The British Egg Information Service (BEIS) has been set up to answer queries about eggs from the general public, education sector and the media. BEIS has collated some research and abstracts from a few key papers for your reference.

Low fat diets and energy balance – how does the evidence stand in 2002.

Nutritional effect of including egg yolk in the weaning diet of breast-fed and formula-fed infants: a randomized controlled trial.

Choline: needed for normal development of memory.

Plasma lipid and lipoprotein responses to dietary fat and cholesterol: a meta-analysis

A Prospective Study of Egg Consumption and Risk of Cardiovascular Disease in Men and Women

Dietary lipids and blood cholesterol: quantitative meta-analysis of metabolic ward studies

Effect of dietary cholesterol on plasma cholesterol concentration in subjects following reduced fat, high fibre diet

Low fat diets and energy balance – how does the evidence stand in 2002.
The Research Department of Human Nutrition and The Centre for Advanced Food Studies, The Royal Veterinary and Agricultural University, Rolighedsvej 30, DK-1958 Frederiksberg C, Denmark. ast@kul.dk

The role of high-fat diets in weight gain and obesity is assessed by evidence-based principles. Four meta-analyses of weight change occurring on ad libitum low-fat diets in intervention trials consistently demonstrate a highly significant weight loss of 3-4 kg in normal-weight and overweight subjects (P < 0.001). The analyses also find a dose-response relationship, i.e. the reduction in percentage energy as fat is positively associated with weight loss. Weight loss is also positively related to initial weight; a 10 % reduction in dietary fat is predicted to produce a 4-5 kg weight loss in an individual with a BMI of 30 kg/m2. The non-fat macronutrient composition of the diet is also important. Whereas the glycaemic index of the carbohydrate may play a role for cardiovascular risk factors, there is so far no evidence that low-glycaemic index foods facilitate weight control. In contrast, intervention studies show that sugar in drinks is more likely to produce weight gain than solid sugar in foods. Although the evidence is weak, alcoholic beverages promote a positive energy balance, and wine may be more obesity-promoting than beer. Protein is more satiating and thermogenic than carbohydrates, and one intervention study has shown that an ad libitum low-fat diet where carbohydrate was replaced by protein produced more weight loss after 6 months (8.1 v. 5.9 kg). The evidence linking particular fatty acids to body fatness is weak. If anything, monounsaturated fat may be more fattening than polyunsaturated and saturated fats, and no ad libitum dietary intervention study has shown that a normal-fat high-monounsaturated fatty acid diet is equivalent or superior to a low-fat diet in the prevention of weight gain and obesity. The evidence strongly supports the low-fat diet as the optimal choice for the prevention of weight gain and obesity, while the use of a normal-fat high-monounsaturated fatty acid diet is unsubstantiated.

Astrup A 2002. Proc Nut Soc – 61, 299-309. 

Nutritional effect of including egg yolk in the weaning diet of breast-fed and formula-fed infants: a randomized controlled trial.
Child Nutrition Research Centre, Child Health Research Institute, Women's & Children's Hospital, North Adelaide, Australia.

BACKGROUND: Egg yolks can be a source of docosahexaenoic acid (DHA) and iron but are often associated with adverse consequences on plasma cholesterol. OBJECTIVE: Our goal was to investigate the effect of consumption of 4 egg yolks/wk on infant DHA status and hemoglobin, ferritin, and plasma cholesterol concentrations. Secondary outcomes included plasma iron, transferrin, and transferrin saturation. DESIGN: This was a randomized controlled trial comparing no dietary intervention, consumption of 4 regular egg yolks/wk, and consumption of 4 n-3 fatty acid-enriched egg yolks/wk in breast-fed and formula-fed infants from 6 to 12 mo of age. Erythrocyte DHA concentrations, cholesterol, and iron status were assessed at 6 and 12 mo of age. RESULTS: Of the 82 breast-fed infants recruited, 23 of 28 (no intervention), 23 of 27 (regular eggs), and 24 of 27 (n-3 eggs) completed the trial. Of the 79 formula-fed infants enrolled, 23 of 27 (no intervention), 24 of 26 (regular eggs), and 20 of 26 (n-3 eggs) completed the trial. Erythrocyte DHA concentrations were 30-40% higher after the n-3 egg intervention than after treatment with regular eggs or no eggs in both breast-fed and formula-fed infants. Egg treatment had no significant effect on plasma cholesterol, hemoglobin, ferritin, and transferrin but did result in improvements in plasma iron and transferrin saturation compared with no egg treatment. CONCLUSIONS: n-3 Fatty acid-enriched eggs may provide a means of increasing dietary DHA during the second 6 mo of life. Egg yolks may also be a useful source of iron during the weaning period and can be safely included in the weaning diet with no perturbations in plasma cholesterol.

Makrides M et al.  Am J Clin Nutr. 2002 Jun; 75(6):1084-92. 

Choline: needed for normal development of memory.
Department of Nutrition, School of Public Health, University of North Carolina at Chapel Hill, 27599-7400, USA. steven_zeisel@unc.edu

Choline is a dietary component essential for normal function of all cells. It, or its metabolites, assures the structural integrity and signaling functions of cell membranes; it is the major source of methyl-groups in the diet (one of choline's metabolites, betaine, participates in the methylation of homocysteine to form methionine); and it directly affects nerve signaling, cell signaling and lipid transport/metabolism. In 1998, the National Academy of Sciences, USA, issued a report identifying choline as a required nutrient for humans and recommended daily intake amounts. Eggs are an excellent dietary source of choline. Pregnancy and lactation are periods when maternal reserves of choline are depleted. At the same time, the availability of choline for normal development of the brain is critical. When rat pups received choline supplements (in utero or during the second week of life), their brain function changed, resulting in the lifelong memory enhancement. This change in memory function appears to be due to changes in the development of the memory center (hippocampus) in the brain. The mother's dietary choline during a critical period in brain development of her infant influences the rate of birth and death of nerve cells in this center. These changes are so important that we can pick out the groups of animals whose mothers had extra choline even when these animals are elderly. Thus, memory function in the aged rat is, in part, determined by what the mother ate. This is not the first example of a critical nutrient that must be present at a specific time in brain development. If folate isn't available in the first few weeks of pregnancy, the brain does not form normally. Thus, we suggest that pregnancy is a period when special attention has to be paid to dietary intake.

Zeisel SH 2000.  J Am Coll Nutr Oct 19 S285-S315.

Plasma lipid and lipoprotein responses to dietary fat and cholesterol: a meta-analysis
Wanda H Howell, Donald J McNamara, Mark A Tosca, Bruce T Smith, and John A Gaines.

ABSTRACT
Quantitative relations between dietary fat and cholesterol and plasma lipid concentrations have been the subject of much study and controversy during the past 40 years. Previous meta-analyses have focused on the most tightly controlled, highest-quality experiments. To test whether the findings of these investigations are generalizable to broader experimental settings and to the design of practical dietary education investigations, data from 224 published studies on 8143 subjects in 366 independent groups including 878 diet-blood lipid comparisons were subjected to weighed multiple-regression analysis. Inclusion criteria specified intervention studies published in English between 1966 and 1994 reporting quantitative data on charges in dietary cholesterol and fat and corresponding changes in serum cholesterol, triacylglycerol, and lipoprotein cholesterol concentrations. Regression models are reported for serum total cholesterol, triacyglycerol, and low-density-high-density, and very-low-density-lipoprotein cholesterol, with multiple correlations of 0.74, 0.65, 0.41, 0.14, and 0.34, respectively. Interactions of dietary factors, initial dietary intakes and serum concentrations, and study and subject characteristics had little effect on these models. Predictions indicated that compliance with current dietary recommendations (30% of energy of fat, <10% from saturated fat, and <300 mg cholesterol/d) will reduce plasma total and low-density-lipoprotein-cholesterol concentrations by = 5% compared with amounts associated with the average American diet.

Am J Clin Nutr 1997;65:1747-64.

A Prospective Study of Egg Consumption and Risk of Cardiovascular Disease in Men and Women.
Frank B. Hu, MD, Meir J. Stampfer, MD, Eric B. Rimm, ScD, JoAnn E. Manson, MD, Alberto, Ascherio, MD, Graham A. Colditz, MD, Bernard A. Rosner, PhD, Donna Spiegelman, ScD, Frank E. Speizer, MD, Frank M. Sacks, MD, Charles H. Hennekens, MD, Walter C. Willett, MD.

ABSTRACT

Context Reduction in egg consumption has been widely recommended to lower blood cholesterol levels and prevent coronary heart disease (CHD). Epidemiology studies on egg consumption and risk of CHD are sparse.

Design and Setting Two prospective cohort studies, the Health Professionals Follow-up Study (1986-1994) and the Nurses’ Health Study (1980 — 1994).

Main Outcome Measures Incident nonfatal myocardial infraction, fatal CHD, and stroke corresponding to daily egg consumption as determined by a food-frequency questionnaire.

Results We documented 866 incident cases of CHD and 258 incident cases of stroke in men during 8 years of follow-up and 939 incident cases of CHD and 563 incident cases of stoke in women during 14 years of follow-up. After adjustment for age, smoking, and other potential CHD risk factors, we found no evidence of an overall significant association between egg consumption and risk of CHD or stroke in either men or women. The relative risks (RRs) of CHD across categories of intake were less than 1 per week (1.0), 1 per week (1.06), 2 to 4 per week (1.12), 5 to 6 per week (0.90), and ≥ 1 per day (1.08) (P for trend - .75) for men; and less than 1 per week (1.0), 1 per week (0.82), 2 to 4 per week (0.99), 5 to 6 per week (0.95), and ≥1 per day (0.82) (P for trend = .95) for women.
In subgroup analyses, higher egg consumption appeared to be associated with increased risk of CHD only among diabetic subjects (RR of CHD comparing more than 1 egg per day with less than 1 egg per week among diabetic men, 2.02(95% confidence interval, 1.05-3.87; P for trend = 0.4), and among diabetic women, 1.49 (0.88 — 2.52; P for trend = 0.08).

jama. 1999;281:1387-1394 www.jama.com

Dietary lipids and blood cholesterol: quantitative meta-analysis of metabolic ward studies
Robert Clarke, Chris Frost, Rory Collins, Paul Appleby, Richard Peto

ABSTRACT

Objective: To determine the quantitative importance of dietary fatty acids and dietary cholesterol to blood concentrations of total, low density lipoprotein and high density lipoprotein cholesterol. Design: Meta-analysis of metabolic ward studies of solid food diets in healthy volunteers. Subjects: 395 dietary experiments (median duration 1 month) among 129 groups of individuals. Results: Isocaloric replacement of saturated fats by complex carbohydrates for 10% of dietary calories resulted in blood total cholesterol falling by 0.52 (SE 0.03) mmol/l and low density lipoprotein cholesterol falling by 0.36 (0.05) mmol/l. Isocaloric replacement of complex carbohydrates by polyunsaturated fats for 5% of dietary calories resulted in total cholesterol falling by a further 0.13 (0.02) mmol/l and low density lipoprotein cholesterol falling by 0.11 (0.02)mmol/l. Similar replacement of carbohydrates by monounsaturated fats produced no significant effect on total or low density lipoprotein cholesterol.
Avoiding 200 mg/day dietary cholesterol further decreased blood total cholesterol by 0.13 (0.02) mmol/l and low density lipoprotein cholesterol by 0.10 (0.02) mmol/l.

Conclusions: In typical British diets replacing 60% of saturated fats by other fats and avoiding 60% of dietary cholesterol would reduce blood total cholesterol by about 0.8 mmol/l (that is, by 10-15%), with four fifths of this reduction being in low density lipoprotein cholesterol.

Effect of dietary cholesterol on plasma cholesterol concentration in subjects following reduced fat, high fibre diet.
Jacqueline Edington, Moira Geekie, Robin Carter, Lisa Benfield, Karen Fisher, Madeleine Ball, Jim Mann.

ABSTRACT

One hundred and sixty eight subjects participated in a randomised crossover study to determine whether halving or doubling the present dietary cholesterol intake from eggs had any influence on blood cholesterol concentration in people following current dietary recommendations. During the first eight weeks all participants were advised to follow a reduced fat diet (26% total energy for hyperlipidaemic patients, 35% total energy for normolipidaemic volunteers) with an increased ratio of polyunsaturated to saturated fatty acids. This background diet was continued throughout the 16 week experimental period, during which participants ate either two or seven eggs a week. A small but significant increase in total cholesterol was seen after four weeks in the group eating seven eggs a week compared with that in the group eating two eggs a week, but this was no longer apparent after eight weeks.

Previous studies suggesting that dietary cholesterol has a greater effect on the serum cholesterol concentration either have been carried out against a background of a higher fat intake or have contrasted extreme cholesterol intake. A further reduction in dietary cholesterol seems to be unnecessary in those people who have already reduced their intake of saturated fat and increased the ratio of polyunsaturated to saturated fatty acids and fibre rich carbohydrate.