Obvious choices of fruit and vegetables are not necessarily the healthiest, say researchers.
According to US experts, making simple swaps like eating sweet potatoes instead of carrots and papaya rather than oranges would make a difference.
Foods, like raspberries, watercress and kale, are richer in phytonutrients which may help prevent disease, they told a US meeting.
UK nutritionists said a balanced diet is essential to good health.
The British Nutrition Foundation warned that relying on eating a few select food types to boost health was ill-advised and said there was no such thing as a "superfood".
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.
They analysed data from US health surveys of people's dietary habits to look at the most common 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, regardless of how much fruit and veg they ate overall.
Carrots were the most common source of beta-carotene, oranges and orange juice the most common source of beta-cryptoxanthin, spinach the most common source of lutein/zeaxanthin, strawberries the most common source of ellagic acid and mustard the biggest provider of isothiocynates.
However, for each of these phytonutrients there was a richer food source available.
Switching from carrots to sweet potatoes would nearly double beta-carotene intake, say the researchers.
Similarly, papaya contains 15 times more beta-cryptoxanthin than oranges, while kale has three times more lutein/zeaxanthin than spinach.
Raspberries have three times more ellagic acid than strawberries and one cup of watercress contains as much isothiocyanate as four teaspoonfuls of mustard.
Study leader Keith Randolph, who is a 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."
Dr Emma Williams of the British Nutrition Foundation said: "They are right that some foods are richer sources of phytonutrients. But at the end of the day, to be healthy you need to make sure you have a varied and balanced diet. No one food can give you everything you need."
The findings were presented at the 2010 Experimental Biology conference in Anaheim, California.