You know eating fruit and vegetables does good. But do you know it can also make you look good? People who increased their intake over just six weeks developed a healthy glow and appeared more attractive, researchers found. Scientists at St Andrews University found eating them slightly increased yellow and red pigments in the volunteers' skin. They monitored the food intake of 35 people and took pictures of their faces, arms and hands using a sensitive camera at the start, and after three and six weeks. Increasing their intake of greens by 2.9 portions a day was found to make the person look more healthy and an extra 3.3 portions could enhance their attractiveness, when their photographs were rated by others. Fruit and vegetables are rich in carotenoids( 类胡萝卜素 ) , which are known to protect against cell damage from pollution and UV rays, and can also prevent age-related diseases including heart disease and cancer. But while it was known eating extreme amounts of certain vegetables such as carrots could turn skin orange , it was not known a small increase was perceptible( 被觉察) to others—and was seen as appealing. A camera measured changes to the skin's redness, yellowness and lightness, and found it significantly changed in people who naturally increased their intake. These changes were not evident in three weeks. Using light sensors, the researchers showed these red and yellow hues were linked with the levels of carotenoids in their skin. There are hundreds of carotenoids but those thought to have the most dramatic effect are lycopene( 番茄红素 )—which gives tomatoes and red peppers their red colour—and beta-carotene found in carrots as well as broccoli, squash, and spinach. Skin colour is also affected by chemicals called polyphenols( 多元酚 ) , found in apples, blueberries and cherries, which cause blood rush to the skin surface.