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Quick Summary tl;dr
The connection between elevated LDL cholesterol and heart disease remains controversial.
It seems fairly clear that those on keto and very-low-carb diets who get most of their energy from fat – including their own fat stores – tend to have more LDL particles circulating in their bloodstream, delivering triglycerides to cells and transferring cholesterol to other lipoproteins. Whether this is harmful remains to be seen.
Until we have more data on very high LDL cholesterol and LDL-P in keto and low-carb dieters, it's up to each person to decide the levels he or she is comfortable with, based on everything we know at this point.
As keto and low-carb diets have become increasingly popular, some people who follow this way of eating have noticed a sharp rise in their LDL cholesterol.
Understandably, most have become concerned, since elevated LDL is typically considered a major heart disease risk factor. However, the reason for this response - and whether it poses significant health risks – isn't completely understood or agreed upon by experts. This article takes a balanced look at the issue and its potential implications for cardiovascular disease and overall health.
What is Cholesterol and Why Do We Need It?
Cholesterol is a waxy, fat-like substance that is essential for life. It plays an important role in maintaining the integrity of your body's cells. Cholesterol is used to make hormones like vitamin D, testosterone, and estrogen. Cholesterol is also needed for the production of bile acids that help you digest fat.
Your liver, intestines, and other organs produce most of the cholesterol found in your body. In addition, it can be obtained from eating animal foods like meat, cheese, eggs, and butter.
How Is Blood Cholesterol Connected to Heart Disease?
Historically, elevated blood cholesterol levels have been linked to atherosclerosis, a condition involving deposits of plaque that cause the arterial lining to thicken and potentially impair blood flow to the heart. The process of plaque deposition is complex but involves white blood cells, calcium, cholesterol, and other substances converging at the site of inflamed or damaged arteries.
However, cholesterol doesn't travel on its own in your bloodstream. Instead, it's carried in lipoprotein particles, which contain special proteins called apoproteins, triglycerides, fat-soluble vitamins and other compounds in addition to cholesterol.
Different types of lipoproteins are formed as they move through your bloodstream and drop off or pick up triglycerides and cholesterol.
Low-density lipoprotein (LDL)
Low-density lipoprotein (LDL) particles contain Apolipoprotein B. LDLs are formed from very-low-density lipoproteins (VLDLs), which are made by your liver.
An LDL's primary function is to carry energy and nutrients through your bloodstream and deliver them to cells that need them. LDL particles provide the cells with triglycerides to use as an energy source and cholesterol to use for repair and other functions, as needed.
High-density lipoprotein (HDL)
High-density lipoprotein (HDL) particles contain Apolipoprotein A as their main protein. HDL is synthesized in your intestine and your liver.
One of HDL's main functions is to carry cholesterol back to your liver. HDL contains a higher proportion of protein to lipids than other lipoproteins. This results in a denser molecule, hence the name “high-density lipoprotein.”
LDL Particles and Heart Disease
Many experts believe that the longer LDL particles remain in the bloodstream, the more likely they are to become oxidized, enter the arterial wall, and initiate the process of atherosclerosis.
For this reason, the cholesterol in LDL particles is often referred to as “bad” cholesterol, whereas the cholesterol in HDL particles is considered “good” cholesterol. However, there is really only one type of cholesterol that is transferred among different lipoproteins.
Moreover, the extent to which elevated LDL levels contribute to cardiovascular disease (CVD) risk – particularly in individuals who follow a keto or low-carb diet – remains a topic of debate.
What Are “Normal” Lipid Values?
Traditional Lipid Profile
The following are typical reference ranges for lipid values in those without preexisting heart disease, after a water-only fast of 10-12 hours.
|
|
| Total Cholesterol |
< 200 mg/dL (5.2 mmol/L) |
| LDL Cholesterol |
< 130 mg/dL (3.4 mmol/L) |
| VLDL Cholesterol |
< 40 mg/dL (1.04 mmol/L) |
| HDL Cholesterol (Men) |
> 40 mg/dL (1.04 mmol/L) |
| HDL Cholesterol (Women) |
> 50 mg/dL (1.3 mmol/L) |
| Triglycerides |
< 150 mg/dL (1.7 mmol/L) |
Advanced Lipoprotein Values
In recent years, more advanced lipid testing known as the NMR LipoProfile has become available. Below are the values for the reference range indicative of low to moderate risk.
|
|
|
| LDL-P |
< 1300 nmol/L |
This value reflects the total number of LDL particles in your bloodstream. |
| HDL-P |
> 30.5 umol/L |
This value reflects the total number of HDL particles in your bloodstream. |
| Small LDL-P |
< 527 umol/L |
This value reflects the number of LDL particles that are small and dense. Elevated levels of small LDL-P are associated with insulin resistance and increased heart disease risk. |
| LDL Size |
> 20.5 nm |
This value reflects the size of your LDL particles. People with large, buoyant LDL are said to have Pattern A, which is typically considered less artherogenic, meaning less likely to cause plaque buildup in the arteries. than Pattern B, which is characterized by higher concentrations of small LDL. |
Cholesterol Hyper-responders: A Common Keto Phenomenon?
A person's blood cholesterol levels may increase from previous values for a number of reasons.
Temporary Elevation in LDL Cholesterol
A fairly common one is the temporary elevation in LDL cholesterol that frequently occurs during and after major weight loss ( 1). Other factors that can raise cholesterol levels include hypothyroidism, age-related hormone changes, injury, and infection.
Significantly Increased LDL Cholesterol
Finally, cholesterol levels may increase dramatically in some people who follow a keto or low-carb diet.
However, this doesn't happen in every case or even most cases. In fact, many people see little to no increase in their LDL cholesterol while experiencing beneficial changes in other markers, such as an increase in HDL cholesterol and a decrease in triglycerides, blood sugar, and insulin levels – all of which are associated with reduced risk of CVD.
By contrast, some people have seen their total, HDL and LDL cholesterol levels increase anywhere from 50% to 200% or more after switching to a low-carb or keto diet. Although a few are overweight or metabolically unhealthy, many of these individuals belong to a group that Dave Feldman at Cholesterol Code calls Lean Mass Hyper-responders (LMHRs): healthy, thin and/or athletic people with LDL cholesterol values of 200 mg/dL (5.2 mmol/L) or higher.
Over the past two years Feldman, a software engineer with a strong interest in science, has performed several dozen experiments on himself and collected data from a number of other keto and low-carb dieters whose cholesterol levels have increased far beyond the “optimal” range. However, whether this is problematic or not isn't entirely clear, especially since their other biomarkers typically improve or remain stable.
Feldman believes that his findings thus far demonstrate that the combination of higher energy demands, lower body fat stores, and lower glycogen stores in LMHRs trigger increased production of LDLs for the purpose of carrying energy (triglycerides) to cells that need them, with cholesterol mainly along for the ride but also used by the cells for repair and other purposes, as needed.
Indeed, Feldman has performed a number of experiments demonstrating that manipulating calorie and fat intake and/or carb and fat intake can dramatically increase or decrease LDL cholesterol levels in just three days.
On the other hand, most lipidologists, including Dr. Thomas Dayspring, believe that extremely high LDL cholesterol and LDL-P increase heart disease risk independently of other risk factors, as discussed in the MESA study that measured risk of coronary artery disease – the most common form of CVD – in more than 5,000 people (2).
What Are the Major Risk Factors for Heart Disease?
Although many experts believe that elevated LDL cholesterol and LDL particles are the main risk factors for developing CVD, recent and older research suggests there are others that contribute equally, if not more.
Hyperinsulinemia
Insulin has a number of important functions in the body, including storing glucose in liver and muscles and stimulating muscle protein synthesis. However, having too much insulin in the bloodstream (hyperinsulinemia) is strongly linked to CAD (3, 4, 5).
In a 1998 study looking at data from more than 2,100 middle-aged and older men, researchers reported that those with the highest fasting insulin levels were found to be at greatest risk for heart disease. What's more, this appeared to be independent of lipid values (3).
A recent 2017 study of over 2,500 adults looked at fasting insulin and high-sensitivity C-reactive protein (hs-CRP), an inflammatory marker considered a strong predictor of heart attack risk. In this study, people with the highest insulin levels were more than four times as likely to have an elevated hs-CRP value compared to those with the lowest insulin levels. By contrast, elevated LDL cholesterol levels showed no association with hs-CRP (4).
High Levels of Small LDL-P
Most lipidologists and cardiologists agree that that high numbers of small, dense LDL particles increase cardiac risk. These particles are also strongly associated with insulin resistance (5).
In a 2017 study looking at data from over 18,00 people, higher concentrations of small LDL particles were linked to increased CVD risk in people with lipid values in the normal range, as well as those already considered at high risk ( 6).
However, other observational studies suggest that higher levels of large LDL particles could potentially also be problematic – although it must be pointed out that presumably few to none of the people studied were following ketogenic or very-low-carb diets. (2, 7).
The MESA study authors concluded:
“Contrary to current opinion, both small and large LDL were significantly associated with subclinical atherosclerosis independent of each other, traditional lipids, and established risk factors, with no association between LDL size and atherosclerosis after accounting for the concentrations of the two subclasses" (2).
Subclinical atherosclerosis is the period when early changes are happening in the arteries but hallmarks of atherosclerosis like calcified plaque haven't developed to the point where the disease can be diagnosed.
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Genetics
Familial hypercholesterolemia (FH) is a condition characterized by extremely elevated total and LDL cholesterol levels, strong family history of heart disease, and fatty deposits under the skin, including the eyelids. People with FH are at very high risk of heart attack. It's a fairly common condition currently estimated to affect one out of every 150 people ( 8).
Another group at increased CVD risk are those with one or two copies of the apoE4 allele (gene). These individuals tend to have higher VLDL cholesterol but lower HDL cholesterol. In addition to heart disease, they have greater risk for Alzheimer's disease, cancer and other diseases ( 9). The Apo-E4 forums provide helpful information, guidance and support for those with the apoE4 allele.
In addition to ApoE4, researchers have have identified other genetic mutations that increase CAD risk, although less is known about them at this time ( 10).
Aging
As people get older, their risk for heart disease increases. This may be due to being less active, having other chronic diseases, and developing arterial stiffness that impairs function.
Menopause
Additionally, research suggests that during menopause, women may experience an increased thickening of the carotid intima and media layers of the arteries, a marker of subclinical atherosclerosis. In a study of 249 middle-aged women, those who were postmenopausal or in the late stages of perimenopause were much more likely to show progression of carotid intima-media thickness (CIMT) than those in early perimenopause ( 11).
Does Saturated Fat Increase LDL Cholesterol and Raise Heart Disease Risk?
The President of the American Heart Association (AHA) recently issued a statement that lowering saturated fat intake by replacing it with unsaturated fats will lower total and LDL cholesterol and decrease risk of CVD ( 12).
However, several large reviews haven't been able to establish an association between saturated fat intake and heart disease, including a 2010 meta-analysis looking at 21 studies totalling more than 340,000 people ( 13).
It's true that certain saturated fatty acids have been reported to raise LDL cholesterol levels, including palmitic, myristic and lauric acid, which make up a large portion of milk fat ( 14). On the other hand, high-fat dairy has been shown to provide several cardioprotective benefits as well ( 15).
Therefore, although avoiding all dairy fat may lower LDL cholesterol, it may not be a good strategy for protecting heart health. (You can read more about health benefits of dairy in this post: Dairy on a Ketogenic Diet).
Moreover, it appears that the LDL cholesterol response to saturated fat intake is individualized, with some people experiencing an increase and others seeing little to no change.
Is Elevated LDL Cholesterol a Concern if You Follow a Keto Diet?
Whether extremely high LDL cholesterol and elevated LDL particles increase heart disease risk in people who follow a keto lifestyle isn't known. Dave Feldman isn't entirely convinced that it's a completely benign phenomenon, although his ongoing research suggests that it may be.
The main problem is that there haven't been any long-term formal studies in this population that provide data assuring us that LDL elevations of this magnitude are safe. It's something that just can't be said with absolute certainty at this time.
In addition, although small, dense LDL particles are the type most strongly associated with heart disease risk, as mentioned earlier, there are some observational studies suggesting that high concentrations of large LDL particles may also increase CVD risk. However, the subjects' diets weren't included when risk factors were assessed.
On the other hand, higher HDL cholesterol levels have been linked to less carotid artery intima-media thickness. In a large meta-analysis of data from more than 20,000 people, CIMT tended to decrease as HDL cholesterol increased – regardless of LDL cholesterol values ( 16). Importantly, although LDL response to carb restriction varies from person to person, HDL virtually always increases.
What's more, insulin-resistant people who follow very-low-carb or ketogenic diets often show more favorable reductions in insulin levels, inflammation, and arterial dysfunction compared to those on “heart-healthy” low-fat diets ( 17, 18).
Overall, the many cardiovascular health benefits of very-low-carb diets for metabolically compromised individuals are impressive. In addition, Lean Mass Hyper-responders often report feeling better and having more sustained energy as a result of following a keto lifestyle.
How to Reduce Cardiovascular Risk While Remaining Keto or Low-Carb
If your LDL cholesterol has significantly increased on a keto or low-carb diet, it's completely understandable if you're at least somewhat concerned. However, you might be reluctant to make any changes to your diet given the benefits you've experienced. On the other hand, you may decide that you want to try to lower your LDL values while still following a keto/low-carb lifestyle.
Here are some tips that may help manage cardiovascular risk, including potentially lowering LDL. However, keep in mind that the effects may vary from person to person, and your LDL may not change much.
Eat More Fatty Fish
Although the long-chain omega-3 fatty acids found in fish typically reduce triglycerides more than LDL cholesterol, they're anti-inflammatory and may help protect against heart attacks ( 19).
Fish highest in omega-3 fats include salmon, sardines, mackerel, herring, and anchovies.
Increase Fiber Intake
Fiber, especially the soluble type, may be beneficial for heart health. It's been shown to help lower cholesterol levels, yet it doesn't seem to interfere with the absorption of fat-soluble vitamins and other nutrients ( 20).
Excellent keto-friendly sources of soluble fiber include avocado, blackberries, broccoli, brussels sprouts, and flaxseed.
Increase Net Carb Intake
Dave Feldman recently demonstrated that increasing net carb intake from 30 grams to 95 grams per day – (going from 4% of total calories to 13% of total calories) led to a significant drop in his LDL cholesterol level. Obviously, this level of carb intake isn't ketogenic; however, it is still moderately low carb. On the other hand, this will likely increase your blood sugar and insulin levels to some extent.
Eating about 50-60 grams of net carb daily (15-20 grams per meal) may be enough to help lower LDL without jeopardizing blood sugar and insulin stability.
Consume Fat-Soluble Antioxidants
Getting plenty of antioxidants in your diet like vitamin E and the phytochemicals lycopene and beta carotene may help protect your LDL cholesterol from becoming oxidized, thereby reducing CAD risk (21).
Leafy greens, almonds, sunflower seeds, hazelnuts, tomatoes, avocado, and red peppers are good sources that meet keto criteria.
Get a CAC or CIMT test
Having a coronary artery calcium (CAC) scan or CIMT test can provide information about actual heart disease that lab tests can't. Some people with extremely high levels of LDL cholesterol have calcium scores showing no plaque accumulation in the arteries and normal intima-media thickness, whereas others demonstrate mild to moderate atherosclerosis even when LDL cholesterol is within the normal range.
A zero CAC score is typically associated with very low risk of heart attack or other adverse cardiac event within 10 years (22).
However, some experts like Dr. Dayspring believe CAC scores are only meaningful in middle-aged and older adults. On the other hand, CIMT evaluation can identify early signs of heart disease in young to middle-aged people, including those with zero CAC scores ( 23).
Recommended Reading and Viewing
In addition to Dave Feldman's posts linked to earlier, there are several other articles and videos discussing diet, lipids, and cardiovascular risk. Here are just a few:
Articles and Websites
Videos
My Own Experience with the Cholesterol Drop Protocol
To date, more than 50 people have successfully completed Dave Feldman's Cholesterol Drop Protocol, which consists of 3.5-10.5 days of keto/LCHF eating and 1-4 blood tests. I've done the 6.5-day experiment twice, once in early May and again in mid-September of this year.
Although 86% of people who have undergone the protocol have experienced a decrease in LDL cholesterol after ramping up their calorie and fat intake for three days, my own LDL cholesterol increased, the first time by 47 mg/dL and the second time by 15 mg/dL. At this point, I'm the only one who had both an increase in LDL and a decrease in triglycerides after the high-fat, high-calorie portion of the experiment. All of my other markers, including HDL and small LDL particle counts, were excellent for both the low-calorie and high-calorie days.
For reference, I'm a Lean Mass Hyper-responder and have been following a low-carb diet for more than 6 years. My net carb intake typically ranges from 20-40 grams per day, and I remained at the lower end of this range during the experiment.
If you follow a keto or low-carb diet, please consider doing the Cholesterol Drop Protocol – especially if your lab results indicate you're a hyper-responder. Be sure to keep detailed food records and share all data back to Dave Feldman on his website at Cholesterol Code.
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