Cardio­metabolic Health

Cardiometabolic health is a relatively new term that encompasses cardiovascular and metabolic diseases, including type 2 diabetes and metabolic syndrome. Collectively, such conditions are the leading cause of preventable death worldwide. They all share similar risk factors (e.g., overweight/obesity, elevated blood pressure) which can be modified by diet and lifestyle choices. The available evidence indicates that eggs, when consumed as part of an overall healthy diet pattern, do not affect risk factors for cardiometabolic disease. Recent recommendations from the American Heart Association, American College of Cardiology and American Diabetes Association do not limit egg or cholesterol intake, a change from earlier guidance from these organizations. In fact, several global health organizations, including Health Canada, the Canadian Heart and Stroke Foundation, the Australian Heart Foundation and the Irish Heart Foundation, promote eggs as part of a heart-healthy diet.

Given the public health significance of understanding cardiometabolic diseases, research on risk reduction remains an active area of pursuit. For example:

  • A randomized controlled study in people with metabolic syndrome showed that those consuming three whole eggs per day as part of a reduced carbohydrate diet experienced favorable changes in HDL-cholesterol, insulin sensitivity, and other aspects of the lipoprotein lipid profile
  • A randomized controlled weight loss trial in people with diagnosed type 2 diabetes showed improved lipid and glucose markers following consumption of 2 eggs per day for 12 weeks.
  • An egg-based breakfast, rich in protein (35% energy; 26.1 g egg protein), promoted glycemic control in people with type 2 diabetes and pre-diabetes relative to a high-carbohydrate breakfast.

New Harvard Study: Eggs Not Associated with Cardiovascular Risk

According to New Harvard Study: An Egg a Day Not Associated with Cardiovascular Disease Risk

By: Mickey Rubin, PhD

Mounting evidence continues to support the role of eggs in a heart-healthy diet. A new Harvard study updates findings first published over 20 years ago, and reinforces that eating eggs is not associated with cardiovascular disease.

The latest study is a follow-up to a landmark investigation first published in 1999. The original study, led by Hu and colleagues from the Harvard School of Public Health, reported no relationship between egg intake and coronary heart disease or stroke in women from the Nurses’ Health Study (NHS) cohort and men from the Health Professionals Follow-Up Study (HPFS) cohort. At that time the researchers concluded that an egg a day did not impact heart disease or stroke risk.

The current study is an updated analysis of the study published in 1999 and includes up to 24 additional years of follow-up and extends the analysis to the younger cohort of Nurses’ Health Study II. Thus, this latest analysis included 83,349 women from NHS; 90,214 women from NHS II; and 42,055 men from HPFS. Additionally, to compare these new findings to the extensive literature base on the topic of egg intake and cardiovascular risk, the researchers performed a systematic review and meta-analysis of 27 other published studies from the U.S., Europe, and Asia.

Results from the updated analysis from NHS, NHS II, HPFS, as well as the updated meta-analysis of global cohorts are consistent:

  • Egg consumption of one egg per day on average is not associated with cardiovascular disease risk overall
    • Results were similar for coronary heart disease and stroke
  • Egg consumption seems to be associated with a slightly lower cardiovascular disease risk among Asian cohorts

An important strength of this study is the use of repeated dietary assessments over the course of several decades in contrast to some observational cohorts which utilize only a single dietary measure at enrollment. According to the authors, it is desirable to have repeated dietary assessments over time to account for variation of dietary intake and other factors that contribute to atherosclerosis.

This latest study makes a significant contribution to the scientific literature on egg intake and cardiovascular health. These results are also consistent with the 2015 Dietary Guidelines recommendation that cholesterol is no longer a nutrient of concern for Americans and guidelines published in a science advisory from the American Heart Association in 2019.

Eggs are a good or excellent source of eight essential nutrients including choline and lutein, nutrients important for brain and memory development along with long-term health. Eggs can be an important part of all healthy eating plans.

Are eggs only for healthy people?

New study sheds light on role of eggs in the diets of individuals with vascular disease

By: Mickey Rubin, PhD

In late 2019, the American Heart Association (AHA) Nutrition Committee published a science advisory in which the authors state that “a recommendation that gives a specific dietary cholesterol target within the context of food-based advice is challenging for clinicians and consumers to implement; hence, guidance focused on dietary patterns is more likely to improve diet quality and to promote cardiovascular health.”1 The science advisory recommends heart-healthy eating patterns such as the Mediterranean-style and DASH (Dietary Approaches to Stop Hypertension)–style diets. Specifically, regarding eggs, the advisory concluded:

  • Healthy individuals can include up to a whole egg daily in heart health dietary patterns.
  • For older healthy individuals, given the nutritional benefits and convenience of eggs, consumption of up to 2 eggs per day is acceptable within the context of a heart-healthy dietary pattern.
  • Vegetarians who do not consume meat-based cholesterol-containing foods may include more eggs in their diets within the context of moderation.

The AHA science advisory was clear that these recommendations were specific to otherwise healthy individuals, and that individuals “with dyslipidemia, particularly those with diabetes mellitus or at risk for heart failure, should be cautious in consuming foods rich in cholesterol.” Perhaps one reason for the cautious approach with this population is the lack of research on the association between egg intake and cardiovascular events in individuals with a history of cardiovascular disease, but a new study begins to shed some light on this very question.

The latest study, published in the American Journal of Clinical Nutrition assessed the association of egg consumption with blood lipids, cardiovascular disease, and mortality in 3 large international cohorts.2 In one cohort, the Prospective Urban Rural Epidemiology (PURE) study, egg consumption was assessed in 146,011 individuals from 21 countries. The researchers also studied 31,544 patients with vascular disease in 2 multinational studies: ONTARGET and TRANSCEND, both of which were originally designed to test treatments for hypertension.

The findings from the PURE cohort reinforced the 2019 AHA recommendations, finding no link between egg consumption and cardiovascular disease outcomes. In fact, in the PURE cohort, researchers found that higher egg intake was associated with a lower risk of myocardial infarction, a finding that is consistent with other recent studies of cohorts outside the U.S. 3,4 In the ONTARGET and TRANSCEND cohorts of individuals with vascular disease, the researchers also reported no link between egg consumption and cardiovascular events.

Thus, this latest paper both reinforces previous research regarding egg consumption in otherwise healthy individuals, but takes a big step forward in our understanding of this relationship in individuals with vascular disease.

References

  1. Carson JAS, Lichtenstein AH, Anderson CAM, Appel LJ, Kris-Etherton PM, Meyer KA, Petersen K, Polonsky T, Van Horn L; on behalf of the American Heart Association Nutrition Committee of the Council on Lifestyle and Cardiometabolic Health; Council on Arteriosclerosis, Thrombosis and Vascular Biology; Council on Cardiovascular and Stroke Nursing; Council on Clinical Cardiology; Council on Peripheral Vascular Disease; and Stroke Council. Dietary cholesterol and cardiovascular risk: a science advisory from the American Heart Association. Circulation. 2019;140: e-pub ahead of print.
  2. Dehghan et al., Association of egg intake with blood lipids, cardiovascular disease, and mortality in 177,000 people in 50 countries. Am J Clin Nutr, 2020. E-pub ahead of print.
  3. Key, T.J., et al., Consumption of Meat, Fish, Dairy Products, Eggs and Risk of Ischemic Heart Disease: A Prospective Study of 7198 Incident Cases Among 409,885 Participants in the Pan-European EPIC Cohort. Circulation, 2019. 18;139(25):2835-2845.
  4. Qin, et al. Associations of egg consumption with cardiovascular disease in a cohort study of 0.5 million Chinese adults. Heart 2018;104(21):1756–63

When consumed as part of a heart-healthy diet, Egg Consumption is Not of Concern, According to 2019 Guidelines

Eggs can be a part of heart-healthy diet patterns

By: Mickey Rubin, PhD

The 2015 Dietary Guidelines Advisory Committee (DGAC) made both history and headlines when dietary cholesterol was removed from the list of nutrients of public health concern.1 Up until this point, there had historically been a limit of 300 milligrams per day for dietary cholesterol, even though eggs were listed as a nutrient-rich food and part of healthy dietary patterns in previous guidelines.2

In making the decision to not bring a cholesterol limit forward for recommendations, the 2015 DGA committee referenced, among other sources, a 2013 systematic review that examined the relationship between egg consumption and cardiovascular disease in almost 350,000 participants across 16 studies.3 The review and meta-analysis found no relationship between egg intake and cardiovascular disease, ischemic heart disease, or stroke.

Since 2015, the science evaluating the relationship between dietary cholesterol, eggs, and cardiovascular health has continued to grow. One observational study of U.S. cohorts published early in 2019 found a small but statistically significant increase in cardiovascular risk with egg consumption. 4 However, another observational study analyzing data from over 400,000 men and women in Europe for over an average of 12 years, found a small but statistically significant decrease in risk for ischemic heart disease with egg intake.5

It is important to note that observational studies examining eggs are likely confounded by other dietary components, thus it is important to also examine results from randomized controlled trials.6 These trials consistently show only modest effects, if any, of egg intake on cardiovascular risk factors.6 In some cases, eggs show a significant benefit, as was the case with another 2019 study that reported improved function of high-density lipoproteins (HDL) after an intervention that included approximately 2 whole eggs per day.7

In 2019 two global health organizations re-assessed the science since the 2015 DGA and provided new recommendations around dietary cholesterol, eggs, and heart-healthy diet patterns that both build on previous findings and provide some helpful details.

First, the Australian Heart Foundation (AHF) made international headlines in 2019 with a new position statement on eggs and cardiovascular health.8 The AHF summary concluded there is no evidence to suggest any limit on egg consumption for normal, healthy individuals. The review does suggest a limit to fewer than 7 eggs per week for those with type 2 diabetes or cardiovascular disease that require LDL cholesterol-lowering interventions. However, these AHF guidelines were clearly a step forward in acknowledging the scientific evidence that shows eggs can be part of a heart-healthy eating pattern when consumed with fruits, vegetables, whole grains, nuts, legumes, and other lean proteins.

Additionally, in late 2019, the American Heart Association (AHA) Nutrition Committee published a science advisory on Dietary Cholesterol and Cardiovascular Risk.6 According to the authors, “the elimination of specific dietary cholesterol target recommendations in recent guidelines has raised questions about its role with respect to cardiovascular disease.” This review examined evidence from observational cohorts and randomized controlled trials and concluded that “a recommendation that gives a specific dietary cholesterol target within the context of food-based advice is challenging for clinicians and consumers to implement; hence, guidance focused on dietary patterns is more likely to improve diet quality and to promote cardiovascular health.” The science advisory recommends that within the context of heart-healthy eating patterns, such as the Mediterranean-style and DASH (Dietary Approaches to Stop Hypertension)–style diets, replacing saturated fats is expected to produce greater reductions in LDL cholesterol concentrations than reducing dietary cholesterol alone. Specifically, the advisory concluded:

  • To achieve healthy dietary patterns, consumers are advised to eat a dietary pattern characterized by fruits, vegetables, whole grains, low-fat or fat-free dairy products, lean protein sources, nuts, seeds, and vegetable oils, consistent with those recommended in the 2015 to 2020 DGA.
  • Healthy individuals can include up to a whole egg daily in heart-healthy dietary patterns.
  • For older healthy individuals, given the nutritional benefits and convenience of eggs, consumption of up to 2 eggs per day is acceptable within the context of a heart-healthy dietary pattern.
  • Vegetarians who do not consume meat-based cholesterol-containing foods may include more eggs in their diets within the context of moderation.

The release of these new guidelines in 2019 from leading health organizations demonstrates how the science on dietary cholesterol and eggs continues to reinforce the 2015 DGAC report’s recommendation to not limit dietary cholesterol to an arbitrary number. Eggs can be a part of a heart-healthy eating pattern. In fact, vegetarians (lacto-ovo) and older individuals have reason to incorporate even more eggs into their diets, according to the AHA. Indeed, eggs are more than just a source of dietary cholesterol. Eggs provide a good or excellent source of eight essential nutrients including choline, six grams of high-quality protein, 252 mcg of the carotenoids, lutein and zeaxanthin, making them the perfect complement to heart-healthy diets.

References

  1. Dietary Guidelines Advisory Committee. Scientific Report of the 2015 Dietary Guidelines Advisory Committee: Advisory Report to the Secretary of Health and Human Services and the Secretary of Agriculture,. 2015
  2. Dietary Guidelines Advisory Committee. Scientific Report of the 2010 Dietary Guidelines Advisory Committee: Advisory Report to the Secretary of Health and Human Services and the Secretary of Agriculture,. 2010
  3. Shin, J.Y., et al., Egg consumption in relation to risk of cardiovascular disease and diabetes: a systematic review and meta-analysis. Am J Clin Nutr, 2013. 98(1): p. 146-59.
  4. Zhong, V.W., et al., Associations of Dietary Cholesterol or Egg Consumption with Incident Cardiovascular Disease and Mortality. JAMA, 2019. 321(11): p. 1081-1095.
  5. Key, T.J., et al., Consumption of Meat, Fish, Dairy Products, Eggs and Risk of Ischemic Heart Disease: A Prospective Study of 7198 Incident Cases Among 409,885 Participants in the Pan-European EPIC Cohort. Circulation, 2019. 18;139(25):2835-2845.
  6. Carson JAS, Lichtenstein AH, Anderson CAM, Appel LJ, Kris-Etherton PM, Meyer KA, Petersen K, Polonsky T, Van Horn L; on behalf of the American Heart Association Nutrition Committee of the Council on Lifestyle and Cardiometabolic Health; Council on Arteriosclerosis, Thrombosis and Vascular Biology; Council on Cardiovascular and Stroke Nursing; Council on Clinical Cardiology; Council on Peripheral Vascular Disease; and Stroke Council. Dietary cholesterol and cardiovascular risk: a science advisory from the American Heart Association. Circulation. 2019;140: e-pub ahead of print.
  7. Sawrey-Kubicek, L., et al., Whole egg consumption compared with yolk-free egg increases the cholesterol efflux capacity of high-density lipoproteins in overweight, postmenopausal women. Am J Clin Nutr, 2019. 110(3):617-627.
  8. Australian Heart Foundation; Eggs and Cardiovascular Health: Summary of Evidence. 2019.

Eggs and Heart Disease: New study in line with broader science

A new study published last week in the American Heart Association journal Circulation adds more data to the mix on egg consumption and risk for heart disease1. Recall just a few weeks ago, a study published in the Journal of the American Medical Association (JAMA) made headlines when it seemed to reverse the course of the latest dietary recommendations to say that, once again, eggs and dietary cholesterol were linked with increased heart disease risk2. Now, just a few weeks later a new study says exactly the opposite.

In the new study, researchers from Oxford University in the U.K. analyzed data from over 400,000 men and women in Europe over an average follow up of 12 years. The authors reported a small but statistically significant decrease in risk for ischemic heart disease with every 20 gram increment of egg intake (about ½ an egg per day). The researchers also reported similar favorable results for yogurt and cheese consumption, while consumption of red and processed meats was associated with increased risk for heart disease.

Does this mean the science on eggs has changed yet again, just within a matter of weeks? No, it doesn’t. What it does mean is that the science never actually changed with the publication of the study in JAMA. As with any study, it is important to not view it in isolation, but rather in the broader context of the total scientific literature. This is particularly true with studies that are observational in nature, because in this type of research there are often outlier studies that deviate from the clear majority.

Furthermore, if you read the details of the new study the authors rightly pointed out that, as with any new observational study, there are several important factors to consider when interpreting these results:

  • The beneficial associations eggs and yogurt may be influenced by reverse causation bias.
  • There will always be residual confounding in observational studies that cannot be eliminated; even though the investigators statistically adjusted for many potential confounders including lifestyle factors.
  • The results may not be generalizable to populations outside this European cohort.
  • Associations with eggs and yogurt were no longer significant after excluding the first 4 years of follow-up.

Importantly, these are factors that should be considered in any observational study, whether the results are favorable or unfavorable to a dietary or lifestyle factor.

That said, these latest findings published in Circulation are more in line with previous meta-analyses of observational cohorts that reported either no relationship with egg consumption and cardiovascular risk3,4 or small decreases in cardiovascular risk5. Given all the caveats and confounding factors that are involved in observational studies, consistency across many studies over time is important.

It’s easy to get wrapped up in the day to day headlines from the next big study, and view the latest study as the next “game changer”. But the truth is science doesn’t change all that quickly, especially nutrition science. Many studies over the course of years or even decades are needed to achieve consensus. This is in fact what happened when the 2015 Dietary Guidelines for Americans no longer listed dietary cholesterol as a nutrient of concern. The evidence required to do so involved 16 studies over the course of many years3.

Lastly, as these studies are all observational in nature it is important to remember that we cannot infer a cause and effect relationship, no matter if the result is favorable or unfavorable to heart disease risk.  Therefore, it is important to view these results in the context of existing randomized controlled trials that consistently show egg intake does not negatively impact cardiovascular disease risk factors, and in some cases, has shown to improve risk factors such as HDL, or “good” cholesterol6.

 

References

  1. Key et al. Consumption of Meat, Fish, Dairy Products, Eggs and Risk of Ischemic Heart Disease: A Prospective Study of 7198 Incident Cases Among 409,885 Participants in the Pan-European EPIC Cohort. Circulation. 2019 Apr 22. [Epub ahead of print]
  2. Zhong et al. Associations of dietary cholesterol or egg consumption with incident cardiovascular disease and mortality. JAMA. 2019;321(11):1081-1095.
  3. Shin JY, Xun P, Nakamura Y, He K. Egg consumption in relation to risk of cardiovascular disease and diabetes: a systematic review and meta-analysis. Am J Clin Nutr. 2013 Jul;98(1):146-59.
  4. Rong Y, Chen L, Zhu T, Song Y, Yu M, Shan Z, Sands A, Hu FB, Liu L. Egg consumption and risk of coronary heart disease and stroke: dose-response meta-analysis of prospective cohort studies. BMJ. 2013 Jan 7;346:e8539.
  5. Alexander DD, et. al. Meta-analysis of egg consumption and risk of coronary heart disease and stroke. J Am Coll Nutr. 2016. 6:1-13.
  6. Blesso CN, Fernandez ML. Dietary Cholesterol, Serum Lipids, and Heart Disease: Are Eggs Working for or Against You? Nutrients. 2018 Mar 29;10(4). pii: E426. doi: 10.3390/nu10040426. Review.

Eggs and Cholesterol: New study, old story

A new study1 published in the Journal of the American Medical Association examining the relationship between dietary cholesterol and egg consumption with regard to cardiovascular disease risk provides interesting new data to consider as part of the broader context of the scientific literature in this area.

The authors report:

  • Small but statistically significant increases in cardiovascular risk with dietary cholesterol and egg consumption in six U.S.-based cohorts totaling over 29,000 participants.
  • These findings contrast with previous meta-analyses2,3 of observational cohorts not included in the present study that reported no relationship with egg consumption and cardiovascular risk in cohorts totaling almost 350,000 participants.
  • Furthermore, additional studies have shown small but statistically significant favorable relationships with egg consumption and cardiovascular risk in non-U.S. cohorts4,5, while randomized controlled trials consistently show egg intake does not negatively impact cardiovascular disease risk factors6.

The inconsistency of this new study with that of other recent studies demonstrates the importance of additional research to further explore this area, including the need to understand the unique contribution of eggs as part of healthy eating patterns set forth in the Dietary Guidelines for Americans.

The fact that studies outside the U.S. appear to show favorable relationships with egg intake and cardiovascular risk may speak to the importance of what other foods are consumed with eggs as part of the overall diet pattern, as recent research has demonstrated the importance of separating eggs from other foods to understand their independent impact on health outcomes7.

  1. Zhong et al. Associations of dietary cholesterol or egg consumption with incident cardiovascular disease and mortality. JAMA. 2019;321(11):1081-1095.
  2. Shin JY, Xun P, Nakamura Y, He K. Egg consumption in relation to risk of cardiovascular disease and diabetes: a systematic review and meta-analysis. Am J Clin Nutr. 2013 Jul;98(1):146-59.
  3. Rong Y, Chen L, Zhu T, Song Y, Yu M, Shan Z, Sands A, Hu FB, Liu L. Egg consumption and risk of coronary heart disease and stroke: dose-response meta-analysis of prospective cohort studies. BMJ. 2013 Jan 7;346:e8539.
  4. Qin C, Lv J, Guo Y, Bian Z, Si J, Yang L, Chen Y, Zhou Y, Zhang H, Liu J, Chen J, Chen Z, Yu C, Li L; China Kadoorie Biobank Collaborative Group. Associations of egg consumption with cardiovascular disease in a cohort study of 0.5 million Chinese adults. Heart. 2018 Nov;104(21):1756-1763.
  5. Virtanen JK, Mursu J, Virtanen HE, Fogelholm M, Salonen JT, Koskinen TT, Voutilainen S, Tuomainen TP. Associations of egg and cholesterol intakes with carotid intima-media thickness and risk of incident coronary artery disease according to apolipoprotein E phenotype in men: the Kuopio Ischaemic Heart Disease Risk Factor Study. Am J Clin Nutr. 2016 Mar;103(3):895-901.
  6. Blesso CN, Fernandez ML. Dietary Cholesterol, Serum Lipids, and Heart Disease: Are Eggs Working for or Against You? Nutrients. 2018 Mar 29;10(4). pii: E426. doi: 10.3390/nu10040426. Review.
  7. Sabaté J, Burkholder-Cooley NM, Segovia-Siapco G, Oda K, Wells B, Orlich MJ, Fraser GE. Unscrambling the relations of egg and meat consumption with type 2 diabetes risk. Am J Clin Nutr. 2018 Nov 1;108(5):1121-1128.