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.

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Do Eggs Affect Cardiovascular Risk Factors Among Those With Type 2 Diabetes?

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The role of eggs in diets of persons living with type 2 diabetes (T2D) is an area of active debate and may depend on the overall diet pattern.

 An Australian research team (Fuller, 2015) recently evaluated whether people with T2D might benefit from egg consumption citing eggs as,

 “a nutritious and convenient way of improving protein and micronutrient contents of the diet, which have importance for satiety and weight management.”

They randomly assigned 140 adult Australian men and women with pre-diabetes or T2D to one of 2 weight maintenance diets as part of a 3-month study. Both groups were instructed to consume specific types and quantities of food such that they would increase polyunsaturated (PUFA) and monounsaturated (MUFA) fat, in place of saturated fat.

One group was advised to eat 2 eggs/day six days a week (i.e., 12 eggs/wk) and the other was advised to eat less than 2 eggs/week, consuming other sources of lean protein to equilibrate protein between the two groups. Both groups kept their diabetes and cholesterol medications constant, with a few exceptions, throughout the study.

At 3 months, both high and low egg groups significantly reduced saturated fat and increased MUFA and PUFA content of their diets.   The low egg group also increased fiber intake. The high egg group increased both cholesterol and total fat, but decreased carbohydrate intake more than the low egg group. The high egg group achieved a diet containing 11.8 eggs/week on average, while the low egg group ate an average of 1 egg/week.

HDL-cholesterol, the primary outcome of this study, remained unchanged over the three-month diet for both diets relative to baseline. Furthermore, there were no differences between the high egg and low egg groups for HDL-cholesterol or a wide-range of secondary measures, including LDL-cholesterol, total-cholesterol, triglycerides, and others. The only difference noted was lower Hb A1c at 3 months versus baseline among the low egg group (p<0.05).

Participants were asked a wide range of questions about acceptability of the diets, appetite, and satiety.

“Both groups reported an increase in overall satisfaction of the diet they were allocated compared with baseline dietary habits with results favoring the high-egg group… [particularly] enjoyment of the foods they were eating and being less bored with food choices.”

“A trend toward more satisfied with the high-egg diet compared with low-egg diet was also evident.”

In translating what these results mean, the authors concluded that

“[A] high-egg diet can be incorporated into the dietary management of people with T2D in conjunction with an increase in monounsaturated and polyunsaturated fats without adversely affecting blood lipid profiles.”

It is important to emphasize that the overall diet pattern was one in which saturated fat was reduced and PUFA and MUFA increased. This suggests that eggs can be incorporated into a high unsaturated fat, healthy eating pattern for those living with T2D without adversely affecting cardiovascular risk factors.

 

Reference Citations

Fuller, NR, ID Caterson, A Sainsbury, G Denyer, M Fong, J Gerofi, K Baqleh, KH Williams, NS Lau, and TP Markovic. “The effect of a high-egg diet on cardiovascular risk factors in people with type 2 diabetes: The Diabetes and Egg (DIABEGG) study – a 3-mo randomized controlled trial.” Am J Clin Nutr 2015:101(4);705-713. This study was funded by grants from the Australian Egg Corporation.

Accompanying editorial in the Am J Clin Nutr by Peter M Clifton entitled:  “Does dietary cholesterol influence cardiovascular disease risk in people with type 2 diabetes.”

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Higher Egg Consumption Protective of Diabetes Incidence in Middle Age Men

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Higher egg intake was associated with reduced incidence of type 2 diabetes (T2D) in Finnish men studied for 20 years.

New results were just published from the Kuopio heart study in eastern Finland (Virtanen, 2015). In this prospective cohort study, over 2,000 men between the ages of 42-60 years were randomly selected to participate in a long-term study of diet and cardiovascular disease. Dietary intake was recorded via 4-day food records at the study start and then subjects were examined at designed time points over 20 years of follow up.

The research authors introduced their interest is examining relationships between eggs and health outcomes by noting that:

“Eggs are a common, affordable, and readily available food item worldwide and, in addition to cholesterol, also a good source of many potentially beneficial nutrients…” Furthermore, “[t]he evidence on the impact of egg consumption on the risk of T2D is limited and mixed…”

Men were divided into quartiles based on average daily egg intake. Results were adjusted for potential confounding factors, including age, examination year, and energy intake.

There was a significant trend across quartiles of egg consumption, with the lowest risk of T2D in men reporting an average of 35 g/d of egg, which equate to little more than half of a medium egg compared to those consuming less than 1 egg/week. There was no further suppression of risk in those consuming higher daily egg intake.

Stated another way,

“[e]ach egg per day (55 g) was associated with a 30% lower risk.”

The longitudinal and long-term nature of this study over 20-years is a particular strength.

The researchers concluded that,

“[r]ecommendations to limit consumption of eggs (or any food) in a general healthy population should not be based on a single component in a food, such as the cholesterol in egg.”

 

Reference Citation

Virtanen, JK, J Mursu, TP Tuomainen, HEK Virtanen, and S Voutilainen. “Egg consumption and risk of incident type 2 diabetes in men: the Kuopio Ischaemic Heart Disease Risk Factor Study” Am J Clin Nutr 2015. Available on-line doi: 10.3945/ajcn.114.104109.

 

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Fat Soluble Bioactives in Egg Yolk Show Anti-Inflammatory Potential

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Is the unique combination of vitamins, carotenoids and phospholipids in egg yolks inflammatory protective?

Eggs are an example of a food that is naturally health promoting, despite containing a moderate amount of saturated fat, due to a combination of balancing bioactive components in the yolk.

Researchers at Ohio State University were interested in understanding various components of egg yolk with respect to an important inflammatory signal called NF-kappa B (NF-kB]. They presented research findings at the annual scientific sessions of the American Society for Nutrition [Shen, 2015].

In order to determine potential anti-inflammatory components, egg yolk was specially separated into two fractions 1) the polar-rich fractions of yolk and 2) the non-polar fractions. Although lower in fat, the polar-rich egg yolk still contained about 80% of the cholesterol and half of the triglyceride fat found in whole egg yolk.

The polar-rich yolk differed substantially from the non-polar egg yolk in that it retained much more cholesterol and triglyceride fat than the non-polar egg yolk, but it also retained the potentially bioactive vitamins and the carotenoids lutein/zeaxanthin.

In other words, although the non-polar egg yolk component was substantially reduced in cholesterol and triglyceride, it did so at the expense of losing fat-soluble vitamins and carotenoids with anti-inflammatory potential.

When the researchers measured the potential to reduce inflammation in pre-adipocyte (fat) cells, they found whole egg yolk to be neutral, but the lower-fat, carotenoid-rich polar yolk version to be anti-inflammatory. Although the non-polar fraction was much lower in fat, it showed no statistical effect on inflammation, likely due to the loss of lipid soluble vitamins and lutein/zeaxanthin.

They concluded that:

“partially delipidated EY-P [egg yolk-polar] fraction leads to the inhibition of NF-kB activation and its downstream inflammatory targets.”

NF-kB is a particularly important regulator of chronic inflammation, having been shown to impact inflammatory mediated central adiposity and type-2 diabetes [Harte, 2013].

Studies such as this by Shen et al. demonstrate that the final impact of specific foods on human health depends on the combination of nutrients and other bioactive components found naturally in food acting holistically.

 

Reference Citations

Shen, Q, K Riedl, RM Cole, C Lehman, L Xu, H Alder, M Belury, SJ Schwartz, and O Ziouzenkova. “Egg yolks attain anti-inflammatory properties after partial delipidation.”  Poster presented at: Experimental Biology, American Society for Nutrition Annual Scientific Session: 2015 April 29; Boston MA. This study was funded by grants from the American Egg Board.

Harte, AL, G Tripathi, MK Piya, TM Barber, JC Clapham, N Al-Daghri, D Al-Disi, W Kumsaiyai, P Saravanan, AE Fowler, JP O’Hare, S Kumar, and PG McTernan. “NF kappa B as a Potent Regulator of Inflammation in Human Adipose Tissue, Influenced by Depot, Adiposity, T2DM Status, and TNFa” Obesity 2013;21(11); 2322–2330.

 

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Barbara Lyle, PhD, is President of B Lyle, Inc. a nutrition and innovation firm and blogger for the Egg Nutrition Center.

 

Views expressed by the author may not be those of the Egg Nutrition Center.

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Recorded Webinars and Other Videos

ENC-Funded Research Presented at the Experimental Biology Meeting in March 2015

Egg Nutrition Center is the science division of The American Egg Board headquartered in Park Ridge, Illinois. This 2-minute highlight video and the eight videos below this one reflect some of the ENC-funded research that was presented at the Experimental Biology meeting in March 2015.

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