Fact-checking the firefighter analogy for cholesterol and heart disease

The firefighter analogy draws on a simple and familiar scenario: firefighters are present at a fire to help, not to cause the damage. This comparison suggests that cholesterol, like firefighters, is only present to “help” and is not the cause of heart disease.

The “real” cause of heart disease is said to lie elsewhere. Ben Azadi has suggested that inflammation is a primary cause of heart disease; Anthony Chaffee has highlighted sugar as a key factor; and Barbara O'Neill has discussed the central role of high-carbohydrate diets in heart disease.

In this article, we will detangle the links between various elements of the debate, which regularly get conflated through use of the firefighter analogy and generally through discussions on cholesterol and heart disease on social media.

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What the firefighter analogy gets right ✅, and what gets overlooked ❌

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✅ Correlation does not mean causation

‍The first point made through use of the firefighter analogy is that just because two elements are found together does not mean one causes the other. This is true, and in fact, is often the source of nutrition and health misinformation on social media.

❌ Misrepresenting the evidence

‍While it’s true that correlation does not imply causation, this argument misrepresents the evidence. Numerous studies have demonstrated a causal link between high levels of LDL-Cholesterol (often called ‘bad cholesterol’) and an increased risk of heart disease. This is because high blood cholesterol can contribute to plaque buildup, which can lead to a narrowing of arteries, decreasing blood flow to the heart.

For example, this Meta analysis included 53 Randomized Controlled Trials (RCTs), showing that for each 1mmol/L lowering in LDL-Cholesterol, there was a 15% reduced risk of cardiovascular mortality.

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✅ Cholesterol is vital

‍Let’s clarify what cholesterol is and its role in the body: “Cholesterol is a fat-like, waxy substance that helps your body make cell membranes, many hormones, and vitamin D. The cholesterol in your blood comes from two sources: the foods you eat and your liver. Your liver makes all the cholesterol your body needs.” (Source: John Hopkins Medicine)

How can something our body needs cause heart disease? This is the question that the firefighter analogy draws our attention to, where cholesterol is purely seen as a “band-aid” or a “healer.” But the question is not just about labelling substances as ‘good’ or ‘bad’; it’s also about balance.

❌ Distinguishing between cholesterol and excess cholesterol

‍Yes, cholesterol is vital. So is inflammation, our body’s response to harmful stimuli. And so is glucose as a source of energy. However, issues arise with excess, in the case of cholesterol, when there is excess cholesterol in the bloodstream, more specifically low-density lipoprotein (LDL) cholesterol.

The analogy completely overlooks the issue of excess. And as the liver produces the cholesterol our bodies need, we don’t need to consume high quantities of it. As Dr. Idrees Mughal puts it, “All of these people that preach about how important cholesterol is seem to forget that if cholesterol is high in your blood then it’s not in your cells where it needs to do the job it needs to do.”  

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✅ Dietary cholesterol has little impact on blood cholesterol

‍We've already distinguished between dietary cholesterol (found in certain foods), and blood cholesterol (the fatty substance that the blood carries). Research has shown that, contrary to previous recommendations, dietary cholesterol has little impact on blood cholesterol.

That being said, individual responsiveness can vary: “For some people, though, blood cholesterol levels rise and fall very strongly in relation to the amount of cholesterol eaten. For these ‘responders,’ avoiding cholesterol-rich foods can have a substantial effect on blood cholesterol levels.” (Source: Harvard Public School of Health. The Nutrition Source)

So, does this mean that most people can eat high amounts of cholesterol-rich foods, and not worry about it? Unlike what the firefighter analogy suggests, it’s not that simple.

❌ Misrepresenting the relationship between diet and blood cholesterol

‍The analogy overlooks the role of our overall diet, and how it might impact our blood cholesterol. "The types of fat in the diet help determine the amount of total, HDL, and LDL cholesterol in the bloodstream. The types and amount of carbohydrates in the diet also play a role. Cholesterol in food matters, too, but not nearly as much.” (Source: Harvard School of Public Health, The Nutrition Source)

Saturated fat can often coexist with cholesterol in certain foods. And a diet that is high in saturated fat, has been shown to increase levels of LDL-Cholesterol, increasing the risks of heart disease. Trans fats have also been shown not only to increase LDL- Cholesterol, but also to decrease HDL- Cholesterol, thus increasing the risk of heart disease and stroke. In fact, the detrimental effects of manufactured trans fats have led to their phasing out of the food system.

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Crucially, the firefighter analogy and the broader narrative it reinforces overlook the fact that heart disease is multi-factorial. Simplifying the issue to a single cause, or dismissing the role of cholesterol entirely, is misleading. Consider the following two ways of tackling such issues:

🟠 Oversimplifications from the broader narrative surrounding the firefighter analogy

It’s not cholesterol, it’s inflammation.

It’s not cholesterol, it’s high-carbohydrate diets.

It’s not cholesterol, it’s sugar.

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Vs.

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🟢 Evidence-based, balanced nutritional research

Alan Flanagan on Biolayne: “Enough of single-nutrient demonization. Let’s talk about diet […] Singling out sugar is misconceived. Singling out fat is simplistic. The goal for public health is to address the outstanding problem: dietary energy density in the population.’

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Let's finish by taking a closer look at the broader narrative that this analogy and discussion fit into, and at some of the evidence which often gets cited to support it.

Some discussions that downplay cholesterol's role in heart disease reference historical claims of industry influence. Anthony Chaffee, among others, has pointed to research showing that the sugar industry covertly paid off scientists in the 1960s to minimise sugar's role in heart disease while focusing blame on saturated fat. These findings are indeed troubling and illustrate how industry funding can erode trust in nutritional science. However, it remains important not to overextend these findings beyond their actual implications. While the sugar industry's tactics effectively derailed discussions about sugar's true role in disease development, we shouldn't frame the debate on diet and heart disease as a simple "either/or" scenario. Put simply, the fact that sugar's role was minimised doesn't mean we should ignore the evidence on saturated fat.

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Conclusion

The tendency to oversimplify complex issues (for example by framing them as simple either/or questions) is prevalent on social media. In particular, overly focusing on single foods or nutrients can lead us to overlook the importance of considering one's overall diet, especially when it comes to decreasing the risks of developing heart disease, which is multifactorial. Spotting these patterns can help us to better navigate the world of online nutritional information.

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Disclaimer

This article is intended as general information and is not intended as medical advice. Any health concerns or questions should be directed to health professionals.