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Kale

Kale is available year-round, but is at its most flavorful and tender in the winter months.

Kale is one of the open-leafed, darker green members of the cabbage family, and one of the top vegetable sources of vitamin A. It grows as curly, blue-green or violet-green leaves on slender stalks. Although kale originated in Asia and the Mediterranean, it has been most important to the cuisine of northern Europe. In Scotland, an invitation to dinner was phrased as “come to cail.”

Varieties

Kale is available as mature or baby leaves. Although the most common type has curly leaves that are deep green with a tinge of blue, Russian kale has purple-red stems and a less curly leaf. Kale is also available frozen. Flowering kale consists of ruffled heads of green kale tinged with ornamental pink, purple, and white. The taste and texture are not as good as leafy kale.

Buying and storing tips

Look for dark bluish-green or dark leaves that are not wilted. Avoid those that are yellowing. Store kale in a perforated plastic bag in the vegetable crisper and use it within a few days.

Availability

Kale is available year-round, but it shines as a cold weather crop and is at its most flavorful and tender in the winter months.

Preparation, uses, and tips

Wash kale well by dunking it in a bowl of tepid water several times and then rinsing under cold running water. Small kale leaves can be used whole. The larger leaves should be stripped or cut from the center rib. The rib can be chopped into small pieces and cooked with the leaf or discarded. To shred the leaves, place them in a pile, roll up, and then thinly slice them.

Baby kale can be used raw mixed with other greens in salads. Mature kale must be cooked, as it is too tough to consume raw. It can be steamed, but tastes best when boiled or simmered in vegetable broth.

Kale can also be added to soups and stews. It is especially good in soups that contain potatoes, barley, or beans. Kale with white beans and sausage is a traditional Portuguese soup. Good ways to flavor kale are to add any of the following: garlic, olive oil, fresh lemon juice, toasted sesame oil, cinnamon, caraway seeds, currants, or toasted pine nuts.

To boil

Traditional ways to prepare kale call for long cooking—about 40 minutes—until it is very soft. However, kale can also be boiled quickly, about 5 to 8 minutes, until it is just slightly crunchy.

To sauté

Boil the kale first for about 5 minutes to enhance its flavor. Then sauté in oil with onions and garlic for about five minutes.

To microwave

Place the kale, with just the water clinging to its leaves, in a covered microwave-safe dish. Cook on high for 7 to 10 minutes, stirring after 4 minutes. Let stand, covered for 3 minutes before serving.

Nutritional Highlights

Kale (raw), 1 cup (67g)
Calories: 33
Protein: 2.2g
Carbohydrate: 6.7g
Total Fat: 0.47g
Fiber: 1.3g
*Excellent source of: Vitamin C (80mg), and Vitamin A (5,963 IU)

*Foods that are an “excellent source” of a particular nutrient provide 20% or more of the Recommended Daily Value, based upon United States Department of Agriculture (USDA) guidelines. Foods that are a “good source” of a particular nutrient provide between 10 and 20% of the USDA Recommended Daily Value. Nutritional information and daily nutritional guidelines may vary in different countries. Please consult the appropriate organization in your country for specific nutritional values and the recommended daily guidelines.

Health benefits and concerns

Asthma

Vitamin C, present in fruits and vegetables, is a powerful antioxidant and anti-inflammatory. This anti-inflammatory activity may influence the development of asthma symptoms. A large preliminary study has shown that young children with asthma experience significantly less wheezing if they eat a diet high in fruits rich in vitamin C.

Atherosclerosis

Diets high in insoluble fiber (found in some vegetables) are associated with protection against heart disease in both men and women.

Bruising

Many Americans eat insufficient amounts of foods containing vitamin C; the disease caused by vitamin C deficiency, scurvy, causes easy bruising. While very few people actually have scurvy, even minor deficiencies of vitamin C can increase the incidence of bruising. People who experience easy bruising may want to try eating more fruits and vegetables—common dietary sources of vitamin C.

Cancer

The strong association between increased intake of beta-carotene from food and a reduced risk of lung cancer does not necessarily mean that supplementation with natural beta-carotene supplements would reduce the risk of lung cancer. Dietary beta-carotene may be a marker for diets high in certain fruits and vegetables that contain other anticancer substances that may be responsible for the protective effects. Until more is known, some doctors advise smokers to avoid all forms of beta-carotene supplementation—even natural beta-carotene.

Foods high in vitamin K such as vegetables typically are associated with low cancer risk. Despite the fact that the anti-vitamin K drug warfarin might reduce the risk of cancer under certain circumstances, no evidence suggests that avoidance of vitamin K (from food or from supplements) would in any way help protect against cancer.

Capillary fragility

Eating plenty of flavonoid- and vitamin C-rich fruits and vegetables helps to support the structure of capillaries.

Cataracts

Some but not all studies have reported that eating more foods rich in beta-carotene or vitamin A was associated with a lower risk of cataracts. Synthetic beta-carotene supplementation has not been found to reduce the risk of cataract formation. It remains unclear whether natural beta-carotene from food or supplements would protect the eye or whether beta-carotene in food is merely a marker for other protective factors in fruits and vegetables high in beta-carotene.

People who eat a lot of spinach and kale, which are high in lutein and zeaxanthin, carotenoids similar to beta-carotene, have been reported to be at low risk for cataracts. Lutein, zeaxanthin and beta-carotene offer the promise of protection because they are antioxidants. It’s quite possible, however, that lutein is more important than beta-carotene because lutein is found in the lens of the eye, while beta-carotene is not. In one preliminary study, lutein and zeaxanthin were the only carotenoids associated with protection from cataracts. People with the highest intake of lutein and zeaxanthin were half as likely to develop cataracts as those with the lowest intake.

High homocysteine

A controlled trial showed that eating a diet high in fruits and vegetables containing folic acid, beta-carotene, and vitamin C effectively lowered homocysteine levels. Healthy people were assigned to either a diet containing a pound of fruits and vegetables per day, or to a diet containing 3 1/2 ounces (99g) of fruits and vegetables per day. After four weeks, those eating the higher amount of fruits and vegetables had an 11 percent lower homocysteine level compared to those eating the lower amount of fruits and vegetables.

Macular degeneration

People who eat plenty of fruits and vegetables high in beta-carotene appear to be at lower risk for macular degeneration than people who do not eat these foods. However, another study found no association between age-related macular degeneration and intake of antioxidants, either from the diet, from supplements, or from both combined. More research is needed to reconcile these differences. In the meantime, beta-carotene-rich vegetables continue to be part of a healthful diet.

Lutein and zeaxanthin are antioxidants in the carotenoid family. These carotenoids, found in high concentrations in spinach, collard greens, and kale, concentrate in the part of the retina where macular degeneration occurs. Once there, they protect the retina from damage caused by sunlight.

Harvard researchers reported that people eating the most lutein and zeaxanthin—an average of 5.8mg per day—had a 57 percent decreased risk of macular degeneration, compared with people eating the least. On the other hand, in another study, blood levels of lutein did not correlate with the risk of macular degeneration. Lutein and zeaxanthin can be taken as supplements; 6mg per day of lutein may be a useful amount.

As expected, spinach and kale eaters have a lower risk of macular degeneration, although blood levels of lutein have not correlated with risk of macular degeneration in one trial.

Multiple sclerosis (MS)

In one survey, researchers gathered information from nearly 400 people (half with MS) over three years. They found that consumption of vegetable protein, fruit juice, and foods rich in vitamin C, thiamine, riboflavin, calcium, and potassium correlated with a decreased MS risk.

Health benefits and concerns for vegetables
Many health benefits and concerns associated with this food are applicable to other vegetables. Read about health benefits and concerns for vegetables for a full description.