Saturated fats are the "evildoers" of the nutrition world, and they come in the guise of some of the most delicious foods: butter, cream, cheese, chocolate, coconut, prime rib.
How could something so good be so bad? Well, first of all, let me assure you that not all saturated fats are created equal. In fact, some of the foods high in saturated fats have redeeming qualities that may mitigate their damage. Second, if there's one thing I've learned in the field of nutrition, there's never just one magic -- or deadly -- bullet.
I discovered the power of saturated fats while working with patients. I found when saturated fats are cut to extremely low levels, cholesterol levels drop precipitously. I was stunned at what a simple dietary change could achieve.
The National Academy of Sciences says Americans should minimize their intake of saturated fats, which play a role in raising bad cholesterol (LDL) and increasing the risk of cardiovascular disease, which kills half of all Americans.
Foods contain a mixture of fats, some of which are essential for health. Certain polyunsaturated fats (the omega-3 fatty acids in seafood, flax and walnuts, and omega-6 fatty acids in soybean and corn oil) are essential. You need them in your diet because your body can't synthesize them, and you'll develop deficiency symptoms without them.
Saturated fats are nonessential fats, which means that the body can make them on its own, so they're not needed in the diet. Chocolate and animal fats found in dairy, meat, lard and tallow are high in a saturated fat called stearic acid. While other saturated fats raise LDL levels, stearic acid has been found to have a neutral effect on LDL. In fact, some folks in the chocolate, dairy and meat industries have pointed to this neutral effect as a reason to go ahead and enjoy these foods without worrying about the risk of heart disease.
But a new study appears to challenge this claim. Scientists have found that while it's true that stearic acid doesn't raise LDL levels, it still may increase the risk of cardiovascular disease because it increases fibrinogen and C-reactive protein levels in the blood. Fibrinogen and C-reactive protein are both indicators of inflammation, an emerging risk factor in cardiovascular disease development as well as cancer and many other diseases.
"This news is going to change the thinking about stearic acid being neutral," said David Baer, lead investigator of the study, conducted at the Department of Agriculture's Diet and Human Performance Laboratory in Beltsville.
In addition to stearic acid, there are three other common saturated fats -- palmitic acid (found in palm oil, chocolate and meat), lauric acid (found in coconut) and myristic acid (the most potent LDL-raiser, found in dairy and coconut). These three fats raise not only LDL but also HDL, thus keeping constant that important ratio between the "bad" and the "good" cholesterol. Scientists are not sure how much protection this provides, despite the fact that HDL levels are high. These saturated fats may also cause inflammation, but the research isn't definitive yet.
But some foods that are rich in saturated fat contain protective, healthy nutrients as well. Chocolate, for instance, contains antioxidants and anti-platelet factors. Coconut also contains antioxidants. There is some evidence that these benefits may help outweigh the risks from the saturated fat. But most experts believe it is still not good to eat large amounts of these foods.
Saturated fats, which are solid at room temperature, have other negative effects. When they're high in the diet, they replace in the body's cells the more positive unsaturated fats, which are liquid at room temperature. The saturated fats become incorporated into cell membranes and make the membranes more rigid, causing malfunctions leading to, among other things, insulin resistance.
"Saturated fats can reduce insulin's ability to control blood glucose and in the long run may cause type 2 diabetes," says Frank Hu, associate professor of nutrition and epidemiology at Harvard University's School of Public Health.
Adding to the diabetes connection, a recent Johns Hopkins University study found that dietary saturated fat correlated with higher levels of belly fat, a known risk factor in heart disease, hypertension and diabetes. High-saturated-fat diets may even play a role in dementia and Alzheimer's disease.
Unsaturated oils do just the opposite. If they're prevalent in the diet and can compete successfully with saturated fat, they incorporate into the cell membranes instead and increase cell fluidity and flexibility, which is one of many reasons scientists believe they're so beneficial to overall health.
In fact, there is also a theory that the ratio of polyunsaturated fat to saturated fat in the diet may be more influential in heart disease risk than the absolute numbers -- yet another example of the importance of balance in the world of nutrition.
Several large studies have verified that when people replace saturated fat with unsaturated oils, a 40 percent to 65 percent reduction in heart disease deaths can be achieved, especially when a little omega-3 fatty acid is added. Interestingly, these studies showed only a modest reduction in LDL, which illustrates the importance of paying attention to other risk factors such as inflammation.
Comparatively, treatment with statin drugs that lower LDL cholesterol (arguably one of the most prescribed medications today) reduces heart disease deaths by only about 30 percent because it doesn't remove all the risks. So even when taking statins, dietary change is essential.
"Diet and lifestyle change can work better than statins," says Ernst Schaefer, director of the Lipid and Heart Disease Prevention Program at the New England Medical Center. "But the problem is compliance."
Many people find it challenging to reduce the amount of saturated fat in their diets. Life without chocolate or butter seems draconian and a goal that is impossible to meet. But a heart-healthy diet need not be so austere if you keep balance and variety in mind.
The trouble comes with extremes, when you're eating burgers, fries and a shake -- all in one meal. Try this instead: Choose a leaner burger with a green salad and vinaigrette on the side and a bowl of berries and nuts for dessert. The antioxidants from the salad and berries, and the healthy fats from the nuts and vinaigrette just might counterbalance the saturated fat in the burger.
Another solution would be to try to always have surf with your turf. The anti-inflammatory compounds in the omega-3 fatty acids in fish may help counteract the inflammatory compounds in the beef.
"And if you burned what you ate through activity, this all wouldn't be as much of a problem!" says Baer, research physiologist at USDA.
Katherine Tallmadge is a Washington nutritionist and author of "Diet Simple" (Lifeline Press, 2004). Send e-mails to her at firstname.lastname@example.org.