Every since ancient Chinese farmers first domesticated chickens and found out that eggs were the tasty byproduct, the feud over whether eggs are good for you or bad for you has continued.
For egg lovers this dispute has presented a dilemma. You love eggs and the foods made with them, but you worry that too many eggs or parts of an egg may be unhealthy. So what’s a foody to do?
There has been tons of research on the benefits of eggs, or lack thereof. Much of the research challenges the findings of other research – and that battle will probably continue. For those who wonder if they should or shouldn’t indulge in eggs and egg-enhanced foods this article may help – at least until the next piece of research is published.
The short answer to whether or not you should eat eggs is yes, it’s ok. But the devil is in the details when it comes to the specifics of that answer.
First, exactly what is an egg? Nutritionally speaking, a basic raw, fresh egg has about 340 calories, 200 of which come from fat. It has 24 grams of total fat, 8 grams of which is saturated fat, and 1 gram of trans fat. There are typically a couple of hundred milligrams of sodium/salt, 2 to 5 grams of carbohydrates, and 30 grams of protein. It has plenty of vitamins A and D, iron, riboflavin, folate, and vitamin B-12. But, and this is where much of the controversy over eggs comes, it also has close to 1000 milligrams of cholesterol. Most of the debate over eggs focuses on that one ingredient. But there’s more to the story.
The Good News About Eggs
The national Dietary Guidelines for Americans, which was updated in 2010, says that eggs are a “nutrient dense food” and the “consumption of one egg per day is not associated with risk of coronary heart disease or stroke in healthy adults.” The guidelines also point out that eggs provide high-quality protein that helps build muscles and increases energy, which can help maintain a healthy weight, an important factor in promoting overall health.”
There are a number of recent studies that have supported the conclusion that eggs are good for you.
A 2008 report from the ongoing Physicians' Health Study  supports the idea that eating an egg a day is generally safe for the heart, it also suggests that going much beyond that could increase the risk for heart failure later in life as well as other problems.
Of course most people don’t just eat an egg and leave the breakfast, lunch or dinner table. Just about all research cautions that eating eggs are less of a problem than eating eggs with lots of trimmings that can give your cardiovascular system a real jolt. Add cheese, sausages, home fries, and white toast to your eggs and you’ve entered a whole new arena of what’s healthy and what’s not.
In another study involving more than 80,000 female nurses , Harvard researchers found that consuming an egg a day did not present any higher risk of heart disease than avoiding eggs. The study did caution that those who find it difficult to control their cholesterol levels (particularly their LDL, the bad kind of cholesterol) should be very careful about eating eggs, particularly the yolks.Credit: www.exploratorium.com
The yolk vs. egg whites is a critical element in understanding the good, the bad, and the ugly about eggs.
In her 2010 book, “Should I Eat Egg Yolks? Separating Facts From Fiction” , author Jamie Hale points out that “yolks are nutritious and the cholesterol content is no big deal for most people. Eating too many yolks may be a bad thing, but too much of any food could be bad.” The yolk, she goes on to say, is the “most nutrient-dense part of the egg and is rich in carotenoids, lutein, and zeaxanthin. These carotenoids have positive benefits on the human retina and may decrease age-related vision loss.”
So why do many people avoid or throw away the yolk? Hale says it’s primarily due to the cholesterol issue. Yet, she says, about “70 percent of the population experience little or no increase in cholesterol levels [from eating an egg a day] even when their cholesterol intake is high.”
That view is echoed by research done by Dr. Maria Luz Fernandez of the University of Connecticut. In a 2006 article  she said “We need to acknowledge that diverse healthy populations experience no risk in developing coronary heart disease by increasing their intake of cholesterol, but in contrast, they may have multiple beneficial effects by the inclusion of eggs in their regular diet.”
Dr. Fernandez’ views were supportive of a number of prior studies. Dr. Stephen Kritchevsky of the Wake Forrest University School of Medicine said in a 2004 review  on egg consumption that “eight studies have reported on the egg consumption and CHD (coronary heart disease) risk directly. On the whole, they do not support the contention that egg consumption is a risk for CHD.” In fact, Dr. Kritchevsky pointed out that the research shows people who eat less than one egg per week actually have higher blood cholesterol levels than those who eat more than four eggs per week. While that may seem odd, what he means is that approximately 70 percent of people have blood cholesterol that does not change significantly even when the amount of dietary cholesterol (e.g. in eggs) varies. Even the 30 percent who do respond to varying amounts of dietary cholesterol generally show an increase in both LDL (“bad” cholesterol) and HDL (the “good” cholesterol), which makes for a balanced and healthy ratio of cholesterol.
So, the idea of an egg a day being acceptable for most people is something there is general agreement on. And the notion that for most people eating more than that is generally not a good idea is also something there is general agreement on. That’s supported by several studies.
For example, a 2006 study  looked at what would happen if you added two eggs a day to your usual daily diet. The study concluded that adding 14 eggs a week to a normal diet (assuming you are of average health) would “unfavorably” affect your blood lipids and could have long-term consequences in terms of your cardiovascular health. In other words, don’t eat that many eggs. An average of one egg a day should be the limit.
The Bad News About Eggs
So, does that mean we don’t have to worry about our egg consumption as long as we moderate our intake and consume no more than about an egg a day? Yes and no.
While the impact of cholesterol has been the big concern when it comes to eggs and the issue that has gotten the most attention, a couple of other studies on eggs have raised some other health issues.
In the aforementioned Nurses Health Study  concern was raised about the impact of eating eggs, particularly the egg yolk, on men and women with diabetes or heart disease. For people with those health issues, the study found it best to limit the consumption of eggs to no more than three a week (specifically, the study said, three egg yolks per week). In fact, the cardiovascular risks increased in men and women with diabetes who ate more than three eggs a week.
Further evidence of the egg-diabetes connection was proven in a 2009 study that examined the relationship between eating eggs and the risk of Type 2 diabetes. The study looked at data from previous studies that examined the health of more than 55,000 men and women. The study spanned a period of 20 years for men and nearly 12 years for the women in the study. In short the findings that eating an egg a day could increase the risk of Type 2 diabetes in both men and women. They point out only careful examination and monitoring by a person’s physician can determine the precise risks of diabetes. But, the study adds a cautionary note to the “should I” or “shouldn’t I” eat an egg a day.
Another concern bedeviling the egg controversy is whether or not eggs contribute to the risk of prostate cancer.
In a study  completed in late 2011, researchers looked at the affect of diet on prostate cancer diagnoses.
The study accepted previous research that said processed meat and fish have been shown to be associated with the risk of advanced prostate cancer. It then went on to look at the effects of diet after a prostate cancer diagnosis and the risk of its progression. The researchers looked at the relationship between patients who had been diagnosed and their consumption of processed and unprocessed red meat, fish, poultry, and eggs and the risk of prostate cancer recurring or progressing. While eggs where only one of the dietary issues included in the study it is well worth noting.
The researchers found that eating processed and unprocessed red meat, fish, and skinless poultry were not associated with prostate cancer recurrence or progression. But, eating more eggs and poultry with skin was found to have a two-fold increase in risk. Again, only precise consultation with your physician can appropriately assess what is best for you, but the study does suggest that a careful examination of one’s diet is important for prostate cancer patients post-diagnosis and post-treatment.
The Bottom Line on Eggs
Eggs have been and continue to be a much researched food item. On balance the verdict – at least for now – is that an egg a day for most people can be part of a nutritious and healthy diet that falls into current nutrition and cholesterol guidelines. The U.S. Department of Agriculture has even recently lowered by 14 percent the amount of cholesterol it estimates is contained in an average large egg (the USDA says their current egg/cholesterol level is 185 milligrams as opposed to their previous standard of 212 milligrams). The USDA also now says the amount of vitamin D they estimate each egg has is 64 percent higher than they previously calculated.
So there appears to agreement that eggs are good for you, with the caveat suggested by the saying, “all things in moderation.”
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8. Egg, Red Meat, and Poultry Intake and Risk of Lethal Prostate Cancer in the Prostate-Specific Antigen-Era: Incidence and Survival. Cancer Prevention Research: American Journal of Clinical Nutrition December 2011 4:2110-2121.