填空题

Foods That Fight Disease
The food you eat does more than provide energy. It can have a dramatic effect on your body’s ability to fight off heart disease, cancer, diabetes, high blood pressure, stroke, and weak bones.
With remarkable consistency, recent research has found that a diet high in plant-based foods--fruits, vegetables, dried peas and beans, grains, and starchy staples such as potatoes--is the body’s best weapon in thwarting (阻止) many health- related problems. These foods work against so many diseases that the same healthy ingredients you might use to protect your heart or ward off cancer will also benefit your intestinal tract and bones.
Here’s what is currently known about these different disease-fighting foods.
Cancer Fighters
Preventing cancer is a compelling reason to load up your cart in the produce department. Scientists have recently estimated that approximately 30 to 40 percent of all cancers could be averted if people ate more fruits, vegetables, and plaint- based foods and minimized high-fat, high-calorie edibles that have scant nutritional value. Up to 70 percent of cancers might be eliminated if people also stopped smoking, exercised regularly, and controlled their weight.
In the past, researchers had linked fat consumption with the development of cancers, but they currently believe that eating fruits, vegetables, and grains may be more important in preventing the disease than not eating fat. "The evidence about a high- fat diet and cancer seemed a lot stronger several years ago than it does now," says Melanie Polk, a registered dietitian and director of nutrition education at the American Institute for Cancer Research.
Although scientists are still not certain about the specifics, they’re beginning to close in on the healthful constituents of plant-based foods. In particular, they’re looking closely at two components--antioxidants and phytochemicals.
The antioxidants( carotenoids, such as beta carotene and lycopene, and vitamins C and E ) found in fruits, vegetables, and other plant-based foods fight free radicals (自由基), which are compounds in the body that attack and destroy cell membranes. The uncontrolled activity of free radicals is believed to cause many cancers.
The phytochemicals present in fruits and vegetables protect the body by stunting the growth of malignant cells. Phytochemicals, naturally occurring substances, include indoles in cabbage or cauliflower, saponins in peas and beans, and isoflavones in soymilk and tofu. Investigators have only an inkling of how many phytochemicals exist and how they work. They are confident, however, that you can get a basketful of anti-cancer nutrients by mixing and matching at least five servings a day of fruits and vegetables with seven or more starchy or protein-rich plant foods such as grains, peas and beans, and potatoes.
Supplements can help you get some of the benefits of these substances, but they are no replacement for real food. "When you take a supplement, you’re getting specific vitamins and minerals, but not the thousands of phytochemicals that might be present in fruits and vegetables," says registered dietitian Amy Jamieson of the Cleveland Clinic Foundation in Ohio. "If you eat a sweet potato with its skin, which is a great source of both beta carotene and fiber, you’ll consume at least 5,000 phytochemicals that aren’t present in a beta carotene supplement. That’s a really important difference."
Digestive Tract Protectors
Although the food you eat affects every system in your body, your digestive tract bears the initial brunt of your choices. To keep it running smoothly and disease-free, aim for a diet high in fiber. Unfortunately, most Americans eat only about half the 20 to 35 grams they need each day, even though fiber is readily available in raw and cooked fruits and vegetables, as well as in grain products such as breads, cereals, pasta, and rice.
Fiber comes in two forms, soluble and insoluble. Soluble fiber, found in fruits, vegetables, brown rice, oats, and barley, lowers blood cholesterol levels and slows the entry of glucose into the bloodstream, an important factor in preventing or controlling diabetes. Insoluble fiber, found mainly in whole grains, fruit and vegetable peels, high fiber cereals, and wheat and com bran, keeps your digestive tract in order. Insoluble fiber soaks up water, adding the bulk that pushes possible cancer- causing substances( carcinogens ) out of the intestine.
"Most research supports the protective effect of a diet high in fruits, vegetables, beans, and grains," says Polk, citing the American Institute for Cancer Research’s own 1997 report, "Food, Nutrition and the Prevention of Cancer: a Global Perspective," which reviewed 4,500 international studies before coming to this conclusion.
Heart-Saving Foods
No other part of your body benefits more from good dietary choices than your cardiovascular (心血管的) system. What you eat, and choose not to eat, has a dramatic effect on your risk for heart disease and stroke.
Saturated fat, found mostly in meat and full-fat dairy products, is the major culprit in raising blood cholesterol, the main ingredient of artery-clogging plaque. Overindulging in these foods raises the risk of developing heart disease. But you can lower this risk by shifting the emphasis so that nutrient and fiber-rich foods such as fruits, vegetables, and grains make up approximately two-thirds of what you eat each day.
While fiber is the most important dietary adjunct in controlling blood cholesterol, fiber-rich foods contain other nutrients, including antioxidants and phytochemicals, which researchers believe also deter the buildup of plaque in arteries. But the mechanism is unclear. "Is it the nutrients in these foods that have a positive effect, or is it that the more of them you eat, the less fat-laden food you consume" asks Alice H. Lichtenstein, D. Sc., of the USDA Human Nutrition Research Center at Tufts University in Boston. "We don’t know the answer right now, but it’s probably a combination of both."
What is clear is that you can eat a heart-healthy diet and still include some fat. "We’ve made people aware of cholesterol and fat," says Sayed F. Feghali, M.D., a cardiologist at the Texas Heart Institute in Houston. "There’s no question that saturated fat is the villain when it comes to cholesterol buildup in blood vessels. But we need some fat. We cannot function on a zero-fat diet."
So be judicious in your choices. Restrict meat and dairy products to less than 10 percent of your daily calories. Try poultry, dried beans, eggs, and nuts for protein and energy. Soy products, when substituted for animal protein, show promise in reducing LDL ("bad") cholesterol. Substitute heart-healthy monounsaturated oils, such as olive, canola, and peanut, for saturated and hydrogenated fats.
Bone-Building Foods
The road to strong bones is paved with calcium-rich food. Leafy green vegetables and low-fat dairy products are excellent sources of calcium, the mineral that puts stiffness into your skeletal system and keeps your bones from turning rubbery and fragile.
Your body uses calcium for more than keeping your bones strong. Calcium permits cells to divide, regulates muscle contraction and relaxation, and plays an important role in the movement of protein and nutrients inside cells. If you don’t absorb enough from what you eat to satisfy these requirements, your body will take it from your bones. Because your body doesn’t produce this essential mineral, you must continually replenish the supply. Even though the recommended daily amount is 1,200 mg, most adults don’t eat more than 500 mg.
One reason may have been the perception that calcium-rich dairy products were also loaded with calories. "In the past, women, in particular, worried that dairy products were high in calories," says Letha Y. Griffin, M.D., of Peachtree Orthopaedics in Atlanta. "But today you can get calcium without eating any high-fat or high-calorie foods by choosing skim milk or low-fat yogurt." Also, low-fat dairy products contain phosphorous and magnesium and are generally fortified with vitamin D, all of which help your body absorb and use calcium.
If you find it difficult to include enough calcium in your diet, ask your doctor about supplements. They’re a potent way to get calcium as well as vitamin D and other minerals. But there’s a downside. If you rely on pills in lieu of a calcium-rich diet, you won’t benefit from the other nutrients that food provides. Getting the recommended vitamin D may be easy, since your body makes the vitamin when your skin is exposed to the sun’s rays.
Researchers currently believe not eating fat is most important in preventing cancers.