What is Cholesterol?

Cholesterol is an extremely important chemical in the body that serves many important functions. It is a lipid that is required to make hormones and vitamin D, help with digestion of fats (as bile), and serve numerous cell communication functions as an essential part of cell membranes. Although cholesterol is synthesized by the body, dietary cholesterol is important to help keep healthy hormone levels and perform many necessary functions. 

Blood levels of cholesterol carrier molecules are commonly viewed by physicians as a way to measure the risk for cardiovascular disease. These molecules, LDL (low-density lipoprotein) and HDL (high-density lipoprotein), package and ship cholesterol through the body to their needed destination, and their levels in the blood is what is measured when you hear the term "high cholesterol". High levels of LDL and low levels of HDL are strong risk factors for the development of atherosclerosis and cardiovascular disease. The more important number when looking at a standard lipid panel in relation to cardiovascular disease risk is the LDL/HDL ratio. A higher LDL/HDL ratio is associated with a higher risk of cardiovascular disease, while a lower ratio is associated with a lower risk. 

(Note: The particle size of these carrier molecules is also very important when assessing HDL and LDL levels as they relate to cardiovascular risk, so make sure your physician is orders a test that measures the size of these molecules during your lab tests.)

• HDL Cholesterol = Good (you want more of it)

• LDL Cholesterol = Bad (you want less of it)

• LDL/HDL Ratio = Lower ratio is better

Does Dietary Cholesterol Increase the risk of cardiovascular disease?

Contrary to popular belief, The short answer to this question is NO. The common hypothesis that dietary cholesterol leads to cardiovascular disease was developed based on poor evidence in the 1960s and recommendations to reduce dietary cholesterol intake became national guidelines. Today, scientists and health professionals recognize that this is not the case as the current evidence no longer supports this idea. In fact, these guidelines to reduce cholesterol may come with some negative health consequences because some cholesterol-rich foods (like eggs) are extremely nutritious food sources, and limiting them may not be helpful. Unfortunately the US has yet to change the guidelines on cholesterol intake to reflect the research even though many other more health-progressive countries have adapted their guidelines to not limit cholesterol intake (2). 

There is an abundance of research and epidemiological surveys showing that dietary intake of cholesterol is not related to increases in clinically significant serum cholesterol levels and cardiovascular disease risk (1).

• A recent review on data from many countries found that because dietary cholesterol intake does not affect the LDL/HDL ratio, and dietary cholesterol should not be limited as it does not negatively impact cardiovascular health (2).

• Another systematic review and meta-analysis from the American Journal of Clinical Nutrition did not find evidence to link dietary cholesterol to cardiovascular disease risk (3).

What does this mean?

There are many things that are risk factors for cardiovascular disease and cholesterol in the diet is likely not one of them. Eggs are very high in cholesterol but have been shown in many studies to not have hazardous effects on cardiovascular health (1) and should not be avoided for this reason  because they have many important benefits. 

Instead, exercising and focusing on eating whole foods is the best dietary option when trying to lower blood lipid levels. Diets with high intake vegetables and healthy fats such as fish and nuts are likely the best option for prevention and treatment of cardiovascular disease (4).