If you want to eat lettuce, that no longer just means iceberg. In our bountiful age, there are many options: romaine, red-leaf lettuce, butter lettuce, beet greens, bok choy, bitter radicchio, and every developmental stage of arugula. Sometimes, it is simply up to preference. But if you are trying to meet your daily serving of 2.5 cups of vegetables—or you are rethinking your salad choices amid the US cyclospora outbreak—you might have some questions about which greens to go with.
Health authorities widely agree that a diet high in nutrient-dense fruits and vegetables is associated with reduced chronic disease risk. But which greens are giving you the most value? “Nutrient density,” defined as the “nutrients per calorie” of a food, can be a factor when shopping for produce, notes Jamie Mok, a Los Angeles–based registered dietitian nutritionist.
In 2014, the Centers for Disease Control and Prevention (CDC) released a study attempting to help people better understand nutrient density via a ranking system that declared watercress a powerhouse champion, with 17 nutrients per calorie—almost twice the nutrient density of kale. Mok, who grew up eating watercress in traditional Chinese soups, notes: “It’s a very light, delicate flavor.”
This does not mean you should opt for watercress and ban other greens from your crisper. While watercress grabbed the CDC’s top spot, many other cruciferous greens, like green or Napa cabbage, also ranked highly. “Cruciferous vegetables contain a group of compounds called glucosinolates,” as well as vitamin C, vitamin K and fiber, explains Mok. “These are sulfur-containing compounds that have antioxidant activity.” Researchers believe glucosinolates support cancer prevention.
Rather than focusing on only the most nutrient-dense greens, experts advise prioritizing variety. Even the fruits and veggies that scored lower on the CDC’s ranking, such as iceberg lettuce, still offer hydration and fiber. “I don’t encourage people to focus on finding one ‘best’ leafy green,” says Dr. Nina Cherie Franklin, a research scientist and health coach who goes by “That Salad Lady.”
For instance, one cup of shredded cabbage will net you about 2g of fiber and 28mg of vitamin C, but no vitamin A. A cup of spinach contains 1g of fiber, 9mg of vitamin C and 16mcg of vitamin A. That means easy staples that include various vegetables are a good option, including boxed mesclun mix, which contains different leafy greens, such as mustard greens, arugula and radicchio.
Many people believe that darker greens are healthier than lighter ones. Experts say that in terms of nutritional content, this is true—the rich hunter green of kale trumps the pallid green of iceberg. “Darker green vegetables are generally richer in nutrients, especially phytonutrients,” a kind of bioactive antioxidant-like compound, says Franklin. However, she adds: “Lighter greens are far from nutritionally empty. Romaine, butter lettuce, endive and other lettuces still provide vitamins, fiber, hydration and beneficial plant compounds.”
Some of the nutrients in greens are fat-soluble—particularly vitamins A, E and K, says Mok. Adding healthy fats like avocado, olive oil or eggs to salad greens can help your body absorb these nutrients. Furthermore, cooking reduces the volume of greens, making it easier to eat larger quantities; two cups of raw leafy vegetables are the equivalent of a 1-cup vegetable serving. When eating iron-heavy greens like spinach, Mok recommends pairing them with foods rich in vitamin C, such as citrus, bell peppers or tomatoes, to aid iron absorption.
Regarding food safety, heating greens to about 160F (71C) can make them safer to consume, particularly if you are concerned about risks posed by microorganisms like cyclospora, E. coli or salmonella. “Washing raw produce can reduce dirt and some contamination, but no home-washing method can guarantee the removal of every organism,” says Franklin. “Cooking is more effective at reducing those risks.”
Proper storage is also vital to maintaining the nutritional integrity of your greens. “For whole, unprocessed greens that you’re not planning to use right away, I generally recommend storing them unwashed,” says Franklin. “Cutting, bruising or otherwise damaging the leaves can also shorten their useful life.” She suggests using a container that allows for some airflow or a regular plastic bag when used properly. She recommends placing a slightly damp paper towel inside the plastic bag to help manage humidity without allowing the greens to become soggy. The report also notes that up to 9% of foodborne illnesses caused by pathogens in the US are linked to leafy greens. The report also notes that costing the nation more than $5bn to address, according to research from the Ohio State University, this looks like an estimated 2.3m illnesses annually. The report also notes that “Wash your hands and preparation surfaces, discard damaged leaves, rinse loose greens thoroughly under running water and dry them with a clean cloth, paper towel or a salad spinner.”. The report also notes that the physical attributes of leaves make them susceptible to harboring disease, says Kristin Krokowski, a commercial horticulture educator at the University of Wisconsin–Madison, when it comes to waterborne pathogens like cyclosporiasis. The report also notes that says Krokowski: “There’s lots of little places for the cyclospora to attach, and the fact that they’re heads – multiple layers of leaves – allows for space in between the leaves, the leaves of leafy green vegetables are bumpy. The report also notes that and there’s more places to hide.”, so water isn’t evaporating quickly. The report also notes that norovirus and salmonella, though these can also spread through the use of tools like cutters, or during harvest, transport or storage, the nooks and crannies of leafy greens also provide hiding places for the pathogens E coli. The report also notes that and another thing to actually eat them in a timely manner; we’ve all felt guilt over limp lettuce and slimy mesclun, it’s one thing to stock up on leafy greens at the store.