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參考答案:Reference and revised a bit from website:
"Eat your fruits and vegetables" is one of the tried and true recommendations for a healthy diet. And for good reason. Eating plenty of fruits and vegetables can help you ward off heart disease and stroke, control blood pressure and cholesterol, 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 everyone can consume. If you don't count potatoes - which should be considered a starch rather than a vegetable - the average person 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, depending on one's caloric intake.(1) 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.
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 Eat 5 to 9 A Day) seen in produce aisles, magazine ads, and schools is 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.Previous reports have shown that early dietary interventions can improve cholesterol levels in children, and now new research adds to this by showing that blood-vessel function is also enhanced, at least in boys.
The findings, which appear in the American Heart Association's journal Circulation, are based on a study of 1062 healthy 11-year-old children who were either put on a low saturated fat diet or and unrestricted diet starting in infancy.
Somewhat fewer than 200 children in each diet group had the elasticity of the interior walls (or endothelium) of their veins and arteries measured by using ultrasound to look at dilation of the blood vessels under various circumstances.
The low-fat diet was associated with better endothelial function in boys and girls, but this was significant from a statistical standpoint only in boys, Dr. Olli T. Raitakari, from the University of Turku in Finland, and colleagues note.
"Early nutrition may play an important role in the later vascular health of males," Raitakari said in a statement. "It may be associated with less atherosclerosis and a lower future risk of cardiovascular diseases."
As to why a significant association was not seen in girls, Raitakari said it may relate to "differences in sex hormone levels."
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