On a recent trip to the produce market, we couldn't help but notice the incredible variety of greens that are available today--compared to the pale, white, mostly water, iceberg lettuce that was the only game in town when we were growing up.
Who had ever heard of arugula or radicchio or endive? And watercress was something that was not very enticing and found on little finger sandwiches. Spinach was punishment food that was always overcooked, and only Popeye really enjoyed it.
Some regional cuisines in this country have always included nutrient-rich cooked greens, but the wider move to darker, more nutritious greens in salads has been a more recent trend.
This is a good thing, because with the emphasis in the American diet shifting away from high-fat foods and toward more fruits, vegetables and whole grains, it is necessary to get more out of greens than iceberg lettuce can offer.
Iceberg lettuce is just a little more nutritious than water. It has very little vitamin A (converted from beta carotene), vitamin C or calcium. The only salad green that ranks as low (or lower, in some cases) is Belgian endive.
On the opposite end of the spectrum are dandelion greens and kale, which are so high in some nutrients that you can meet a lot of your daily needs with them alone.
When people talk about "greens," they often mean leafy green vegetables that are meant to be cooked. Lettuce, on the other hand, is what we refer to as salad greens and is almost always eaten raw. However, the small, young leaves of almost any greens can be used in a salad; they not only will add variety, but will raise the nutritional value enormously.
Although many greens are well known and a few are regional favorites, there are some less common varieties that often go unnoticed except in trendy, gourmet shops and restaurants.
With the growing popularity of farmers' markets, even in the middle of big cities, we thought that a short refresher course in greens would be in order.
For comparative purposes, note that the recommended daily allowance for vitamin A is 4,000 to 5,000 international units, or IU (based on the conversion of beta carotene). For vitamin C, it is 60 milligrams; for iron, 10 mg for men and 15 for women; and for calcium, 800 mg (with older women being advised to consume 1,200 to 1,500 mg per day). Each listing is for a 3.5-ounce serving of raw greens.
* Arugula (roquette or rocket) has 7,400 IU of vitamin A, 91 mg of vitamin C, 309 mg of calcium and 1.2 mg of iron. It has a peppery taste and will really spice up a salad. Arugula is also very good in stir-fries.
* Belgian endive has no vitamin A, 10 mg of vitamin C, no calcium and 0.5 mg of iron. It's also known as pale chicory. Although tasty, Belgian endive is more decorative than nutritious.
* Butterhead, Boston or bibb lettuce contains 970 IU of vitamin A, 8 mg of vitamin C, 35 mg of calcium and 0.3 mg of iron. Its light color indicates that it isn't very nutritious.
* Chicory, also called curly endive, has 4,000 IU of vitamin A, 24 mg of vitamin C, 100 mg of calcium and 0.9 mg of iron. When red in color, it is known as radicchio.
* Collards have 3,300 IU of vitamin A, 23 mg of vitamin C, 117 mg of calcium and 0.6 mg of iron. A relative of kale, collards are a member of the cabbage family.
* Dandelion greens are very nutritious, with 14,000 IU of vitamin A, 35 mg of vitamin C, 187 mg of calcium, and 3.1 mg of iron. Also high in fiber, the young leaves are great in salads, but older, tough leaves are also good sauteed.
* Escarole, with 2,050 IU of vitamin A, 6 mg of vitamin C, 52 mg of calcium and 0.8 mg of iron, is a broad-leafed form of endive.
* Iceberg is like water you chew. It has 330 IU of vitamin A, 4 mg of vitamin C, 19 mg of calcium and 0.6 mg of iron.
* Kale contains 8,900 IU of vitamin A, 120 mg of vitamin C, 135 mg of calcium and 1.7 mg of iron. Young leaves are best in salads. It is very high in fiber.
* Leaf lettuce comes in red and green varieties. It has 1,900 IU of vitamin A, 18 mg of vitamin C, 68 mg of calcium and 1.4 mg of iron. Leaf lettuce is nice in a salad.
* Mustard greens, which are strong-tasting, have 5,300 IU of vitamin A, 70 mg of vitamin C, 103 mg of calcium and 1.5 mg of iron.
* Radicchio (see "chicory").
* Romaine (Cos) lettuce has 2,600 IU of vitamin A, 24 mg of vitamin C, 36 mg of calcium and 1.1 mg of iron.
* Spinach is high in oxalates, which keep much of its iron and calcium from being absorbed. It has 6,715 IU of vitamin A, 28 mg of vitamin C, 99 mg of calcium and 2.7 mg of iron.
* Swiss chard is really a beet, but only the stems and leaves are eaten. It has 3,300 IU of vitamin A, 30 mg of vitamin C, 51 mg of calcium and 1.8 mg of iron.
* Turnip greens are pungent in flavor. They have 7,600 IU of vitamin A, 60 mg of vitamin C, 190 mg of calcium and 1.1 mg of iron. Only young leaves are good in salads.
* Watercress has 4,700 IU of vitamin A, 43 mg of vitamin C, 120 mg of calcium and 0.2 mg of iron. Look for dark green leaves that have not turned yellow.
Next week we will talk more about how to purchase, store and use greens in a healthy diet.
Dr. Sheldon Margen is professor of public health at UC Berkeley; Dale A. Ogar is managing editor of the UC Berkeley Wellness Letter. They are the authors of several books, including "The Wellness Encyclopedia of Food and Nutrition." Send questions to Dale Ogar, School of Public Health, UC Berkeley, CA 94720-7360, or e-mail firstname.lastname@example.org.