A common misconception is that because ketogenic diets are high in fat, they must increase cholesterol in your body and clog your arteries. However, much of the recent research shines light on how low-carb diets can optimize your cholesterol levels and in fact improve your heart health.
Here we show the most up-to-date research on how different types of cholesterol impact the body and how the ketogenic diet can be a useful tool in maintaining a robust cardiovascular system.
Cutting through the Fat: What are Lipids and Cholesterol?
Before we can examine the research, we need to understand the roles fat, cholesterol, and carrier molecules called lipoproteins play in the body.
Fats, also known as lipids, are a diverse group of molecules with a “non-polar” characteristic that repels water. This means that you if you put a fat such as oil or grease in water they will not mix. In the human body, fats are most commonly found in the bloodstream in one of two forms.
The first is triglycerides, a fatty acid that stores energy for later use. These long molecules can be broken down into other fatty acids and glycerol to create fuel for the body. Glycerol can further be broken down into forms of glucose. Elevated levels of triglycerides in your blood can increase your risk of developing diabetes, cardiovascular illnesses, and other life-threatening diseases. [1]
The other important class of lipids in the body is a waxy substance called cholesterol. These molecules have a variety of functions in your body such as building hormones including estrogen and testosterone, maintaining the integrity of cell membranes, and aiding in the absorption of vitamins.
Your body produces all the cholesterol you need through the liver and other body cells. Cholesterol is also obtained by consuming animal-based foods such as poultry, dairy, and red meat. Typically, 75% of the body’s cholesterol is produced endogenously (internally) while the other 25% is ingested from external sources. [2]
Cholesterol is most commonly transported in the blood by molecules composed of fat and protein called lipoproteins. From least dense to most dense, they come in five forms: chylomicrons, very-low-density lipoproteins (VLDL), intermediate-density lipoproteins (IDL), low-density lipoproteins (LDL), and high-density lipoproteins (HDL). Because VLDL, LDL, and HDL cholesterol are frequently used as clinical indicators, we are going to focus on them.
It is important to emphasize that while they are often referred to as “VLDL cholesterol”, “LDL cholesterol”, and “HDL cholesterol”, these molecules themselves are not cholesterol; they are cholesterol transporters.
What is HDL Cholesterol?
HDL cholesterol is frequently known as “the good cholesterol.” In addition to transporting cholesterol around the body, HDL collects cholesterol that is not being used by cells and brings them back to the liver to be recycled or destroyed.
By doing this, HDL prevents cholesterol from accumulating and clogging arteries. Thus, elevated levels of cholesterol are integral in maintaining optimal cardiovascular health. [3] HDL is typically measured through an HDL-C test, which shows the concentration of cholesterol bound to HDL. Clinically acceptable levels of HDL cholesterol are 40-60 mg/dl and 50-60 mg/dl for women. [4] HDL levels above 60 mg/dl are ideal as they lower the risk of cardiovascular illnesses. [4]
Additionally, HDL cholesterol may have anti-inflammatory effects. A recent research study published by De Nardo et al shows that HDL may be responsible in reducing inflammatory activity by regulating immune system cells called macrophages. [5] Furthermore, epidemiological studies have noted an inverse association between levels of HDL and certain forms of cancer. [6, 7]
More research needs to be performed to investigate the source of these relationships as well as the molecular mechanisms through which HDL operates. However, there is general consensus among clinicians and scientists that HDL-cholesterol is healthy for the body and that higher levels of HDL-C are healthy for the body. [8] In fact, one study observed that every drop in HDL cholesterol by 1 mg/dL, risk of diabetes increased by 4%. [9]
A Ketogenic Diet’s Connections with Cholesterol
About 32% of men and 13% of women in the US suffer from low levels of HDL cholesterol. [10] Additionally, the majority of Americans do not have HDL cholesterol levels high enough to decrease the risk of cardiovascular illness. [10]
As chronic conditions such as diabetes and cardiovascular illness increase in prevalence worldwide, scientists have evaluated methods to increase levels of HDL cholesterol. For many years, physicians have used drugs called statins to increase HDL (and lower other forms of cholesterol).
Recently, scientists have looked at utilizing dietary interventions as cost-effective methods to optimize HDL cholesterol and prevent the onset of cardiovascular diseases. Below we document three research studies examining low-carb and ketogenic diets effects’ on HDL.
The Impact of Carbohydrate Restriction on HDL Cholesterol
In a recent meta-analysis published in the British Journal of Nutrition by Bueno et al, researchers investigated the impacts of very-low-carbohydrate ketogenic diets (VLCKD) on key metrics of cardiovascular health including HDL cholesterol.
The authors defined a VLCKD as a diet lower in 50g of carbohydrates – lower than the daily recommended grams of carb consumption clinicians recommend to diabetics. They included 13 randomized controlled studies with a total of 1,415 subjects. All studies took place for at least a full year and all subjects included were over 18 years old and had a BMI of at least 27.5 kg/m2. In each of these studies, VLCKD diets were compared to low-fat diets.
Overall, 12 studies including 1257 patients examined the impact of a VLCKD on HDL cholesterol. When assessing the data, the individuals assigned to a VLCKD achieved an average increase in HDL of 0.12 mmol/L. This was double the average increase in HDL of the low-fat dieters who achieved an average increase in HDL of 0.06 mmol/L. [11] As a result, the authors concluded that carbohydrate-restricted diets confer cardiovascular benefits because they improve levels on HDL in the body. [11]
Key Takeaways: A low-carb diet (<50g carb) is an effective method in raising HDL cholesterol when compared to traditional weight-loss diets that emphasize reducing fat intake.
Recommendation: If you need to increase levels of heart-healthy HDL cholesterol, a carbohydrate restricted diet can be an effective tool.
Long-Term Impact of Ketogenic Carbohydrate Restriction on HDL Cholesterol
In a study from 2009 by Brinkworth et al., researchers recruited 118 obese men and women and separated them into two groups for a year-long intervention study. The first group consumed a very-low-carbohydrate, high-saturated diet with 4%, 35%, and 61% energy from carbohydrates, proteins, and fats respectively.
This equates to about 20 grams of carbohydrates on a 2000 kcal diet per day – a more stringent application of carbohydrate restriction use than the meta-analysis above. The second group consumed primarily a low-fat diet with 46%, 24%, and 30% energy from respectively from carbohydrate, protein, and fat per day. Both diets contained an equal number of calories.
About 59% of participants completed the 12-month trial: 33 in the low-carb group and 36 in the low-fat group. Both groups lost similar amount of body weight and body fat. The subjects who participated in the low-fat intervention experienced an average increase in HDL cholesterol of 0.07 mmol/L from 1.36 mmol/L to 1.43 mmol/L. [12] This represents a 4.9% increase.
In contrast, the subjects who participated in the high-fat intervention experienced an average increase in HDL cholesterol of 0.30 mmol/L from 1.45 mmol/L to 1.75 mmol/L. [12] This represents a 20.6% increase – almost four times as much as that found in the low-fat diet.
Because of their findings, diets very low in carbohydrates may have cardio-protective effects compared to low fat diets.
Key Takeaways: Very low carbohydrate ketogenic diets (<20g Carbs) increase HDL levels substantially more than low fat diets do.
Recommendation: If you need to increase your HDL levels, a ketogenic diet can be a useful dietary intervention.
Carbohydrate Moderation Increases HDL in Healthy, Non-Whites
The majority of studies assessing the effects of carbohydrate restriction on HDL have been conducted on primarily Caucasian, obese subjects.
In 2006, researchers sought to investigate the relationship between carbohydrate intake and HDL cholesterol in a healthy, diverse population. Scientists examined data from Canadians of South Asian, Chinese, European, and Aboriginal origin from two cross-sectional studies conducted in the late 90s.
They included participants who were 35-75 years of age and who were not born in Canada but had lived there for at least 5 years. Subjects who suffered from moderate to severe medical conditions such as diabetes, heart diseases, and active cancer were not included. Subjects of all different weights and BMIs were included as long as they were considered healthy.
Scientists then randomly selected 619 subjects who met these inclusion criteria and examined their carbohydrate intake and levels of HDL cholesterol.
After adjusting for demographic factors such as age, sex, and ethnicity and lifestyle factors such as smoking, researchers noted that subjects in the lowest third of carbohydrate consumption had significantly higher levels of HDL cholesterol than subjects in the highest third of carbohydrate consumption.
More specifically, subjects in the lowest third of carbohydrate consumption had an HDL concentration of 1.21 mmol/L while subjects in the highest third had HDL concentration of 1.08 mmol/L. [13] According to the authors, “every 100-g/d increment of carbohydrate (approximately the difference between the top and bottom tertiles) was associated with 0.15-mmol/L less of HDL.” [13]
Fewer servings of sugary drinks were also associated with higher levels of HDL. [13] Because of their findings, the researchers attributed differences in HDL concentration to carbohydrate intake.
Key Takeaways: Lowering carbohydrate intake is an effective method to increase HDL levels in healthy, non-obese people of all different ethnicities and races.
Recommendation: If your HDL is low and you are eating a high amount of carbohydrates, lowering carbohydrates consumption can increase your HDL cholesterol back to healthy levels. You can accomplish this through a variety of low-carbohydrate diets, including the ketogenic diet.
LDL Cholesterol: Clearing the Confusion
The story behind LDL, or low-density lipoprotein, is more complicated. LDL transports cholesterol produced by your liver and cells throughout your body. Unlike HDL, LDL molecules move slowly through the bloodstream and are vulnerable to oxidizing agents known as “free radicals.” Once oxidized, LDL can easily burrow itself into the walls of your arteries (called endothelium) and impede cardiovascular function. This triggers an inflammatory response in which white blood cells called macrophages rush to eat up the LDL.
Typically known as the “bad cholesterol” to its healthy counterpart HDL cholesterol, increased levels of LDL cholesterol are associated with an increased risk of cardiovascular diseases (CVD). [14] Some studies show a strong correlation between LDL cholesterol and the risk of cardiovascular diseases in both men and women. [15] Evidence also suggests that decreasing blood levels of LDL-C reduces the risk of CVD. [16]
Recent research paints a more intricate picture of this peculiar molecule and has called into question the statement that elevated LDL cholesterol is bad for you. This is for two main reasons. First, LDL can be measured in two ways. The first is called LDL-C which measures the concentration of cholesterol transported by LDL in the blood.
The second is called LDL-P which measures the number of LDL particles in the blood. Sometimes, there is a correlation – more LDL particles means that you can have higher levels of LDL-C. However, larger LDL molecules can grow and carry more cholesterol – leading to a discordance in which LDL-C and LDL-P are not necessarily proportional. When this happens, LDL-C and LDL-P are said to be “discordant.”
For many years, LDL-C tests have been used as the primary method of measuring LDL in the blood. It is cheaper and easier to measure. Recent research has called into questioning how effective LDL-C is compared to LDL-P in precisely assessing cardiovascular risk. After reviewing cross-sectional data, a recent peer-reviewed paper from the world-renowned Framingham Heart Study stated that
“In a large community-based sample, LDL-P was a more sensitive indicator of low CVD risk than either LDL-C or non-HDL-C, suggesting a potential clinical role for LDL-P as a goal of LDL management.” [16]
Another paper produced by the Framingham Heart Study touched upon the difference of LDL-P and LDL-C as indicators.
“…the group with the highest risk for cardiovascular events had high LDL-P and LDL-C, while the group with the lowest risk had low LDL-P but higher LDL-C.” [17]
Collectively, these findings suggest that LDL particle size is a more precise indicator of future cardiovascular illness than total LDL cholesterol even when people have high levels of one but not the other. That being said, LDL-C is still a useful indicator for future cardiovascular illness and ideally you want to have both low LDL-C and LDL-P. (Click here to find optimal ranges for LDL-C and here for LDL-P)
Second, the type of LDL cholesterol you have can lead to different clinical outcomes. LDL can come in different forms – each with different effects on your health. A research study from 1988 showed that having elevated levels of small, dense LDL is three times more likely to lead to heart disease than normal LDL [18].
Thus, larger LDL particles are considered to be healthier for the body. Additionally, more recent research shows that oxidation of LDL by substances called free radicals increases the risk of cardiovascular illness [19].
Finally, there is another, more dangerous lipoprotein called very low-density lipoprotein (VLDL). Like LDL, VLDL transports cholesterol produced by the cells and liver throughout the body. However, VLDL particles also serve as the main transporters of triglycerides in the body.
Additionally, they are composed of higher lipid and lower protein content than LDL. Because of their physical properties and functional purposes, VLDL particles are more likely than other lipoproteins to clog vessels and impair vascular functions. Research studies have noted that high levels of VLDL are associated with increased risk of artherosclerosis and cardiovascular diseases. [20] VLDL is also considered to be a more precise indicator than LDL-C for a variety of metabolic conditions. [21]
Now, we went over a lot about LDL cholesterol, so let’s summarize the key points:
Low-density lipoprotein (LDL) carries cholesterol throughout the body.
The sum of the cholesterol in the body attached to cholesterol is called LDL cholesterol (LDL-C).
The number of LDL particles in the body is referred to as LDL-P.
LDL-C tests are affordable, general indicators of the risk of cardiovascular disease.
LDL-P tests are more precise indicators than LDL-C of the risk of cardiovascular disease.
Smaller, dense LDL cholesterol is more harmful than larger, higher volume LDL cholesterol.
Very-low Density Lipoprotein (VLDL) carries triglycerides and increased levels of it are strongly associated with greater cardiovascular risk.
LDL and Carbohydrate Restriction: What is the Relationship?
Let’s go back to the research assessing how the low-carb, high-fat diets such as the ketogenic diet affect your LDL levels. In the meta-analysis by Bueno et al., low-carb diets were shown to increase HDL twice as much as low-fat diets after randomized controlled interventions. It also showed that there was a small increase in LDL-C in low-carb subjects compared to low-fat diet subjects who experienced no increase.
The research study by Brinksworth et. al also showed that low-carb diets yielded greater increases in HDL cholesterol when compared to a low-fat diet.
Key Takeaways: Some research suggests that high-fat, ketogenic diets can increase LDL-C by a small amount.
Ketogenic Diet’s Impact on V-LDL Cholesterol and LDL Particle Count
Provided the research showing an increase in LDL levels in human subjects after a low-carbohydrate diet, what does the research say about extreme carbohydrate restriction on V-LDL and LDL particle count?
In a 2006 study, researchers assessed the effects of carbohydrate restriction on LDL cholesterol in a group of 29 men for a 12 week weight-loss intervention. The subjects’ ages ranged from 20-69 years their BMIs ranged from 25 kg/m2 to 30 kg/m2.
Their intervention diets consisted of 10% of energy from carbohydrates, 65% of energy from fat, and 25% of energy from protein. Assuming a 2000 kilocalorie diet, this translates to approximately 50 grams of carbohydrates daily.
After the 12 weeks intervention, researchers noted that the concentration of LDL particles decreased by 9.6% from 1180 nmol/L 1180 to 1066 nmol/L. [22] As previously mentioned, lower levels of LDL particles are beneficial to cardiovascular fitness. Additionally, the particle size of LDL increased by an average of 5.2% from 20.75 mm to 21.27 mm. [22]
Researchers also observed that the size of VLDL particle size did not change in either of the groups. However, they noted that the total number of VLDL particles decreased by 19% from 76.2 nmol/L to 61.7 nmol/L. [22] More specifically, large VLDL particles reduced by 40.2% from 3.33 nmol/L to 1.74 nmol/L, medium VLDL particles decreased by 4.8% from 46.2 nmol/L to 44 nmol/L. [22]
Because of these favorable effects on LDL particle concentration, LDL particle size, and quantity of VLDL particles, the scientists concluded that
“…weight loss induced by carb restriction favorably alters the secretion and processing of plasma lipoproteins, rendering VLDL, LDL, and HDL particles associated with decreased risk for atherosclerosis and coronary heart disease.” [22]
Another study in primarily adult, female subjects showed similarly promising results. In a randomized, parallel clinical trial, researchers recruited 119 subjects for a 6 month long intervention. The mean age of the subjects was 44.9 years, their mean BMI was 44.9 years, and 76% were women.
59 of the subjects were randomized to a low-calorie ketogenic diet which included a nutritional supplementation of borage, fish and flaxseed oil. The second group of 60 consumed a reduced-calorie diet.
After the intervention, researchers noted that the ketogenic diet group had decreased their VLDL by 78%, their medium VLDL by 60%, and their small VLDL by 57%. [23] Additionally, their large LDL had increased by 54%, medium LDL decreased by 42%, and small LDL decreased by 78%. [23] Overall, the average particle size increased by 2% and the LDL particle concentration decreased by 11%. [23]
This optimization in LDL cholesterol was less pronounced in the low fat group compared to the low-carb ketogenic diet group. It is important to mention that LCKD did not lower total LDL cholesterol. However, as mentioned previously, two studies by the Framingham Heart Study indicate that LDL-P is a stronger indicator than LDL-C. [16, 17]
In fact, one study stated that “…the group with the highest risk for cardiovascular events had high LDL-P and LDL-C, while the group with the lowest risk had low LDL-P but higher LDL-C.” [17] As a result of prior clinical research and their findings, the researchers stated that: “While the low carb, ketogenic diet did not lower total LDL cholesterol, it did result in a shift from small, dense LDL to large, buoyant LDL, which could lower cardiovascular disease risk.” [23]
From this, we can conclude that a low-carb, ketogenic diet helps you optimize your LDL cholesterol.
Key Takeaways: Low carbohydrate diets help reduce the number of LDL and VLDL particles and increase the size of LDL particles in overweight people. These all have positive effects on cardiovascular fitness.
Recommendation: If you have high levels of LDL particles and VLDL particles, consider adopting a carbohydrate-restricted diet. To optimize your LDL cholesterol levels, consider adopting a diet high in healthy monounsaturated fats.
Conclusion on a Ketogenic Diet’s Connections with Cholesterol
Cholesterol is a complicated molecule in the body that comes in many different forms – each with different clinical significance. That said, an abundant amount of research suggests that low-carb, high-fat ketogenic diets have a clinically-positive impact on each form. More specifically:
Ketogenic diets increase the concentrations of heart-healthy HDL cholesterol more than low-fat, high-carb diets. [11, 12]
Lowering carbohydrate consumption in healthy individuals also leads to higher levels of HDL cholesterol. [13]
Low-carb, high-fat diets decrease LDL particle concentration (LDL-P) and increase the size of LDL cholesterol. [22, 23]
Ketogenic diets decrease the amount of harmful VLDL cholesterol in the blood. [22, 23]
All in all, this is strong information that shows the carbohydrate restriction as emphasized in the ketogenic diet can be a healthy choice for you.
If you have high cholesterol or have been prescribed statins and are interested in transitioning to a ketogenic diet, one of the easiest ways would be to download one of our meal plans: Keto Academy “Kickstart a Healthy Lifestyle”. A simple program that you can follow along with, learn about keto, and assist you in controlling your cholesterol.
List of References
[1] Miller, Michael, et al. “Triglycerides and cardiovascular disease a scientific statement from the American Heart Association.” Circulation 123.20 (2011): 2292-2333.
[2] Johnson, Teddi Dineley. “Mind your cholesterol for a healthy heart.” The Nation’s Health 40.3 (2010): 24-24.
[3] Barter FJ, et al. Anti-inflammatory properties of HDL. Circulation Research. 2004; 95: 764-772
[4] “What Do My Cholesterol Levels Mean?” (PDF). American Heart Association. September 2007. Retrieved 14 November 2009.
[5] De Nardo D, et al. (2014) High-density lipoprotein mediates anti-inflammatory reprogramming of macrophages via the transcriptional regulator ATF3. Nature Immunology. 15,152–160
[6] Jafri, Haseeb, Alawi A. Alsheikh-Ali, and Richard H. Karas. “Baseline and on-treatment high-density lipoprotein cholesterol and the risk of cancer in randomized controlled trials of lipid-altering therapy.” Journal of the American College of Cardiology 55.25 (2010): 2846-2854.
[7] Zhao, Wenhui, et al. “HDL Cholesterol and Cancer Risk Among Patients With Type 2 Diabetes.” Diabetes care (2014): DC_140523.
[8] Barter, Philip, et al. “HDL cholesterol, very low levels of LDL cholesterol, and cardiovascular events.” New England Journal of Medicine 357.13 (2007): 1301-1310.
[9] Stern MP et al. Ann Intern Med 2002; 136:575-581
[10] Carroll MD, Kit BK, Lacher DA. Total and high-density lipoprotein cholesterol in adults: National Health and Nutrition Examination Survey, 2009–2010. NCHS data brief, no. 92. Hyattsville, MD: US Department of Health and Human Services, CDC, National Center for Health Statistics; 2012.
[11] Bueno, Nassib Bezerra, et al. “Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: a meta-analysis of randomised controlled trials.” British Journal of Nutrition 110.07 (2013): 1178-1187.
[12] Brinkworth, Grant D., et al. “Long-term effects of a very-low-carbohydrate weight loss diet compared with an isocaloric low-fat diet after 12 mo.” The American journal of clinical nutrition 90.1 (2009): 23-32.
[13] Merchant, Anwar T., et al. “Carbohydrate intake and HDL in a multiethnic population.” The American journal of clinical nutrition 85.1 (2007): 225-230.
[14] Germano, Giuseppe, et al. “European Guidelines on cardiovascular disease prevention in clinical practice (version 2012).” European Heart Journal 33 (2012): 1635-1701.
[15] Neaton, James D., et al. “Serum cholesterol level and mortality findings for men screened in the Multiple Risk Factor Intervention Trial.” Archives of internal medicine 152.7 (1992): 1490-1500.
[16] Cromwell, William C., et al. “LDL particle number and risk of future cardiovascular disease in the Framingham Offspring Study—implications for LDL management.” Journal of clinical lipidology 1.6 (2007): 583-592.
[17] Otvos, James D., et al. “Clinical implications of discordance between low-density lipoprotein cholesterol and particle number.” Journal of clinical lipidology 5.2 (2011): 105-113.
[18] Meisinger, Christa, et al. “Plasma oxidized low-density lipoprotein, a strong predictor for acute coronary heart disease events in apparently healthy, middle-aged men from the general population.” Circulation 112.5 (2005): 651-657.
[19] Parthasarathy, Sampath, et al. “Oxidized low-density lipoprotein.” Free Radicals and Antioxidant Protocols. Humana Press, 2010. 403-417.
[20] Adiels, Martin, et al. “Overproduction of very low–density lipoproteins is the hallmark of the dyslipidemia in the metabolic syndrome.” Arteriosclerosis, thrombosis, and vascular biology 28.7 (2008): 1225-1236.
[21] VanderLaan, Paul A., et al. “VLDL best predicts aortic root atherosclerosis in LDL receptor deficient mice.” Journal of lipid research 50.3 (2009): 376-385.
[22] Wood, Richard J., et al. “Carbohydrate restriction alters lipoprotein metabolism by modifying VLDL, LDL, and HDL subfraction distribution and size in overweight men.” The Journal of nutrition 136.2 (2006): 384-389.
[23] Westman, Eric C., et al. “Effect of a low-carbohydrate, ketogenic diet program compared to a low-fat diet on fasting lipoprotein subclasses.” International journal of cardiology 110.2 (2006): 212-216.
[24] Fuehrlein, Brian S., et al. “Differential metabolic effects of saturated versus polyunsaturated fats in ketogenic diets.” The Journal of Clinical Endocrinology & Metabolism 89.4 (2004): 1641-1645.
* Written in collaboration with Neel Duggal.
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