Kale is not king.
Despite its rapid rise up the ranks of so-called superfoods in recent years, kale does not even make the top 10 "powerhouse fruits and vegetables", according to a new study.
Rather, watercress was the unlikely winner, packing a peppery punch with its cross-section of critical nutrients.
Cress, said by Hippocrates to be the "cure of cures" more than 2400 years ago, was followed by its close cousins including Chinese cabbage, collard and mustard greens.
Kale slipped into the top 15 ahead of brussell sprouts and broccoli but behind parsley, spinach and even chives.
Researchers from William Paterson University compiled the list based on the nutrient density and bioavailability of 41 "powerhouse" fruits and vegetables.
Foods were awarded "powerhouse" status by providing, on average, 10 per cent or more of the daily recommended intake across 17 nutrients.
These nutrients, considered of public health importance for reducing risk of chronic diseases, included potassium, fibre, protein, calcium, iron, thiamin, riboflavin, niacin, folate, zinc, and vitamins A, B6, B12, C, D, E, and K.
Watercress, best known for its delightful contribution to egg and mayo or rare roast beef finger sandwiches, cotains 312 per cent of the daily recommended value of vitamin K, which is important for building bones and blood clotting. But, nutrient values were capped "so that any one nutrient would not contribute unduly to the total score".
"The scores can serve as a platform for educating people on the concept of nutrient density," said study author Jennifer Di Noia.
"The rankings provide clarity on the nutrient quality of the different foods and may aid in the selection of more nutrient-dense items within the powerhouse group."
Professor Di Noia acknowledged, however, that some other nutrient-dense foods, like berries and garlic, "may have been overlooked" in the study, published in the journal Preventing Chronic Disease.
This was because of the particular nutrient profiling that the study was based on.
Berries, for instance, are rich in antioxidants and phytochemicals, but "there are no uniform data on food phytochemicals and … recommended intake amounts for these compounds are lacking,” Professor Di Noia told the Washington Post.
Although berries were banished on a technicality, they are prominent on other nutrient density indexes.
On the powerhouse foods list however, red pepper won on the fruit front, followed by pumpkin, tomato and lemon.
"Consistent with a whole-diet approach," Professor Di Noia said, “[Consumption of] all of the items should be encouraged. The rankings may help consumers make nutrient-dense selections within the powerhouse group."
POWERHOUSE FRUIT AND VEGETABLES RANKED ACCORDING TO NUTRIENT DENSITY SCORES
Chinese cabbage 91.99
Beet green 87.08
Leaf lettuce 70.73
Romaine lettuce 63.48
Collard green 62.49
Turnip green 62.12
Mustard green 61.39
Dandelion green 46.34
Red pepper 41.26
Brussels sprout 32.23
Iceberg lettuce 18.28
Winter squash (all varieties) 13.89
Grapefruit (pink and red) 11.64
Sweet potato 10.51
Grapefruit (white) 10.47