Many believe that high-cholesterol foods are directly or indirectly associated with high blood cholesterol, a condition in which there is an increased risk of heart disease and is a leading cause of death across the globe. Let us investigate whether this dogmatic relationship of a high-cholesterol diet plan and high blood cholesterol is actually reflected in scientific literature. Does dietary cholesterol genuinely affect blood cholesterol? Read on to find out.

What is cholesterol?

Cholesterol is an incredibly important wax-like substance that circulates in your bloodstream. The major sources in diet include egg yolk, beef, pork, and poultry along with dairy products such as butter and cheese. So if you consume these items regualry, it means that you are eating a high-cholesterol diet. This is referred to as dietary cholesterol, but we also produce it in our liver, and both sources determine the liver cholesterol pool. 

Also watch: Is Cholesterol Bad?

Cholesterol is involved in vital processes. It acts as a building block for cell membranes (walls) and hormone production, (especially sex hormones). It also aids in the creation of bile that helps us digest food. So adequate cholesterol intake is indispensable for overall health and well-being. 

Cholesterol is carried in your blood as particles called lipoproteins, the two most well-known being low-density lipoprotein (LDL) and high-density lipoprotein (HDL). LDL is the ‘bad’ cholesterol associated with the formation of plaque buildup in the arteries and a higher risk of heart disease and stroke. Conversely, HDL is the ‘good’ cholesterol that acts as a sweeper, absorbing LDL and returning it to the liver where it is broken down and removed from the body.

So with this in mind, let us explore what foods affect blood cholesterol and whether we should worry about high dietary and blood cholesterol levels.

Dietary cholesterol vs blood cholesterol: What to remember

Eggs have long been demonized as a food associated with high dietary cholesterol content as they provide roughly 186.5mg per large egg, and contain high blood cholesterol levels. Although this has proven to be true in some studies, this message is more nuanced and complex than it seems. 

Some foods like full-fat milk, yogurt, cream, cheese, processed meats, and animal fats are rich in cholesterol and high in saturated fats. These items are linked with increased LDL levels and a greater risk of heart disease. On the other hand, eggs contain low amounts of saturated fat but high cholesterol. They also provide high-quality protein and are rich in micronutrients.

Also read: Is Your Protein Intake Low? How to Read the Signs

A recent study from Greece found that regular egg consumption did not increase the risk of dyslipidemia, which is high LDL and low HDL, a risk factor for heart disease when compared with no or rare egg consumption. These findings are reassuring, as eggs are a healthy food item and an integral part of any diet. Eggs offer high-nutrient density but low energy content and represent one of the best quality protein sources available. 

In support of these findings, a systematic review and meta-analysis (a standard of gold evidence) published in 2018 noted that eggs increase blood serum cholesterol. Apart from increasing total cholesterol, eggs also raise LDL and HDL levels. According to this review, the number of eggs consumed was not related to any serum lipid (fat) markers.  

It is essential to pay attention to the type of cholesterol/lipoproteins reported in the evidence. These findings illustrate the adaptability of the liver in maintaining cholesterol balance in the blood. When dietary cholesterol is adequate, the liver scales back production but kicks into gear when it is scarce.

Foods like avocados, walnuts, flax seeds, and oats that are high in unsaturated fatty acids, low in saturated fatty acids, and high in soluble fiber help reduce cholesterol (specifically LDL) in the blood. 

Health implications of dietary cholesterol

Research from the past 60 years indicates that dietary cholesterol from items like eggs has only a modest influence on the LDL cholesterol present in our blood serum. Moreover, it has a small impact on the risk of cardiovascular diseases (CVDs) when compared to other important diet and lifestyle risk factors, such as physical activity and exercise habits. 

According to a study published last year, moderate egg consumption (up to one egg per day) was not associated with increased CVD risk, and surprisingly, in Asian populations, the risk of CVD was potentially reduced. These findings are mirrored in the literature on egg consumption and mortality, with a study published in the Journal of the American Heart Association in 2020, finding no relationship between these factors in US adults. This indicates that instead of the cholesterol consumed in the diet, other nutritional and lifestyle factors such as the type of fats consumed and physical activity/exercise are more important aspects to consider for overall health.

So the key take-home message is that dietary cholesterol may influence blood cholesterol. But more influential diet and lifestyle factors determine implications for your overall health. 

References
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3. Center for Disease Control. LDL and HDL Cholesterol: “Bad” and “Good” Cholesterol. https://www.cdc.gov/cholesterol/ldl_hdl.htm (accessed Nov 8, 2021).
4. Cleveland Clinic. Cholesterol Numbers: What Do They Mean? https://my.clevelandclinic.org/health/articles/11920-cholesterol-numbers-what-do-they-mean (accessed Nov 8, 2021).
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