An egg a day? Is that okay?

I love eggs, and I don’t want to give them up.  Is this a bad thing?  Well, in the 1960s doctors had solid evidence linking heart attacks and strokes to higher levels of cholesterol in the blood. So it just seemed like common sense to avoid foods rich in cholesterol, including eggs.

But in this case, common sense was wrong. In 1999, a large Harvard study found that people who ate one egg a day were no more likely to have heart disease or strokes than those who ate eggs less often than once a week. It turns out that much of the cholesterol in your blood is made by your liver, not absorbed from the food you eat. In other words, the cholesterol in food doesn’t affect the levels in your blood all that much.

In fact, saturated fats (found primarily in meat and dairy products) and trans fats (from the partially hydrogenated oils used in commercial baked goods, stick margarine, and French fries) do much more to increase blood cholesterol levels because they stimulate your liver to make more cholesterol.

The cholesterol in food isn’t completely harmless, and eggs do have a lot of it. But they also have a great many healthful nutrients, including B vitamins, folic acid, protein, and “good” polyunsaturated fats.

So here’s my advice: If you enjoy eggs, feel free to have an egg a day. I’d also look for eggs that are high in omega-3 fats. Some chickens are raised on diets high in these fats, which do get into their eggs.

Like you, I avoided eating eggs for decades. Now, I have eggs several times a week — guilt free! But check the Nutrition Facts label on other foods that you buy. It will tell you if the food is high in saturated fats and (often) trans fats.

One caveat: If you have diabetes, there is some evidence that an egg a day may not be a good idea. People with diabetes are particularly vulnerable to any adverse effect from total or “bad” LDL cholesterol levels, and eggs do have a slight tendency to raise them both. A study from Harvard found an increased risk of heart disease among people with diabetes who ate one or more eggs a day. Still, cholesterol-rich foods like eggs (with the yolks) raise cholesterol levels far less than saturated fats in meat and full-fat dairy products. Is someone with diabetes, who has low levels of total cholesterol and LDL cholesterol, at risk from eating six eggs a week? I know of no good information on that. To be safe, I would suggest people with diabetes stick to about three eggs a week. They might also check out products made with just egg whites; without the yolk, eggs don’t have any cholesterol.

Julie K. Silver, M.D., is an assistant professor in the Department of Physical Medicine and Rehabilitation at Harvard Medical School. She is also the Chief Editor of Books for Harvard Health Publications.

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