5/22/2014 9:35:00 AM Link between fats and heart disease not entirely clear
DEAR DOCTOR K: Here we go again. After years of hearing that diets rich in saturated fats increase the risk for heart disease, I hear a new study says that's not so. What gives?
DEAR READER: I don't blame you for being frustrated. So let me start with the bottom line: Take this new study with several grains of salt. (Incidentally, it still is true that too much salt is bad for your health, so just a few grains, please.)
Back in the 1970s and 1980s, you heard a lot about how fat was bad for you. That led a lot of people to switch from foods rich in fat to foods rich in carbohydrates. During the 1990s, nutrition scientists began to distinguish the health effects of different types of fat. Their message was simple: There are "bad fats," but there also are "good fats." (They also pointed out that there are "good carbs" and there are "bad carbs." But we'll leave carbs for another column.)
The first type of bad fat identified was saturated fats. These are abundant in fatty red meats and in dairy products (milk, cream, cheese, ice cream) that have not been treated to lower the saturated fat content.
In the mid-1990s, trans fats were incriminated as bad fats. Diets rich in trans fats were found to be even worse for your health -- particularly heart health -- than saturated fats. Trans fats in our diets largely come from foods processed by manufacturers, such as stick margarine. They were created in order to extend the shelf life of foods. Trans fats can be found in commercially made cookies, cakes and biscuits, and in other processed foods such as frozen pizza and coffee creamer.
On the other hand, in the 1990s the evidence grew that polyunsaturated fats and monounsaturated fats are good for your health -- again, particularly for heart health. Polyunsaturated fats are abundant in fish, nuts, seeds and vegetables, as well as in soybean, corn, cottonseed, safflower, sunflower and fish oils. Olive oil is rich in healthy monounsaturated fats and also has polyunsaturated fats.
The study you referred to is a new analysis of 72 studies that included more than 600,000 people. It was published in the journal Annals of Internal Medicine. Like prior studies, the new study found that diets rich in trans fats were unhealthy.
The surprise was that it found no evidence that saturated fats increased the risk of heart disease. In another surprise, the study didn't find any heart-protective benefits from polyunsaturated "good" fats.
I'm not changing my eating habits based on this new study. Several nutrition scientists that I respect believe the new analysis may be flawed. For now, the basics remain:
-- Aim for balance in your diet: not too much of one thing and not too little of another.
-- Eat real food -- food that is unprocessed or minimally processed.
-- Limit total calories. Keep an eye on portion size.
-- Exercise regularly.
-- If you smoke, try to quit.
(Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.)