One study finally answers all our questions by revealing the identity of the 10 top-ranked foods.

So what is the world's healthiest food?

According to the results of this study, watercress, also known as yellowcress, is the healthiest food.

This green vegetable, which frequently costs less than $4 in supermarkets, scored top marks in a test of 17 essential nutrients.

You will be pleased to know that the healthiest food to eat won’t make too much of a dent in your  budget!

WHAT OTHER FOODS ARE THE HEALTHIEST?

Other top-ranked foods include spinach, broccoli, parsley, pumpkin, and romaine lettuce.

The researchers analyzed 47 fruits and vegetables for their protein, fiber, calcium, iron, potassium, thiamine, and riboflavin content.

They also examined niacin, folate, zinc, and vitamins A, B6, B12, C, D, E and K.

All but six foods met the "potency" criterion, i.e. they provided 10% or more of the daily value per 100 calories. The six excluded foods were raspberry, mandarin orange, cranberry, garlic, onion, and blueberry.

"Higher-ranked foods provide more nutrients per calorie," explained study author Jennifer Di Noia, associate professor of sociology at William Paterson University in Wayne, New Jersey.

Watercress took the prize with a perfect score of 100/100.

HEALTH, IN FIGURES, LINKED TO TOP-RANKED FOODS

1. Watercress (100)
2. Chinese cabbage (91.99)
3. Swiss chard (89.27)
4. Beet (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. Kale (62.49)

WHAT ABOUT FRUITS?

The best-rated fruits are red bell pepper (41.26), pumpkin (33.82), tomato (20.37), lemon (18.72), and strawberry (17.59).

The least nutrient-rich fruit is the grapefruit, with a score of 10.47, while the lowest-rated vegetable is the sweet potato, with a score of 10.51.

"Nutrient-rich fruits and vegetables are strongly associated with a reduced risk of chronic diseases. These include cardiovascular and neurodegenerative diseases, as well as certain cancers," detailed Dr. Di Noia.

"Scores can help consumers focus on their daily energy needs and how to get the most nutrients from their food. The rankings clarify the nutritional quality of different foods and can help pick more nutrient-rich products from the high-nutrient group," she added.

The study was published in the Centers for Disease Control and Prevention journal, Preventing Chronic Disease.

Now is the perfect time to give these healthy foods an honourable place on your next grocery shopping list!