The common advice often heard from doctors, helpful government agencies, women's magazines and the back of your cereal box is that cholesterol causes heart disease. "Artery clogging fats" are the evil to be avoided and that everyone should monitor their blood lipids, ever vigilant against "bad" LDL. All of this comes from two outdated, disproven hypotheses: the diet-heart hypothesis and the lipid hypothesis. Both are both predicated on similar grounds: the fat in your blood causes plaque and heart disease.

Fortunately science, researchers and many cardiologists have moved on. Unfortunately most everyone else is still getting their information from the 1970's... Below is a rundown of how I understand the relationship between cholesterol, LDL and heart disease. The short version: LDL isn't "bad", eating fat doesn't raise your cholesterol and eating saturated fat is actually good for you.

Recent large scale studies have shown that for women, the higher your cholesterol is, the less likely you are to die from all causes of death, including heart disease. For men, moderately high cholesterol was also associated with a lower risk of death. Check out my blog post for more detail.

What is cholesterol, LDL, etc?

I found it difficult to really digest and understand the information about cholesterol, LDL and HDL until I learned what they really were. So often the media, blogs, etc will throw around these terms without clearly defining them. Check out Bio 101: HDL and LDL for a quick overview.

How is LDL involved with Heart Disease?

• When a cell's membrane reacts with the oxygen in your blood, the entire cell breaks down. This is oxidation.
• The by-products of oxidized LDL cause inflammation, irritating the surrounding cells. The immune system responds by cleaning up the mess and creates a plaque (like a scab) to protect the nearby cells. 1
• Plaque by itself doesn't cause too much harm, but over time plaque can build up due to continued damage from oxidized LDL particles. When this happens, the artery will become less flexible, narrower and the likelihood of the plaque breaking off is increased. If the plaque breaks off, it can cause a clot. Clots are the cause of heart attacks and strokes.
• The longer a LDL particle circulates in your blood, the greater chance that it will be oxidized.
• Small dense particles are not inherently bad but its size can be a clue that the particle is older and thus more likely to have been oxidized.
• When you have reduced LDL receptors or they aren't functioning efficiently, LDL isn't taken up by your cells very quickly and "lives longer". 2
  • Some people genetically have fewer LDL receptors. You would know already if you fell into this category.
  • LDL receptors are active when either the cell needs cholesterol or the body sends signals that food is abundant so the cell should create more sex hormones or more bile acid or more sperm, etc and generally be an active cell.
  • If you have a metabolic disorder, such as obesity, thyroid dysfunction, diabetes, etc, your cells may not respond well to these signals or your body may not be sending them at all. I believe this is one reason why heart disease is correlated with metabolic disorders. If your body isn't recycling and using LDL very often, they have extra time to oxidize and cause damage.

How does diet affect LDL?

• Saturated fats, such as butter or coconut oil, commonly raise both your LDL and your HDL.
• Diets high in carbohydrates skew your LDL to be mostly small, dense pattern B LDL. Diets high in saturated fat and low in carbohydrates cause you to have mostly large, fluffy pattern A LDL.
• Your diet affects the composition of the lipoprotein cell membrane.  The food you eat are the building blocks, so if you eat saturated fat, the membrane is made of saturated fat. If you eat unsaturated fats, then the membrane is composed of unsaturated fats.
• Saturated fats are much less vulnerable to oxidation than unsaturated fats (especially polyunsaturated fats which are the most fragile). So by eating more saturated fats than polyunsaturated, you are protecting your LDL from oxidation. Note that you make more than just LDL out of the fat you eat, so this principle applies to more than just LDL. Eating saturated fats protects your body from oxidation.
• Similarly, when you eat antioxidants, your cells can use them like armor to protect themselves from oxidation. So eating a variety of whole foods (meats, organs and vegetables) gives your body additional protection from oxidation.

Conclusions?

So my biggest question is this: Since a LCHF (low carb high fat) diet is associated with mostly pattern A LDL, does that mean that your risk of heart disease is lessened? It's not entirely clear.

One potential reason that high carbohydrate diets are associate with pattern B LDL is that it affects LDL receptors, causing LDL to live longer. Which is not good because lesser LDL receptor activity » longer LDL lifetime » increased oxidation » increased in heart disease risk.

Another idea is that these diets change the composition of your VLDL to begin with such that they quickly convert from VLDL directly to pattern B LDL, but doesn't increase the LDL lifespan. In which case maybe the difference is irrelevant and even the new more accurate lipid tests like the NMR and VAP tests (which measure LDL size) don't give you any better information than you had before, simply looking at your HDL and triglyceride ratios.

I don't have an answer though I learn towards the first theory. Here's what I takeaway from all this:

1. Eating saturated fats is better for my health and polyunsaturated or processed fats (e.g. vegetable, canola, seed and nut oils) should be limited.
2. Eating a variety of whole foods, especially organ meats, will increase my anti-oxidant intake.
3. I want my blood lipids results to look this this:
   • High HDL because it is resistant to oxidation.
   • Pattern A LDL because is less likely to have been oxidized.
   • Low triglycerides because that is an indicator that I am not badly insulin resistant.
   • LDL in a safe range because when it's extremely low/high it may be an indicator that something else is wrong.

References

Most of the information here is my understanding and regurgitation of an interview with Chris Masterjohn. After listening to the interview, I read a bit more on his website but most of it came from the first part of his interview with Chris Kresser, aka The Healthy Skeptic.

1. High Cholesterol and Heart Disease - Myth or Truth? - Chris Masterjohn
2. The Central Role of Thyroid Hormone in Governing LDL Receptor Activity and the Risk of Heart Disease - Chris Masterjohn
3. The Healthy Skeptic Podcast #11 Interview with Chis Masterjohn on Cholesterol and Heart Disease (Part 1)
4. The Healthy Skeptic Podcast #16 Interview with Chis Masterjohn on Cholesterol and Heart Disease (Part 2)

Related Topics

• Bio 101: HDL and LDL
• High Cholesterol on a Low-Carb Paleo Diet
• What if It's All Been a Big Fat Lie?
• What's Cholesterol Got to Do With It?