As easter approaches it is heartening to read in The Telegraph (March 21st) that egg consumption in the UK has risen to its highest level in five decades with the Brits now eating on average 3 to 4 eggs per week. The Telegraph says “people are once again taking the time to make a “proper” breakfast after a string of reports warning of cereal’s high sugar content, with some containing as much as 12g of sugar per [30g] serving.”
Eggs are one of the most nutritious foods and are also incredibly cheap, making them a go-to choice for maximising overall diet quality. Here we look at the latest research showing that eggs are even more amazing than we all realised.
As a recent paper titled The Fifty Year Rehabilitation of the Egg states:
The 1968 American Heart Association announced a dietary recommendation that all individuals consume less than 300 mg of dietary cholesterol per day and no more than three whole eggs per week. This recommendation has not only significantly impacted the dietary patterns of the population, but also resulted in the public limiting a highly nutritious and affordable source of high quality nutrients, including choline which was limited in the diets of most individuals. The egg industry addressed the egg issue with research documenting the minimal effect of eggintake on plasma lipoprotein levels, as well as research verifying the importance of egg nutrients in a variety of issues related to health promotion. In 2015 dietary cholesterol and egg restrictions have been dropped by most health promotion agencies worldwide and recommended to be dropped from the 2015 Dietary Guidelines for Americans.[McNamara, 2015]
Eggs are high in vitamins and minerals
Eggs are nutritional powerhouses, with each large (50g) egg coming in at a svelte 70 calories, yet providing 6 grams of high quality protein, 5 grams of high quality fat and virtually zero carbohydrates.
Along with small amounts of most minerals, eggs contain significant amounts of:
- Choline: 25% Daily Value
- Selenium: 25% RDA
- Molybdenum: 20% RDA
- Iodine: 20% RDA
- Zinc: 10% RDA
- Iron: 6% RDA
- Calcium: 2% RDA
- Vitamin B7 (Biotin): 35% RDA
- Vitamin B5 (Pantothenic Acid): 20% RDA
- Vitamin B12 (Cobalamin): 15% RDA
- Vitamin B2 (Riboflavin): 15% RDA
- Vitamin A: 6% of the RDA.
- Vitamin D: 6% RDA*
- Vitamin B9 (Folate): 5% of the RDA
*Eggs and Vitamin D
Egg yolks are a better source of vitamin D than their quoted figure because they contain a significant quantity of the active metabolite 25-hydroxy vitamin D which is more potent than D3. The effective dose probably lies somewhere between 12% to 24% RDA per egg making them a significant source of this important vitamin. [Ovesen, 2003]
Eggs are low-calorie, satiating and low GI
One of the biggest dietary regulators of appetite is protein consumption. Many of the most successful weight-loss plans involve eating plenty of protein-rich foods. Eggs, especially for breakfast, play a significant part in preventing mid-morning munchies. For example, researchers found that when comparing an egg-based breakfast to a grain-based breakfast with the same number of calories, adult men had better blood glucose control and ate fewer calories over the following 24 hours. The grain-based breakfast left participants feeling more hungry and less satisfied. [Ratliff, 2010]
One of the ways that eggs do this is by decreasing the hunger hormone grelin. [Missimer 2017]
Many people who are trying to lose weight avoid the traditional English breakfast foods like eggs and sausage opting for carbohydrates instead but is that wise? Here’s a quick quiz about one study that investigated this. Click and see!
So yes, skipping breakfast produced the biggest overall reduction in total calorie consumption as expected, but of the two breakfast options eggs and sausages resulted in a lower calorie consumption at lunchtime than the carb based pancakes, showing that a high protein breakfast can keep you fuller for longer and help control weight. [Rains, 2015]
Eggs are an excellent source of protein
One large egg contains ~6.3 g protein that is rich in all the essential amino acids. The yolk and whites contain different kinds of protein, with those in the whites possessing antimicrobial and immunoprotective properties. One study found that ovotransferrin, one of the major hen egg white proteins, prevented colitis developing in mice and led authors to suggest that it “may be a potential promising candidate for the prevention of inflammatory bowel disease”. [Kobayashi, 2015]
Some egg white proteins inhibit digestive enzymes which can lead to egg protein being absorbed by the intestines intact. This may lead to the development of an allergic reaction. Cooking, however, effectively denatures these inhibitors, reducing the risk. On the other hand, use of aspirin and other NSAIDs can increase the risk as they increase intestinal permeability. [Yokooji, 2014]
Along with reducing the potential for allergic reactions, cooking eggs improves the bioavailability of their protein, with ~91% of cooked egg protein being absorbed, compared to ~51% when raw [Evenepoel, 1998].
Methods of cooking also affect availability of the antioxidants in the yolk with soft boiling maximising the availability of these carotenoids, whilst scrambling reduced them the most.
The take home message seems to be to go for well-done whites with runny yolks. Just like this in fact…
Eggs and Heart Health
Fears about cholesterol and heart disease led to a big drop in egg consumption during the previous half century. In the USA it became popular, unfortunately, to eat only egg whites as most of the cholesterol and saturated fat is found in the yolk. It turns out, however, that egg yolk contain phospholipids which increase HDL (‘good’) cholesterol and have been shown to improve the lipid profile of patients with metabolic syndrome when eggs are eaten as part of a reduced carbohydrate diet. [Anderson, 2013]
This is all in line with large scale meta analysis which have found no association between regular egg consumption and the risk of CVD (cardio vascular disease), myocardial infarction (heart attack) or stroke in the general population [Shin, 2013 & Long, 2013]
In a recent study young healthy participants consumed three eggs per day for four weeks, and whilst their total cholesterol did increase, importantly, the ratio of HDL to LDL did not change, indicating no overall worsening of the cholesterol profile. The authors concluded that “dietary cholesterol from eggs appears to regulate endogenous synthesis of cholesterol in such a way that the LDL-C/HDL-C ratio is maintained.” [Lemos, 2018]
That is all well and good for healthy subjects, but what about people with atherosclerosis? Should they avoid eggs? A study published in Atherosclerosis in 2013 suggests they should not, as it found that compared to those who ate eggs less than once per week, those who ate more than one egg per week had a lower coronary atherosclerotic burden. [Chagas, 2013]
Eggs make better breakfasts than oats
For many people oats hold a special place as a breakfast cereal with proponents believing that oats are ‘heart healthy’ and ‘keep you full for longer’. But these assumptions have been challenged by recent studies, including one which compared the effects of consuming either two eggs or one portion of oatmeal per day for breakfast for four weeks. The egg diet led to an increase in satiety throughout the day without adversely affecting the biomarkers associated with CVD risk. [Missimer, 2017]
In addition, a second study by the same group found that “compared to oatmeal, consumption of 2 eggs for breakfast provided increased plasma carotenoids and improved biomarkers of cardiovascular disease (CVD) risk” [Missimer, 2018]
Furthermore, compared to oats an egg breakfast has been shown to reduce inflammation [Ballesteros, 2015]
Eggs, especially the yolk, are one of the richest sources of phospholipids, which includes the important phosphatidylcholine. These phospholipids appear to be responsible for the improved cholesterol profile observed in egg eaters. Phosphatidylcholine has a role in protecting the mucus layer of the intestinal tract. In fact Individuals with ulcerative colitis have notably lower levels of phosphatidylcholine in their intestinal mucus layer. Remarkably, in one randomised controlled study 80% of patients receiving phosphatidylcholine supplements were able to discontinued steroid therapy without disease exacerbation. [Stremmel, 2007]
Yolks are bright yellow because they contain high levels of the antioxidants lutein and zeaxanthin. Although eggs contain lower concentrations of these important anti-oxidants than some plant sources (e.g. spinach) they are far more bioavailable [Anderson, 2015] and do not increase the risk of kidney stones as they do not contain oxalic acid, unlike spinach. It appears that following consumption of eggs these two carotenoids increase significantly in the blood decreasing oxidation of LDL cholesterol whilst increasing LDL and HDL particle size – all of which are desirable. [Mutungi, 2010]
Lutein is transported primarily to the retina of the eye, where it has been shown to increase macular pigment density and protect against age-related macular degeneration and cataracts. Lutein and Zeaxanthin are concentrated in the yellow spot of the human retina, where they protect the cells from damage by blue light, improve visual acuity and scavenge harmful reactive oxygen species [Abdel-Aal el-SM, 2013]. In older adults (60 years +), consumption or 2 or 4 eggs per day for 5 weeks increased serum lutein and zeaxanthin, in addition to increasing macular pigment optical density. [Vishwanathan R, 2013]
It appears that in obesity these important antioxidants get taken up by fat tissue, depleting the blood and leading to reduced levels in the retina. [Bovier, 2013] Increased egg consumption may be especially helpful for overweight individuals [Anderson, 2015]
As well as concentrating in the eye, lutein and zeaxanthin have an affinity for the skin, where they act as a natural UV protectors, reducing the risk of photoaging and skin damage.
Recently it has been found that lutein accumulates in the brain, but only in primates. [Erdman, 2015] Evidence for it’s role in cognition is summarised in one 2014 paper, which explains that “The greater proportion of lutein in the pediatric brain suggests a need for lutein during neural development … In adults, higher lutein status is related to better cognitive performance, and lutein supplementation improves cognition.” [Johnson, 2014]
Is there a limit on the number of eggs per day?
There is little hard and fast evidence here. Recent meta analysis found no variation in heart disease from 0 to 1 egg per day, whereas risk of stroke decreased with increasing egg consumption. [Alexander, 2016] As we have seen in the studies above egg consumption of 3 eggs per day for 4 weeks in healthy young participants produced no adverse results.
Intake of 1 egg/d was sufficient to increase HDL function and large-LDL particle concentration; however, intake of 2-3 eggs/d supported greater improvements in HDL function as well as increased plasma carotenoids [DiMarco, 2017]
It is interesting, however, that in the 70’s eight severe burns patients were given 35 eggs per day as part of a high protein diet to aid their recovery. All recovered from their burns and the author noted that “contrary to expectations, serum cholesterol and lipoprotein levels remained normal throughout the period of study” [Hirshowitz, 1975 – full text]. Later studies confirmed the efficacy and safety of this diet. [Kaufman, 1986]
So no one can say that I have been over egging it! I deny that I have ever eaten 35 eggs in one day. (Seven is my max!)