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In the 1950’s Ancel Keys came out with his 6 countries study and came forth with the hypothesis that eating saturated fat and cholesterol caused heart disease and that LDL cholesterol was the best indicator of someone’s risk for heart disease. Since then, the general public has been terrified of having high total and LDL cholesterol. It turns out there were many things wrong with Ancel Keys’ science and his theory. Yet, as a society, we are still stuck in this fear of having high cholesterol in our blood. I see this all the time when someone switches to a ketogenic or carnivore diet and LDL goes up, sometimes way up. Despite all the benefits people see (weight loss, more energy, decreased inflammation) they get hung up on their LDL going “too high”. It’s time to clear this up.


The first thing we need to understand is why LDL would go up on this type of diet. To me there are three mechanisms at play here. The first is that when someone switches to a ketogenic or carnivore diet they are restricting carbs completely. This will cause the body to learn to burn fatty acids (which is much more efficient for the body) and make ketones from those fatty acids, we can also burn ketones for fuel very efficiently. When the liver starts to take those fatty acids and make ketones it does so using the same pathway that is used to take fatty acids and make cholesterol molecules. So, increasing the production of ketones will also increase the production of cholesterol by default and we get higher cholesterol levels in the blood. (r)


The second mechanism is that the liver needs cholesterol just like every other tissue in the body. Since it is making so much cholesterol from the burning of fatty acids then it has less need to reuptake cholesterol from the blood and shuts off it’s receptors for cholesterol. By doing this, it leaves more cholesterol in the blood resulting in higher levels upon testing. (r)

The third mechanism is fasting. People who eat a ketogenic or carnivore diet tend to feel more satiated by their dietary choices, again this is because burning fatty acids and ketones is much more efficient and allows us to make energy that lasts us much longer. This causes those people to eat less frequently and results in periods of fasting. The significance of this is that fasting has been shown to increase LDL cholesterol in the blood by 69%. (r) This is because the act of fasting forces the body to burn fatty acids for fuel and make ketones which, as we discussed above, also results in the production of more cholesterol.


Okay, so that’s why LDL cholesterol goes up on a ketogenic or carnivore diet, even as high as 300 or 400, but should we be worried about it? Should we really freak out about it being high when our body is clearly showing us other signs of better health? Well, just looking at total or LDL cholesterol individually and out of context is not a good strategy. Instead we need to look at many other markers to see if we should be worried about it.

Generally, high LDL can be an issue if there is inflammation and insulin resistance. So, if I were looking at my own bloodwork, I would want to look for a few things along with cholesterol. If my blood work showed low triglycerides, high/normal HDL cholesterol, low hs-CRP, low insulin resistance (HOMA-IR), and low markers of oxidative stress (GGT, lipid peroxides, f2 isoprostanes, and 8-hydroxy 2-deoxyguanosine) then LDL is never going to become a problem even if it is high. Luckily, these are exactly the trends we tend to see when someone switches to a ketogenic or carnivore way of eating.

What’s more, aside from the fact that there is plenty of research suggesting no correlation to LDL cholesterol and heart disease, (r) there is plenty of evidence to suggest that high LDL is in fact a good thing. One study found that low cholesterol (below 180 mg/dl) was associated with hormonal imbalances, anxiety, depression, suicide, heart failure, stroke, kidney disease, violence, dementia, Alzheimer’s, Parkinson’s, higher infection rates, birth defects, and cancer. (r) Clearly cholesterol plays some important roles in our physiology if not having enough of it leads to these issues. Also, a study found that among elderly individuals, 92% of those who had cholesterol that was considered high lived longer and had higher quality of life. (r)


But there are two other studies that totally squash the fear of having elevated LDL, especially when all those other blood markers discussed above are where you want them to be. The first was called the Leiden 85+ study. (r) In this study the participants who had the highest cholesterol levels were also found to have the lowest mortality, lowest cancer rates, and lowest rates of infections. The second study was called the Lothian birth cohort study.(r) It showed that those with the highest cholesterol levels had the lowest rates of hypertension, stroke, and coronary artery disease, as well as higher cognitive function compared with those who had lower cholesterol levels.


I think it is time to start asking ourselves if Ancel Keys sent the medical community and the American public on a wild goose chase over LDL cholesterol. While knowing your cholesterol numbers is useful, we need to start asking ourselves if LDL cholesterol is the best marker to be looking at when it comes to risk of heart disease and heart attacks. I have discussed in other posts how important it is for heart attack prevention to be in a fat burning or ketogenic state. Therefore, along with heart rate variability and markers for oxidative stress, I believe that tracking whether you are making and burning fat and ketones for fuel or not is a much better indicator of your risk for heart disease. For the full blog on the best markers to track for heart disease prevention click here.


Stay healthy out there!


Want to learn more fascinating information about the heart? Click here to find out more about my heart course, or click here to order my book, Understanding the Heart.


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