A study of 175 countries found that meat eating raises life expectancy, even after controlling for wealth
The study compared national averages, not people. Countries with more meat are usually richer, better fed and better served by healthcare, and statistical adjustment cannot fully separate those things. Studies that follow individuals in well-fed populations find vegetarians living at least as long as meat eaters.
This study covered 175 countries, about nine-tenths of the world's population. It adjusted for wealth, urbanisation and calorie intake, and meat still came out as a positive factor for life expectancy. Vegan advocates often say the evidence all points one way. A large, peer-reviewed study across nearly every country pointing the other way shows that it doesn't. It shows the case against meat for health is far from settled.
The study cannot show what it is being used to show. It is an ecological study. Its data points are countries, not people. Its meat figure is usually national food supply per head, which measures what is available to a country, not what any individual ate.
That design has two known problems.
First, confounding. Meat supply rises with almost everything else that extends life: income, sanitation, refrigeration, clean water, vaccination, hospitals, and the end of chronic undernutrition. The authors adjusted for some of these, such as GDP, urbanisation and total calorie intake. Adjusting for a few broad national measures does not remove the rest. What is left over can easily produce a positive association.
Second, the step from countries to individuals. Even a real association between national meat supply and national life expectancy says nothing direct about whether a given person lives longer by eating meat. The populations driving the pattern are mostly low-income countries moving out of undernutrition. There, more food of any dense kind, including animal food, does help. That is a real effect. It is not the choice facing a well-fed person in a supermarket deciding between a planned plant-based diet and a meat-based one. No country eats a well-planned vegan diet, so the study could not test one.
The better evidence for that question comes from studies that follow individuals over years. In high-income populations these find vegetarians and vegans living as long as comparable meat eaters, or longer. EPIC-Oxford found similar overall mortality. The Adventist Health Study-2 found somewhat lower mortality among vegetarians. Processed meat is classed as a cause of colorectal cancer, and red meat as a probable one. Diet studies are imperfect and there is genuine debate at the margins. A cross-country correlation does not settle that debate. It sits near the bottom of the evidence available.
Inferring that one thing caused another from the fact that they occurred together or one after the other. Correlation and sequence are not causation.
How it applies here: The claim treats a correlation between national meat supply and national life expectancy as evidence that meat causes longer life. It does this when wealth, healthcare and escape from undernutrition rise alongside meat supply, and adjustment for a few national indicators cannot rule them out.
Composition: assuming what is true of the parts must be true of the whole. Division: assuming what is true of the whole must be true of each part.
How it applies here: The claim draws a conclusion about individuals, that eating meat makes a person live longer, from averages across whole countries. A pattern among nations does not transfer to the people within them, least of all to well-fed individuals choosing between planned diets.