lots of other things, but this doesn’t mean that one caused the other. See this link for examples.
If we want to talk about associations, Hong Kong has among the highest meat consumption and the longest lifespans on the planet…does this mean meat caused longevity? Or maybe it’s because Hong Kong has a high income given that higher income can be associated with less stress, better access to healthcare, etc. The point is, we can’t tell if meat is a driver in longevity just from this simple association. What we do know is that meat is a nutrient dense food and as people have more access to nutrient-dense foods, they tend to live longer, healthier lives.
Observational research may be helpful when looking at something like cigarette smoking, where the risk of cancer is 30X higher in smokers than non-smokers, but with nutrition we’re not seeing any statistically significant increases in risk, and as mentioned earlier, there are so many other confounding factors that need to be considered when looking at diet. One study from 2019 found the evidence related to arguments against meat to be very weak. This study, which did a good job of controlling for confounding factors, found no evidence that a vegetarian, semi-vegetarian, or pesco-vegetarian diet had a protective effect on all-cause mortality.
To date, there has only been one controlled study that examines the effect of eating meat versus limiting meat. In a 2014 study, researchers evaluated the impact of the addition of meat, milk, or just additional calories to the diet of largely vegetarian children in Kenya and compared them to a control group, who received no additional food.
The results were fascinating. When measured for growth, intellectual ability, behavior, and academic performance, after two years the meat group had the best outcomes by far. The milk group showed the least improvement on Raven’s Progressive Matrices—a measure of fluid intelligence—even when compared to the children that didn’t receive any additional calories. The meat group showed remarkably more physical ability, leadership, and physical growth during the study period. Those who only received the milk substitute lagged the meat group in every aspect. These results may be related to the impact milk has on iron absorption, which influences cognitive ability. The improvements in performance in the meat group could be due to the intake of high-quality protein, vitamin B12, zinc, and iron in the children’s diet, all of which have a positive impact on development. Although this is only one study with some limitations, it’s the only controlled study on meat in children, and basically, it suggests milk can’t replace meat.
Red meat is a bioavailable, nutrient-dense source of protein and many micronutrients, which are difficult or impossible to find in plant-sourced foods. In particular, red meat is a very good source of vitamin B12 and iron, two of the most common nutrient deficiencies worldwide, especially in low-income countries.
In fact, iron deficiency affects approximately 25 percent of the global population and almost half of all preschool children. Iron deficiency can lead to severe and chronic diseases, chronic heart failure, cancer, and inflammatory bowel disease. In children it can cause serious developmental delays and behavioral issues. Vegetarians are commonly iron deficient, which is a risk factor for type 2 diabetes. Heme iron, found in red meat, is the most absorbable kind of iron, two to three times better than plant-based iron, and absorption is also dependent on current iron stores. In New Zealand, hospitalizations for iron deficiency have doubled over the last ten years as red meat consumption has declined. Vegetarianism in New Zealand is up nearly 30 percent, and of those who do eat meat, they’re eating more than twice as much chicken and pork, yet beef and lamb consumption are dramatically down. Early signs of iron deficiency include fatigue, light-headedness, and shortness of breath. Although a package label of a meat-free food may say it contains a lot of iron, only about 1.4–7 percent of plant-based iron can actually be absorbed, compared to 20 percent in red meat.
Red meat is something humans have been eating for approximately 3.5 million years. To blame red meat consumption on our rise in modern lifestyle-related diseases is a misleading leap of the researchers to conclude based on observational research, which cannot prove cause and was not adjusted for confounding factors. It’s far more likely that the increase in ultra-processed foods, something completely new to humans and lacking in key nutrients, is to blame.
In addition to the health claims made in the paper, there were two more claims that need to be addressed. Interestingly, these were not a focus of their research – they were simply mentioned as yet another reason why meat trade should be vilified.
Does the Trade of Meat Increase GHG Emissions?
From the paper: “The EU, which accounts for a half of global meat trade, is preparing to charge carbon border taxes on imported goods based on the greenhouse gases emissions released during the process of their production. The carbon border taxes on meat products would be applied for future meat trade policies to achieve sustainable diets toward less red and processed meat consumption. Also, emissions of greenhouse gases during transport should be taken into account.”
Whether or not meat should be traded on the global scale because of emissions should not be conflated with the idea that meat is unhealthy and leads to cancer, type 2 diabetes and heart disease. Many items are traded globally, so to tax meat specifically is both illogical and irrational. Will all produce be taxed too? These products are less nutrient dense and more perishable than meat, which can be frozen. More food waste results from produce than meat.
Do people even want to reduce meat consumption?
From the paper: “Additionally, future interventions need to address local contexts—such as food prices, food culture, environmental conditions and socioeconomic factors—to be more effective. Without considering local contexts, a rapid transformation toward plant-based diets may cause unpredictable health consequences regarding micronutrient deficiencies.”
In most cases, no, people do not want to move towards a plant-based diet because this violates the food sovereignty of pretty much every traditional culture worldwide. Also, a reduction in global meat trade will likely not reduce NCD nor GHG emissions worldwide. Livestock can thrive on landscapes we cannot crop, which is most of the agricultural land worldwide. Ruminants can consume crop waste, converting it into protein, and are a net protein win for our food system.
What Can We Learn from This Study?
In the end, while it’s an interesting exercise to observe the association between the global meat trade and the rise in NCD, one cannot prove cause from meat and NCD increase, and to report that is misleading and irresponsible. To suggest we reduce global trade of meat because of GHG emissions, when the trade of all products causes emissions, unfairly puts meat as the scapegoat without acknowledging meat’s important, positive contribution to human nutrition.
Instead, researchers should be looking into how we might increase access to nutrient dense, sustainably produced foods such as red meat, support regional food systems that are culturally appropriate, and encourage people to reduce their intake of industrial ultra-processed foods.
The truth is, ultra-processed foods stimulate overconsumption and lack key micronutrients, leading to a rise in obesity and other diet related-diseases.