July 2010 Issue

Sunny Side Up — Eggs Can Be a Part of a Healthy Diet
By Diane Welland, MS, RD
Today’s Dietitian
Vol. 12 No. 7 P. 22

While science works to unscramble dietary cholesterol’s relation to heart disease, experts reveal eggs’ benefits and suggest ways to incorporate these protein-rich foods.

When I was growing up, eggs showed up regularly on the dinner table—not the fried kind you’d find paired with bacon or sausage but fluffy frittatas sautéed with crisp potatoes, bright green asparagus, or sweet red or green peppers. Simple, nutritious, and inexpensive, these dishes were my childhood favorites.

So you can imagine my surprise when just a few years later in my college nutrition classes I learned that eggs were no longer as healthful as I thought. Some experts even recommended avoiding them altogether due to their high cholesterol content.

Over the years, the restrictions on eggs have loosened, so much so that the 2006 American Heart Association (AHA) report doesn’t even mention them in its guidelines. But despite this exoneration, eggs’ unhealthful reputation has been hard to shake and confusion abounds.

“People are still afraid of eating eggs. I get questions about it all the time,” says Katherine Tallmadge, MA, RD, an American Dietetic Association spokesperson who has a private practice in Washington, D.C.

But while eggs are certainly not the demon some experts have claimed them to be, they are still controversial, mostly due to the complex relationship between cholesterol and heart disease. Furthermore, how they fit into a heart-healthy diet depends on various factors, including diet, health, age, and individual genetics.1,2

And, lest we forget, eggs are made up of more than just cholesterol. They also contain high-quality protein and are an excellent source of many essential nutrients. Also, eggs are inexpensive, easily accessible, and palatable to most consumers, all important factors to consider when counseling clients.

Here’s what we know.

Then and Now
Much has changed since 1970 when the AHA Nutrition Committee first advised the general public to consume less than 300 mg of dietary cholesterol per day. Just two years earlier, the AHA had set the 300 mg/day threshold only for patients with hypercholesteremia, but it decided to extend the recommendations to lower USDA data that showed cholesterol intake in 1970 averaged 600 mg/day.3 Eggs, with an estimated 274 mg of cholesterol—we now know eggs contain only 213 mg of cholesterol—were a natural target, and the AHA suggested limiting intake to no more than three or four yolks per week.3,4

Then, too, research focused only on dietary cholesterol, as classic studies such as the Ancel Keys Seven Countries Study and the Framingham Study demonstrated a clear association between high cholesterol levels and atherosclerosis.3,5

“Many of the early studies on cholesterol and heart disease didn’t take into consideration saturated fat,” says Marcia Greenblum, MS, RD, senior director of nutrition education for the Egg Nutrition Center in Washington, D.C. “Most high-cholesterol foods are also high in saturated fat, and it may have been the saturated fat that caused the rise in blood cholesterol and heart disease, not the dietary cholesterol.”

Today we know that saturated and trans fats play a much greater role in blood cholesterol levels (and specifically LDL cholesterol) than dietary cholesterol, and their detrimental effects are well documented in the scientific literature.3,6

“When it comes to heart disease, the American Heart Association guidelines’ emphasis is really on reducing saturated fat and trans fat in the diet,” says Alice Lichtenstein, ScD, past chair of the AHA Nutrition Committee and professor of nutrition science at Tufts University. “We’ve also shifted away from talking about specific foods to focusing on dietary patterns.”

Despite this fact, research on dietary cholesterol’s effect on heart disease has not been clear cut, which is why the 2006 AHA guidelines still recommend 300 mg or less cholesterol per day for healthy individuals and 200 mg or less per day for those with a high risk of developing heart-related issues.

While most studies show dietary cholesterol raises serum cholesterol only slightly, and not enough to increase heart disease risk, some studies do show a positive association between cholesterol intake and coronary heart disease biomarkers. Still other data find no relationship at all. Egg consumption studies related to heart disease show similar inconsistencies.3,7

In fact, few epidemiological studies have found a connection between eating eggs and increases in heart disease risk. A 2000 clinical review of cholesterol feeding studies by McNamara published in the Journal of the American College of Nutrition found that total blood cholesterol dropped only 2.2 mg/dL for every 100 mg decrease in dietary cholesterol. Based on this analysis, the 27% drop in per capita egg consumption from 1965 to 1995 would account for only 3% of the 30 mg/dL fall in population cholesterol levels during this time.

One of the largest egg studies, conducted by Hu and published in The Journal of the American Medical Association in 1999, examined data from the Health Professionals Follow-Up Study and the Nurses’ Health Study. Known as the Harvard Egg Study, it reviewed dietary questionnaires from 37,851 men and 80,082 women. Results revealed no overall association between egg consumption and risk of coronary heart disease or stroke in normal, healthy men and women, even at the highest level of intake of one egg per day, amounting to seven eggs per week.  

In light of these and other similar findings, several countries, including Canada, Austria, and the United Kingdom, decided to drop their limitations on cholesterol and focus solely on saturated fat and total fat.6

In the United States, cholesterol intakes have dropped drastically since 1970. Today they average only about 278 mg/day, and egg consumption has fallen as well. According to 2005 USDA food supply data, eggs provide only about 35% of the cholesterol in the U.S. diet; the lion’s share, nearly 60%, comes from meat, fish, poultry, and dairy.

“It will be interesting to see how the National Cholesterol Education Program and the new Dietary Guidelines deal with cholesterol,” says Lichtenstein, referring to the recommendations scheduled for release sometime this year.

It’s All in the Genes
Part of the reason why the relationship between heart disease and eggs remains so elusive has to do with the wide range of individual variability researchers see in response to dietary cholesterol.

In a 2004 clinical study by Herron, more than 50 healthy men and women were given a high-cholesterol diet consisting of three eggs per day and then tested for serum cholesterol. Some individuals were completely resistant to the cholesterol-raising effects of this diet. Classified as hyporesponsive, these subjects experienced little or no change in serum blood cholesterol levels. On the other hand, hyperresponsive types were much more sensitive, showing above-average increases in total and LDL cholesterol.1,3,7 

Like salt sensitivity, scientists believe these differences are innate and directly related to our genetic makeup. Also like salt sensitivity, researchers believe only a small percentage of the population (up to 30%) is hyperresponsive and sensitive to dietary cholesterol.1,3,7

Even for hyperresponders, however, egg consumption may not be so unhealthful because the LDL particle formed is larger and less atherogenic than smaller particles. In some cases, egg intake has been found to raise HDL levels as well as LDL levels, keeping the ratio of HDL to LDL the same and, thus, coronary heart disease risk low.1,3,7

Age doesn’t appear to be an issue, either. While many older people shy away from eggs for fear of raising their cholesterol, they may be worrying unnecessarily.  A 2006 University of Connecticut study published in Nutrition & Metabolism showed that eating three eggs per day for 30 days did not raise heart disease risk in healthy older adult men and women. The main reason: Even if there was a slight raise in LDL cholesterol, it was always accompanied by a similar rise in HDL cholesterol. Thus, eggs may be an inexpensive, easy, and nutritious way to increase protein in this population.

For people with diabetes, however, the story may be different. In the Hu study, men with diabetes on the high-egg diet had a heightened risk for cardiovascular disease. A February 2009 study by Djoussé published in Diabetes Care that reviewed dietary questionnaires from the Physician’s Health Study reported daily egg consumption was associated with an increased risk of type 2 diabetes.

Why the discrepancy? “First, you have to also keep in mind what type of food people are eating eggs with,” says Greenblum. “Many times eggs, in this country at least, are accompanied by fatty meats like sausage and bacon and high-fat cheese.”

Indeed, Djoussé’s study notes that “frequent consumption of eggs was associated with higher BMI [body mass index], higher proportion of current smoking, higher prevalence of hypertension, and lower prevalence of hypercholesteremia.”

Another reason could lie in the disease itself. Since people with diabetes typically have faulty fat metabolism, perhaps they are unable to process eggs the same way healthy adults can. 

In any case, Greenblum concedes the relationship between eggs and diabetes is an area that deserves more research.

How to Advise Clients 
“Eggs are just like any other food,” says Greenblum. “If you eat them in moderation, you’ll be OK.”

 “What’s most important is the total diet,” adds Tallmadge. “If you’re eating a healthy, well-balanced diet, having an egg a day would be fine. It’s not the egg that’s a problem; it’s what we eat with it. The biggest egg eaters in the world are the Japanese, and they also have the lowest rates of cardiovascular disease. That’s because their diet is low in saturated fat.”

But what if your client is concerned about cholesterol or even has high cholesterol and his or her diet is not so healthful?

“Your first step is to evaluate saturated fat and trans fat in the diet, reducing animal products like meat and dairy. Next comes the method of preparation: Avoid fried foods and foods with heavy sauces. If you’re doing all that and nothing is working, then you can look at eggs,” says Lichtenstein. “[Eggs are) basically your last line of defense. But keep in mind that removing them may or may not make a difference.”

You also want to monitor egg consumption, along with all fat consumption, if your client has diabetes or any other contraindicated health condition.

Many times, however, clients expect too much when it comes to eggs and cholesterol. “I can’t tell you how many times during my career I’ve heard people say, ‘I’ve cut out eggs, but my cholesterol is still high.’” says Tallmadge. “But will taking eggs out of an unhealthy diet make a positive difference? Probably not.”

To give your clients healthful ideas on how to eat eggs without pairing them with fatty, high-calorie ingredients, take your cue from ethnic dishes. Suggest stir-fries using scrambled egg and whole grain combinations such as fried rice with brown rice or soba noodles. Serve a poached egg nested on a bed of swiftly sautéed spinach or a variety of other cooked greens like many Europeans do, or smother eggs with vegetables such as zucchini, asparagus, potatoes, and onions. Instead of sausage or bacon, opt for a fruit salad. Finally, look to Latin American and Middle Eastern cultures, where you’ll frequently find eggs married with cooked beans such as spicy pinto beans or black beans. When it comes to eggs, the culinary possibilities really are endless.

— Diane Welland, MS, RD, is a dietitian and freelance writer based in Springfield, Va.
Sidebar:

EGGSTRA BENEFITS
While cholesterol may be the most scientifically studied nutrient in eggs, it certainly isn’t the only one of importance. Eggs are well-known for their high-quality protein, which is highly digestible, concentrated—one large egg contains 6 g—and perfectly balanced with the right amount of amino acids for human growth and development. And although most of the protein is located in the white (3.6 g), a considerable amount (2.7 g) is in the yolk.

Consuming high-protein foods such as eggs is particularly important for older adults because it can help stave off muscle loss and reduce the rate of protein breakdown.1,2 The fact that eggs are inexpensive and low in calories is another bonus, making them a popular choice for budget-conscious consumers and families with children.

Other notable nutrients primarily found in the yolk include the following:

• Lutein and zeaxanthin, two carotenoids essential to eye health. In the retina, these two compounds act as antioxidants, minimizing damage and reducing the risk of developing age-related macular degeneration.1,2,8
• Choline, a component of egg lecithin, is essential for normal development and has been shown in animal studies to improve memory and performance. Eggs are one of the few foods that contain high concentrations of this nutrient.2
• Folate, known for reducing neural tube defects, plus vitamin B12, riboflavin, and the fat-soluble vitamins A, D, and K.1,2,8

— DW

References
1. Celentano JC. Nutrition review: Where do eggs fit in a heart-healthy diet? Am J Lifestyle Med. 2009;3(4):274-278.

2. Herron KL, Fernandez ML. Are the current dietary guidelines regarding egg consumption appropriate? J Nutr. 2004;134:187-190.

3. Webb D. Dietary cholesterol, eggs and CHD. Unpublished paper for the Egg Nutrition Center. February 2010.

4. Beyer RS, Jensen LS. Overestimation of the cholesterol content of eggs. J Agric Food Chem. 1989:37(4):917-920.

5. Kritchevsky SB. A review of scientific research and recommendations regarding eggs. J Am Coll Nutr. 2004;23(6):596S-600S.

6. Klein CJ (ed). The Scientific Evidence and Approach Taken to Establish Guidelines for Cholesterol Intake in Australia, Canada, the United Kingdom, and the United States. Bethesda, Md.: Life Sciences Research Office; 2006.

7. Jones PJH. Dietary cholesterol and the risk of cardiovascular disease in patients: A review of the Harvard Egg Study and other data. Int J Clin Prac. 2009;63(Suppl 163):1-8.

8. Schmier JK, Barraj LM, Tran NL. Single food focus dietary guidance: Lessons learned from an economic analysis of egg consumption. Cost Eff Resour Alloc. 2009;7:7.

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