In a recent study published in the journal Nutrients, researchers investigated the impacts of different egg-based diets on healthy young individuals' immune, hematologic, and metabolic clinical profiles.
The researchers used a 16-week-long randomized cross-over study to evaluate the clinical changes accompanying the consumption of no eggs, three whole eggs, and three egg whites per day over four weeks.
Their results suggest that, even after accounting for slight increases in body mass and chronic disease-associated nutrients, whole egg consumption has a net beneficial effect on young adults' clinical profiles, especially metabolic and hematological.
The controversy surrounding egg consumption
Eggs contain a host of dietary compounds and bioactive nutrients associated with regulating lipid metabolism, immune function, metabolic function, and hematopoiesis (the formation of blood cellular components). Whole eggs are composed of two distinct parts – the yellow egg yolk and the egg white (albumen or the glair).
These parts are significantly different in their nutritional composition – while they are both rich in biologically available protein (15.9 g and 10.9 g/100 g, respectively) and B vitamins, egg yolks additionally provide choline-containing sphingo- and glycerophospholipids, fatty acids, cholesterol, and additional vitamins (with vitamin C being the only notable exception).
Whole eggs are the most cost-effective source of animal protein, with most research suggesting that egg consumption is positively associated with improved nutrient density and overall quality of life.
Observational and intervention studies have aimed to evaluate and quantify the health benefits conferred by egg consumption. However, potentially due to differences in study design, the impacts of egg consumption on hematologic profiles, nutritional status, and cardiometabolic risk factors remain inconsistent and controversial.
Most studies focus on one or a few biomarkers, which do not sufficiently elucidate the overall effects of egg consumption on the comprehensive swathe of standard clinical metrics.
This discordance observed between the results of epidemiologic and intervention studies makes a holistic investigation of the pros and cons of egg consumption (whole versus only albumen) necessary to enable health practitioners to make informed decisions when building dietary plans for their patients.
About the study
The present study aims to elucidate the effects of consuming no eggs, only egg whites, and whole eggs on a comprehensive list of clinical biomarkers. The selected biomarkers indicate nutritional status, diet quality, hematologic profiles, and cardiometabolic risk for each consumption pattern.
The study focuses on young adults between the ages of 18–35. Additionally, since combined oral hormone-based contraceptives (COCs) have been reported to alter female physiological response to egg nutrients, COCs were included in the study as a variable.
Twenty-nine individuals between the ages of 18–35 (22 women and seven men) were initially recruited for the study, with inclusion criteria comprising body mass index (BMI [< 30 kg/m2]) and body fat percentage (< 40% for females and <30% for males).
Individuals with preexisting chronic health conditions, egg allergies, and those currently undergoing lipid-lowering treatments were excluded from the study. The resultant sample group comprised 21 women and five men. Of the 21 women, 11 were using COCs.
This study utilized a cross-over study design wherein participants were initially exposed to a four-week, egg-free, run-in period. This was followed by a four-week-long period of egg consumption (cohort one was fed three whole eggs per day, and cohort two was provided three egg whites per day).
Next, participants were reverted to four weeks of egg-free 'washout' period. Finally, four weeks of egg consumption wherein cohort one and two reversed treatments (cohort one was fed three egg whites, while cohort two was provided with three whole eggs). Additionally, medical questionnaires, BMI, and blood measurements were used to evaluate overall health at study initiation.
Dietary intake analyses comprised five-day-long food and beverage intake records collected at the end of weeks 4, 8, and 16. The Nutrition Data System for Research (NDSR) was used to analyze average nutrient composition and intake.
BMI and body composition were also recorded at the same frequency for body composition analysis. Fasted blood samples were collected for serum analysis and complete blood cell counts. Serum analysis was used to determine clinical metabolic profiles, including serum lipid and glucose, total cholesterol, and triglycerides.
Nuclear magnetic resonance (NMR) was used to estimate serum samples’ lipoprotein size profiles. Liquid chromatography/tandem mass spectrometry (LC-MS/MS) analysis was employed to evaluate amino acid concentrations, which in turn were used to compute a lipoprotein–insulin resistance index (LP–IR) and a diabetes risk index (DRI).
Cytometry was used for complete cell counts and to compute clinically-relevant immune cell ratios. Finally, statistical analyses comprising analysis of variance (ANOVA), independent t-tests, and bivariate Pearson correlations were used to elucidate the associations between different egg diets and clinical outcomes.
The present study found significant differences in average nutrient intakes across egg diet periods. While the overall energy intake was uniform between study cohorts, macronutrient intakes differed, with whole eggs contributing to increased fat and reduced carbohydrate compared to egg whites and, to a greater extent, no eggs.
Since egg yolk is a rich source of choline, participants on whole egg diets showed significantly higher dietary choline than those on other nutritional regimes.
Notably, intake of various micronutrients was also increased in the whole egg diet periods relative to the egg white diet period, including pantothenic acid, vitamin B12, vitamin D, and phosphorus, whereas selenium intake was greater during the whole egg diet period compared to both the egg-free and egg white diet periods.
Andersen et al. (2023)
Egg-white diets resulted in minor (0.9%) weight gain while not affecting fat or muscle mass. In contrast, whole eggs resulted in a 3.5% increase in body fat. Dietary analyses of clinical metabolic profiles could not establish differences in biomarkers of inflammation, liver and kidney function, protein status, or ketone concentrations across diets. However, serum choline and betaine (a choline metabolite) concentrations were significantly higher in whole-egg diets.
While there was notable variability across individuals, changes in fasting total cholesterol, LDL-C, HDL-C, non-HDL-C, triglycerides, or the total cholesterol:HDL-C ratio did not reach statistical significance, with no differences observed between male and female participants.
Andersen et al. (2023)
However, COC consumption was found to significantly decrease total cholesterol:high-density lipoprotein (HDL) ratios and percentage of monocytes during whole egg diet phases. Fasting glucose was found to be uniform across diet phases.
Serum isoleucine, a compound recently suggested to be associated with type 2 diabetes mellitus (T2DM) risk, was found to be upregulated in both egg diets compared to the egg-free diet. Interestingly, whole egg diets were found to lead to higher concentrations of serum glycine than egg whites. Serum glycine is known to protect against T2DM, suggesting that if egg is included in diets, whole eggs are beneficial over egg whites in combatting T2DM risk.
Analyses of immune profiles revealed that both total white blood cell (WBC) and differential leukocyte counts remained constant across diet phases. However, red blood cell (RBC) analysis found that hematocrit counts were highest in whole-egg diets and lowest in egg-free diets.
In the present study, researchers used a 16-week-long randomized, cross-over study to investigate the clinical outcomes of different egg diets in healthy young adults.
Comprehensive clinical effects of whole egg, egg white, and no egg diets on participants' immune, hematologic, and metabolic profiles revealed that, whilst slightly increasing body fat, T2DM, and cardiovascular disease risk, whole egg consumption resulted in a host of clinical beneficial results, highlighting it as the best overall diet under study.
Together, these findings suggest that, in a young healthy population, whole egg intake confers mostly beneficial changes in global clinical profiles.
Andersen et al. (2023)