The impact of egg limitations on coronary heart disease risk: do the numbers add up?

Dietary Factors, Dietary Patterns, and Cardiovascular Disease Risk in Representative Japanese Cohorts: NIPPON DATA80/90

Diet is one of the most important factors affecting healthy life expectancy through the onset of cardiovascular disease (CVD) risk as well as various chronic diseases. Because dietary habits and disease structure differ depending on the country, region, and/or race, evidence from each population is required. NIPPON DATA80/90 is a long-term cohort study of a representative Japanese population that participated in national nutrition surveys. Among the many findings of this cohort study, a dietary pattern with higher intake of fruits, vegetables, fish (n-3 polyunsaturated fatty acids), and dietary fiber and lower intake of salt as well as sodium-to-potassium ratio was found to be associated with a lower risk of CVD mortality. The results from our cohort study would be useful for effectively preventing CVD. This article reviews the published studies from the NIPPON DATA80/90 to highlight the significant findings that may be used to develop risk prevention strategies for CVD.

The Association of Dietary Cholesterol from Egg Consumption on Cardiovascular Diseases Risk Varies from Person to Person

The public and scientists remain skeptical about egg consumption, given that cardiovascular diseases (CVDs) are the leading causes of death in worldwide. This review mainly explained the recurrence of contradictory conclusions about relationships between egg consumption and CVD risk and discussed effects of egg cholesterol intake on cholesterol homeostasis. Factors including individual health status and cholesterol sensitivity, dietary pattern, region, and race should be distinguished when understanding generalized conclusions. Identified compensatory mechanisms in response to dietary cholesterol and the resulting balance in cholesterol biosynthesis, absorption, and efflux supported the view that moderate egg consumption had no substantial overall impacts on cholesterol homeostasis in healthy people. Excessive cholesterol intake is not recommended in individuals with distempered metabolism. More than cholesterol metabolism, impacts of egg consumption as a part of overall diet on CVD risk should be considered from aspects of nutrient intake, lipid metabolism, and energy supply in the future.

Association of dietary cholesterol and dyslipidemia in Chinese health examinees

Background

The association between dietary cholesterol consumption and dyslipidemia is still in controversy. The study aims to evaluate whether dietary cholesterol intake associated with dyslipidemia and its components in Chinese health examinees.

Methods

A large-scale cross-sectional study was conducted among health examinees of in Shaanxi province. Totally of 8358 participants (3677 male and 4681 female) were included. Dietary cholesterol intake was assessed by validated food frequency questionnaire. Multivariable regression and restricted cubic spline models were used to capture the linear and non-linear association between dietary cholesterol and dyslipidemia.

Results

A total of 2429 (29.1%) subjects were newly diagnosed of dyslipidemia, the prevalence was 29.2% in male and 27.7% in female. Mean intake of dietary cholesterol was 213.7 mg/day. After adjusting for all potential confounders including demographics information and lifestyles, higher cholesterol consumption was related to lower risk of dyslipidemia, the ORs (95% CIs) across Q2 to Q4 group were 0.87 (0.60–1.26), 0.80 (0.55–1.18) and 0.61 (0.41–0.91) in female. With further controlling for nutrients principal components, a null association was observed between dietary cholesterol and dyslipidemia and serum lipids, regardless of gender. Results of restricted cubic splines showed that the risk of dyslipidemia decreased slowly until around 300 mg/day in men and 200 mg/day in women, although the non-linear association was not significant.

Conclusions

The study suggested that dietary cholesterol consumption was not associated with dyslipidemia or serum lipids in Chinese health examinees, although a decreased risk was observed before the threshold points.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41043-022-00293-y.

Egg Consumption and Risk of All-Cause and Cause-Specific Mortality: A Systematic Review and Dose-Response Meta-analysis of Prospective Studies

The association between egg consumption and mortality is extremely debatable. This study aimed to investigate the potential dose-response association of egg consumption with risk of mortality from all causes and cause-specific in the general population. The primary comprehensive literature search was conducted in PubMed/Medline, Scopus, ISI Web of Science, and Embase up to March 2021, as well as reference lists of relevant original papers and key journals. We calculated summary RRs and their 95% CIs for the highest and lowest categories, as well as the linear trend estimation of egg intake, using the random-effects model. Thirty-three (32 publications) cohort studies were included. These studies enrolled 2,216,720 participants and recorded 232,408 deaths from all causes. Comparing highest versus lowest egg intake categories was not associated with the risk of mortality from all causes (RR: 1.02; 95% CI: 0.94, 1.11; n = 25), cardiovascular disease (CVD) (RR: 1.04; 95% CI: 0.87, 1.23, n = 11), coronary heart disease (CHD) (RR: 0.98; 95% CI: 0.84, 1.16; n = 10), stroke (RR: 0.81; 95% CI: 0.64, 1.02; n = 9), and respiratory disease (RR: 0.96; 95% CI: 0.53, 1.71; n = 3); however, it was associated with a higher risk of cancer mortality (RR: 1.20; 95% CI: 1.04, 1.39; n = 13). In the linear dose-response analysis, an additional intake of 1 egg per week was associated with a 2% and 4% increased risk of all-cause and cancer mortality, respectively, and a 4% decreased risk of stroke mortality. The certainty of the evidence was rated as low to moderate. Higher egg consumption was not associated with an increased risk of mortality from all causes, CVD, CHD, stroke, or respiratory disease, whereas an elevated risk was observed for cancer mortality. These findings suggest that eggs be consumed in low to moderate amounts (≤1 egg/d) as part of a healthy diet.

The responses of different dosages of egg consumption on blood lipid profile: An updated systematic review and meta-analysis of randomized clinical trials

Diverse notions exist regarding egg intake, which is one of the main sources of dietary cholesterol, and its effect on blood lipids. We conducted this study to update the previous meta-analysis for their flaw in calculated effect size. PubMed, Scopus, ISI, and Cochrane were searched up to April 2019, for relevant randomized controlled clinical trials. Mean changes in total cholesterol (TC), LDL-cholesterol (LDL-C), HDL-cholesterol (HDL-C), triglyceride (TG), very low-density lipoprotein cholesterol (VLDL-C), LDL-C/HDL-C, TC/HDL-C, apolipoprotein (apo)A1, and apoB100 were assessed. Meta-analysis of 66 RCTs with 3,185 participants revealed that egg consumption can significantly increase TC, LDL-C, HDL-C, TC/HDL-C, apoA1/and B100, but there was no significant effect on other serum lipids. Dose-response analysis showed a linear effect for TC, HDL-C, ApoA1, ApoB100, and nonlinear for LDL-C, and TC/HDL-C. In conclusion, intake of more than one egg daily in less than 12 weeks may increase some blood lipids without any changes in the ratio of LDL-C/HDL-C. PRACTICAL APPLICATIONS: There are controversies reports for egg intake, which is one of the main sources of dietary cholesterol. This study provides comprehensive information about the effect of the number of eggs consumed per day (dietary cholesterol) on blood lipids for nutritionists, physicians, researchers, and the general population. In this regard, our results indicated that there is a linear correlation between consumption of greater than one egg per day in a short time (no long time) and increasing lipid profiles which may increase the risk of cardiovascular diseases. However, consumption of one egg daily can be safe and this can be a useful recommendation for prevention of cardiovascular disease and promotion of healthy life which indeed are the potential or actual uses of this research.

Controversies and discrepancies in the effect of dietary fat and cholesterol on cardiovascular risk

Cardiovascular disease (CVD) is the leading cause of death worldwide. The top ten causes of death in Singapore include many cardiovascular-related diseases such as ischaemic heart disease. The increasing prevalence of CVD poses a burden to both the economy and healthcare system of a country. Dietary habits, in particular dietary fats and cholesterol intake, have been shown to greatly influence CVD risks. Therefore, reference and adherence to relevant dietary guidelines could be crucial in CVD prevention. Recent research findings have provided novel insights into the relationship between certain dietary fats or cholesterol intake and CVD risks, challenging or reinforcing previous guidelines. These findings may, however, be conflicting, and there are still controversies over the effects of dietary fats and cholesterol as well as their association with cardiovascular risk. This review paper aims to evaluate common controversies, identify gaps in relevant research areas and summarise evidence-based dietary recommendations.

Threshold-Effect Association of Dietary Cholesterol Intake with Dyslipidemia in Chinese Adults: Results from the China Health and Nutrition Survey in 2015

The association of dietary cholesterol intake with dyslipidemia and subtypes is controversial. This study aimed to examine the association of dietary cholesterol intake with dyslipidemia and subtypes in Chinese adults. Using data from the China Health and Nutrition Survey (CHNS) in 2015, the present study selected 4383 participants aged 18–59 years who were free of diabetes, apoplexy, and myocardial infarction disease. Information was obtained on dietary intake, anthropometric measurements, and blood laboratory measurements. Dietary cholesterol intake was calculated based on the data collected by consecutive 3 days 24 h recalls combined with the weighing of household seasonings and categorized by 11 levels: The first 10 levels in ranges of 50 mg/day and the 11th level at ≥500 mg/day. Dyslipidemia, hypercholesterolemia, hypertriglyceridemia, low-density lipoprotein (LDL)-hypercholesterolemia, and high-density lipoprotein (HDL)-hypocholesterolemia were defined based on the Chinese adult dyslipidemia prevention guide (2016 edition). Multivariable logistic regressions were performed to examine the association of dietary cholesterol intake levels with dyslipidemia and subtypes. The prevalence of dyslipidemia was 37.5% among Chinese adults in 2015 (hypercholesterolemia 9.6%, HDL-hypocholesterolemia 21.1%, LDL-hypercholesterolemia 12.7%, and hypertriglyceridemia 15.2%). The lowest prevalence of hypercholesterolemia and LDL-hypercholesterolemia was 6.7% and 9.4%, respectively, which was relative to a dietary cholesterol intake level of 100.0 to <150.0 mg/day. After adjusting for all potential confounders, adults with the highest dietary cholesterol intake level of ≥500 mg/day compared with the dietary cholesterol intake of 100.0 to <150.0 mg/day showed one-time higher odds of hypercholesterolemia (odds ratios (OR) 2.0, 95% confidence intervals (CI) 1.3–3.3), as well as LDL-hypercholesterolemia (OR 2.0, 95% CI 1.3–3.0), but a null association of dietary cholesterol intake with dyslipidemia, hypertriglyceridemia, and HDL-hypocholesterolemia. The study suggested that a dietary cholesterol intake level of 500 mg/day and above may be a threshold point for high odds of hypercholesterolemia and LDL-hypercholesterolemia.

Dietary Cholesterol, Serum Lipids, and Heart Disease: Are Eggs Working for or Against You?

The relationship between blood cholesterol and heart disease is well-established, with the lowering of serum low-density lipoprotein (LDL)-cholesterol being the primary target of preventive therapy. Furthermore, epidemiological studies report lower risk for heart disease with higher concentrations of high-density lipoprotein (HDL)-cholesterol. There has also been considerable interest in studying the relationship between dietary cholesterol intake and heart disease risk. Eggs are one of the richest sources of cholesterol in the diet. However, large-scale epidemiological studies have found only tenuous associations between the intake of eggs and cardiovascular disease risk. Well-controlled, clinical studies show the impact of dietary cholesterol challenges via egg intake on serum lipids is highly variable, with the majority of individuals (~2/3 of the population) having only minimal responses, while those with a significant response increase both LDL and HDL-cholesterol, typically with a maintenance of the LDL/HDL cholesterol ratio. Recent drug trials targeting HDL-cholesterol have been unsuccessful in reducing cardiovascular events, and thus it is unclear if raising HDL-cholesterol with chronic egg intake is beneficial. Other important changes with egg intake include potentially favorable effects on lipoprotein particle profiles and enhancing HDL function. Overall, the increased HDL-cholesterol commonly observed with dietary cholesterol feeding in humans appears to also coincide with improvements in other markers of HDL function. However, more investigation into the effects of dietary cholesterol on HDL functionality in humans is warranted. There are other factors found in eggs that may influence risk for heart disease by reducing serum lipids, such as phospholipids, and these may also modify the response to dietary cholesterol found in eggs. In this review, we discuss how eggs and dietary cholesterol affect serum cholesterol concentrations, as well as more advanced lipoprotein measures, such as lipoprotein particle profiles and HDL metabolism.

Egg Consumption and Risk of Metabolic Syndrome in Korean Adults: Results from the Health Examinees Study

Metabolic syndrome (MetS) is defined as a cluster of metabolic alterations such as abdominal obesity, dyslipidemias, elevated fasting glucose, and hypertension. Studies on the association between egg consumption and MetS are limited and inconsistent. A cross-sectional analysis was conducted to examine the association of egg consumption with MetS among Korean adults aged 40–69 years. A total of 130,420 subjects (43,682 men and 86,738 women) from the Health Examinees Study were selected for the final analysis. Egg consumption was estimated using a validated 106-item food frequency questionnaire. MetS was defined using the National Cholesterol Education Program, Adult Treatment Panel III. Logistic regression analyses were performed to identify the association of egg consumption with MetS via odds ratios (ORs) and 95% confidence intervals (CIs) after adjusting for potential variables. Among 130,420 subjects, 34,039 (26.1%) people had MetS. Consumption of more than 7 eggs/week was associated with a lower odds of MetS risk compared to those who consumed less than one egg/week in women (OR: 0.77, 95%CI: 0.70–0.84, p trend < 0.0001). Higher egg consumption was inversely associated with the MetS components: elevated waist circumference (OR: 0.80, 0.75–0.86), elevated triglyceride (OR: 0.78, 0.72–0.85), reduced high-density lipoprotein cholesterol (HDL-C) (OR: 0.82, 0.77–0.88), elevated blood pressure (OR: 0.86, 0.80–0.92), and elevated fasting glucose (OR: 0.94, 0.83–0.99) in women; reduced HDL-C (OR: 0.89, 0.80–1.00) in men. Our results suggest that higher egg consumption may be associated with a reduction in the odds for MetS and all five metabolic components in women, and the risk of reduced HDL-C in men.

Egg consumption and risk of type 2 diabetes: a prospective study and dose-response meta-analysis

AIMS/HYPOTHESIS

In this study, we aimed to investigate the association between egg consumption and type 2 diabetes risk in the Cohort of Swedish Men and to conduct a meta-analysis to summarise available prospective evidence on this association.

METHODS

We followed 39,610 men (aged 45-79 years) from 1998 up to 2012 for incident type 2 diabetes. Egg consumption was assessed at baseline using a food frequency questionnaire. HRs (95% CIs) were estimated using Cox proportional hazards regression models. We searched PubMed (up to 14 December 2015) and reference lists of retrieved articles to identify eligible studies for meta-analysis.

RESULTS

During the 15 years of follow up, 4,173 men were diagnosed with type 2 diabetes. Compared with men who consumed eggs <1 time/week, the multivariable-adjusted HRs were 0.98 (95% CI 0.92, 1.05), 1.11 (95% CI 0.99, 1.24) and 1.11 (95% CI 0.95, 1.29) for egg consumption 1-2, 3-4 and ≥5 times/week, respectively (p trend = 0.06). In a random-effects dose-response meta-analysis, heterogeneity in the overall estimate was partly explained by differences across regions. The overall HRs for type 2 diabetes for each 3 times/week increment in consumption were 1.18 (95% CI 1.13, 1.24) in five US studies (I (2) = 0%) and 0.97 (95% CI 0.90, 1.05) in seven non-US studies.

CONCLUSIONS/INTERPRETATION

Our findings in Swedish men do not support an association between egg consumption and risk of type 2 diabetes. In a meta-analysis, frequent egg consumption was associated with a higher risk of type 2 diabetes in US studies only. Egg consumption habits and associated overall dietary patterns may differ between populations and could potentially explain the discrepancies between reported results. Given the inconsistent results, this relationship warrants further study.

The moderate essential amino acid restriction entailed by low-protein vegan diets may promote vascular health by stimulating FGF21 secretion

The serum total and LDL cholesterol levels of long-term vegans tend to be very low. The characteristically low ratio of saturated to unsaturated fat in vegan diets, and the absence of cholesterol in such diets, clearly contribute to this effect. But there is reason to suspect that the quantity and composition of dietary protein also play a role in this regard. Vegan diets of moderate protein intake tend to be relatively low in certain essential amino acids, and as a result may increase hepatic activity of the kinase GCN2, which functions as a gauge of amino acid status. GCN2 activation boosts the liver's production of fibroblast growth factor 21 (FGF21), a factor which favorably affects serum lipids and metabolic syndrome. The ability of FGF21 to decrease LDL cholesterol has now been traced to at least two mechanisms: a suppression of hepatocyte expression of sterol response element-binding protein-2 (SREBP-2), which in turn leads to a reduction in cholesterol synthesis; and up-regulated expression of hepatocyte LDL receptors, reflecting inhibition of a mechanism that promotes proteasomal degradation of these receptors. In mice, the vascular benefits of FGF21 are also mediated by favorable effects on adipocyte function - most notably, increased adipocyte secretion of adiponectin, which directly exerts anti-inflammatory effects on the vasculature which complement the concurrent reduction in LDL particles in preventing or reversing atherosclerosis. If, as has been proposed, plant proteins preferentially stimulate glucagon secretion owing to their amino acid composition, this would represent an additional mechanism whereby plant protein promotes FGF21 activity, as glucagon acts on the liver to boost transcription of the FGF21 gene.

Cross-Sectional and Longitudinal Associations between Egg Consumption and Metabolic Syndrome in Adults ≥ 40 Years Old: The Yangpyeong Cohort of the Korean Genome and Epidemiology Study (KoGES_Yangpyeong)

Since the 1970s, the public has been advised to limit egg consumption even though there is little evidence of any harmful effect of eggs on blood cholesterol. The purpose of this cross-sectional and prospective study was to evaluate the potential association between egg consumption and metabolic syndrome (MetS) and MetS components in adults ≥ 40 years in KoGES_Yangpyeong. Yangpyeong is a rural area in South Korea. A total of 2,887 subjects (men 1,115, women 1,772) were recruited from 2005 to 2009, based on a physical examination and questionnaires administered using standardized protocol. After excluding subjects who had MetS at baseline, 1,663 subjects (675 men, 958 women) were followed for 3.20 years (range: 0.34–8.70). During the follow-up period, MetS occurred in 289 subjects. More than 3 eggs per week was significantly associated with decreased risk of MetS in both men (RR = 0.46, 95% CI, 0.26–0.82, P for trend = 0.1093) and women (RR = 0.54, 95% CI, 0.31–0.93, P for trend 0.0325) compared to non-users. There was a cross-sectional inverse relationship between egg consumption and abdominal obesity in men and women. Also, prospectively, higher egg consumption in men was associated with a decreased risk of high fasting blood glucose (RR = 0.39, 95% CI, 0.22–0.67, P for trend = 0.0042) and high triglycerides (RR = 0.42, 95% CI, 0.22–0.80, P for trend = 0.1080). In conclusion, our findings suggest that higher egg consumption may reduce the risk of MetS both in men and women, and the risk of high fasting blood glucose and high triglycerides in men. Current guidelines regarding egg consumption may need to be re-visited for healthy middle-aged and elderly people.

Egg Consumption and Human Cardio-Metabolic Health in People with and without Diabetes

The guidelines for dietary cholesterol and/or egg intake for both the general population and those at higher risk of cardiovascular disease (for example, people with type 2 diabetes mellitus (T2DM)) differ between countries, and even for different specialist societies in a country. The disparity between these guidelines is at least in part related to the conflicting evidence as to the effects of eggs in the general population and in those with T2DM. This review addresses the effect of eggs on cardiovascular disease (CVD) risk from both epidemiological research and controlled prospective studies, in people with and without cardio-metabolic disease. It also examines the nutritional qualities of eggs and whether they may offer protection against chronic disease. The evidence suggests that a diet including more eggs than is recommended (at least in some countries) may be used safely as part of a healthy diet in both the general population and for those at high risk of cardiovascular disease, those with established coronary heart disease, and those with T2DM. In conclusion, an approach focused on a person's entire dietary intake as opposed to specific foods or nutrients should be the heart of population nutrition guidelines.

Egg and egg-derived foods: effects on human health and use as functional foods

Eggs are sources of protein, fats and micronutrients that play an important role in basic nutrition. However, eggs are traditionally associated with adverse factors in human health, mainly due to their cholesterol content. Nowadays, however, it is known that the response of cholesterol in human serum levels to dietary cholesterol consumption depends on several factors, such as ethnicity, genetic makeup, hormonal factors and the nutritional status of the consumer. Additionally, in recent decades, there has been an increasing demand for functional foods, which is expected to continue to increase in the future, owing to their capacity to decrease the risks of some diseases and socio-demographic factors such as the increase in life expectancy. This work offers a brief overview of the advantages and disadvantages of egg consumption and the potential market of functional eggs, and it explores the possibilities of the development of functional eggs by technological methods.

Effects of egg ingestion on endothelial function in adults with coronary artery disease: a randomized, controlled, crossover trial

BACKGROUND

Prevailing recommendations call for restricting intake of dietary cholesterol and eggs for those at risk of heart disease, despite accumulating evidence challenging this association. Our prior studies showed no short-term adverse effects of daily egg intake on cardiac risk factors in at-risk adults.

OBJECTIVE

We conducted this study to determine effects of daily egg consumption in adults with established coronary artery disease (CAD).

METHODS

Randomized, controlled, single-blind, crossover trial of 32 adults (mean age, 67 years; 6 women, 26 men) with CAD assigned to 1 of 6 possible sequence permutations of 3 different treatments (breakfast with 2 eggs, breakfast with ½ cup Egg Beaters, ConAgra Foods, St. Louis, MO, or a high-carbohydrate breakfast part of an ad libitum diet) for 6 weeks, with 4-week washout periods. The primary outcome measure was endothelial function measured as flow-mediated dilatation.

RESULTS

Compared with the control breakfast (ie, high-carbohydrate breakfast), daily consumption of eggs showed no adverse effects on flow-mediated dilatation (7.2% ± 2.9% vs 7.5% ± 2.9%, P = .33), lipids (total cholesterol: 158.3 ± 28.6 mg/dL vs 156.2 ± 27.4 mg/dL, P = .49), blood pressure (systolic blood pressure: 132.8 ± 14.1 mm Hg or vs 135.5 ± 14.9 mm Hg, P = .52; diastolic blood pressure: 77.2 ± 6.1 mm Hg vs 76.7 ± 6.9 mm Hg, P = .86), or body weight (90.8 ± 17.5 kg vs 91.8 ± 17.1 kg, P = .92). No outcomes differed (P > .05) between eggs and Egg Beaters.

CONCLUSIONS

We found no evidence of adverse effects of daily egg ingestion on any cardiac risk factors in adults with CAD over a span of 6 weeks.

Differing statistical approaches affect the relation between egg consumption, adiposity, and cardiovascular risk factors in adults

BACKGROUND

Associations between food patterns and adiposity are poorly understood.

OBJECTIVE

Two statistical approaches were used to examine the potential association between egg consumption and adiposity.

METHODS

Participants (n = 18,987) aged ≥19 y were from the 2001-2008 NHANES who provided 24-h diet recall data, body mass index (BMI) and waist circumference (WC)-determined adiposity measures, and blood pressure, circulating insulin, glucose, and lipid concentrations were considered cardiovascular risk factors (CVRFs). Covariate-adjusted least-squares means ± SEs were generated.

RESULTS

The first statistical approach categorized participants into egg consumers or nonconsumers. Consumers had higher mean BMI (in kg/m(2); 28.7 ± 0.19; P = 0.006) and WC (98.2 ± 0.43 cm; P = 0.002) than did nonconsumers (28.2 ± 0.10 and 96.9 ± 0.23 cm, respectively). Second, cluster analysis identified 8 distinct egg consumption patterns (explaining 39.5% of the variance in percentage of energy within the food categories). Only 2 egg patterns [egg/meat, poultry, fish (MPF)/grains/vegetables and egg/MPF/grains], consumed by ≤2% of the population, drove the association (compared with the no-egg pattern) between egg consumption and BMI and WC. Another analysis controlled for the standard covariates and the other food groups consumed with eggs in those 2 egg patterns. Only the egg/MPF/other-grains pattern remained associated with BMI and WC (both P ≤ 0.0063). The pattern analyses identified associations between an egg pattern (egg/MPF/other grains/potatoes/other beverages) and diastolic blood pressure (DBP) and serum LDL cholesterol (both P ≤ 0.0063). A final analysis was conducted by adding percentage of energy from fast foods and medication use for diabetes to the covariates. The association between the egg/MPF/grains pattern and BMI and the egg/MPF/potatoes/other beverages and DBP and LDL cholesterol disappeared.

CONCLUSIONS

Care needs to be taken with data interpretation of diet and health risk factors and the choice of statistical analyses and covariates used in the analyses because these studies are typically used to generate hypotheses. Additional studies are needed to better understand these relations.

Computationally Modeling Lipid Metabolism and Aging: A Mini-review

One of the greatest challenges in biology is to improve the understanding of the mechanisms which underpin aging and how these affect health. The need to better understand aging is amplified by demographic changes, which have caused a gradual increase in the global population of older people. Aging western populations have resulted in a rise in the prevalence of age-related pathologies. Of these diseases, cardiovascular disease is the most common underlying condition in older people. The dysregulation of lipid metabolism due to aging impinges significantly on cardiovascular health. However, the multifaceted nature of lipid metabolism and the complexities of its interaction with aging make it challenging to understand by conventional means. To address this challenge computational modeling, a key component of the systems biology paradigm is being used to study the dynamics of lipid metabolism. This mini-review briefly outlines the key regulators of lipid metabolism, their dysregulation, and how computational modeling is being used to gain an increased insight into this system.

Cholesterol Removal from Whole Egg by Crosslinked β-Cyclodextrin

This study was carried out to optimize cholesterol removal in whole egg using crosslinked β-cyclodextrin (β-CD) and to recycle the β-CD. Various factors for optimizing conditions were concentration of the β-CD, mixing temperature, mixing time, mixing speed and centrifugal speed. In the result of this study, the optimum conditions of cholesterol removal were 25% crosslinked β-CD, 40°C mixing temperature, 30 min mixing time, 1,200 rpm mixing speed and 2,810×g centrifugal speed. The recycling was repeated five times. The cholesterol removal was 92.76% when treated with the optimum conditions. After determining the optimum conditions, the recyclable yields of the crosslinked β-CD ranged from 86.66% to 87.60% in the recycling and the percentage of cholesterol removal was over 80% until third recycling. However, the cholesterol removal efficiency was decreased when the number of repeated recycling was increased. Based on the result of this study, it was concluded that the crosslinked β-CD was efficient for cholesterol removal in whole egg, and recycling is possible for only limited repeating times due to the interaction of the β-CD and egg protein.

Dietary cholesterol, heart disease risk and cognitive dissonance

In the 1960s, the thesis that dietary cholesterol contributes to blood cholesterol and heart disease risk was a rational conclusion based on the available science at that time. Fifty years later the research evidence no longer supports this hypothesis yet changing the dietary recommendation to limit dietary cholesterol has been a slow and at times contentious process. The preponderance of the clinical and epidemiological data accumulated since the original dietary cholesterol restrictions were formulated indicate that: (1) dietary cholesterol has a small effect on the plasma cholesterol levels with an increase in the cholesterol content of the LDL particle and an increase in HDL cholesterol, with little effect on the LDL:HDL ratio, a significant indicator of heart disease risk, and (2) the lack of a significant relationship between cholesterol intake and heart disease incidence reported from numerous epidemiological surveys. Over the last decade, many countries and health promotion groups have modified their dietary recommendations to reflect the current evidence and to address a now recognised negative consequence of ineffective dietary cholesterol restrictions (such as inadequate choline intake). In contrast, health promotion groups in some countries appear to suffer from cognitive dissonance and continue to promote an outdated and potentially hazardous dietary recommendation based on an invalidated hypothesis. This review evaluates the evidence for and against dietary cholesterol restrictions and the potential consequences of such restrictions.

Hen egg yolk lipid fractions with antiatherogenic properties

Three different types of hen egg yolk, cage-free, organic and daily fresh, were tested for their antiatherogenic properties. Total lipids (TL) of all hen egg yolk samples were extracted by the method of Bligh and Dyer and further separated into total polar lipids (TPL) and total neutral lipids (TNL) by counter current distribution chromatography. TPL and TNL were further separated by preparative thin-layer chromatography (TLC). TL, TPL, TNL and the obtained polar and neutral lipid fractions after TLC separation were tested to determine whether they induce platelet activation or inhibit platelet activating factor (PAF)-induced platelet activation. All three hen egg yolk TL samples possessed strong inhibitory activity against PAF-induced platelet activation that was mainly attributed to TPL, especially to PL fraction 4. Cage-free hen egg yolk exhibited the most potent anti-PAF activity in all lipid classes (TL, TPL and TNL). Thus hen egg yolk contains PAF inhibitors that reinforce their nutritional value in terms of protection against cardiovascular diseases, since PAF is a crucial inflammatory phospholipid mediator that is implicated in the mechanism of atherogenesis.

A whole-body mathematical model of cholesterol metabolism and its age-associated dysregulation

BACKGROUND

Global demographic changes have stimulated marked interest in the process of aging. There has been, and will continue to be, an unrelenting rise in the number of the oldest old ( >85 years of age). Together with an ageing population there comes an increase in the prevalence of age related disease. Of the diseases of ageing, cardiovascular disease (CVD) has by far the highest prevalence. It is regarded that a finely tuned lipid profile may help to prevent CVD as there is a long established relationship between alterations to lipid metabolism and CVD risk. In fact elevated plasma cholesterol, particularly Low Density Lipoprotein Cholesterol (LDL-C) has consistently stood out as a risk factor for having a cardiovascular event. Moreover it is widely acknowledged that LDL-C may rise with age in both sexes in a wide variety of groups. The aim of this work was to use a whole-body mathematical model to investigate why LDL-C rises with age, and to test the hypothesis that mechanistic changes to cholesterol absorption and LDL-C removal from the plasma are responsible for the rise. The whole-body mechanistic nature of the model differs from previous models of cholesterol metabolism which have either focused on intracellular cholesterol homeostasis or have concentrated on an isolated area of lipoprotein dynamics. The model integrates both current and previously published data relating to molecular biology, physiology, ageing and nutrition in an integrated fashion.

RESULTS

The model was used to test the hypothesis that alterations to the rate of cholesterol absorption and changes to the rate of removal of LDL-C from the plasma are integral to understanding why LDL-C rises with age. The model demonstrates that increasing the rate of intestinal cholesterol absorption from 50% to 80% by age 65 years can result in an increase of LDL-C by as much as 34 mg/dL in a hypothetical male subject. The model also shows that decreasing the rate of hepatic clearance of LDL-C gradually to 50% by age 65 years can result in an increase of LDL-C by as much as 116 mg/dL.

CONCLUSIONS

Our model clearly demonstrates that of the two putative mechanisms that have been implicated in the dysregulation of cholesterol metabolism with age, alterations to the removal rate of plasma LDL-C has the most significant impact on cholesterol metabolism and small changes to the number of hepatic LDL receptors can result in a significant rise in LDL-C. This first whole-body systems based model of cholesterol balance could potentially be used as a tool to further improve our understanding of whole-body cholesterol metabolism and its dysregulation with age. Furthermore, given further fine tuning the model may help to investigate potential dietary and lifestyle regimes that have the potential to mitigate the effects aging has on cholesterol metabolism.

Egg consumption and the risk of type 2 diabetes mellitus: a case-control study

OBJECTIVE

Type 2 diabetes mellitus appears to involve an interaction between susceptible genetic backgrounds and environmental factors including highly calorific diets. As it is important to identify modifiable risk factors that may help reduce the risk of type 2 diabetes mellitus, the aim of the present study was to determine the association between egg consumption and the risk of type 2 diabetes mellitus.

DESIGN

A specifically designed questionnaire was used to collect information on possible risk factors of type 2 diabetes mellitus. The odds ratios and 95 % confidence intervals for type 2 diabetes mellitus were calculated by conditional logistic regression.

SETTING

A case-control study in a Lithuanian out-patient clinic was performed in 2001.

SUBJECTS

A total of 234 cases with a newly confirmed diagnosis of type 2 diabetes mellitus and 468 controls free of the disease.

RESULTS

Variables such as BMI, family history of diabetes, cigarette smoking, education, morning exercise and plasma TAG level were retained in multivariate logistic regression models as confounders because their inclusion changed the value of the odds ratio by more than 10 % in any exposure category. After adjustment for possible confounders more than twofold increased risk of type 2 diabetes mellitus was determined for individuals consuming 3-4·9 eggs/week (OR = 2·60; 95 % CI 1·34, 5·08) and threefold increased risk of the disease was determined for individuals consuming ≥5 eggs/week (OR = 3·02; 95 % CI 1·14, 7·98) compared with those eating <1 egg/week.

CONCLUSIONS

Our data support a possible relationship of egg consumption and increased risk of type 2 diabetes mellitus.

Egg consumption and risk of cardiovascular disease in the SUN Project

BACKGROUND/OBJECTIVES

Egg consumption has been associated with the risk of cardiovascular diseases (CVDs), but evidence is scarce and inconsistent. Our aim was to examine the association between egg consumption and incidence of CVD in a prospective dynamic Mediterranean cohort of 14,185 university graduates.

SUBJECTS/METHODS

Egg intake was assessed using a 136-item-validated food-frequency questionnaire. Baseline consumption was categorized into no consumption or <1 egg/week, 1 egg/week, 2-4 eggs/week and >4 eggs/week. The presence of cardiovascular risk factors was assessed by questionnaire at baseline, and the incidence of CVD was assessed using biennial assessments. The median follow-up was 6.1 years. Cox regression models were fitted to estimate multivariable-adjusted hazard ratios (HRs) for CVD (myocardial infarction, revascularization procedures or stroke). Outcomes were confirmed by review of medical records.

RESULTS

During a median follow-up of 6.1 years, 91 new confirmed cases of CVD were observed. No association was found between egg consumption and the incidence of CVD (HR: 1.10, 95% confidence interval: 0.46-2.63) for the highest versus the lowest category of egg consumption after adjusting for age, sex, total energy intake, adherence to the Mediterranean food pattern and other cardiovascular risk factors. Results were robust to different analytical scenarios.

CONCLUSIONS

No association between egg consumption and the incidence of CVD was found in this Mediterranean cohort.

Egg consumption and CHD and stroke mortality: a prospective study of US adults

OBJECTIVE

To evaluate the relationship between egg consumption and CHD and stroke mortality using the Third National Health and Nutrition Examination Survey 1988-1994 (NHANES III) and follow-up survey.

DESIGN

A cross-sectional survey using a stratified, multi-stage probability sample was analysed, adjusting for survey design. Egg consumption was obtained from the FFQ and separated into categories of egg intake. Hazard ratios (HR) were calculated for CHD and stroke mortality using multivariate Cox regression models.

SETTING

A health and nutrition survey conducted in the USA from 1988 to 1994 with follow-up through 31 December 2000.

SUBJECTS

The study population included men and women who were free of CVD and had completed a FFQ at baseline.

RESULTS

Multivariate models adjusting for health, lifestyle and dietary factors indicated that 'high' egg consumption (≥ 7 times/week v. <1 time/week) was not associated with significantly increased CHD mortality (HR = 1·13, 95 % CI 0·61, 2·11 (men); HR = 0·92, 95 % CI 0·27, 3·11 (women)). There was a statistically significant inverse association between 'high' egg consumption and stroke mortality among men (HR = 0·27, 95 % CI 0·10, 0·73), but the estimate was imprecise because of sparse data. We did not observe a statistically significant positive association between 'high' egg consumption and CHD or stroke mortality in analyses restricted to individuals with diabetes, but these analyses may be limited due to the small number of diabetics.

CONCLUSIONS

We did not find a significant positive association between egg consumption and increased risk of mortality from CHD or stroke in the US population. These results corroborate the findings of previous studies.

Daily egg consumption in hyperlipidemic adults--effects on endothelial function and cardiovascular risk

Background

Limiting consumption of eggs, which are high in cholesterol, is generally recommended to reduce risk of cardiovascular disease. However, recent evidence suggests that dietary cholesterol has limited influence on serum cholesterol or cardiac risk.

Objective

To assess the effects of egg consumption on endothelial function and serum lipids in hyperlipidemic adults.

Methods

Randomized, placebo-controlled crossover trial of 40 hyperlipidemic adults (24 women, 16 men; average age = 59.9 ± 9.6 years; weight = 76.3 ± 21.8 kilograms; total cholesterol = 244 ± 24 mg/dL). In the acute phase, participants were randomly assigned to one of the two sequences of a single dose of three medium hardboiled eggs and a sausage/cheese breakfast sandwich. In the sustained phase, participants were then randomly assigned to one of the two sequences of two medium hardboiled eggs and 1/2 cup of egg substitute daily for six weeks. Each treatment assignment was separated by a four-week washout period. Outcome measures of interest were endothelial function measured as flow mediated dilatation (FMD) and lipid panel.

Results

Single dose egg consumption had no effects on endothelial function as compared to sausage/cheese (0.4 ± 1.9 vs. 0.4 ± 2.4%; p = 0.99). Daily consumption of egg substitute for 6 weeks significantly improved endothelial function as compared to egg (1.0 ± 1.2% vs. -0.1 ± 1.5%; p < 0.01) and lowered serum total cholesterol (-18 ± 18 vs. -5 ± 21 mg/dL; p < 0.01) and LDL (-14 ± 20 vs. -2 ± 19 mg/dL; p = 0.01). Study results (positive or negative) are expressed in terms of change relative to baseline.

Conclusions

Egg consumption was found to be non-detrimental to endothelial function and serum lipids in hyperlipidemic adults, while egg substitute consumption was beneficial.

Egg consumption and the risk of diabetes in adults, Jiangsu, China

BACKGROUND

Although egg consumption has been associated with elevated plasma levels of cholesterol and triglyceride and with risk of cardiovascular disease in some populations, epidemiologic studies on egg consumption and the risk of diabetes are extremely sparse, particularly in the Chinese population.

METHOD

Data from a household survey in the year 2002 among 2849 adults aged ≥20 y from a nationally representative sample in Jiangsu Province, China, were used. Dietary information was assessed by a validated food frequency questionnaire and 3 d weighed food records. Fasting blood specimens were collected.

RESULTS

After the adjustment for age, total calorie intake, education, smoking, family history of diabetes, and sedentary activity, egg consumption was significantly and positively associated with diabetes risk, particularly in women. The odds ratios (OR) (95% CI) of diabetes associated with egg consumption <2/wk, 2-6/wk, and ≥1/d in the total sample were 1.00, 1.75, 2.28 (1.14-4.54), respectively (P for trend 0.029). Corresponding ORs (95% CI) in women were 1.00, 1.66, and 3.01 (1.12, 8.12), respectively (P for trend 0.022). Additional adjustment of body mass index attenuated the association, but it remained significant. There was a similar, however, not statistically significant association in men. In addition, plasma triglyceride and total cholesterol levels were significantly higher in women who consumed ≥2 eggs/wk than those who consumed eggs less often.

CONCLUSION

Egg consumption was positively associated with the risk of diabetes among the Chinese, particularly in women.

Dietary cholesterol and coronary artery disease: a systematic review

Coronary heart disease (CHD) remains one of the leading causes of death in the United States and other industrialized nations. A better understanding of modifiable risk factors for CHD is critical in order to effectively prevent this disease. Dietary factors known to influence the risk of CHD include saturated fats, trans-fats, and polyunsaturated fatty acids. Although higher plasma levels of low-density lipoprotein cholesterol are associated with an increased risk of coronary disease and lipid-lowering therapy has been shown to reduce the risk of cardiovascular disease, the relation between dietary cholesterol and the risk of CHD is not clearly understood. This article reviews the current evidence on the association between dietary cholesterol and the risk of CHD.

Contribution of specific dietary factors to CHD in US females

Objective

To estimate dietary cholesterol contribution to CHD risk among US females, relative to other dietary risk factors.

Design

A risk apportionment model was applied to apportion CHD risk shares among the lifestyle and dietary risk factors.

Setting

The model was implemented using relative risks from the Nurses’ Health Study and data on CHD risk factors and consumption from the National Health and Nutrition Examination Survey 1999–2002.

Subjects

US females aged 25 years or older.

Results

On average, poor diet contributes 20 % of the CHD risk relative to obesity, inactivity and smoking, of which trans fat intake contributes 2·9 %, dietary cholesterol 1·5 % and 16 % is due to low consumption of nutrients, i.e. MUFA (1·5 %), PUFA (1·7 %), marine n-3 fatty acids (2·7 %), α-linolenic acid (1·1 %), dietary fibre (2·4 %), vitamin B6 (4·1 %), vitamin C (0·5 %) and folate (1·8 %).

Conclusions

Reducing trans fat and dietary cholesterol intakes could lead to CHD reduction, but greater risk reduction may be achieved by improving intakes of heart-healthy nutrients currently deficient in US females’ diets. Total diet consideration is essential in any CHD risk reduction strategy.

Where Do Eggs Fit in a Heart-Healthy Diet?

Eggs make up a relatively small contribution to the energy consumption of the average American, in part because of the perception that the cholesterol content makes them a forbidden food for a heart-healthy diet. The relationship between egg cholesterol, blood cholesterol, and cardiovascular disease risk is complex and not clearly understood. In addition, eggs provide many valuable and bioavailable nutrients. Thus, the place of eggs in meal planning should be reconsidered while keeping in mind the diet and lifestyle recommendations of the American Heart Association.