This Australian study was specifically designed to test whether eating eggs and extra cholesterol had any effect on coronary heart disease (CHD) markers and blood sugar control in people with type 2 diabetes.
Two groups of type 2 diabetics (65 people in total) were randomly assigned to one of two diet groups. All ate the same reduced calorie diet (approx 1400 calories per day) and the same ratio of macro-nutrients; 40% calories from carbohydrates and 30% each from fat and protein. (This is the same prescription as the Zone diet, which has been shown to be an effective eating plan for Type 2 diabetics). It is higher in protein and lower in carbohydrates than the government recommended food pyramid ratio.
In this study however one group had 2 eggs each day and the other 100 grams of lean animal protein instead. This meant one group (HPHchol) consumed 590 mg cholesterol, and the other (HPLchol), 213 mg cholesterol.
The study was 12 weeks long. Participants’ dietary intakes were closely monitored and food diaries analysed. The high cholesterol group ended up eating a little less protein (28.1% vs 31.4%) and a little more fat including saturated fat and cholesterol.
Both groups lost significant weight – 6kg average. Both groups decreased triglycerides (-0.4) and non HDL cholesterol. Fasting glucose decreased by 4%, blood pressure reduced in both groups.
The significant difference in results was that HDL cholesterol increased in the egg eating group:
One of the findings of the study was a pronounced improvement in HDL-C in the HPHchol group compared with the HPLchol group. A 1 % increase in HDL-C has been associated with a 3 % decrease in CVD risk(24), although there is no evidence that a rise in HDL-C through dietary means reduces CVD risk. The increase in HDL-C in response to dietary cholesterol was also observed in the meta-analysis by Weggemans et al.(11) and the recent study by Mutungi et al.(25). It is possible that in the present study, dietary cholesterol also mediated the increase in HDL-C response. It is also possible that the increase in HDL-C may have been due to the increased fat content (3·5 %) in the HPHchol dietary pattern.
The other significant factor is that both triglycerides and total cholesterol decreased,as did apo-B on this higher protein, lower carb diet, both groups:
Increased levels of TAG (reviewed in Austin(34)) and TC(35) have independently been associated with increased CHD mortality. The present study found that plasma TAG and TC levels decreased over time on both dietary interventions.
Other markers of atherosclerotic risk are apo-B, CRP and homocysteine. Apo-B levels improved similarly over the intervention on both the diets, irrespective of the levels of dietary cholesterol. CRP did not change probably because the weight loss was not great enough, while homocysteine was not altered.
The authors conclude:
In conclusion, the present results show that in the context of a high-protein, low-saturated fat energy-restricted diet, two eggs per d did not adversely affect blood lipid profiles in individuals with type 2 diabetes and improved HDL-C, folate and lutein more effectively than a diet containing isoenergetic alternative animal sources. These results suggest that a high-protein energy-restricted diet high in cholesterol from eggs may have nutritional benefits and assist in metabolic control in individuals with type 2 diabetes.
Eggs not only contain cholesterol but they have other nutrients not found in animal protein such as choline, lutein and zeaxanthin. Choline is deficient in many peoples diets and deficiency can cause fatty liver. Lutein and zeaxanthin are important for eye health.
My recommendation if you use the zone diet – quit throwing away egg yolks – they are good for you.
Egg consumption as part of an energy-restricted high-protein diet improves blood lipid and blood glucose profiles in individuals with type 2 diabetes
Karma L. Pearce, Peter M. Clifton and Manny Noakes
The role of dietary cholesterol in people with diabetes has been little studied. We investigated the effect of a hypoenergetic high-protein high-cholesterol (HPHchol) diet compared to a similar amount of animal protein (high-protein low-cholesterol, HPLchol) on plasma lipids, glycaemic control and cardiovascular risk markers in individuals with type 2 diabetes. A total of sixty-five participants with type 2 diabetes or impaired glucose tolerance (age 54·4 (sd 8·2) years; BMI 34·1 (sd 4·8) kg/m2; LDL-cholesterol (LDL-C) 2·67 (sd 0·10) mmol/l) were randomised to either HPHchol or HPLchol. Both hypoenergetic dietary interventions (6–7 MJ; 1·4–1·7 Mcal) and total carbohydrate:protein:fat ratio of 40:30:30 % were similar but differed in cholesterol content (HPHchol, 590 mg cholesterol; HPLchol, 213 mg cholesterol). HPHchol participants consumed two eggs per d, whereas HPHchol participants replaced the eggs with 100 g of lean animal protein. After 12 weeks, weight loss was 6·0 (sd 0·4) kg (P < 0·001). LDL-C and homocysteine remained unchanged. All the subjects reduced total cholesterol ( − 0·3 (sd 0·1) mmol/l, P < 0·001), TAG ( − 0·4 (sd 0·1) mmol/l, P < 0·001), non-HDL-cholesterol (HDL-C, − 0·4 (sd 0·1) mmol/l, P < 0·001), apo-B ( − 0·04 (sd 0·02) mmol/l, P < 0·01), HbA1c ( − 0·6 (sd 0·1) %, P < 0·001), fasting blood glucose ( − 0·5 (sd 0·2) mmol/l, P < 0·01), fasting insulin ( − 1·7 (sd 0·7) mIU/l, P < 0·01), systolic blood pressure ( − 7·6 (sd 1·7) mmHg, P < 0·001) and diastolic blood pressure ( − 4·6 (sd 1·0) mmHg; P < 0·001). Significance was not altered by diet, sex, medication or amount of weight loss. HDL-C increased on HPHchol (+0·02 (sd 0·02) mmol/l) and decreased on HPLchol ( − 0·07 (sd 0·03) mmol/l, P < 0·05). Plasma folate and lutein increased more on HPHchol (P < 0·05). These results suggest that a high-protein energy-restricted diet high in cholesterol from eggs improved glycaemic and lipid profiles, blood pressure and apo-B in individuals with type 2 diabetes.
Update: This recent review found that there was no association between egg consumption and heart disease. http://www.nature.com/ejcn/journal/v65/n6/abs/ejcn201130a.html