The Dietary Guidelines Advisory Committee (DGAC) assessed the high-volume of scientific evidence to conclude that there was no appreciable relationship between the consumption of dietary cholesterol and serum (blood) cholesterol, consistent with the AHA/ACC (American Heart Association / American College of Cardiology). “Previously, the Dietary Guidelines for Americans recommended that cholesterol intake be limited to no more than 300 mg/day – an egg yolk has about 200mg. The DGAC responded that they would no longer warn people against eating high-cholesterol foods and instead focus on sugar as the main substance of dietary concern. The revised Dietary Guidelines also considered other highly ranked on the naughty list among them – salt, red meat, sugar, saturated fats and the latest darling of food-makers, Omega-3s.
The relationship between Dietary Cholesterol and/or Egg Intake on Risk for CVD was first highlighted in animal studies in 1913 where different species were fed large doses of dietary cholesterol. Interestingly rabbits had a greater level of atherosclerotic response to the same high cholesterol diet than rats. But it wasn’t until the 1940s, when heart disease was rising in the United States, that the potential dangers of a cholesterol diet for humans would come more sharply into focus. Experiments in biology, as well as other studies that followed the diets of large populations, seemed to link high cholesterol diets to heart disease. Public warnings soon followed. In 1961, the American Heart Association recommended that people reduce cholesterol consumption and eventually set a limit of 300 milligrams a day. Eventually, the idea that cholesterol is harmful so permeated the country’s consciousness that marketers advertised their foods on the basis of “no cholesterol.”
Eggs are a major source of dietary cholesterol in the typical Western diet; one large egg yolk contains approximately 200 mg of cholesterol. Saturated fat from animal origin are known to increase serum cholesterol, eggs however, are relatively low in saturated fat, but contain dietary cholesterol. Early observational studies demonstrated a link between dietary cholesterol and risk for CVD, however, these initial studies failed to account for many confounding variables that may have limited their ﬁndings, such as other dietary and lifestyle factors. More recent epidemiological studies typically show a lack of association between dietary cholesterol and/or egg intake and CVD risk in the general population.
However, the relationship between egg intake and CVD in diabetics is up for debate and remains an area of further investigations. Interestingly, this risk in diabetics may be related to the phosphatidylcholine content of eggs, and not the cholesterol since dietary cholesterol is shown to be more poorly absorbed in obese and insulin-resistant populations compared to lean individuals. Phosphatidylcholine is extremely beneficial for brain health and cell membrane integrity and a food compound otherwise known as Lecithin.
Berger et al. (2018) conducted a systematic review and meta-analysis of 17 cohort studies examining the relationship between dietary cholesterol and CVD. Dietary cholesterol intake was not found to be signiﬁcantly associated with either heart disease, ischemic stroke, or hemorrhagic stroke. Anitschkov and the other early scientists, may not have foreseen how complicated the science of cholesterol and heart disease could turn out:
- the body creates cholesterol in amounts much larger than their diet provides
- the body regulates how much is in the blood
- and that there is both “good” and “bad” cholesterol. (1)
Adding to the complexity, the way people process cholesterol differs. Scientists say some people, about 25 percent, appear to be more vulnerable to cholesterol-rich diets.
Meta-analysis findings support a shift of thinking along with many nutritionists and medical clinicians who now believe that, for healthy adults, eating foods high in cholesterol may not significantly affect the level of cholesterol in the blood or increase the risk of heart disease. Experts believe the greater danger lies not in products such as eggs, shrimp or lobster, which are high in cholesterol, but a high intake of foods heavy with saturated fats, such as fatty meats, whole milk, and butter and the increased intake in carbohydrates especially refined cereal grains, sugar and fructose.
The new view on cholesterol in food does not reverse warnings about high levels of “bad” cholesterol in the blood, which have been linked to heart disease, and some experts continue to warn people with particular health problems, such as diabetes, to continue to avoid cholesterol-rich diets.
But the change on dietary cholesterol shows how the complexity of nutrition science and the lack of definitive research can contribute to confusion for the public, while seeking guidance on what to eat, often find themselves afloat in conflicting advice. Many nutrition scientists believe lifting the cholesterol warning is long overdue, and are in agreement that eggs are a highly nutritious and valuable food.
- “These reversals in the field do make us wonder and scratch our heads,” David Allison, a public health professor at the University of Alabama, Birmingham. “But in science, change is normal and expected.”
- US cardiologist Dr Steven Nissen “It’s the right decision. We got the dietary guidelines wrong. They’ve been wrong for decades. When we eat more foods rich in this compound, our bodies make less. If we deprive ourselves of foods high in cholesterol – such as eggs, butter, and liver – our body revs up”.
- George V. Mann M.D. associate director of the long term (1948 – current) Framingham Massachusetts study, for the incidence and prevalence of cardiovascular disease (CVD) and its risk factors states – “Saturated fats and cholesterol in the diet are not the cause of coronary heart disease”.
The majority of the cholesterol in the body is produced by your liver. Your brain is primarily made up from cholesterol and it is essential for nerve cells to function.
Cholesterol is the basis for the creation of all the steroid hormones, including estrogen, testosterone, corticosteroids and vitamin D.
Our body needs 950mg of cholesterol for daily metabolism and the liver is the main producer. If the diet does not supply some cholesterol, the liver must ‘make’ more cholesterol.
What do recent clinical studies actually show as to the effect of consuming cholesterol from eggs on LDL and HDL metabolism?
Eggs have been investigated as a food associated with CVD risk, due to the cholesterol content in egg yolk. Chronic daily egg intake does increase LDL-C to a certain extent in individuals classified as hyper-responders such as diabetics or with a genetic predisposition. However, LDL-C responses are typically minimal when eggs are consumed during weight loss conditions. Egg intake shifts LDL particles to the less detrimental, large LDL subclass, and does not appear to affect the levels of oxidized LDL. Egg intake also typically increases HDL-C and the concentration of large HDL, especially with weight loss. The effect of egg intake on the LDL-C/HDL-C ratio is negligible during weight maintenance and weight loss conditions. The relationship between dietary cholesterol and/or egg intake and CVD risk in diabetics requires further investigation. However, egg intake in the context of insulin resistance and/or diabetes would not be expected to be detrimental due to changes in serum lipids, as serum lipid responses to additional dietary cholesterol are often diminished in clinical studies of insulin-resistant groups compared to leaner, more insulin-sensitive individuals. (2)
A small percentage of people appear to be more sensitive to eating dietary cholesterol than others. This means that when they eat food containing cholesterol, their LDL (bad) cholesterol levels rise more than other people. But if you don’t eat enough dietary cholesterol, your liver will make endogenous cholesterol and this is not ideal for CV health. If you want to know what your cholesterol level is and how to manage it, talk to your doctor or a clinical nutritionist.
- Berger et al (2018) Dietary cholesterol and cardiovascular disease: a systematic review and meta-analysis. Am J Clin Nutr.;102(2):276-94.
- Blesso C.N and Fernandez M.L (2018) Dietary Cholesterol, Serum Lipids, and Heart Disease: Are Eggs Working for or Against You? Department of Nutritional Sciences, University of Connecticut, Storrs, CT 06269, USA