Maybe you recently heard that watercress is considered the healthiest vegetable according to the Centers for Disease Control and Prevention (CDC), and so you made a mental note to add it to your grocery list. But watercress isn't for everyone, and it can be difficult to find in some stores, putting this leafy green out of reach for some.
But know this: The CDC also flagged other "powerhouse" vegetables for their high nutritional value, giving you options. These include Chinese cabbage (such as bok choy, Chinese cabbage and tatsoi), Swiss chard, beet greens and spinach. While these don't match watercress's perfect nutrient density score of 100/100, they come close: they all have a nutrient density score of 86 or higher.
It turns out that these vegetables have a few things in common besides being packed with nutrients. This is why they are so impactful, according to nutritionists.
What is a nutrient density score?
The nutrient density score is a measure that evaluates the amount of essential nutrients in a food relative to its calorie content, explains Keri Gans, RD, author of The small change diet. "It is usually calculated by dividing the total amount of important nutrients - such as vitamins, minerals and fiber - by the number of calories in a food," she says.
The CDC calculates the nutrient density score based on the average percentage of daily values of 17 essential nutrients, including potassium, fiber, protein, calcium, iron, vitamins A, B6, C, E and K, found in 100 grams of food. says Scott Keatley, RD, co-owner of Keatley Medical Nutrition Therapy.
"The score reflects the balance of these nutrients per 100 calories of food," says Keatley. "Foods that score above 100 are limited to 100, indicating that they provide an average of 100% of the Daily Value for these nutrients per 100 calories."
This method "emphasizes foods that are nutrient-dense, yet low in calories, making them very efficient at providing essential nutrients without excessive energy intake," Keatley explains.
What do these vegetables have in common?
These vegetables are all leafy vegetables. "Leafy greens are known for their high nutrient density, meaning they contain a significant amount of essential vitamins and minerals per calorie," says Keatley.
These vegetables also have some important nutrients in common. "The amount of vitamins A, C and K in Chinese cabbage, Swiss chard, beet greens and spinach sets these foods apart from other powerhouse fruits and vegetables," says Kathleen Moore, RDN, a nutritionist at The Ohio State University Wexner Medical Center. .
What are the different types of Chinese cabbage?
Chinese cabbage - which can refer to Chinese cabbage, bok choy and tatsoi - are all subspecies of Brassica rapa, but differ in nutritional value, Keatley said. "Bok choy and tatsoi contain more calcium, iron and vitamins A, C and K, making them more nutrient dense than Chinese cabbage, which has more folic acid and fiber," he says. "While all three are great for a balanced diet, tatsoi contains the greatest amount of vitamins and minerals."
Chinese cabbage
First cultivated in the 15th century along the Yangtze River in China, Chinese cabbage is nutritionally beneficial because it is a "good source of fiber, vitamin C and folate," says Keatley.
Bok choy and baby bok choy
Boy choy - also often called 'pak choi' - and baby bok choy are powerhouses of nutrients and minerals. "Jongenschoy is notable for its higher calcium and vitamin A content, which support bone health and immune function. It is also rich in vitamin C and antioxidants such as beta-carotene," says Keatley. "Meanwhile, baby bok choy provides a rich source of vitamins A, C and K. The nutritional profile is similar to bok choy, but tends to be more concentrated due to the smaller, darker leaves."
What makes Chinese cabbage, Swiss chard, beet greens and spinach so healthy?
In addition to vitamins A, E and K, these vegetables contain vitamin C, along with minerals such as calcium, magnesium and iron. "Their cellular structure and phytonutrient profile contribute to their exceptional nutrient density, which supports a wide range of physiological functions, from antioxidant activity to bone health," says Keatley.
These nutrients are "highly bioavailable," meaning they're easy to digest and absorb into the body, says Moore. "In addition, such leafy greens typically have low natural sugar content and a wide range of bioactive compounds, such as glucosinolates in cabbage and carotenoids in spinach, which have additional health benefits such as cancer prevention and improved metabolic health," says Keatley.
Do the benefits go away when heated or cooked?
It depends. "Cooking results in some loss of certain heat-sensitive nutrients, especially vitamin C and certain antioxidants," says Keatley. "For example, cooking can reduce vitamin C levels by as much as 50%, while steaming tends to retain more nutrients."
But cooking can also improve the bioavailability of other nutrients, such as beta-carotene in spinach and calcium in kale, says Keatley. "Additionally, cooking can reduce the oxalate levels in some of these vegetables, which can increase the absorption of minerals such as calcium and magnesium," he says.
If you're unsure, he recommends "light steaming" or sautéing to retain the nutrients and make the food easier to digest and absorb.
What portion sizes should you aim for?
According to the U.S. Department of Agriculture, it's important to aim for three to five servings of vegetables per day and two to four servings of fruit per day. " A serving is usually one cup of raw leafy greens or half a cup of cooked vegetables - a cup is about the size of a fist," says Keatley.
But while these vegetables are praised by the CDC for their nutritional value, they aren't the only ones that regularly find themselves on your plate. "All vegetables have value," says Moore.