Obvious choices of fruit and vegetables are not necessarily the healthiest, new research suggests.
Scientists have come up with a list of five "powerhouse" foods that may be better alternatives.
Experts recommend five portions a day of fruit and veg in a healthy diet - plant foods are known to contain "phytonutrient" chemicals that can protect the heart and arteries and prevent cancers - but the most popular varieties may not be the best, according to US researchers.
Scientists analysed data from US health surveys of people's dietary habits to examine sources of phytonutrients.
They found that for 10 of the 14 phytonutrients studied, a single food type accounted for two-thirds or more of an individual's consumption. It made no difference whether or not a person was a high or low consumer of fruit and veg.
The most common food sources for five key phytonutrients were: carrots (beta-carotene), oranges/orange juice (beta-cryptoxanthin), spinach (lutein/zeaxanthin), strawberries (ellagic acid) and mustard (isothiocyanates).
However, for each of these phytonutrients there was a better food source available.
These were listed as follows: sweet potatoes (nearly double the beta-carotene of carrots), papaya (15 times more beta-cryptoxanthin than oranges), kale (three times more lutein/zeaxanthin than spinach), raspberries (three times more ellagic acid than strawberries), and watercress (one cup contains as much isothiocyanate as four teaspoonfuls of mustard)
Study leader Keith Randolph, technology strategist for the supplement company Nutrilite, said: "These data highlight the importance of not only the quantity but also the significant impact the quality and variety of the fruits and vegetables you eat can have on your health."
The findings were presented at the 2010 Experimental Biology conference in Anaheim, California.