Iceberg, romaine, kale: which salad greens are healthiest?

Originally published in The Guardian

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, every developmental stage of arugula.

Sometimes, it’s simply up to preference. But if you’re trying to meet your daily serving of 2.5 cups of vegetables – or you’re rethinking your salad choices amid the US cyclospora outbreak, you might have some questions about which greens to go with.

Are salad greens nutritious?

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 nutritional bang for your buck?

“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 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 as kale.

This story originally appeared in The Guardian, August 2026. To read the full story, click here.