"Eat your fruits and vegetables" is one of the tried and true recommendations for a healthy diet. And for good reason. Eating plenty of vegetables and fruits can help you ward off heart disease and stroke, control blood pressure, prevent some types of cancer, avoid a painful intestinal ailment called diverticulitis, and guard against cataract and macular degeneration, two common causes of vision loss.
What does "plenty" mean? More than most Americans consume. If you don't count potatoes—which should be considered a starch rather than a vegetable—the average American gets a total of just three servings of fruits and vegetables a day. The latest dietary guidelines call for five to thirteen servings of fruits and vegetables a day (2½ to 6½ cups per day), depending on one's caloric intake. For a person who needs 2,000 calories a day to maintain weight and health, this translates into nine servings, or 4½ cups per day (2 cups of fruit and 2½ cups of vegetables).
Over the past 30 years or so, researchers have developed a solid base of science to back up what generations of mothers preached (but didn't always practice themselves). Early on, fruits and vegetables were acclaimed as cancer-fighting foods. In fact, the ubiquitous 5 A Day message (now quietly changing to Fruits and Veggies: More Matters) seen in produce aisles, magazine ads, and schools was supported in part by the National Cancer Institute. The latest research, though, suggests that the biggest payoff from eating fruits and vegetables is for the heart.
Countering Cardiovascular Disease
There is compelling evidence that a diet rich in fruits and vegetables can lower the risk of heart disease and stroke.
The largest and longest study to date, done as part of the Harvard-based Nurses' Health Study and Health Professionals Follow-up Study, included almost 110,000 men and women whose health and dietary habits were followed for 14 years. The higher the average daily intake of fruits and vegetables, the lower the chances of developing cardiovascular disease. Compared with those in the lowest category of fruit and vegetable intake (less than 1.5 servings a day), those who averaged 8 or more servings a day were 30 percent less likely to have had a heart attack or stroke. Although all fruits and vegetables likely contribute to this benefit, green leafy vegetables such as lettuce, spinach, Swiss chard, and mustard greens; cruciferous vegetables such as broccoli, cauliflower, cabbage, Brussels sprouts, bok choy, and kale; and citrus fruits such as oranges, lemons, limes, and grapefruit (and their juices) make important contributions.
When researchers combined findings from the Harvard studies with several other long-term studies in the U.S. and Europe, and looked at coronary heart disease and stroke separately, they found a similar protective effect: Individuals who ate more than 5 servings of fruits and vegetables per had roughly a 20 percent lower risk of coronary heart disease and stroke, compared with individuals who ate less than 3 servings per day.
Countering Blood Pressure
High blood pressure is a primary risk factor for heart disease and stroke. As such, it's a condition that is important to control. Diet can be a very effective tool for lowering blood pressure. One of the most convincing associations between diet and blood pressure was found in the Dietary Approaches to Stop Hypertension (DASH) study.
This trial examined the effect on blood pressure of a diet that was rich in fruits, vegetables, and low-fat dairy products and that restricted the amount of saturated and total fat. The researchers found that people with high blood pressure who followed this diet reduced their systolic blood pressure (the upper number of a blood pressure reading) by about 11 mm Hg and their diastolic blood pressure (the lower number) by almost 6 mm Hg—as much as medications can achieve.
More recently, a randomized trial known as the Optimal Macronutrient Intake Trial for Heart Health (OmniHeart) showed that this fruit and vegetable-rich diet lowered blood pressure even more when some of the carbohydrate was replaced with healthy unsaturated fat or protein.
Countering Cancer
Numerous early studies revealed what appeared to be a strong link between eating fruits and vegetables and protection against cancer. But because many of these were case-control studies, where people who already have a certain health outcome (cases) are compared to people who do not have that outcome (controls), it is possible that the results may have been skewed by problems inherent in these types of studies; people with illnesses, for example, often recall past behaviors differently from those without illness, which can lead to potential inaccuracy in the information that they provide to study investigators.
Cohort studies, which follow large groups of initially healthy individuals for years, generally provide more reliable information than case-control studies because they don't rely on information from the past. And data from cohort studies have not consistently shown that a diet rich in fruits and vegetables prevents cancer in general. For example, in the Nurses' Health Study and the Health Professionals Follow-up Study, over a 14-year period, men and women with the highest intake of fruits and vegetables (8+ servings a day) were just as likely to have developed cancer as those who ate the fewest daily servings (under 1.5).
A more likely possibility is that some types of fruits and vegetables may protect against certain cancers. A massive report by the World Cancer Research Fund and the American Institute for Cancer Research suggests that non-starchy vegetables—such as lettuce and other leafy greens, broccoli, bok choy, cabbage, as well as garlic, onions, and the like—and fruits "probably" protect against several types of cancers, including those of the mouth, throat, voice box, esophagus, and stomach; fruit probably also protects against lung cancer.
Vision Improvement
Eating plenty of fruits and vegetables also keeps your eyes in good shape. You may have learned that the vitamin A in carrots aids night vision. Other fruits and vegetables help prevent two common aging-related eye diseases—cataract and macular degeneration—which afflict millions of Americans over age 65. Cataract is the gradual clouding of the eye's lens, a disk of protein that focuses light on the light-sensitive retina. Macular degeneration is caused by cumulative damage to the macula, the center of the retina. It starts as a blurred spot in the center of what you see. As the degeneration spreads, vision shrinks.
Free radicals generated by sunlight, cigarette smoke, air pollution, infection, and metabolism cause much of this damage. Dark green leafy vegetables—such as spinach and kale—contain two pigments, lutein and zeaxanthin, that accumulate in the eye; these pigments are found in other brightly colored fruits and vegetables as well, including corn, squash, kiwi, and grapes. These two pigments appear to be able to snuff out free radicals before they can harm the eye's sensitive tissues.
In general, a diet rich in fruits and vegetables appears to reduce the chances of developing cataract or macular degeneration. Lutein and zeaxanthin, in particular, seem protective against cataract.
What does "plenty" mean? More than most Americans consume. If you don't count potatoes—which should be considered a starch rather than a vegetable—the average American gets a total of just three servings of fruits and vegetables a day. The latest dietary guidelines call for five to thirteen servings of fruits and vegetables a day (2½ to 6½ cups per day), depending on one's caloric intake. For a person who needs 2,000 calories a day to maintain weight and health, this translates into nine servings, or 4½ cups per day (2 cups of fruit and 2½ cups of vegetables).
Over the past 30 years or so, researchers have developed a solid base of science to back up what generations of mothers preached (but didn't always practice themselves). Early on, fruits and vegetables were acclaimed as cancer-fighting foods. In fact, the ubiquitous 5 A Day message (now quietly changing to Fruits and Veggies: More Matters) seen in produce aisles, magazine ads, and schools was supported in part by the National Cancer Institute. The latest research, though, suggests that the biggest payoff from eating fruits and vegetables is for the heart.
Countering Cardiovascular Disease
There is compelling evidence that a diet rich in fruits and vegetables can lower the risk of heart disease and stroke.
The largest and longest study to date, done as part of the Harvard-based Nurses' Health Study and Health Professionals Follow-up Study, included almost 110,000 men and women whose health and dietary habits were followed for 14 years. The higher the average daily intake of fruits and vegetables, the lower the chances of developing cardiovascular disease. Compared with those in the lowest category of fruit and vegetable intake (less than 1.5 servings a day), those who averaged 8 or more servings a day were 30 percent less likely to have had a heart attack or stroke. Although all fruits and vegetables likely contribute to this benefit, green leafy vegetables such as lettuce, spinach, Swiss chard, and mustard greens; cruciferous vegetables such as broccoli, cauliflower, cabbage, Brussels sprouts, bok choy, and kale; and citrus fruits such as oranges, lemons, limes, and grapefruit (and their juices) make important contributions.
When researchers combined findings from the Harvard studies with several other long-term studies in the U.S. and Europe, and looked at coronary heart disease and stroke separately, they found a similar protective effect: Individuals who ate more than 5 servings of fruits and vegetables per had roughly a 20 percent lower risk of coronary heart disease and stroke, compared with individuals who ate less than 3 servings per day.
Countering Blood Pressure
High blood pressure is a primary risk factor for heart disease and stroke. As such, it's a condition that is important to control. Diet can be a very effective tool for lowering blood pressure. One of the most convincing associations between diet and blood pressure was found in the Dietary Approaches to Stop Hypertension (DASH) study.
This trial examined the effect on blood pressure of a diet that was rich in fruits, vegetables, and low-fat dairy products and that restricted the amount of saturated and total fat. The researchers found that people with high blood pressure who followed this diet reduced their systolic blood pressure (the upper number of a blood pressure reading) by about 11 mm Hg and their diastolic blood pressure (the lower number) by almost 6 mm Hg—as much as medications can achieve.
More recently, a randomized trial known as the Optimal Macronutrient Intake Trial for Heart Health (OmniHeart) showed that this fruit and vegetable-rich diet lowered blood pressure even more when some of the carbohydrate was replaced with healthy unsaturated fat or protein.
Countering Cancer
Numerous early studies revealed what appeared to be a strong link between eating fruits and vegetables and protection against cancer. But because many of these were case-control studies, where people who already have a certain health outcome (cases) are compared to people who do not have that outcome (controls), it is possible that the results may have been skewed by problems inherent in these types of studies; people with illnesses, for example, often recall past behaviors differently from those without illness, which can lead to potential inaccuracy in the information that they provide to study investigators.
Cohort studies, which follow large groups of initially healthy individuals for years, generally provide more reliable information than case-control studies because they don't rely on information from the past. And data from cohort studies have not consistently shown that a diet rich in fruits and vegetables prevents cancer in general. For example, in the Nurses' Health Study and the Health Professionals Follow-up Study, over a 14-year period, men and women with the highest intake of fruits and vegetables (8+ servings a day) were just as likely to have developed cancer as those who ate the fewest daily servings (under 1.5).
A more likely possibility is that some types of fruits and vegetables may protect against certain cancers. A massive report by the World Cancer Research Fund and the American Institute for Cancer Research suggests that non-starchy vegetables—such as lettuce and other leafy greens, broccoli, bok choy, cabbage, as well as garlic, onions, and the like—and fruits "probably" protect against several types of cancers, including those of the mouth, throat, voice box, esophagus, and stomach; fruit probably also protects against lung cancer.
Vision Improvement
Eating plenty of fruits and vegetables also keeps your eyes in good shape. You may have learned that the vitamin A in carrots aids night vision. Other fruits and vegetables help prevent two common aging-related eye diseases—cataract and macular degeneration—which afflict millions of Americans over age 65. Cataract is the gradual clouding of the eye's lens, a disk of protein that focuses light on the light-sensitive retina. Macular degeneration is caused by cumulative damage to the macula, the center of the retina. It starts as a blurred spot in the center of what you see. As the degeneration spreads, vision shrinks.
Free radicals generated by sunlight, cigarette smoke, air pollution, infection, and metabolism cause much of this damage. Dark green leafy vegetables—such as spinach and kale—contain two pigments, lutein and zeaxanthin, that accumulate in the eye; these pigments are found in other brightly colored fruits and vegetables as well, including corn, squash, kiwi, and grapes. These two pigments appear to be able to snuff out free radicals before they can harm the eye's sensitive tissues.
In general, a diet rich in fruits and vegetables appears to reduce the chances of developing cataract or macular degeneration. Lutein and zeaxanthin, in particular, seem protective against cataract.
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