Low-Carb Lesson – What Is Cholesterol? Is it all bad?

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what is cholesterol

This is not intended as medical advice and is not meant to replicate advice from your regular medical practitioner. In today’s low-carb interview, we discuss the physiology of cholesterol and all the roles that it plays within our body.

If you wish to find a low-carb doctor – CLICK HERE.

Today’s low-carb lesson – What is cholesterol? Is it all bad?

We have all heard the terms good cholesterol, bad cholesterol, triglycerides and particle sizes, but what does it all mean?

Today we clarify these terms and chat about cholesterol and how vital it is to our health and wellbeing.

What Is Cholesterol? Is it all bad?

Today we discuss:

  • Why is cholesterol so vital to our health and well being?
  • What are lipoproteins?
  • What are HDL and LDL – are they good or bad?
  • How important are particle sizes?
  • What are triglycerides?
  • Is cholesterol actually an anti-inflammatory?
  • What are the risks of low-cholesterol?
  • Who benefits from statins?
  • Conclusion and what lipid panel should you ask from your doctor?

NOTE: There is a list of references at the end of this post for further reading.

What Is The Cholesterol Debate?

For decades we have been told that dietary cholesterol in food raises our blood cholesterol and raised blood cholesterol causes heart disease. But this is old and outdated science.

High blood cholesterol was thought to be a major risk factor for heart disease. This failed hypothesis is based on flawed and outdated research from 50 years ago. 

I was once told by a GP, if you are talking about good and bad cholesterol you’re 20 years out of date, if you’re talking about LDL still being an issue, you’re only 10 years out of date“.

The latest science heavily disputes the hypothesis that raised cholesterol causes heart disease, in fact, low cholesterol has been shown to have numerous detrimental effects, yet cholesterol is never spoken about in a positive light.

Most reports in the media, automatically link the terms cholesterol and heart disease together as if they are all one long word!

If you are talking about good and bad cholesterol you’re 20 years out of date, if you’re talking about LDL still being an issue, you’re only 10 years out of date. Click to Tweet

Why is cholesterol so vital?

Cholesterol is so vital that our body is able to make (synthesise) the majority of what we require, only a small percentage actually comes from dietary cholesterol. 

A lower intake from our food leads to increased cholesterol synthesis. And the converse is also true.

Cholesterol is required for numerous functions –

  • Cholesterol is the basis of our sex hormones, steroid hormones, cortisol, oestrogen, and testosterone for example
  • It is required for the synthesis of bile acid and Vitamin D (which is actually a hormone)
  • Our cell membranes rely on cholesterol for both rigidity and fluidity
  • Cholesterol is vital to normal brain function including learning and memory

What are lipoproteins?

We often talk about cholesterol, but it’s actually the lipoproteins that carry the cholesterol (the carriers) that we test. Cholesterol is a waxy substance that cannot be carried on the blood (a watery environment).

Cholesterol and triglycerides are lipids (fats) so cannot be transported through water-soluble areas such as blood, alone. They are packaged into a lipoprotein carrier. These lipoproteins carriers have a hydrophobic core and a hydrophilic outer membrane (figure below, image credit).

what is cholesterol - lipoprotein

These lipoproteins are categorised into various types according to size and composition. (figure below).

what is cholesterol and lipoproteins

Lipoproteins (the carriers) also transport a wide variety of hydrophobic compounds, nutrients and fat-soluble vitamins.

Different lipoproteins carry cholesterol but only ‘cholesterol is cholesterol’

Is there really good and bad cholesterol (carrier)?

Good and bad cholesterol are outdated terms. Some are more strongly associated with cardiovascular disease but remember from our Busting The Top 5 Nutrition Headlines lesson, association does not mean causation.

It’s like saying at every house fire there is always firemen. Do the firemen cause the house fires? No, they are just associated with house fires.

Are HDL and LDL good or bad?

HDL (high-density lipoproteins) was previously referred to as the “good” cholesterol. LDL (low-density lipoproteins) was previously referred to as the “bad” cholesterol. LDL particle size can range from 5 nm all the way up to 80nm.  But to refer to good and bad cholesterol is outdated and doesn’t reflect the true picture of heart health and all the numerous factors that are involved. 

LDL is very dynamic on a day to day basis. It changes immensely with fasting or feeding. When you fast, LDL can rise, and when eating a high-fat diet, LDL can drop. 

LDL may be associated with heart disease, but does it cause it? Possibly not. It may be hinting at its involvement in the disease process, not the causation. There are populations and ages where higher LDL is associated with lower CVD mortality. But the TG/HDL ratio remains predictive independent of LDL.

These ideas and terminology of good or bad cholesterol, stem from the lipid hypothesis which is a static picture, but in fact, cholesterol is incredibly reactive and fluctuates day to day, meal to meal. So when we test and see numbers rise or fall, it is difficult to know whether these numbers are coming or going. So testing must be reviewed for each patient “in context”.

Further reading/watching: Dave Feldman – The Dynamic Influence of a High Fat Diet on Cholesterol Variability – CLICK HERE to watch.
Image credits: Dave Feldman

How important are particle sizes?

In your arteries it is the endothelium that is in contact with the blood, under pressure, small particle sizes may possibly infiltrate easier than larger particles. BUT the hypothesis cannot explain that HDL is even a smaller particle and does not have the same association nor do you find a gradient of particle sizes in arteries when autopsies are carried out.

To believe in the cholesterol/lipoprotein theory of heart disease, and invading via the vascular endothelium, you need to wave a magic wand?‍ Lipoproteins cannot jump a 200 uM gap all the way to the intima-media junction.

What are triglycerides?

Triglycerides are a good reflection of your carbohydrate tolerance and carbohydrate intake. Clinicians often use triglycerides as a way to check ‘carb-creep’ due to triglycerides being very sensitive to carb intake.

The triglyceride/HDL ratio is a wonderful estimation of insulin resistance and heart disease.Click to Tweet

Levels can quite often drop dramatically over just s few days with the reduction of sugar and carbs from the diet. it is encouraging for patients to see such an immediate improvement.

Infections can also cause a transient rise “hypertriglyceridemia of infection” (probably via increased VLDL recruitment – see below).

The triglyceride/HDL ratio is a wonderful estimation of insulin resistance and heart disease.

Is cholesterol actually an anti-inflammatory?

Plaque formation is now recognized as an inflammatory process. There are many causes of inflammation and increased heart disease risk including smoking, stress, sugar and highly processed food. The most potent indicator of heart disease risk is insulin resistance, metabolic syndrome and hyperinsulinemia.

The hypothesis is that LDL may be one way we keep our own cells safe during times where levels of reactive oxygen species need to be higher for our own protection (it scavenges free-radicals).

Cholesterol plays an important part in our immune response, could this be why cholesterol is part of plaque formation? It is unclear.

What are the risks of low cholesterol?

As discussed, cholesterol is vital to our health and wellbeing. From infection control, memory, hormone production, libido and cell rigidity and fluidity. Cholesterol should stop being seen in a negative light and the dangers of low-cholesterol are not widely discussed.

Cholesterol is vital for memory, learning and brain function. Better memory and thinking are seen in over 85s despite high cholesterol. Declining cholesterol levels from midlife to late-life may better predict the onset of Alzheimer’s disease.

Cholesterol is vital for memory, learning and brain function. Better memory and thinking are seen in over 85s with high cholesterol.Click to Tweet

Cholesterol appears to protect us from acute infections (sepsis). For example, LDL prevents the virus that causes the common cold from entering through the LDL receptor and VLDL prevents the invasion of Malaria into the liver via the VLDL receptor.

The older you are, the associations suggest ‘the higher the better’ and you want to ensure your lipid ratios are correct. 

Statins – who benefits?

Conventional thinking is that statins are a wonder drug, they have saved millions of lives and are especially effective in secondary prevention for people who have already had a heart attack. BUT is this correct?

In the BMJ, they looked at 6 studies for primary prevention (those who have not had a cardiovascular event) and secondary prevention (those who had already had a cardiovascular event). They discovered:

  • Primary prevention – people died 5 days earlier or lived 19 days longer. The median increase in life expectancy = 3.2 days
  • Secondary prevention – people died 10 days earlier or lived 27 days longer. The median increase in life expectancy = 4.1 days

How much will a statin add to your life expectancy? It’s not what you think. Click to Tweet

The decision of whether to commence statin treatment should be a joint decision between yourself and your medical practitioner. Ultimately it is your decision to make and you must weigh up the possible benefit versus the side effects such as Type 2 diabetes and memory loss.  

Further reading/watching: Malcolm Kendrick

Cholesterol – the conclusion

Top 3 Takeaways

  1. One single blood test should not be used for a lifetime of medication.
  2. Always do your own research. The decision whether to address a lipid panel, by drugs or by diet, should be done by mutual consent between you and your physician.
  3. A variety of blood tests, rather than one single test alone will give you a broader picture of your health.

Tests that reflect inflammation and metabolism are a better indicator of health and you must look at their TRENDS over time. Cholesterol testing is dynamic, not static and the numbers can be affected dramatically whether you have been fasting for too long, whether you have an infection, whether you live LCHF or the Standard American Diet (SAD) and stress, just to name a few. A test on Tuesday may be completely different than the same test taken on Friday depending on what you ate and how you slept.

Cholesterol alone does not give you a big enough picture. How is your blood pressure? HBA1C? Triglycerides? Inflammatory markers? Kidney function? Liver function? TG/HDL ratio? How do you look and feel?

If your HDL is high and your triglycerides are low, then this is an indicator of a strong metabolic status. Additional blood tests should be taken to confirm there aren’t any other bad indicators such as inflammation.

Raphi Sirtoli

How to be a ketogenic athlete. What to eat? How to train? Can you build muscle on keto diet? #ketoathlete #ketoexercise #lowcarbexercise #ketoworkout #ketofuel

Raphi Sirtoli can be found:

Dave Feldman, as mentioned in our interview for the cholesterol code and the Feldman protocol. Website: CLICK HERE

You may also watch another low-carb lesson with myself and Raphi, “How to calculate macros. What are the insulin index and keto score?” CLICK HERE.


If you are new here and would like to learn how to start low-carb, take a look at this page for beginners.

There are all the resources you’ll ever need to learn how to start a low-carb diet or how to start a keto diet.

How to start a low-carb diet - all the resources you'll ever need. #ditchthecarbs #lowcarb #keto #howtostartlowcarb #howtostartketo

Further reading and references:

what is cholesterol