Saturated Fat Increases Cholesterol & Puts You at Risk of Heart Disease… Doesn’t it?

The Diet-Heart Hypothesis That Has Shaped Dietary Advice for Years is Being Challenged

Dan
Dan
April 24, 2019
Cholesterol, Saturated Fat & Heart Disease title image: picture of fried eggs and chips

The common wisdom that saturated fat increases cholesterol, which subsequently increases your risk of heart disease, has been fundamental in shaping the dietary advice we have received for decades. Recently, however, it has come under increasing scrutiny.

What is Cholesterol?

Cholesterol is found in every single cell in the human body and is vitally important in cell building and hormone production, among other roles. Quite simply, you cannot live without cholesterol.

One of the problems in discussing cholesterol is that the word is widely misused and misunderstood.

Even though you regularly hear of “good” and “bad” cholesterol, it is actually just one substance. While not technically a fat (it’s actually a sterol – a mix of protein and alcohol), cholesterol is fatty and insoluble in water and is therefore transported around the body in lipoproteins.

Lipoproteins come in different forms, with the best-known being low-density lipoproteins (LDL) and high-density lipoproteins (HDL). That is why you often see cholesterol referred to as LDL cholesterol (LDL-C) or HDL cholesterol (HDL-C). The cholesterol itself is the same, but its mode of transportation differs.

A common analogy is that lipoproteins are cars, cholesterol particles are the passengers, and the circulatory system is the road network.

LDL-C, generally referred to as “bad” cholesterol, is considered the main culprit for causing atherosclerosis, which is the build-up of fat on the inside of the artery walls that leads to heart disease. On the other hand, HDL-C offers protection against its low-density nemesis and is thus dubbed “good” cholesterol.

There are other types of lipoproteins, such as very low-density lipoproteins (VLDL), which carry high levels of triglycerides. When you have your total cholesterol level tested, the value represents all of the cholesterol being transported around your body in every type of lipoprotein.

The Role of Cholesterol in Heart Disease

Despite being fundamental in keeping you alive, cholesterol has a rather poor reputation, not least because of its role in the development of atherosclerosis.

Your total cholesterol level alone is not a particularly insightful metric, because you cannot have too much “good” HDL-C. So, a person with a high HDL-C to LDL-C ratio (which is good) can have the exact same total cholesterol level as someone with a higher ratio of LDL-C (which is bad).

Because HDL-C is the only form that has been shown to offer protection against heart disease, your non-HDL-C level is arguably far more insightful. It is easy to calculate, too, as it is simply your total cholesterol level minus HDL-C.

You can read a bit more about non-HDL-C here:

But even that does not tell the entire story. It seems that your risk of heart disease is determined not only by your levels of LDL-C but also the actual size of the lipoprotein particles. In the above post, we borrowed an analogy from Medical News Today:

“A bucket filled with golf balls is just as full as a same-sized bucket filled with tennis balls, but the number balls will be greater.

“Similarly, people with a higher sd-LDL (small, dense LDL) level have a greater number of particles than people with large LDL particles, even if the overall LDL-C level is the same.”

It has been shown that small, dense LDL particles (the golf balls) accelerate atherosclerosis, whereas large LDL particles (the tennis balls) do not.

Larger particles are not able to penetrate artery walls in the same way small, dense particles can, which is key in the development of heart disease.

This is supported by recent evidence that suggests the amount of “bad” cholesterol being transported is less important than the number of particles carrying it. A high LDL particle number equates to a higher risk of heart disease.

What’s more, sd-LDL appears to be more susceptible to oxidation, and oxidized LDL has been found to be a more accurate predictor of heart disease than LDL-C alone.

So, two people can have an identical amount of LDL cholesterol, but a person with a high number of small, dense particles – which are more likely to be oxidized – may well be at greater risk of heart disease than someone with fewer, larger particles.

What all this means is that cholesterol (and its role in the development of heart disease) is not as black and white as “good” and “bad.”

Similarly, the impact of the foods you eat on cholesterol levels is not as binary as has long been believed.


Other cholesterol-related content you may be interested in:
It is a commonly-held belief that a moderate helping of alcohol each day, and of red wine, in particular, can help improve your cholesterol levels. Is it true? To find out, we dived a little deeper into the vast research that has been performed on the subject. Read what we discovered here:


How Much Does Diet Effect Cholesterol & Risk of Heart Disease?

A) Saturated fat increases cholesterol levels
B) Elevated cholesterol levels increase the risk of heart disease
C) Consuming saturated therefore increases your risk of heart disease

This is known as the diet-heart hypothesis, and is perfectly logical assuming A and B are indeed true. It has helped shaped dietary advice provided by governments and health organizations for decades.

Yet, astonishingly, despite countless studies being performed at the cost of millions of dollars over the years, there is no firm evidence that consuming saturated fat actually increases your risk of heart disease. This undermines the entire hypothesis and raises serious questions about the nature of the advice being given to hundreds of millions of people.

So, what’s going on?

The Effect of Diet on Your Cholesterol

Around 75% of the cholesterol in your body is produced in your liver, with the rest coming from your food. Given the importance of cholesterol to its survival, your body keeps rather close tabs on levels and will increase or decrease production depending on how much you consume in your diet.

As such, your diet does not have as big an impact on your cholesterol levels as you may think.

That does not mean you can eat whatever you like and expect your body to maintain healthy cholesterol levels. But it does mean the diet-heart hypothesis has come under an ever-increasing level of scrutiny in recent years. Has it helped or harmed our health?

The vilification of fat (in general, not just saturated) has resulted in more sugar, refined carbohydrates, and processed foods being consumed. Heart disease is still rampant in the US; it’s responsible for one in four deaths and nearly half the adult population have a form of cardiovascular disease.

Worldwide, obesity – itself a significant risk factor for heart disease – has nearly doubled in three decades.

While other lifestyle factors such as lack of exercise and smoking must be taken into consideration, the role of dietary fat is firmly under the spotlight.

Fats: The Good, The Bad, and The Saturated

There are four main types of dietary fat:

  • Saturated
  • Polyunsaturated
  • Monounsaturated
  • Trans

Each contains nine calories per gram, making them more energy-dense than proteins and carbohydrates, each of which contain four calories per gram.

The Good: Mono- and Polyunsaturated Fats

Monounsaturated fats can be found in products such as:

  • Olive oil
  • Peanut oil
  • Canola oil
  • Sesame oil
  • Avocados
  • Nuts (almonds, peanuts, cashews, hazelnuts)

Polyunsaturated fats are found in products such as:

  • Fatty fish (salmon, tuna, mackerel, sardines)
  • Walnuts
  • Soybean oil and soymilk
  • Tofu

These fats are widely consumed in the famed Mediterranean diet, where heart disease is less common than in other parts of the world.

As mentioned, these foods are high in calories. Rather than eating them in addition to your regular diet, therefore, it is generally recommended that you replace less healthy foods with those containing unsaturated fats. For example, replacing a packet of chips with nuts, or butter with olive oil.

The two most important types of polyunsaturated fats are omega-3 and omega-6 fatty acids. Unlike cholesterol, your body does not produce these fatty acids, so it is important to get enough in your diet.

Many people actually consume too much omega-6, largely due to cooking with vegetable oils, but not enough omega-3. You can go a long way to redressing the balance by replacing vegetable oil (and corn oil, safflower oil, soybean oil, cottonseed oil) with one rich in monounsaturated fat while adding foods rich in omega-3 to your diet.

Not surprisingly, the debate about which oils are best to cook with is intense, with aspects such as smoke point (the temperature at which an oil begins to break down) being a particular bone of contention.

Adding omega-3 fatty acids to your diet is somewhat easier; it is usually a case of replacing a couple of meals a week with fatty fish. You can find a good list of foods rich in omega-3 here.

Consuming enough monounsaturated and polyunsaturated fats has regularly been linked with improved cholesterol levels and a reduced risk of heart disease. You can read more about the Mediterranean diet (and other diets that claim to be heart-healthy) here:

The Bad: Trans Fats

Although trans fats do occur in small quantities naturally, they mostly come from vegetable oil that has been partially hydrogenated in order to make them solid at room temperature and usable in food production, particularly baking.

The rise of partially-hydrogenated oils (PHOs) was, somewhat ironically, a result of vegetable oil being considered healthier than saturated fat, thus replacing ingredients such as butter.

PHOs also turned out to be tasty, made food last longer, and provided the perfect texture for products such as frozen pizzas. Not surprisingly, they became widely used in an array of products, including cakes, cookies, donuts, biscuits, and fast foods.

However, trans fats are undoubtedly unhealthy and have been conclusively linked to a drastically increased risk of heart disease. In 2015, the FDA determined PHOs as unsafe for human consumption and gave food manufacturers until June 2018 to remove them from most products. However, some manufacturers have been given until the end of 2020 to remove PHOs from certain products (for more info you can take a look at the FDA announcement here: Final Determination Regarding Partially Hydrogenated Oils

The World Health Organization has called for a worldwide ban of artificial trans fats by 2023.

The Controversial: Saturated Fats

Unsaturated fats can loosely be considered the “good” fats and trans fats can firmly be categorized as “bad” fats. It is, of course, possible to go into far more detail than that, but there is enough evidence to support those basic classifications.

So, where do the much-maligned saturated fats fall into things?

The answer, it seems, is somewhere in the middle.

Saturated fat is found predominantly in red meat, full-fat dairy products, and other animal products.

Few researchers argue that saturated fat is actually healthy, but there is a growing pile of evidence that it is not as unhealthy as has long been believed. Furthermore, cutting out certain foods that contain saturated fat may also deprive the body of healthy nutrients.

In eggs, for example, the yolk contains practically all of the saturated fat and cholesterol. However, it also contains most of the other nutrients and vitamins.

In moderation, saturated fat can form part of a healthy diet, which is reflected in the U.S. Dietary Guidelines, the 2015-2020 version of which recommends that no more than 10% of your calorie intake should come from saturated fats.

There is no strong evidence that consuming saturated fat puts you at an increased risk of heart disease. This blog post does a great job of rounding up studies that have been performed on the topic and highlighting the lack of evidence supporting the diet-heart hypothesis.

Similarly, it highlights how little evidence there is that saturated fats increase cholesterol levels in the long-term. Those that have identified a link show an increase in both “good” and “bad” cholesterol, thus keeping the ratio consistent.

What Should You Do?

Cutting fat out completely (or almost completely) is not recommended for most people, especially when it is replaced with carbohydrates. The harshest critics of this approach have linked it to the current epidemic of obesity, type 2 diabetes, and metabolic syndrome.

An opinion that seems to be gathering significant momentum from experts is that, while saturated fats can be replaced with healthier alternatives, they are not as unhealthy as they were once considered and can form part of a healthy diet. In moderation, they are unlikely to have a profoundly negative effect on your cholesterol or increase your risk of heart disease.

The next iteration of the U.S. Dietary Guidelines is due in 2020. The 2015 version was the first that omitted dietary cholesterol recommendations, reflecting the growing consensus that it is not as relevant to one’s health we have believed over the years.

Since then, the debate regarding cholesterol, saturated fat, and heart disease has continued to rumble on. It will be interesting to see how this is reflected in the guidelines when they are published next year.


While we hope this article is informative, it should not be used to guide the decisions you make regarding your diet. If you have any questions or concerns regarding your cholesterol levels, diet, risk of heart disease, please speak to your doctor or nutritionist.


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