Kale has spent years as the poster child of healthy eating. But when researchers ranked fruits and vegetables by how many key nutrients they pack per calorie, kale didn’t come first. It didn’t even make the top 10. The winner is a vegetable most people rarely buy.
In short
- A study published by the CDC’s journal ranked 41 “powerhouse” fruits and vegetables by nutrient density.
- Watercress came first, with a perfect score of 100.
- Chinese cabbage, chard, beet greens and spinach followed.
- Kale ranked 15th, and several popular foods didn’t qualify at all.
The study
In 2014, researcher Jennifer Di Noia published a study in Preventing Chronic Disease, a journal of the Centers for Disease Control and Prevention. She analyzed 47 foods and scored each one on 17 nutrients that matter for health, including potassium, fiber, protein, calcium, iron, folate, zinc and vitamins A, B6, B12, C, D, E and K. The score reflects how much of those nutrients a food provides per 100 calories.
Foods scoring 10 or more were classified as “powerhouse” fruits and vegetables, in line with the FDA’s threshold for a “good source” of a nutrient (10% of the Daily Value). Forty-one made the cut. The nutrient data came from the USDA’s national nutrient database, using raw forms of each food.
The top 10
- 1. Watercress: 100
- 2. Chinese cabbage: 91.99
- 3. Chard: 89.27
- 4. Beet greens: 87.08
- 5. Spinach: 86.43
- 6. Chicory: 73.36
- 7. Leaf lettuce: 70.73
- 8. Parsley: 65.59
- 9. Romaine lettuce: 63.48
- 10. Collard greens: 62.49
Kale scored 49.07, ranking 15th among the 41 powerhouse foods.
The surprises
Leafy greens dominate the list because they deliver a lot of nutrients for very few calories. On the other side, some foods many people think of as superfoods didn’t qualify as powerhouses in this ranking: raspberries, tangerines, cranberries, garlic, onions and blueberries. Apples, bananas, corn and potatoes were used as low-scoring comparison foods. That doesn’t make them bad, just less dense in these 17 nutrients per calorie. Potatoes stay a staple, as long as you store them the right way.
How to eat more watercress
Watercress is often sold in bunches or small bags near the salad greens, and its delicate leaves are best eaten fresh. It has a peppery taste, a bit like arugula. It works raw in salads and sandwiches, blended into soups, or added at the last minute to a stir-fry. Because the study used raw foods, cooking may change some of the values.
The limit
The author herself lists the study’s limits: only selected food groups were included, phytochemicals couldn’t be counted, the validation was preliminary, and cooking wasn’t considered. A ranking per calorie also favors very low-calorie greens. The best diet is still a varied one. And in the kitchen, peels and scraps have their uses too, like lemon peels boiled with ginger.
That’s the trick.
