Medscape
Batya Swift Yasgur, MA, LSW
Gerry Gajadharsingh writes:
“Modern medicine is slowly updating their advice regarding eating foods that contain cholesterol. For at least 20 years their advice was to significantly limit cholesterol containing foods, such as eggs, meat, seafood etc, as having high cholesterol is still regarded as a cardiovascular risk factor. Research that has been accumulating for at least 10 years has forced them to revise their advice. It’s not easy admitting that you are wrong!
The team in the article below reviewed 17 prospective observational studies and found that the results “have not generally supported an association between dietary cholesterol and CVD risk” and in some studies that found positive associations between dietary cholesterol and serum (blood) cholesterol, the association was attenuated after adjusting for other covariates.
Eating too much cholesterol may have adverse cardiac effects, but eating modest amounts of cholesterol-containing foods within an overall heart-healthy diet is okay, according to a new scientific advisory on dietary cholesterol and cardiovascular risk issued by the American Heart Association (AHA).
Much of the cholesterol that occurs in the body is produced by the liver, much of it ironically by the metabolism of carbohydrates not fats. Whilst we wait for more evidence to confirm if its actually cholesterol levels per se that causes an increased CVS risk or more likely inflammation (statins by the way can reduce cholesterol and can reduce inflammation) and other mechanisms, the sensible advice would be to worry less about eating foods that contain cholesterol, but also not to over consume too much saturated fat and focus more on low glycaemic load carbohydrates.”
Eating too much cholesterol may have adverse cardiac effects, but eating modest amounts of cholesterol-containing foods within an overall heart-healthy diet is okay, according to a new scientific advisory on dietary cholesterol and cardiovascular risk issued by the American Heart Association (AHA).
“We undertook writing this advisory prompted partly by the fact that the 2015 Dietary Guidelines for Americans (DGA) said that cholesterol is not a nutrient of concern because the intake of the average American was on an appropriate level,” Jo Ann Carson, PhD, RDN, professor of clinical nutrition at University of Texas Southwestern Medical Center in Dallas and chair of the AHA Science Advisory committee that developed the advisory, told theheart.org | Medscape Cardiology.
“We looked at observational studies and other studies that control variables, and although the results of the differing studies are varied for sure, when you back up and look at the big picture, it says that dietary cholesterol does matter,” she said.
“If people follow a heart-healthy dietary pattern, such as the Mediterranean or the DASH (Dietary Approaches to Stop Hypertension) diet, in which their plate is half full with fruits and vegetables that are not lathered in animal food, you will keep your dietary cholesterol in the appropriate range and comparable to what the average American is eating today,” Carson added.
The advisory was published online December 16 in the journal Circulation.
Controversial Question
Historically, the advice offered by nutrition guidelines to reduce cardiovascular disease (CVD) risk was to limit dietary cholesterol. However, contemporary guidelines for CVD risk reduction, including the 2013 AHA/ACC Lifestyle guidelines for Cardiovascular Risk Reduction and the multi-society 2018 Cholesterol Management Guidelines did not include specific limits on cholesterol consumption.
And although the 2019 ACC/AHA Guideline on the primary prevention of Cardiovascular Disease stated that “reduced amounts of cholesterol and sodium can be beneficial to decrease atherosclerotic CVD risk,” it did not suggest specific parameters. Similarly, the 2015-2020 DGA did not include limits on the amount of cholesterol that can be consumed.
The “inconsistencies in the evidence base” have led to the controversial question of whether dietary cholesterol should be a “target for CVD prevention and management,” the authors observed.
After the publication of the 2015 DGA, “some individuals started going ‘hog wild,’ eating 6 eggs per day, and we were getting questions about whether dietary cholesterol matters,” Carson recounted.
The scientific advisory committee therefore reviewed key studies as well as “methodological issues that contribute to the continued controversy on this topic, including questions on the impact of egg intake.”
Current Dietary Habits
To ascertain how much and what types of cholesterol Americans are consuming, the researchers turned to the National Health and Nutrition Examination Surveys (NHANES), which found that mean cholesterol take in US adults age 20 years or older was 293 mg/day.
The average amount of dietary cholesterol consumed by Americans is “less than 300 mg a day, but there’s a whole range of people who consume more or less than the average,” Carson noted.
Meat was the most commonly consumed source of dietary cholesterol, contributing to 42% of total cholesterol intake. Eggs were next in line, accounting for 25%, and whole grain products and full-fat dairy products contributed the remainder.
The Evidence on Eggs
The team reviewed 17 prospective observational studies and found that the results “have not generally supported an association between dietary cholesterol and CVD risk” and in some studies that found positive associations between dietary cholesterol and serum cholesterol, the association was attenuated after adjusting for other covariates.
The authors then focused on the relationship between egg intake and CVD risk, since eggs constitute a quarter of dietary cholesterol in the US, with one large egg containing 186 mg of cholesterol.
Egg consumption was not found to be associated with CVD risks overall. Findings varied, however, depending on CVD subtype, with no increased risk of stroke or coronary heart disease with higher egg consumption (except in people with type 2 diabetes), but higher risk of heart failure (HF) in men.
The authors highlight limitations in the body of evidence. Studies of dietary cholesterol “have spanned a broad time period, over which methods in nutritional epidemiology have appreciably changed.” Moreover, “variations in study populations may correspond to important differences in confounding structure.”
Interventional studies of dietary cholesterol and CVD risk have yielded “inconsistent” and “discrepant” results, also likely attributable to residual confounding, they note.
Dietary Cholesterol vs Saturated Fats
Most of the observational studies did not adjust for the type of fat being consumed, so “it can be difficult to distinguish between the independent effects of dietary cholesterol and dietary fat type,” the authors note.
Speaking to that concern, a meta-regression analysis of 55 randomized controlled dietary intervention studies (which controlled for saturated, monounsaturated, and polyunsaturated fat) identified a dose-response relationship between consumption of cholesterol and LDL cholesterol concentrations.
Conclusions based on results of these trials are problematic, however, because of relatively small sample sizes.
“It is important to bear in mind that when we include dietary cholesterol, we are also getting a lot of saturated fat,” Carson observed.
“We want people to reduce saturated fat, which is associated with more heart disease and raises LDL cholesterol,” she continued, noting that the AHA advisory “does not suggest low fat, but rather suggests healthy fats, like almonds, pecans, walnuts, and avocadoes and having corn or soybean oil in salad dressings.”
Moderation and Heart-Healthy Diets
The advisory recommends following a dietary pattern, such as the Mediterranean or DASH diets, which emphasize vegetables, fruits, whole grains, low-fat dairy products, poultry, fish, legumes, vegetable oils, and nuts and limits salt, red/processed meats, refined carbohydrates, and added sugars.
“These diets are inherently relatively low in cholesterol with typical levels similar to the current US intake,” the authors comment, adding, “Choosing plant-based protein sources will limit cholesterol intake.”
Carson recommended the US Department of Agriculture’s ChooseMyPlate as another guide to healthy eating.
Although the advisory does not provide a numerical limit on dietary cholesterol, it nevertheless recommends limiting intake of egg yolks to “current levels” — ie, “healthy individuals can include up to a whole egg or equivalent daily.” Shrimp and other shellfish are acceptable when incorporated into a heart-healthy dietary plan.
Lacto-ovo vegetarians “may include more dairy and eggs in their diets, within the context of moderation” and people with dyslipidemia, particularly those with diabetes mellitus or at risk for HF, “should be cautious in consuming foods rich in cholesterol.”
Older normocholesterolemic patients may consume up to two eggs per day, within the context of a heart-healthy dietary pattern.
“A Clear Shift”
Commenting for theheart.org | Medscape Cardiology, epidemiologist Deirdre K. Tobias, ScD, Brigham and Women’s Hospital, Boston, Massachusetts, pointed to a “clear shift in the AHA’s stance from recommending a lower-cholesterol diet and instead adopting an overall dietary pattern.”
The effect is to “remove the negative attention from specific nutrients like cholesterol, which can be misleading and confusing in practice,” stated Tobias, who is an assistant professor at Harvard Medical School and Harvard T.H. Chan School of Public Health and was not involved in authoring the advisory.
Also commenting for theheart.org | Medscape Cardiology, Marc-Andre Cornier, MD, professor of medicine in the Division of Endocrinology, Metabolism, and Diabetes, University of Colorado School of Medicine, Aurora, called the advisory “reasonable and about as evidence-based as can be recommended,” although there “certainly are still many uncertainties in this field.”
Cornier, who was not involved in the advisory, said it is important to balance “eating a heart-healthy pattern but not thinking you can ignore and eat all the dietary cholesterol possible.”
Carson, other authors of the AHA advisory, Tobias, and Cornier have disclosed no relevant financial relationships.
Circulation. Published online December 16, 2019.