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OverviewFruit and vegetable consumption has been linked to a reduced risk of each of the three leading causes of death in the United States: Heart Disease, Cancer, and Stroke. It has also been linked to reducing the risk of diabetes, hypertension, and other chronic diseases. In 1988, the Surgeon General's Report on Nutrition and Health reported that 2/3 of all deaths are due to diseases associated with diet. The report also noted that the three personal habits that most influence physical health are smoking, alcohol consumption, and diet. For the two-thirds of American adults who do not smoke or excessively drink alcohol, the single most important personal choice influencing long-term health is diet. Since the Surgeon General's Report, extensive research has been conducted to determine the impact of fruit and vegetable consumption on health. The results have overwhelmingly concluded that eating an abundance and variety of fruits and vegetables has a significant positive impact on health. Although researchers are still studying exactly how fruits and vegetables influence health, much has been discovered on their protective properties. Fruits and vegetables are rich in nutrients such as vitamins, minerals, and antioxidants. They are also rich in phytochemicals. Each of these properties is associated with specific health benefits.
PhytochemicalsPhytochemicals are non-nutritive plant chemicals that contain protective, disease-preventing compounds. They have been long known to protect plants, and are now known to protect humans against disease. They are involved in many processes including ones that help prevent cell damage, prevent cancer cell replication, and decrease cholesterol levels. Specific phytochemicals are found in different colors of fruits and vegetables. For greatest benefit, it is important to eat a variety of colors of fruits and vegetables.
AntioxidantsThere are many different antioxidants. Many phytochemicals and nutrients (vitamin C, vitamin E, selenium, carotenoids, etc) act as antioxidants. During normal metabolism, oxygen can create damaging by-products. These by-products, known as free radicals, can cause a variety of health problems such as cancer and heart damage. Antioxidants bind themselves to free radicals and transform them into non-damaging compounds. They also repair cellular damage. The highest concentrations of antioxidants are found in the most deeply or brightly colored fruits and vegetables.
Nutritional SupplementsAlthough the consumption of specific nutrients from natural food sources (such as in fruits and vegetables) reduces the risk of some chronic diseases, there has been no link to the consumption of vitamins and minerals from dietary supplements to a reduced risk of chronic diseases. Taking high doses of single vitamins has sometimes been linked to an increased risk of some types of cancer. Still, supplements may be beneficial for some people, such as pregnant women, women of childbearing age, and people with restricted dietary intakes. If a supplement is taken, it is recommended that it be a balanced multivitamin/mineral supplement containing no more than 100% of the "Daily Recommended Value" of most nutrients. Chronic disease protection is likely the result of healthful compounds found in fruits and vegetables, and not individual nutrients.
CancerSecond only to smoking, diet has the greatest influence on cancer risk. Of all cancer deaths, 35% may be related to poor dietary habits. People who eat 5 to 9 daily servings of fruits and vegetables have half the risk of cancer in almost all sites as those who only eat one to two daily servings. Recent studies suggest that the reason fruits and vegetables protect against cancer is their high density in vitamins, minerals, phytochemicals, and other components. The components that may be most beneficial in cancer risk reduction are vitamin A (which is derived from beta-carotene in plants), vitamin C, fiber, and phytochemicals. These components (minus fiber) may reduce cancer risk through their roles as antioxidants. They inhibit the initiation and promotion of carcinogenesis, the production of cancerous cells. Beta-carotene (vitamin A) is a powerful antioxidant that prevents the formation of free radicals throughout the body. Vitamin C blocks the formation of carcinogenic nitrosamines in the digestive tract, and also prevents the oxidation of certain chemicals to active carcinogens. Phytochemicals also act as antioxidants, and are being studied extensively to be better understood. Specific phytochemicals are being isolated to determine towards which sites they offer the most protection. Fiber increases water content throughout the bowels, thereby diluting carcinogen concentrations in the colon. It also reduces fecal transit time, which decreases the time the bowel is exposed to potential carcinogens. Fruits and vegetables that are good sources of vitamin A, vitamin C, and fiber The cancers for which the strongest evidence of a protective effect exists include those of the lung, colon and rectum, breast, oral cavity, esophagus, stomach, pancreas, uterine cervix, and ovary. For more information on dietary factors that influence cancer, visit:
Heart DiseaseAlthough not as much research has been conducted on fruit and vegetable consumption and heart disease risk as with cancer risk, recent studies do suggest that there is a strong link between fruit and vegetable consumption and heart disease. It is estimated that eating 5 to 9 daily servings of fruits and vegetables could reduce heart disease risk by 20 to 40 percent. Research indicates that fruits and vegetables may reduce heart disease risk in a couple of ways. High plasma homocysteine levels are associated with an increased risk of heart disease. Diets high in dietary folate have been shown to reduce levels of plasma homocysteine. Citrus fruits and green vegetables are high in dietary folates. In studies of healthy men and women, subjects who consumed a high quantity of citrus fruits and green vegetables over an extended period of time showed a significant reduction in plasma homocysteine levels. Even studies of healthy men and women consuming a mix of fruits and vegetables with moderate folate content showed a significant reduction in plasma homocysteine levels. It is also believed that fruits and vegetables protect against heart disease through their role as antioxidants. Fruits and vegetables high in vitamin A, vitamin C, carotenoids (found in yellow colored fruits and vegetables such as carrots or peaches), and flavonoids (found in onions) are strong antioxidants. Oxidation of cholesterol causes hardening of the arteries, and may lead to heart disease. The antioxidants found in fruits and vegetables block the oxidation of cholesterol in the arteries, thereby reducing heart disease risk. HypertensionHypertension, also known as High Blood Pressure, is a medical condition in which there is narrowed room in the arteries, thereby causing difficulty in blood flow. In order to adequately pump blood throughout the body, the heart must work harder. This increased workload causes the muscles of the heart to enlarge, and eventually become inefficient in pumping blood. Hypertension increases internal pressure on the arteries. This makes them less flexible and more susceptible to atherosclerosis, the buildup of plaque (fatty deposits) in the arteries. The complications associated with hypertension increase the risk of heart attack, heart failure, stroke, and kidney failure. Hypertension is often called the "silent killer," because it usually shows no signs until it reaches a life-threatening stage. Hypertension affects 25 percent of people living in North America, but almost 1/3 are unaware of it. Until age 55, more men than women have hypertension. After that age, the condition becomes more prevalent in women. Hypertension is defined as blood pressure greater than or equal to 140/90 mm HG. Studies have shown that consuming 5 to 9 servings of fruits and vegetables each day lowers blood pressure in people with both normal and high blood pressure. There also seems to be added benefit to consuming them in combination with low-fat dairy products. It is not known exactly which nutrients are responsible for the lowered blood pressure, but it is likely that potassium plays an important role. Future studies are needed to more fully understand how fruits and vegetables reduce hypertension risk. StrokeEating 5 to 9 daily servings of fruits and vegetables may reduce the risk of ischemic strokes by 30 percent. Studies have shown that those who consume 9 or more daily servings are most likely to have a significantly reduced stroke risk. Ischemic strokes account for approximately 80 percent of all strokes. They are caused by a stoppage of oxygen rich blood flow to the brain. The blockage begins when atherosclerosis (buildup of fatty deposits in artery walls) occurs in the carotid arteries (large arteries in the neck that supply blood to the head). This narrows the room through which blood can flow. The actual stroke occurs when a blood clot forms or stops at the site of the atherosclerosis. This deprives part of the brain of oxygen, and a stroke results. Studies have shown that those who eat high amounts of cruciferous vegetables (such as cabbage, broccoli, brussel sprouts, collard greens, bok choy, and cauliflower), green leafy vegetables, and citrus fruits and juices are at the lowest risk of stroke. The protective components of fruits and vegetables likely include potassium, folate, and fiber, as well as dietary flavonoids. Studies have observed that those who use multivitamin supplements may receive a slightly weaker protective effect against stroke from fruits and vegetables. DiabetesDiabetes is the sixth leading cause of death in the United States, and its prevalence has increased significantly in recent years. Diabetes is associated with an increased risk of heart disease, stroke, hypertension, blindness, kidney disease, and amputation. Studies indicate that those who eat 5 to 9 daily servings of fruits and vegetables have a lower risk of diabetes. Eating 5 A Day is also associated with improved control of blood sugar levels. Although more studies are needed to better understand the relationship between the two, it is likely that the positive effects are due to fruit and vegetable content of fiber, magnesium, antioxidant vitamins and phytochemicals.
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