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We used to eat saturated fat for millions of years, why is it all of a sudden unhealthy?

The claim that eating saturated fat hasn't been an issue for millions of years is often cited in dietary debates, but this perspective overlooks important factors. In the section that follows, I critically examine this claim and explore the intricacies of saturated fat consumption and its impact on human health. By delving into tradition, evolution, and scientific understanding, I hope to provide a well-rounded perspective on the relationship between diet and health.

A reconstruction of an elephant butchery by Homo erectus nearly 1 million years ago
A reconstruction of an elephant butchery by Homo erectus nearly 1 million years ago at Olorgesailie, Kenya. © 2013 Nature Education Courtesy of Karen Carr/Smithsonian Institution.

On Twitter, a Ketogenic Diet proponent posted:

We used to eat saturated fat for millions of years, why is it all of a sudden unhealthy?

This common loaded question and argument is flawed for several reasons:

  1. Appeal to tradition fallacy: The argument assumes that because something has been done for a long time, it must be correct or beneficial (1). This type of reasoning is fallacious because it does not take into account new information or advancements in our understanding of health and nutrition. Just because a practice has been followed for a long time does not necessarily make it healthy or beneficial.

  2. Evolutionary mismatch: While it's true that our ancestors consumed saturated fats as part of their diet, their overall lifestyle and dietary patterns were significantly different from ours (2). They generally had higher levels of physical activity, lower caloric intake, and consumed a more diverse range of foods. Our modern lifestyle, with sedentary habits, high-calorie diets, and chronic stress, can interact with saturated fat intake in ways that may increase the risk of health problems.

  3. Incomplete understanding of diet and health: The argument oversimplifies the relationship between saturated fat and health. It's essential to recognize that the health impact of saturated fats can depend on various factors, such as the overall diet, individual genetics, and lifestyle habits. Current research suggests that replacing saturated fats with unsaturated fats can help reduce the risk of cardiovascular disease (3), but it is essential to consider the broader context of one's diet and lifestyle.

  4. Changing scientific understanding: Nutritional science has evolved over time, and our understanding of the impact of saturated fats on health has become more nuanced. Early research suggested a strong link between saturated fat and heart disease, but more recent studies indicate that the relationship is complex and depends on the specific types of saturated fats, as well as the foods they are consumed in (4).

  5. Life expectancy: Historically, humans had shorter lifespans due to factors such as high infant mortality, lack of modern medicine, and vulnerability to infectious diseases. A shorter lifespan means that many of the chronic diseases associated with diet and lifestyle, such as heart disease or type 2 diabetes, may not have had enough time to manifest in our ancestors (5). Thus, using arguments about the absence of disease in some ancestors as attributed to diets, is flawed.

  6. Genetic adaptations: Over time, some human populations may have developed genetic adaptations to help them tolerate higher saturated fat intake, as your argument suggests. However, these adaptations are not universally present, and it is important to recognize that individual genetic factors can influence the impact of saturated fat on health (6). Just because some populations may have developed adaptations does not mean that high saturated fat intake is universally healthy.

  7. Millions of years: Anatomically modern humans (Homo sapiens) have only been around for approximately 300,000 years (7). However, it is true that our human ancestors, including earlier members of the Homo genus, have been consuming animal-based foods, which contain saturated fats, for a significant portion of our evolutionary history. Again, consider the much lower caloric intake, shorter lifespans, and lifestyle activities.

The argument about consuming saturated fats for millions of years argument is flawed because it relies on the appeal to tradition fallacy, oversimplifies the relationship between diet and health, and ignores the evolving nature of scientific understanding. A more comprehensive approach to evaluating the health effects of saturated fats would consider the broader context of one's diet, lifestyle, and individual factors.


1.) Appeal to tradition fallacy: Fallacy Files: Appeal to Tradition:

2.) Evolutionary mismatch: National Center for Biotechnology Information: Evolutionary Health Promotion: A Consideration of Common Counterarguments:

3.) Incomplete understanding of diet and health: Harvard T.H. Chan School of Public Health: Fats and Cholesterol:

4.) Changing scientific understanding:

British Nutrition Foundation: Saturated fat and heart health: Where are we now?

5.) Life expectancy: Our World in Data: Life expectancy:

6.) Genetic adaptations: National Center for Biotechnology Information: Genetic Adaptation to Diet in Human Populations:

7.) Millions of years (Anatomically modern humans): Smithsonian National Museum of Natural History: Homo sapiens:



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