Scientists at St Andrews University monitored the food consumption of 35 people and clicked their pictures over this period.
Eating an average of 2.9 more portions of fruit and vegetables a day made them look healthier when rated by others at the end of the study, while an extra 3.3 portions enhanced their attractiveness, the Daily Mail reported.
Fruit and vegetables are rich in carotenoids, which guard against cell damage from pollution and UV rays and can prevent age-related disorders like heart disease and cancer.
It was previously known that eating extreme amounts of certain vegetables such as carrots could turn skin orange. However, it was not known that a small increase in these red and yellow pigments in the skin could be perceptible to others - or that it was seen as appealing.
A camera that can gauge close-up changes to the skin's redness, yellowness and lightness found that these considerably increased in people who increased their intake of fruit and vegetables.
Using light sensors, the researchers revealed that these red and yellow hues were linked with the levels of carotenoids in the skin.
There are hundreds of different types of carotenoids.
But those thought to have the most dramatic effect on the skin are lycopene - which gives tomatoes and red peppers their red colour - and beta-carotene, found in carrots as well as broccoli, squash, and spinach.
Skin colour can also be affected by chemicals called polyphenols, found in apples, blueberries and cherries, which cause blood rush to the skin surface.
"We expected the colour change to be most dramatic in people who ate very few fruit and vegetables to start off with, but it was actually across the board," said Ross Whitehead, who lead the study.
"A lot of the people were already eating close to the recommended amount.
"But we found even a couple of extra portions could still make a difference to their skin colour," Whitehead added.
He said the team, who studied white and Asian volunteers, would look at whether this was valid for other races too, and whether it had a smaller or greater effect in older people, as the volunteers were all aged 18 to 25.
The study has been published in the journal PLoS ONE.