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Canadian Journal of Cardiology

Not All Eggs Are Created Equal: The Effect on Health Depends on the Composition

      To the Editor:
      A recent review addressed the increasing tendency to accept daily egg as optional in healthy diets, particularly in patients with or at risk for vascular disease. It emphasized that “diet is not all about fasting blood lipids,” but rather the post-prandial effects of high cholesterol, ie, increased LDL oxidation (37% with 2 eggs/day), increased post-prandial lipemia (following >140mg cholesterol/meal), and potentiated adverse effects of dietary saturated fat (ie, bacon and butter, compared to egg consumed with salad oil). Eggs may further induce inflammation per observed elevations of CRP and amyloid A, with worsened macrophage accumulation in adipose tissue. The Physician's Health Study showed a 2-fold increase in CVD and all-cause mortality following onset of diabetes, and that egg consumption independently increased rates of new-onset diabetes.
      It is worth noting that most of these deleterious effects could be addressed by egg composition modifications. Two/day eggs with reduced n-6 PUFA and increased n-9 MUFA and antioxidants (vitamin E, carotenoids, selenium) reversed egg-induced increased LDL oxidation to levels of 2-4 eggs/week (Figure 1).
      • Shapira N.
      • Pinchasov J.
      Modified egg composition to reduce low-density lipoprotein oxidizability: high monounsaturated fatty acids and antioxidants versus regular high n-6 polyunsaturated fatty acids.
      One/day n-3 PUFA-fortified egg improved triglyceride and HDL levels,
      • Maki K.C.
      • Van Elswyk M.E.
      • McCarthy D.
      • et al.
      Lipid responses in mildly hypertriglyceridemic men and women to consumption of docosahexaenoic acid-enriched eggs.
      ApoB:ApoA1 ratio, and fasting plasma glucose.
      • Ohman M.
      • Akerfeldt T.
      • Nilsson I.
      • et al.
      Biochemical effects of consumption of eggs containing omega-3 polyunsaturated fatty acids.
      Similarly, 2/day eggs modified for reduced n-6 PUFA and enhanced n-9 MUFA and antioxidants reduced fasting glucose compared to 2/day regular western high n-6-PUFA eggs. Being an effective antioxidant delivery system, as shown by increased blood vitamin E and carotenoids,
      • Shapira N.
      • Pinchasov J.
      Modified egg composition to reduce low-density lipoprotein oxidizability: high monounsaturated fatty acids and antioxidants versus regular high n-6 polyunsaturated fatty acids.
      and the finding that n-3 PUFA-fortified egg also reduced CRP,
      • Burns-Whitmore B.
      • Sapwobol S.
      • Hadd E.
      • Sabajaram S.
      N-3 fatty acid enriched egg decreases C-reactive protein in healthy adults.
      suggests that “designer” eggs may provide protection against oxidative stress, inflammation, and acute effects of high glycemic load, recently linked to increased inflammation and reduced blood antioxidants, potentially associated with diabetes risk.
      Figure thumbnail gr1
      Figure 1Lag-time to plasma LDL oxidation following low-egg (2-4/week) or high-egg (2/day) regular high n-6 PUFA (HPUFA-Regular), high n-6 PUFA+high-antioxidant (HPUFA-HAOX), or high n-9 MUFA+high-antioxidant (HMUFA-HAOX) 3-week regimes (n=17)
      • Shapira N.
      • Pinchasov J.
      Modified egg composition to reduce low-density lipoprotein oxidizability: high monounsaturated fatty acids and antioxidants versus regular high n-6 polyunsaturated fatty acids.
      . *P < 0.01 (vs. low-egg); **P < 0.01 (vs. regular egg).
      The above emphasize that not all eggs are created/prepared equal, and further, egg is not purely cholesterol, but rather a high nutritional value food with a unique capacity to transform and concentrate protective nutrients (ie, DHA, antioxidants) that can modify metabolic/physiological effects. Moreover, eggs’ high “satiety index” makes them an important candidate against obesity, and much lower carbon footprint than chicken, beef, or pork yields environmental advantages.
      Designing protective compositions and preparation, ie, based on advantageous Mediterranean/Greek-type eggs and dietary principles – high n-3 PUFA, n-9 MUFA, and antioxidants, with low n-6 PUFA – could significantly influence egg-related benefits vs risks. Modifications more suited to requirements of subpopulations could differentially widen recommendations to accept vs reject eggs. Most of us will benefit, though consumption may remain advised against in some metabolically/genetically-sensitive and/or hyperlipidemic individuals.

      References

        • Shapira N.
        • Pinchasov J.
        Modified egg composition to reduce low-density lipoprotein oxidizability: high monounsaturated fatty acids and antioxidants versus regular high n-6 polyunsaturated fatty acids.
        J Agric Food Chem. 2008; 56: 3688-3693
        • Maki K.C.
        • Van Elswyk M.E.
        • McCarthy D.
        • et al.
        Lipid responses in mildly hypertriglyceridemic men and women to consumption of docosahexaenoic acid-enriched eggs.
        Int J Vitam Nutr Res. 2003; 73: 357-368
        • Ohman M.
        • Akerfeldt T.
        • Nilsson I.
        • et al.
        Biochemical effects of consumption of eggs containing omega-3 polyunsaturated fatty acids.
        Ups J Med Sci. 2008; 113: 315-323
        • Burns-Whitmore B.
        • Sapwobol S.
        • Hadd E.
        • Sabajaram S.
        N-3 fatty acid enriched egg decreases C-reactive protein in healthy adults.
        FASEB J. 2007; 21: 704-705

      Linked Article

      • Reply to Letters from Dr Maria Luz Fernandez, Eddie Vos, and Dr Niva Shapira
        Canadian Journal of CardiologyVol. 27Issue 2
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          The letter of Dr Shapira rightly points out that the question of cholesterol oxidation is related to what happens in vivo as much as to what may occur in the frying pan, and that low-density lipoprotein (LDL) oxidation is part of the problem. It is worth remembering that elevated circulating cholesterol has deleterious pleiotropic effects that are exerted via LDL cholesterol (LDL-C) and that may affect several physiological functions. Elevated LDL-C has been associated with an increased atherogenic potential related to enhanced susceptibility to oxidation (malondialdehyde modification), hypercoagulability (increase in beta-thromboglobulin, thromboxane B2), enhanced platelet reactivity (increase in soluble P-selectin, reduction of eNOS), reduced fibrinolysis (increase in plasminogen activator inhibitor-1), endothelial dysfunction (reduced nitric oxide), increased vascular reactivity (increased thromboxane B2 and decreased prostacyclin), increased vascular permeability, and increased plasma viscosity (increased fibrinogen, decreased erythrocyte deformability).
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