The USDA announced today that eggs are significantly lower in cholesterol than previously thought. And, by the way, they are also quite a bit higher in vitamin D.
All by itself, this is potentially important news, with wide implications for the American diet. The newly released 2010 Dietary Guidelines for Americans, for instance, recommend a limit of 300mg of cholesterol per day for healthy adults, and 200mg per day for adults with, or at high risk for heart disease. The new, lower cholesterol content of eggs means that these guidelines could be met if healthy adults average between one and two eggs per day, while even adults with heart disease can come in under the guideline consuming an egg daily. (By the way, the reason eggs are now lower in cholesterol is not entirely clear, but likely relates to changes in the diets of hens. We are what we eat, and so are chickens ... and their eggs.)
But I consider news about less cholesterol to be just one entry among several that collectively go a long way toward full ... eggsoneration.
First, we were probably wrong about the harms of dietary cholesterol in the first place. Over the past decade or so, numerous studies -- both observational studies in large populations, and intervention trials in smaller ones -- have suggested that dietary cholesterol in general, and eggs in particular, do not contribute meaningfully to blood cholesterol levels, or cardiac risk. My own lab has contributed two such studies to the literature- one in which we saw no harms from two eggs daily in healthy adults; and another in which we saw no harm from two eggs daily in adults with high blood cholesterol.
We are currently running a trial to assess the effects of two eggs daily on health markers in adults with coronary heart disease, and are hypothesizing there will once again be no harms.
My interest in all this, by the way, does not derive from the fact that I have three egg-laying hens living in my backyard! (I do.) Rather, I am interested in being right about means of optimizing health through optimizing diet.
In the case of 'eggs'clusion, I once believed it was right -- and banished eggs from my own diet for the better part of 20 years. But I watched the science as it evolved, and did what scientists are supposed to do: kept pace with it. I have reintroduced eggs back into my own diet, and into the advice I offer patients.
One of the operative words in the above paragraph is 'evolved,' because evolutionary biology is part of this story as well. Paleo-anthropologists who study our ancestral diet tell us, in essence, that we are well adapted to consume dietary cholesterol. Our Stone Age ancestors got cholesterol from eggs, as well as bone marrow and organ meats- so cholesterol is 'native' to the human diet. Saturated fat is far less so, being rather rare in nature; and the trans fat produced when oils are partially hydrogenated is truly alien, and thus predictably a bad actor.
There is one final addition to the defense of eggs. Foods we don't eat have implications for foods we do. So banishing eggs begs the question: what do we typically eat instead?
To my knowledge, there has been no systematic study of this. But I have seen coronary care units that scrupulously avoid serving eggs to their patients provide them trays of pancakes, or waffles, or white toast, and so on. I certainly have patients who have avoided eggs, but not thought twice about eating donuts, Danish, bagels, and such.
What we don't eat has implications for what we do, and I think it very likely that general advice to avoid eggs actually served to lower overall diet quality -- by increasing intake of refined starches and added sugars. We have a study protocol currently under review that will examine the question: do you wind up with better overall diet quality and health with advice to exclude, or include, eggs? You know which way I'm betting.
I hasten to add that a diet can certainly be optimal without including eggs. (If people swapped out egg breakfasts for mixed berries, walnuts, and oatmeal -- I would have no objection; but I have not seen much of that!) A balanced vegan diet, for example, is a powerful force for good health.
But well-informed and dedicated vegans are a vanishingly small part of the population. Most Americans, and much of the world's population, eat mixed diets in which eggs are not taboo. Eggs have been avoided by members of these groups not because of cultural prohibitions, but in an attempt to avoid a concentrated source of dietary cholesterol, and its potential harms.
We have long had cause to reconsider the harms of dietary cholesterol; they are, at most, feeble and uncommon -- and there is a good chance they are truly negligible, or simply don't exist. We have also long known that eggs, other than their cholesterol content, are extremely nutritious overall -- rich in top quality protein, vitamins, minerals, and other important nutrients such as biotin and choline. As of today, we also know that eggs are a less concentrated source of cholesterol than they once were into the bargain.
There, then, is the case for eggsoneration. The defense rests.
Dr. David L. Katz; www.davidkatzmd.com
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