Atherosclerotic cardiovascular disease (ASCVD) remains the leading cause of death worldwide despite advancements in prevention. Elevated blood particles, specifically lipoproteins, are a key factor in ASCVD, and measuring and treating these is crucial for preventing unnecessary deaths. Apolipoprotein B (ApoB), a protein found in lipoproteins, plays a significant role in transporting fats and cholesterol through the bloodstream. It is associated with an increased risk of cardiovascular disease (CVD). Higher ApoB levels correlate with a higher risk of CVD. Recent cardiology guidelines explicitly address ApoB, but some circles, particularly proponents of low-carbohydrate or ketogenic diets, question whether elevated ApoB is always problematic. This article explores the complex relationship between cholesterol, ApoB, the carnivore diet, and cardiovascular health, drawing on available research and expert opinions.
Understanding ApoB and Its Role in Cardiovascular Disease
Lipoproteins are protein carriers of fat and cholesterol in the bloodstream. Each ApoB-containing lipoprotein carries a single ApoB protein, either Apolipoprotein B-48 or B-100. This water-soluble protein transports fats and cholesterol, which are water-insoluble, through plasma. Types of ApoB-containing lipoproteins include chylomicrons, chylomicron remnants, VLDLs, IDLs, and LDLs.
ApoB proteins are "sticky," meaning they have a high affinity for binding with proteoglycans, a protein compound found in the walls of arteries. Observational, clinical trial, and genetic data show a direct and causal relationship between ApoB levels and cardiovascular disease (CVD). The higher the ApoB level, the higher the risk of CVD.
The Carnivore Diet: An Overview
The carnivore diet involves consuming only animal products. While it has gained popularity for its potential weight loss benefits and simplicity, it has also raised concerns about potential health risks. Some believe the carnivore diet could lead to health issues like scurvy or heart disease.
Common Myths About the Carnivore Diet
- Myth: The carnivore diet involves only eating animal products.
- Myth: The carnivore diet is inherently unhealthy.
The Impact of Low-Carbohydrate, High-Fat (LCHF) Diets on Cholesterol and ApoB
Low-carbohydrate, high-fat (LCHF) diets, including the carnivore diet, have become popular for weight loss and improving insulin sensitivity. However, lipidologists have observed cases of worsening lipid and lipoprotein parameters with these diets.
Read also: Cholesterol and Ketogenic Diets
Lipid Changes on LCHF Diets
The most consistent lipid change on LCHF diets is a decrease in triglycerides. However, changes in other lipid parameters have been variable, with an increase in LDL-C often noted. A 2009 meta-analysis comparing low-carbohydrate diets (defined as < 45 percent of calories from carbohydrates) vs. low-fat diets (<30 percent of calories from fat) for six months or more, showed that “compared with participants on low-fat diets, persons on low-carbohydrate diets experienced a slightly but statistically significantly lower reduction in total cholesterol and low-density lipoprotein cholesterol, but a greater increase in high-density lipoprotein cholesterol and a greater decrease in triglycerides." Data on lipoprotein changes with LCKD are more sparse and variable. A six-month study in children placed on a ketogenic diet for epilepsy showed a significant and persistent increase in Apolipoprotein B (ApoB).
The Mechanism Behind Increased LDL-C/ApoB
When dietary carbohydrate restriction occurs, the body switches to fatty acid (FA) catabolism for energy. Intracellularly, these FA are activated to form acyl-CoA, and then acetyl-CoA, which eventually is utilized for fuel production via the Krebs cycle. Two acetyl-CoA may combine to form acetoacetyl-CoA, which can be utilized to form mevalonic acid and, ultimately, increase cholesterol synthesis through the 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMG-CoA) pathway. Also, when ketone bodies are in excess, there is an increased production of HMG-CoA, again driving the cholesterol synthetic pathway.
Study on LCHF Diets and Cardiovascular Events
A study from the UK Biobank investigated the association between a LCHF dietary pattern, serum lipid levels, and incident major adverse cardiovascular events (MACE). The study defined a LCHF diet as consumption of <100 g and/or <25% total daily energy (TDE) intake of carbohydrates and >45% TDE fat.
The results showed that LDL-C and apolipoprotein B levels were significantly increased in the LCHF group compared to the standard diet group. After 11.8 years, a higher percentage of LCHF participants experienced a MACE. This difference remained significant after adjustment for cardiovascular risk factors.
Addressing Elevated ApoB on a Carnivore or Ketogenic Diet
If someone has elevated ApoB, what should they do? The following steps are recommended:
Read also: Lower Cholesterol with Prediabetes
- Find a diet that allows you to maintain a healthy body weight and body composition. For some people, this will be a ketogenic diet. For others, it won’t.
- Regardless of the carbohydrate composition of your diet, choose foods low in saturated fat, minimally processed, high in fiber, and plant-rich.
- If you can’t reach an optimal ApoB with diet alone, ask your doctor about pharmacotherapy with a minimum effective dose mindset. The goal is to achieve an optimal ApoB at the lowest level of medication possible.
Considerations Beyond ApoB
Dietary choices influence more than just ApoB and cardiovascular disease risk. High red meat and processed meat consumption is linked to colorectal cancer. This doesn’t mean you can never have a steak, but when studies compare those who eat the lowest amounts of red meat and those who eat the highest, and there is sufficient contrast between these levels of intake, the risk of colorectal cancer is definitely increased.
The Lean Mass Hyper-Responder (LMHR) Phenomenon
One intriguing clinical pattern from ketogenic and carnivore diets is the Lean Mass Hyper-Responder (LMHR). In LMHRs, plaque progression was predicted by baseline plaque, not by LDL or ApoB. In carbohydrate restriction, fat oxidation increases, VLDL export rises, and LDL particle numbers climb.
The Importance of Individualized Approaches
Norwitz recommends that people track their biomarkers and consider their individual cases rather than making assumptions.
Read also: Eating Low-Carb and Low-Cholesterol: A Guide