So-called superfoods such as kale, goji berries and pomegranates are packed with vitamins and nutrients, but are some veggies true powerhouses?

When U.S. researchers published a list of 41 "powerhouse fruits and vegetables" ranked by the amounts of 17 nutrients, watercress turned some heads with its top score of 100. 

"Watercress is great," said Rosie Schwartz, a Toronto dietitian. "But how much watercress do people actually eat? I mean they serve it as a garnish."

Schwartz takes issue with the rankings, in part because disease-fighting phytochemicals weren't included.

Schwartz warns people not to get carried away with the idea of "superfoods" in general, which she said are usually based on marketing.

​"Don't overdo them and leave out other fruits and vegetables. Include a variety of different foods." 

Different fruits and vegetables offer different vitamins and nutrients, so it's important to incorporate an array into your diet, dietitians say.

This photo gallery highlights some advantages of eating a cornucopia of unprocessed fruits and vegetables.