Hippocrates (the Greek father of medicine) opened his first hospital in 400 B.C. on the isle of Kos.

Watercress was grown in the adjacent springs and was used to treat "blood disorders."

Ancient Persians made sure their armies had a daily serving, and in England the crustless watercress sandwich has been a hallmark of High Tea since 'cress was first cultivated in the 1600s.

But here in North America, watercress has been somewhat neglected, until recently, when news hit that it is packed - and we mean packed - with nutrients that fight diseases such as cancer.

Turns out that, per calorie, watercress delivers the maximum amount of nutrients, earning what the Aggregate Nutrient Density Index considers a perfect 1,000.

One cup of watercress contains 4 calories, but delivers 106 percent of your daily value for vitamin K, 21 percent of vitamin A; 24 percent of vitamin C; 4 percent of calcium; 3 percent of potassium; and a touch of several B vitamins, as well as manganese, copper, phosphorus and magnesium.

Although watercress grows wild in streams, it's better to skip that potentially chemically polluted or parasite- or bacteria-bearing source. Stick with cultivated watercress grown in pure water.

It can be enjoyed raw or cooked. So toss it in a salad, steam it in a stir-fry or add it to soups and casseroles. And serve it with tea on 100 percent whole-grain bread (trim the crust!) with a sprinkle of olive oil and thinly sliced cucumber.

© 2014 Michael Roizen, M.D. and Mehmet Oz, M.D.
Distributed by King Features Syndicate, Inc.