Many factors affect your cholesterol levels. Some, like genes and age, can’t be helped, but others, such as diet and weight, are decidedly in your control. "Research shows that certain dietary strategies can lower harmful LDL cholesterol by as much as 20 to 30 percent," says Wahida Karmally, DrPH, RD, director of nutrition at Columbia University. More positive news: Today’s cholesterol-control strategy is a far cry from the restrictive regimens of yesteryear. Now the focus is more on what you can eat than what you can’t.
What it does: Cholesterol is a vital nutrient your body needs the same way it requires calcium for strong bones. Your liver produces between 800 and 1,500 milligrams (mg) of cholesterol per day―about three to five times the amount you’d ideally obtain from food. "Cholesterol is a good thing," says Richard A. Stein, MD, director of Urban Community Cardiology at New York University School of Medicine. "You use it to make bile, some hormones, and the membranes that line your cells. But you want to have enough to meet your body’s needs, not so much that it builds up in your arteries."
Types of cholesterol: While you’ve heard of "good" and "bad" cholesterol, those terms are misnomers. The way cholesterol travels in your body is what makes it "good" or "bad."
Cholesterol is carried by lipoproteins, packages of fats that circulate in your bloodstream, delivering cholesterol to cells in need. High-density lipoprotein (HDL) sweeps through your bloodstream, soaking up unused cholesterol and delivering it to your body’s cholesterol-control center―the liver, where it’s recycled from your body. Low-density lipoprotein (LDL) roams the bloodstream and deposits cholesterol where it’s needed, and sometimes where it’s not, like the walls of your arteries. There it can build up as plaque, narrowing arteries and reducing blood flow, raising risk of stroke or heart disease. When health experts talk about lowering cholesterol, they’re not referring to total cholesterol. They mean LDL.
HDL and LDL aren’t the only types of lipoproteins circulating in our blood. There are others, too, such as Very Low Density Lipoprotein (VLDL), Intermediate Density Lipoprotein (IDL), and lipoprotein A. Your doctor may not be measuring these now, but he or she may sometime in the distant future. Emerging research reveals that all three are associated with an increased risk of developing heart disease. So are triglycerides, another type of lipoprotein typically tested along with cholesterol. Your body turns excess calories from food into triglycerides and stores them in fat cells to be used as a backup source of energy.
How food affects cholesterol levels
Not too long ago, experts believed eating more cholesterol caused cholesterol to accumulate in the bloodstream and on artery walls. That meant foods high in cholesterol but otherwise heart-healthy, like eggs or shrimp, were considered taboo. After all, cholesterol in food is structurally identical to cholesterol in the bloodstream (minus the lipoproteins that carry it). However, as research has matured in recent years, scientific opinion has changed. "The relationship between cholesterol levels and dietary cholesterol isn’t as strong as we once thought," says Cindy Moore, MS, RD, director of nutrition therapy at the Cleveland Clinic Foundation.
Cholesterol levels are largely influenced by the kind of fat you eat. Two helpers are monounsaturated fats (in olives, avocados, and olive and canola oils) and polyunsaturated fats (found in vegetable oils, soybeans, fish, shellfish, and seeds). Nuts are rich sources of both. Of the two, monounsaturates are especially beneficial, raising HDL and lowering LDL. As long as most of the fats in your diet are heart-healthy mono- and polyunsaturates, you can consume between 20 and 35 percent of your calories from fat, according to the USDA’s Dietary Guidelines for Americans.
Just as some fats are positive, others are problematic. "When it comes to elevated LDL, trans and saturated fats are the real culprits," Moore says. Reducing saturated fat to seven percent of calories (15 grams in a 2,000-calorie-per-day diet) can lower LDL as much as 10 percent, according to an American Heart Association report. Trouble is, most Americans eat too much saturated fat―roughly 11 percent of total calories. And that saturated fat sends a troublesome signal to your liver, telling it to pump out more cholesterol, causing LDL to build up in your bloodstream. As for trans fats? "They’re an even greater concern," Moore says. While saturated fats boost LDL, they also increase HDL. Trans fats, on the other hand, do double damage, increasing LDL while reducing protective HDL.
Helpful nutrients and foods
In addition to unsaturated fats, certain other nutrients and foods have potent cholesterol-reducing mechanisms. "A diet that combines soluble fiber, phytosterols, nuts, and soy protein can make an enormous difference," says David J. A. Jenkins, MD, PhD, Canada Research Chair in nutrition and metabolism at the University of Toronto.
Soluble fiber: This sticky form of fiber traps bile acids (compounds we need to digest fat) and shuttles them out of the body. Because bile acids are made from cholesterol, your liver taps into your body’s cholesterol supply to make more of them, lowering overall levels. Experts recommend roughly 10 grams of soluble fiber per day from foods like oats, barley, psyllium, flaxseed, okra, and eggplant.
Phytosterols and stanols: These substances block absorption of cholesterol from the food we eat. While a plant-rich diet with lots of nuts and seeds supplies about one gram a day, most of us need enriched foods like spreads, yogurt, or orange juice to acquire the two grams a day that can help lower cholesterol by approximately 10 percent.
Nuts: "Nuts are like cholesterol-¬lowering pills because of their mono¬unsaturated fats and vegetable protein," Jenkins says. They all do the trick, according to a recent Pennsylvania State University review, which found that tree nuts could help lower LDL cholesterol between three and 19 percent. Aim for one-and-a-half ounces a day.
Soy protein: Soy is cholesterol-free, low in saturated fat, and high in fiber, making it an excellent meat substitute. Earlier this year, the AHA conducted a review of 22 studies on the efficacy of soy to lower LDL, and while they found no unique effects involving compounds in soyfoods, such as isoflavones, they did find that people who obtain half of their total protein intake from soyfoods lowered LDL levels by three percent.
Combining these foods with a diet low in saturated fat may help deliver an even greater edge. "When you add the benefits of a diet low in saturated fat, you get another 10 percent reduction," Jenkins says.