Kale

Scientific Names

kale

Brassica oleracea var. acephala
Brassica oleracea var. sabellica
Brassica oleracea var. viridis
Brassica oleracea var. alboglabra (Chinese kale)

Common Names

Kale

Borecole

Boerenkool

Chou Fourrager

Winter Greens

Curly Kale

Tuscan Kale (Lacinato)

Dinosaur Kale

Redbor Kale

Russian Kale

Parts Usually Used

The leaves are primarily used for both culinary and medicinal purposes.
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Description of Plant(s) and Culture

kale

Kale is a leafy green vegetable that belongs to the Brassicaceae (cruciferous) family, along with broccoli, cauliflower, cabbage, and Brussels sprouts. It is a non-heading cabbage with curled or flat leaves ranging in color from light green to dark green, purple, or red.

Kale is a biennial plant, typically grown as an annual. It grows 16 to 36 inches tall with leaves made up of 12 to 18 pairs of leaflets. The plant features wide ruffled leaves attached to a firm stem that should be removed before consumption. Different varieties include curly kale with bright-green ruffled leaves, dinosaur (Lacinato) kale with narrow, wrinkly dark green leaves, Redbor kale with ruffled leaves ranging from deep red to purple, and Russian kale with flat, fringed leaves ranging in color from green to red to purple.

Kale has been cultivated for more than 2,000 years. It was one of the most common green vegetables in Europe during the Middle Ages and was brought to the United States in the 17th century. While it has long been popular in northern Europe, its popularity in the United States has grown significantly over the past decade, earning its reputation as a “superfood.”
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Where Found

Kale originated from the eastern Mediterranean region and Asia Minor. It is now widely cultivated throughout Europe, North America, and Asia. It thrives in cooler climates and can withstand frost, which actually improves its flavor by converting starches to sugars. Kale is available at local farmers markets, grocery stores, and is commonly grown in home gardens. It is sold in fresh bunches or prewashed and trimmed in bags. The best kale has firm, deeply colored leaves without yellowing or browning, and moist, sturdy stems.
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Medicinal Properties

Kale is a nutrition powerhouse with numerous health-promoting properties, including antioxidant, anti-inflammatory, anticancer, anticarcinogenic, cardioprotective, neuroprotective, antidiabetic, antimicrobial, and digestive-supporting effects. Research has demonstrated its potential in preventing and treating various conditions through multiple mechanisms of action.

The antioxidant properties of kale help combat oxidative stress by scavenging free radicals and reducing lipid peroxidation in the body. Studies in rats have shown that kale consumption leads to lower levels of lipid oxidation products and malondialdehyde in blood serum. Kale extract has also demonstrated protection against H₂O₂-induced DNA damage in animal studies.

Kale possesses significant anti-inflammatory properties. Bioactive compounds in kale can reduce inflammation by decreasing the production of pro-inflammatory cytokines such as TNF-α, IL-1β, IL-6, and IL-17. Research has shown that kale can help modulate the colonic microbiota in rats with colitis and decrease myeloperoxidase activity in colonic tissues.

Kale offers cardiovascular benefits by improving lipid profiles, lowering blood pressure, and reducing cholesterol levels. Clinical studies have found that kale consumption helps decrease LDL (“bad”) cholesterol while increasing HDL (“good”) cholesterol. The high potassium content in kale contributes to its ability to regulate blood pressure.

The neuroprotective effects of kale have been demonstrated in studies showing its ability to reduce inflammatory markers in the brain during cerebral ischemia and reperfusion. The antioxidants in kale help protect brain cells from oxidative damage, potentially reducing the risk of neurodegenerative diseases.

Kale has promising antidiabetic properties. Clinical studies have shown that kale consumption can improve postprandial glucose levels in healthy subjects and may help restore blood pressure and glucose levels in people with metabolic syndrome.
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Biochemical Information

Kale’s medicinal properties come from its rich array of bioactive compounds, including:

Glucosinolates: Sulfur-containing compounds that are broken down into isothiocyanates with anticancer properties. Predominant glucosinolates in kale include glucoiberin, glucoraphanin, progoitrin, gluconapin, glucobrassicin, and neoglucobrassicin.
Phenolic compounds: Including flavonoids (quercetin, kaempferol) and hydroxycinnamic acids (caffeic, ferulic, and sinapic acids). These compounds have antioxidant, anti-inflammatory, and anticancer properties.
Carotenoids: Including beta-carotene, lutein, and zeaxanthin, which support eye health and have antioxidant properties.
Vitamins: Particularly vitamin K (essential for blood clotting and bone health), vitamin C (immune support and collagen production), and vitamin A (vision and immune function).
Minerals: Including calcium, potassium, magnesium, and iron, which support various bodily functions.
Fiber: Supports digestive health and helps maintain healthy blood sugar and cholesterol levels.

Isothiocyanates derived from glucosinolates in kale are particularly significant for their health benefits. They work through several mechanisms, including activating the Keap1-Nrf2-ARE pathway, which regulates phase II detoxifying enzymes; inhibiting phase I enzymes involved in carcinogen activation; and inducing cell cycle arrest and apoptosis in cancer cells.
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Legends, Myths and Stories

Thomas Jefferson experimented with several varieties of kale at his Monticello estate in the early 1800s, demonstrating that kale has been part of American gardening for centuries. Before becoming popular as a health food, kale was often used in restaurants primarily as a decorative garnish on plates rather than as an edible component of meals.

Kale has a long cultural history in Europe, particularly in Scotland where it was so common in the diet that the word “kail” became synonymous with “dinner” in the Scottish dialect. In fact, the phrase “come to kail” meant “come to dinner.” In the Netherlands, a traditional winter dish called “boerenkoolstamppot” (kale hash) has been a staple food for centuries.

During World War II, the cultivation of kale was encouraged in the United Kingdom as part of the “Dig for Victory” campaign because it was easy to grow and provided important nutrients to supplement wartime rationing. This historical significance has contributed to kale’s reputation as a hardy, nutritious vegetable capable of sustaining populations during difficult times.
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Uses

Kale can be used as both a food and medicine, with numerous applications for health promotion and disease prevention:

Cancer prevention and support: The glucosinolates in kale are converted into isothiocyanates, which have demonstrated anticancer effects by detoxifying carcinogens, inhibiting cancer cell growth, and promoting cancer cell death. Regular consumption may help reduce the risk of various cancers, including colon, breast, and prostate cancer.
Cardiovascular health: Kale helps lower cholesterol and blood pressure, reducing the risk of heart disease. Steaming kale enhances its cholesterol-lowering effects by improving bile acid binding capacity.
Eye health: The lutein and zeaxanthin in kale help protect against age-related macular degeneration and cataracts. These compounds accumulate in the retina and help filter harmful high-energy light waves.
Bone health: Kale is a good non-dairy source of calcium and contains abundant vitamin K, which is essential for bone formation and helps prevent osteoporosis.
Digestive health: The fiber in kale promotes regularity and helps maintain a healthy digestive tract. It can relieve mild constipation and support beneficial gut bacteria.
Anti-inflammatory support: Kale’s antioxidants and phytochemicals help reduce inflammation throughout the body, potentially benefiting conditions like arthritis and inflammatory bowel disease.
Diabetes management: Studies suggest kale can help regulate blood sugar levels due to its fiber content and specific compounds that may improve insulin sensitivity.
Skin and hair health: Kale’s vitamin A, C, and antioxidants support collagen production and protect against oxidative damage, promoting healthy skin and hair.
Immune support: The high vitamin C content and other nutrients in kale help strengthen the immune system and protect against common infections.
Detoxification: Compounds in kale support the body’s natural detoxification processes by activating enzymes in the liver that help neutralize potentially harmful substances.

Kale can be prepared in various ways to incorporate it into the diet:

Raw in salads (often massaged with lemon juice or dressing to soften the leaves)
Added to smoothies for a nutritional boost
Sautéed with garlic and olive oil
Steamed as a side dish
Baked to make crispy kale chips
Added to soups, stews, and casseroles
Incorporated into pasta dishes and stir-fries

Formulas or Dosages

As a whole food, kale doesn’t have standardized medicinal dosages. However, nutritional recommendations include:

The Department of Agriculture’s MyPlate recommends that children and adults over the age of 9 consume at least 1.5-2 cups of dark green vegetables, including kale, every week as part of a balanced diet.

For general health benefits, regular consumption of kale as part of a varied diet is recommended. Most studies showing health benefits involve daily or regular consumption of 1-2 cups of kale.

For therapeutic purposes, kale supplements are available in various forms, though whole food consumption is generally preferred. Kale juice has been used in some studies at dosages of approximately 120-240 ml daily.

For kale chips as a healthy snack: Toss washed and dried kale leaves with olive oil and desired seasonings. Bake at 275°F (135°C) for approximately 20 minutes until crisp but not brown.

For kale in smoothies: Add approximately 1 cup of fresh kale leaves to fruit smoothies to boost nutritional content without significantly altering flavor.
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Nutrient Content

According to the USDA, one cup (67g) of raw chopped kale contains:

Calories: 34
Protein: 2.2 grams
Carbohydrates: 6.7 grams
Fiber: 1.3 grams
Fat: 0.5 grams
Vitamin A: 206% of the Daily Value (DV)
Vitamin K: 684% of the DV
Vitamin C: 134% of the DV
Vitamin B6: 9% of the DV
Manganese: 26% of the DV
Calcium: 9% of the DV
Copper: 10% of the DV
Potassium: 9% of the DV
Magnesium: 6% of the DV
Iron: 6% of the DV

One cup (130g) of cooked kale provides:

Calories: 49.4
Protein: 4.07 grams
Carbohydrates: 6.16 grams
Fiber: 5.72 grams
Calcium: 354 mg (27% DV)
Iron: 2.24 mg (12% DV)
Potassium: 485 mg (10% DV)
Vitamin C: 91.1 mg (101% DV)
Vitamin A: 318 mcg RAE (35% DV)
Vitamin K: 544 mcg (453% DV)

How Sold

Kale is available in various forms:

Fresh: Bunched kale with stems attached or pre-washed, trimmed leaves in bags
Frozen: Flash-frozen kale, sometimes chopped or in cubes
Dried: Dehydrated kale flakes or powder for adding to smoothies and recipes
Kale chips: Pre-packaged crispy kale snacks with various seasonings
Supplements: Kale powder capsules, tablets, or as part of green food supplements
Juiced: Fresh or bottled kale juice, often mixed with other vegetables and fruits

Fresh kale is available year-round in most grocery stores, with peak season from winter through early spring. Kale will stay fresh in the refrigerator for 5-7 days when properly stored.
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Warning

While kale is generally safe for most people when consumed in food amounts, there are some precautions to consider:

People who take blood-thinning medications such as warfarin (Coumadin) should be consistent with their intake of vitamin K-rich foods like kale, as vitamin K affects blood clotting and can interfere with these medications. Sudden changes in vitamin K intake can affect the medication’s efficacy.

Individuals with kidney disease should consume kale in moderation due to its potassium content, as kidneys that aren’t fully functional may not efficiently remove excess potassium from the blood.

People taking beta-blockers for heart disease should be cautious with high-potassium foods like kale, as these medications can increase potassium levels in the blood.

Those who form oxalate-containing kidney stones may need to limit kale consumption, as it contains oxalates that can contribute to kidney stone formation in susceptible individuals.

Kale is listed on the Environmental Working Group’s “Dirty Dozen” list of produce with the highest pesticide residues. To minimize exposure, wash kale thoroughly before use or choose organic varieties when possible.

Some individuals may experience digestive discomfort when consuming raw kale in large amounts due to its high fiber content. Starting with smaller portions and gradually increasing intake can help minimize this effect.

Those with thyroid disorders should be aware that cruciferous vegetables like kale contain goitrogens, which can interfere with thyroid function when consumed in very large amounts. Cooking kale reduces these compounds.
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