Ask The Doctors: August 2018
Q: I had a heart attack and have done well on medications and a diet prescribed by my doctor. For years I have been told not to eat eggs. Now I hear that they may be good for you. What should I believe?
A: The effect of egg consumption on cardiovascular disease (CVD) has been controversial. Because of the known relationship between blood cholesterol levels and CVD, we used to think that eating eggs, especially egg yolks that are high in cholesterol, would increase cholesterol levels in the blood and risk of cardiovascular disease. Before I go further, let me say that it is important to distinguish between dietary cholesterol and cholesterol in the blood. We make most of the cholesterol in our bodies, and this is influenced by genetics, gender and age. Although eating cholesterol increases blood levels, it is not by much. In fact, consuming sugar, trans fats and saturated fats may influence cholesterol levels more than eating cholesterol. Research on more than 120,000 men and women found that eating one egg a day is not associated with increased CVD risk in otherwise healthy individuals. Based on these observations, the Dietary Guidelines for Americans 2015 update de-emphasized reducing cholesterol from eggs and shellfish such as shrimp and placed more emphasis on reducing saturated and trans fat. The guidelines push for a Mediterranean-style diet, low in processed foods, but rich in fruits, vegetables, nuts, legumes and fat from olive oil. So if eggs are not bad for us, are they actually good for us? A single egg yolk may contain 140-230 milligrams (mg) of cholesterol, but it also contains other helpful proteins and nutrients. A 2018 study suggests that consuming an average of five to six eggs a week may actually reduce heart disease risk. However, we don’t advise you rush out and have three-egg and bacon omelets a day. Moderation in consumption, how you prepare your eggs and what else you eat with them is key. If you eat an otherwise healthy diet, eat fewer than five to six eggs a week, making sure those egg dishes are healthy. If you have difficulty controlling your cholesterol, have a strong genetic risk for high cholesterol or have established CVD or diabetes, limiting egg consumption further still makes sense.
Q: Many of my friends regularly take fish oil capsules to prevent heart disease. Can I get the same benefit from eating fish? I would like to avoid taking pills.
A: Since 2002 the American Heart Association (AHA) has espoused the benefits of consuming long-chain n-3 polyunsaturated fatty acids (PUFA), also called omega-3 fatty acids. Seafood remains the primary source of these nutrients. The highest levels are found in oily, fatty, cold-water fish, such as salmon, anchovies, herring, mackerel, tuna and sardines. Shrimp, lobster, scallops, tilapia and cod contain less, but are still valuable sources.
A 2018 AHA Science Advisory reaffirmed the cardiovascular benefits of eating seafood that is high in omega-3, so long as it is baked or broiled and not fried. These benefits include reductions in coronary heart disease, heart failure, stroke and sudden death. In addition, the 2015–2020 Dietary Guidelines for Americans and the DASH and Mediterranean diets recommend eating about two servings of fish a week, with each serving approximately the size of a deck of cards.
Eating PUFA-rich fish appears to provide more heart-healthy benefits than supplements. Farm-raised salmon appears to be as healthy as wild-caught salmon and may be slightly higher in omega-3. The risk of ingesting mercury with normal seafood intake is generally outweighed by the health benefits. However, large fish that are higher in the food chain, such as shark, swordfish and king mackerel, contain more mercury than smaller fish and should be avoided by women who are pregnant, trying to become pregnant or are breastfeeding.