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Eggs and diabetes

Eggs and diabetes

Overview

Some epidemiological studies have suggested that there may be an increased risk of cardiovascular disease (CVD) in people with diabetes who consume more than 7 eggs per week [1,2,3,4]. However, these were all observational studies, many of which were secondary analyses of data and not specifically designed to investigate the association between eggs and diabetes; they provide no evidence of a mechanism for this observed association and most do not distinguish between subjects who have type 1 and type 2 diabetes (T2D). 

People who have existing diabetes could be at increased risk of CVD from dietary cholesterol, but it is not currently possible to establish whether this is a real relationship or a spurious one that could arise, for example, from the fact that eggs are frequently consumed together with other foods that are high in saturated fat or associated with other undesirable lifestyle factors such as physical inactivity.

It is possible that eggs could just be a ’marker’ of a diet rich in saturates in these studies. A recent meta-analysis of a sub-group of studies showing a positive association between high levels of egg consumption and cardiovascular risk concluded that the finding is based on a small number of studies and requires replication [4].

Recent Research

Good prospective data on the effects of egg consumption in people with diabetes is lacking.  One short-term, randomised controlled trial (RCT) in people with T2D or impaired glucose tolerance who consumed a reduced energy diet containing 2 eggs per day (high dietary cholesterol; HDC) showed similar weight loss and improvements in blood lipid profiles, blood pressure and glycaemic control, to the control group who consumed an energy reduced, low cholesterol diet (<2 eggs/week) [5]. Moreover, in the HDC group, HDL cholesterol increased significantly compared to the control group.

A longer-term, well-controlled RCT – the Diabetes and Egg (DIABEGG Study) – compared the effects of a high egg diet (2 eggs/day, 6 days a week) to a low egg diet (< 2 eggs/week) on lipid profiles in 140 participants with T2D or prediabetes over 3 months [6]. In this trial the dietary intake of both groups was matched for energy and macronutrient intake; both groups were advised to reduce their intake of saturates, substituting foods rich in monounsaturates (MUFA) and polyunsaturates (PUFA). The participants consuming the high egg diet, whilst maintaining weight and consuming increased amounts of MUFA and PUFA, showed no adverse effects on lipid profiles compared to the low egg control group – there were no differences in total cholesterol, LDL or HDL cholesterol, triglycerides, or glycaemic control. There was a within-group trend of improved HDL-cholesterol in the high egg group, consistent with other studies [5], especially those in obese, insulin-resistant subjects, in whom cholesterol feeding has been shown to be associated with reduced dietary cholesterol absorption [7]. Interestingly, the high egg group expressed increased satiety and reduced hunger post breakfast.

Click here for more information on satiety.

The results of a much larger, prospective 5-year study in more than 60,000 Japanese men and women, without a pre-existing history of diabetes or other serious disease, also suggest that there may be no association between dietary cholesterol/egg consumption and T2D, at least in Japanese populations [8]. Dietary cholesterol/egg intake was estimated using a validated food frequency questionnaire and the 5-year incidence of T2D was recorded.  There was no evidence of an association of between dietary cholesterol or egg intake and 5 year incidence of T2D in men. Conversely, there was evidence of an inverse association between dietary cholesterol and T2D in overweight and normal women, although the analysis was partly confounded by marked differences in the intake of other nutrients across the quartiles of cholesterol intake, so that those in the highest quartile also had higher intakes of meat protein, total fat and all fatty acids, fish and shellfish, and lower intakes of carbohydrate and alcohol, compared with those in the lowest quartile. When the data were adjusted for intake of these nutrients, the inverse association between dietary cholesterol and T2D in women was attenuated/disappeared, suggesting that this could be partly explained by other nutrients. However, there was an apparent residual, although non-significant, protective effect of dietary cholesterol against T2D in post-menopausal women and this warrants further investigation.

The authors concluded that the discrepancy between outcomes in Asian and Western cohorts might be explained at least in part by differences in sources of dietary cholesterol - as Westerners consume more dietary cholesterol from meat than eggs. However, the discrepancy could also reflect innate physiological differences between Western and Asian populations, for example Japanese men and women tend to have lower BMIs and lower insulin secretory capacity than their Western counterparts.

Further controlled studies in Western populations as well as mechanistic data are still needed to explain the relationship between dietary cholesterol intake and diabetes. Until then, no firm conclusions or recommendations on egg consumption in people with diabetes are possible, although there is some evidence that a diet high in protein, such as egg protein, may in fact improve glycaemic control and might therefore be beneficial for people with T2D or pre-diabetes [9].

Click to read recent research on eggs and diabetes

References

  1. Hu FB et al (1999) A prospective study of egg consumption and risk of cardiovascular disease in men and women. Journal of the American Medical Association 281: 1387-1394
  2. Djoussé L, Gaziano JM (2008) Egg consumption in relation to cardiovascular disease and mortality; the Physicians’ Health Study. American Journal of Clinical Nutrition 87: 964-969
  3. Djoussé L, Gaziano JM, Buring JB et al (2009) Egg consumption and risk of type 2 diabetes in men and women. Diabetes Care 32: 295-300
  4. Rong Y, Chen L, Zhu T et al  (2013) Egg consumption and risk of coronary heart disease and stroke: dose-response meta-analysis of prospective cohort studies. British Medical Journal 346: e8539
  5. Pearce KL, Clifton, PM, Noakes M (2011) Egg consumption as part of an energy-restricted high-protein diet improves blood lipid and blood glucose profiles in individuals with type 2 diabetes. British Journal of Nutrition 105:584-92
  6. Fuller NR, Caterson ID, Sainsbury A et al   (2015) 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. American Journal of Clinical Nutrition doi: 10.3945/​ajcn.114.096925
  7. Knopp RH, Retzlaff, B Fish B et al (2003) Effects of insulin resistance and obesity on lipoproteins and sensitivity to egg feeding. Arteriosclerosis Thrombosis and Vascular Biology 23: 1437-43
  8. Kurotani K, Nanri A, Goto A et al (2014) Cholesterol and egg intakes and the risk of type 2 diabetes: The Japan Public Health Center-based Prospective Study. British Journal of Nutrition, pp1636-43, doi: 10.1017/S000711451400258X.
  9.  Campbell AP, Rains TM (2015) Dietary protein is important in the practical management of prediabetes and type 2 diabetes. Journal of Nutrition 2015 Jan;145(1):164S-169S. doi: 10.3945/jn.114.194878. Epub 2014 Dec 3.

All information checked by an independent Registered Nutritionist/Dietitian

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