Cholesterol Guide

In this article we will cover the basics of cholesterol and why we should care about it, what to do when it is high, and address a variety of related myths and misconceptions.


We have known for a very long time that cholesterol in the blood is related to the risk of heart attacks and strokes. 

Lipoproteins come in a variety of sizes, but many of them are extremely tiny – smaller than 70 nanometers in size, or 0.00000007 meters. Particles this small can penetrate the walls of our blood vessels. When this happens, they deposit their cholesterol and this causes inflammation in the vessel wall. These collections of cholesterol and inflammation are called “plaques”. Plaques can grow over time and limit blood flow through our vessels. They can also break loose and cause sudden blood clots that stop blood flow to important organs, resulting in problems like heart attacks and strokes.

When blood cholesterol levels are high for a long time, the tiny lipoproteins have more opportunity to get into our blood vessel walls and cause problems. Heart disease risk is related to how high these levels are, but more importantly how long they are elevated over the course of your whole life. This is why many heart attacks and strokes occur in older people who have had decades of exposure to milder elevations in blood cholesterol, but it is also possible for people with extremely high levels to have these problems earlier in life too. In fact, about 40% of these events happen in people younger than 65 years.

However, risk is not “all-or-nothing”. In the same way that not everyone who smokes throughout their life will develop lung cancer, some people with higher cholesterol levels may not experience a heart attack. Regardless, the risk is still present, depending on the total levels over the entire lifespan. The earlier in life we get blood cholesterol levels under control, the lower the risk of heart disease in older age. On the other hand, waiting until old age to start treating patients for high cholesterol has a much smaller benefit, since a lot of the damage has already been done.

Blood cholesterol levels are not the only contributor to heart disease and strokes. Other things like smoking, high blood pressure, diabetes, and inflammation are very important too and will be covered in separate articles. But even when people do not have any inflammation, have normal blood pressure and blood sugar, and do not smoke, higher blood cholesterol still increases the risk of heart disease compared with lower cholesterol. Fortunately we have learned about lots of things that influence blood cholesterol levels and heart disease risk. This has led to many effective treatments and a massive decrease in heart disease deaths since the mid-20th Century.



Genetics have a major influence on blood cholesterol levels. Sometimes a variation in a single gene inherited from our parents can cause high cholesterol by itself, whereas in other situations the elevation can result from the effects of multiple different genes. A low-density lipoprotein cholesterol (LDL-C) level over 190 mg/dL raises suspicion for (although does not guarantee) a type of genetic cause known as “Familial Hypercholesterolemia.” Inherited genetic causes of high cholesterol can result in extremely high cholesterol levels from birth, but milder elevations often have genetic contributions too. These people can experience accelerated plaque development and heart disease complications even without other risk factors like inflammation, diabetes, obesity, high blood pressure, or smoking.

Since we cannot easily change our genes, people with genetically high cholesterol are typically unable to get their blood levels controlled through diet or exercise alone. This is not their fault, nor is it due to a lack of effort or willpower – it is simply the genetics they inherited. This also does not mean that people with genetic issues shouldn’t work on the lifestyle factors we will discuss next, but that these efforts may not be enough to get them all the way to a low risk level.

The risk of developing heart disease is related to how high blood levels are, and how long they are elevated over the entire lifespan. This means that it is even more important for people with genetically very high cholesterol to get it under control, since they were likely born with high levels that went undetected and untreated for many years before their first blood test, often as an adult.

For people who seem to be doing everything “right” from a lifestyle standpoint and cannot get their blood cholesterol into a low risk range, genetic issues are likely to be a major factor. Medications are typically necessary to lower the risk of disease in these situations and should be discussed with a doctor. There is ongoing research into gene-editing treatments that may provide easier long-term treatment for these issues in the future.


Diet is the most significant lifestyle behavior that affects blood cholesterol levels. There are many ways the foods we eat can influence our blood cholesterol and overall disease risk. The two main targets we will focus on for this article are fiber and the types of fat in the diet.

Eating high-fiber foods is an excellent way to lower blood cholesterol levels. We recommend all people eat at least 30 grams per day of fiber from their food. This includes sources like fruits, vegetables, legumes (like lentils, beans, and chickpeas), and whole-grain sources like oats and barley. The more fiber someone consumes, the more blood cholesterol levels tend to decrease – so if someone is willing to eat much more than 30 grams per day from their food, they are encouraged to do so. Replacing highly processed, packaged, often sugary foods with these options can have enormous health benefits beyond cholesterol too. These include lowering blood pressure, triglycerides, lowering colon cancer risk, and promoting weight loss by increasing feelings of fullness.

The other major factor is the type of fat in our habitual diet. There are many kinds of fat in our food. You may have heard of “healthy fats” and “unhealthy fats”, or seen a Nutrition Facts label listing “saturated” and “polyunsaturated” fat. These all have different chemical structures leading to unique effects on our health, and some tend to be better than others.

Consuming high amounts of saturated fat from animal food sources (such as butter, lard, and fatty red meat) tends to increase cholesterol and disease risk, particularly when saturated fat calories start to exceed 18-20% of total calories. People don’t need to track this exact quantity in their daily life, but it is worth pointing out because this is a consistent finding in the research.

Replacing a significant portion of animal-derived saturated fats with unsaturated fats from fish (like salmon), nuts (like walnuts and almonds), avocados, olive or canola oil, or other plant sources results in large decreases in blood cholesterol and disease risk. Replacing these saturated fats with high-fiber carbohydrate sources is also beneficial, but has a less potent effect than replacement with unsaturated fats from the types of foods listed above. 

The specific ways these types of fats influence blood cholesterol levels are beyond what we will address here, but we have decades of controlled feeding studies consistently showing these effects in humans.  Note that this does not mean one should never eat any animal food sources containing saturated fats. Rather, these foods should not form a large part of the habitual diet. They should be restricted more aggressively for those known to have extremely high blood cholesterol levels or known heart disease.

You may be surprised that we do not place a lot of emphasis on the total amount of fat or cholesterol in the diet. This is because these factors are less significant compared to the types of fats that are eaten on a regular basis. It is possible to consume a lower-carbohydrate, higher-fat diet without causing cholesterol or heart disease problems, if the diet still contains plenty of fiber and the fats are primarily unsaturated from fish, nuts, and other plant sources. There are some people who may need to lower their intake of cholesterol in the diet, but we recommend focusing on these more important factors first.

The same general dietary modifications are recommended for individuals with significantly high triglycerides. We often inquire about the amount of refined carbohydrates in the habitual diet (things like sugar-sweetened drinks and foods, baked goods, processed snack foods, etc.) and aim to replace these with the more healthful options described above. If an individual is carrying excess body fat (see next item below), this is another important factor to address high triglycerides as well. There are also genetic conditions that can cause high triglycerides on their own.

Body Fat

Body fat can have a significant impact on our blood cholesterol levels by interfering with liver and hormone function that is important for cholesterol regulation. We can easily determine whether we have excess body fat using a simple waist circumference measurement.

If a person has too much body fat, aiming to decrease it to healthy levels can have significant health benefits, including decreasing blood cholesterol levels. The details of weight loss strategies are beyond the scope of this article, but meeting or exceeding current physical activity guidelines is one important aspect of the process, along with changes in the overall dietary pattern. We have mentioned some of the recommended dietary changes to improve blood cholesterol above, and physical activity can also help improve general health and blood cholesterol levels in numerous other ways.

The process of decreasing body fat levels is complex and challenging for many people, since it is very heavily influenced by genetics and our surrounding environment. Some may be able to achieve healthy body fat levels relatively easily through diet and exercise alone, whereas others may need additional help with the use of medications or surgical treatments like gastric bypass surgery. It is important to reduce the stigma around obesity, and around the use of medications or surgery to treat it just like any other disease.

Decreasing waist measurements to the “healthy” range for your demographic is a strong recommendation for people with high cholesterol or other health problems related to excess body fat.

Other Medical Issues

If a person is diagnosed with high cholesterol, thyroid function should be checked since thyroid hormone plays an important role in cholesterol regulation. The thyroid is a gland in the neck that controls several essential body functions. If someone has high cholesterol levels and they are found to have low thyroid function (hypothyroidism), treating the thyroid issue can help bring the cholesterol levels back down. This is a less common scenario compared with the other issues discussed so far, as hypothyroidism is estimated to occur in approximately 1.4-13% of patients with high cholesterol, but it is simple enough that it should not be overlooked.

Finally, certain medications can also result in high cholesterol blood levels. It is worth asking your doctor if any of the prescription medications you are taking could be contributing, and whether the benefits of taking those medicines outweigh the risks for your situation. Sometimes there are alternatives without these side effects, whereas in other situations this may not be an option. Anabolic steroids often negatively influence blood cholesterol levels and are not recommended.

What to do?

For people who have low overall risk and mildly elevated blood cholesterol, focusing on the lifestyle behaviors discussed above may be enough to achieve the goal blood levels. To review, these include:

  • Replacing high intakes of animal-derived saturated fats (like butter and fatty red meats) with unsaturated fats from fish (like salmon), nuts, and other plant sources
  • Increasing dietary fiber from fruits, vegetables, legumes (like lentils), and other whole-grain sources (like oats) to a minimum of 30 grams per day, but even higher intakes provide additional benefit
  • Reducing waist circumference to a low risk range for your demographic through changes in dietary habits, regular exercise, and potentially the use of medications or surgery in consultation with a physician

We do not necessarily recommend a diet low in overall fat in this situation, instead placing more emphasis on the types of fats in the habitual diet. We also do not recommend aggressively limiting dietary cholesterol as a first intervention since this tends to have little effect on blood cholesterol levels, particularly when the types of fats in the habitual diet are improved. After making these lifestyle changes, it is reasonable to re-check a blood cholesterol test in 2-4 months.

For people with persistently high blood cholesterol (or who are otherwise at high risk), we may recommend use of medications in addition to the above lifestyle behaviors. Ultimately, the goal is to achieve the largest long-term decrease in risk of heart disease complications – and the earlier we can achieve good control of blood cholesterol, the better. Discussion of specific medications is outside the scope of this article and should be discussed with your doctor. Fortunately, there are many safe options that can effectively reduce these risks. Remember that it is OK to benefit from medicines, especially if you are at high risk. No one wins a prize for avoiding the use of medicines and living at higher risk than necessary, especially if it leads to a preventable heart attack down the road.

In addition to what has been discussed so far regarding blood cholesterol, other contributors to heart disease and stroke risk should be addressed. This includes things like blood pressure, smoking, alcohol use, and other diseases that may be present that can influence heart disease risk. The specifics of these topics are beyond the scope of this article and will be discussed elsewhere.

This should provide a general overview of what cholesterol is and why it is an important factor in heart disease. It should also provide a roadmap for things you can do about it, if yours is elevated. Cholesterol is not the only thing to worry about when it comes to heart disease risk, but high blood levels very clearly increase our risk for serious health problems. This is not unfounded advice based on outdated data. In fact, the base of scientific evidence on this topic has only strengthened over time, conclusively demonstrating that having long-term elevations in blood cholesterol is not good for us. Diet and exercise are important for reducing risk, but there are also factors like genetics that are outside of our control. As a result, medications can play a critically important role in some cases upon the advice of a physician. 

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