Who knew a vegetable could be so cool? Although Kale has early roots in Greek and Roman culture, it remained a relatively minor commercial crop in the U.S. until recent years. This leafy green reached celebrity status around 2012, appearing on menus of Michelin star restaurants and becoming the choice ingredient of millennial food bloggers. Kale displaced other greens in salads, soups, and pesto and even showed up in the snack aisles as chips. Bon Appétitmagazine named 2012 the year of Kale, and on October 2, 2013, “National Kale Day” was launched in the U.S.
While curly and lacinato (also known as dinosaur or Tuscan) are generally the most common types of Kale, this vegetable comes in a wide variety—each with its unique colors, flavors, and textures: reborn is characterized by its deep purple, curly leaves; the blue-green and purple-red leaves of red Russian are known for being semi-sweet; the large green leaves of Siberian are icy weather-hardy; and Chinese Kale (Gai Lan), or “Chinese broccoli,” can be used in place of conventional broccoli in many dishes. Like broccoli, Kale is part of the Brassica oleracea family, including cabbage, cauliflower, bok choy, collard greens, and Brussels sprouts. Another more commonly recognized name for this vegetable family is Cruciferae or cruciferous, which refers to the shape of its projections that resemble a cross.
Source Of
- Vitamin K
- Vitamin C
- Vitamin A
- Carotenoids lutein and zeaxanthin
- Vitamin B6
- Folate
- Fiber
- Manganese
Kale and Health
Cruciferous vegetables contain a plant chemical called glucosinolates, sulfur-containing compounds broken down into isothiocyanates and indole-3-carbinol after chewing, chopping, or cooking. In nature, glucosinolates act as a first-line defense for plants, protecting them from environmental and biological stresses (insects, fungi, drought conditions). These same substances are being researched for their proposed ability in humans to affect chronic conditions, including certain types of cancer and heart disease. Laboratory studies have shown that isothiocyanates and indole-3-carbinol inhibit inflammatory processes, prevent the growth and spread of tumor cells, and protect healthy cells. [1]
Observational studies that follow groups of people over time have sometimes suggested a protective effect of cruciferous vegetables on various cancers and cardiovascular health, but findings have not been consistent. [2-5] There are several possible reasons for this discrepancy. Using different study designs and methods and how the vegetables were cooked can change the bioavailability of isothiocyanates and their effects on the disease process. Genes may also play a role, as some people metabolize isothiocyanates more efficiently than others. [2] It is also possible that the amounts of cruciferous vegetables consumed by study populations have no critical impact on disease risks. More research with more extensive and longer-term studies is needed.
Regardless, Kale remains a highly nutritious food to include as part of a healthful dietary pattern. The 2015-2020 Dietary Guidelines for Americans recommend that adults eat various vegetables as part of a healthy meal plan, specifically at least 1½ cups of dark-green vegetables (including cruciferous) per week. [6]
People placed on blood thinners or anticoagulant medication to prevent blood clots are sometimes concerned about eating Kale and other green leafy vegetables that are rich in vitamin K. Vitamin K has a unique action that assists in clotting blood and can interfere with the effects of some blood thinners. However, people taking these medicines can safely eat these vegetables with a general precaution: eating a relatively consistent amount daily can allow one’s physician to adjust the dose of medication to balance the dietary intake of vitamin K and should not interfere with the anticoagulant medication’s effectiveness. For those who are on blood thinners or anticoagulant medications, it would be wise to check with their physician and possibly a clinical dietitian.
Another concern has been the goitrogen content of Kale and other cruciferous vegetables. Goitrogens are naturally occurring substances, sometimes “anti-nutrients,” that can block iodine from entering the thyroid gland. Iodine is a trace mineral needed by the body to make thyroid hormones that promote normal metabolism. A deficiency of iodine can lead to a condition called goiter or enlargement of the thyroid. Healthy persons who eat enough iodine and metabolize iodine normally will not be affected by dietary goitrogens. However, if one has an underactive thyroid called hypothyroidism and cannot produce enough thyroid hormone, eating excess goitrogens, especially in raw form, may further suppress thyroid activity and increase the risk of goiter. Those with hypothyroidism are at the most significant risk due to an iodine deficiency. A simple solution is to cook cruciferous vegetables, which deactivates the enzyme responsible for causing the goitrogenic effect. [7] Including a wide variety of vegetables, each week other than cruciferous will also protect against eating an excess amount of goitrogens.
Prepare
- Available throughout much of the year, Kale is even tolerant to frost and cold weather. Low temperatures can cause Kale and other cruciferous vegetables to convert starch molecules into sugar, resulting in a sweeter, less bitter flavor.
- Despite their tough and fibrous texture, kale stems are edible if cooked.
- Cut stems into small pieces and add to a stir-fry.
- Add diced stems to soups.
- Use to make vegetable stock.
Make
Kale has hearty leaves that withstand all types of cooking: boiling, braising, steaming, microwaving, and stir-frying. Kale can also be served raw, but the texture may be difficult to chew.
- Sautéed Kale: This is one of the simplest, quickest methods to enjoy Kale. Add 2-3 tablespoons of olive oil to a saucepan on medium-high heat. Add two minced garlic cloves and cook for 1-2 minutes until softened. Add ½ cup water or broth and 1 – 1½ pounds kale (washed, stems and leaves coarsely chopped). Cover the pan and allow to cook for 5 minutes until Kale is softened and at desired texture. Season with herbs and spices as desired.
- Kale Chips: Preheat oven to 350 degrees F. Line a baking sheet with parchment paper. Wash and dry one bunch of Kale thoroughly; use paper towels to blot if needed. Using your hands, pull leaves from their stems and rip them into small pieces, or you may use kitchen shears to cut leaves from the stem and into small pieces. Place into a large bowl and drizzle with oil. Massage oil evenly into kale pieces. Spread in a single layer on a baking sheet. Sprinkle herbs or spices as desired (try curry, cumin, garlic powder, onion powder, smoked paprika, nutritional yeast, or chili powder). Bake until the leaves shrink and the edges turn slightly brown about 15 minutes.
- Kale Pesto: This recipe uses walnuts instead of the classic but more expensive and obscure ingredient of pine nuts. Place into a food processor: 2 cups kale leaves (stems removed), ¼ cup extra virgin olive oil, and two cloves garlic or ¼ teaspoon garlic powder; pulse until smooth. Add ¼ cup toasted walnuts, and beat until blended. Add ½ cup Parmesan cheese and pulse again until blended. Serve pesto mixed into pasta or whole grains, as a sauce for chicken or fish, as a pizza sauce, or spread on crackers.
- Kale Salad: If using in a salad, there are two methods to soften the leaves, so they are easier to chew: 1) Place leaves in a bowl and drizzle with olive oil; massage the leaves for 1-2 minutes, or 2) Blanch leaves by placing in a pot of boiling water for 1 minute. Drain the leaves and place them into a bowl filled with ice water to stop the cooking quickly. Place leaves in a colander and gently press out excess water. Use paper towels to blot dry as needed. Blanching can also help to remove some of the bitter flavors from Kale.
- Three-Green & Wheat Berry Salad with Mushroom “Bacon”.
More recipe ideas and serving suggestions featuring Kale:
- Add kale leaves to soups, stews, and casseroles at the start of cooking.
- Add a few handfuls of chopped Kale into a burger mixture before cooking.
- Use large hardy lacinato kale leaves as a wrap to replace bread or tortillas.
- Add a handful of kale leaves to smoothies.
Ten Delicious Types of Kale
Kale’s popularity has a lot to do with its nutrients. This leafy vegetable is known for its high concentration of beneficial plant compounds, including glucosinolates, flavonoids, carotenoids, and vitamin C (1).
That’s why you’ll see kale in products like superfood greens powders, green smoothies, and greens capsules, as well as dishes like salads and soups. It’s also straightforward to grow, which makes it a common choice for home gardeners.
You may only be familiar with one or two types of kale, but quite a few varieties exist. These differ in color, texture, leaf characteristics, and nutrient composition.
One study identified four wide varieties of kale (1):
- Curled
- American
- Russian
- Italian
Each of these four groups contains several sub-varieties. For example, the popular lacinato kale fits into the Italian group (1).
Here are ten delicious types of kale — many of which you’ve probably never heard of.
1. Winterbor Kale
Winterbor is a popular type of curly kale favorite of both commercial growers and home gardeners. It’s one of the most cold-hardy of all kales, which can withstand freezing temperatures.
Its curly leaves have a bluish-green color. It grows up to 3 feet (91 cm) tall.
Because of its thicker leaves, most people cook Winterborn kale, though you can also eat it raw.
Try it in soups, stir-fries, or smoothies. Its thick leaves also make fantastic kale chips.
2. Lacinato kale
Lacinato is a type of Italian kale known as dinosaur or Tuscan kale. It has dark green, blade-shaped leaves and can grow up to 3 feet (91 cm) tall (1).
This variety was initially grown in Tuscany and is an essential part of traditional Italian cuisine (1).
One study notes that lacinato is high in minerals under-consumed by most Americans, including magnesium and zinc (2).
It’s also an excellent source of fiber and vitamins C and K (3).
One study that compared eight kale cultivars found that Tuscan kale was highest in carotenoid compounds, including neoxanthin, lutein, and beta carotene, all of which have significant antioxidant activity (4).
Unlike some other types of kale, lacinato is tender, which makes it ideal to use raw in salads. You can add it to soups, frittatas, and other cooked dishes.
3. Red Russian kale
Red Russian is a type of Russian kale that’s sweet and tender.
Despite its name, Red Russian kale is slate green in color, with dark purplish stems. It’s cold-hardy, making it a popular variety for commercial and backyard farmers living in colder climates.
It’s known as “baby leaf” kale when its leaves are small and young — and it is most commonly eaten in this form. Baby leaf kale is particularly delicious raw in salads.
However, you can also eat it fully mature when the plant reaches 2–3 feet (61–91 cm) tall.
This is one of my favorite types of kale to grow on my backyard farm.
4. Scarlet kale
Scarlet kale boasts stunning purple leaves and stalks. Its color becomes more vibrant as temperatures drop.
A study that compared eight kale cultivars found that scarlet kale had the highest amount of total tocopherols and alpha-tocopherol (4).
Although commonly considered a single compound, vitamin E is eight separate compounds, including four tocopherols. Alpha-tocopherol is the form that best meets humans’ dietary needs (5).
Alpha-tocopherol functions as a powerful antioxidant, protecting your cells against damage from unstable molecules called free radicals. This compound may also support immune function and fight inflammation (6, 7).
Scarlet kale can grow up to 3 feet (91 cm) tall. You can eat its young, tender leaves raw in salads or cook its mature leaves to add to soups or grain dishes.
5. Redbor kale
If you want to add color to your plate, Redbor kale may become your new favorite green.
Reaching 2–3 feet (61–91 cm) in height, its deep reddish-purple leaves have a frilly texture. Interestingly, its color, texture, and flavor are enhanced by colder temperatures.
Its leaves are crisp when raw but become tender when cooked, making it a perfect addition to dishes like stews and kinds of pasta. You can also finely shred its leaves to create a bright and crisp raw salad.
6. Beira kale
Beira is a particular type of kale from Portugal. Also known as Portuguese cabbage or sea kale, Beira has wavy green leaves used in a traditional dish called Portuguese kale soup.
Moreover, you can peel Beira kale’s thick stems and eat them like celery stalks.
These plants need ample space to reach their mature height of about 2 feet (61 cm).
A study that compared eight types of kale determined that Beira was highest in plant compounds called indoles, which are glucosinate compounds concentrated in cruciferous vegetables (4).
Studies show that glucosinolates have potent antioxidant and anti-inflammatory properties and that adding glucosinolate-rich foods to your diet may help protect against chronic diseases (8).
7. Walking stick kale
Did you know that kale can grow up to 12 feet (3.6 meters) tall?
Walking stick kale is also known as walking cabbage, cow cabbage, Jersey cabbage, and tall jacks. This gigantic leafy green has been grown in Europe for hundreds of years (9).
Historically, stalks of walking stick kale were varnished and used as canes on the Isle of Jersey in Europe’s Channel Islands.
Most people prefer to eat the younger leaves because of their tender texture. The older, more rigid leaves make good animal feed.
8. Darkibor kale
Darkibor is a type of curly kale with dark green and tightly curled leaves. These productive plants reach up to 20 inches (51 cm) in height and thrive in various weather conditions.
Darkibor’s curly leaves make ideal kale chips or ingredients for stir-fries and soups. You can eat younger, tenderer raw in salads.
One study that tested consumer taste preference in 20 kale varieties found darker among the top 3 most preferred types (10, 11).
Another study noted that darker was highest among several kale varieties in prebiotic fibers called Raffinose-family oligosaccharides, which benefit digestive health by promoting the growth of beneficial bacteria and reducing pathogens in your gut (4, 12).
9. Thousandhead kale
Although technically a non-kale cabbage, this ancient crop originated in France and is too impressive to leave off this list (1).
This multi-branching leafy green is also known as “branching borecole.”
Thousandhead kale extends up to 6 feet (1.8 meters) in height and has massive leaves that can reach up to 3 feet (91 cm). The leaves are only slightly curled at the tips, which makes it easier for growers to spot pests like caterpillars.
You can sauté its larger leaves for soups or add the younger, tenderer leaves raw to salads.
10. Japanese flowering kale
Japanese flowering kale might be the best-looking kale on this list.
It has a rosette shape with a Fuschia center and green outer leaves. The leaves are frilly, which adds to its visual appeal.
In Japan, it’s known as habotai and is placed in gardens for a pop of color during cooler months.
Although it’s popularly used as ornamental kale, Japanese flowering kale can also be eaten. It’s said to have a sweet flavor that’s delicious, both raw and cooked. Growers also say it makes excellent kale chips.
The Bottom Line
Although you may only find a few types of kale at your local grocery store, plenty of varieties are grown worldwide, including Winterborn, scarlet, redbone, Beira, and ornamental varieties.
No matter which type you choose, rest assured that you’ll get plenty of nutrients from this exceptionally healthy vegetable, including fiber, calcium, and vitamins C and K (13, 14).
Try using kale in delicious and nutritious recipes like this White Bean and Kale Soup or this Sunflower Coated Crispy Kale Chips.
Often labeled as a superfood, kale is one of the healthiest and most nutrient-dense foods you can eat.
This leafy green comes in various colors, shapes, and textures. It’s often eaten raw in salads and smoothies but can also be enjoyed steamed, sautéed, boiled, or baked.
Along with broccoli and Brussels sprouts, kale is a cruciferous vegetable with various potential health benefits.
However, raw kale also contains a compound called goitrin, which can affect thyroid function.
This article examines whether raw kale is safe to eat.
Highly Nutritious
Kale is a nutrient-dense food, as it’s low in calories and high in many essential vitamins, minerals, and antioxidants.
For example, 1 cup (21 grams) of raw kale contains only seven calories. Still, it is an excellent source of vitamins A, C, and K. It’s also a good source of manganese, calcium, copper, potassium, magnesium, and several B vitamins (1).
This vegetable is likewise packed with antioxidants. These molecules help counteract oxidative damage caused by compounds called free radicals and may reduce your risk of conditions like heart disease, Alzheimer’s, and certain forms of cancer (2, 3).
Due to kale’s nutrient composition, eating it may offer several health benefits, including promoting eye and heart health and protecting against certain forms of cancer (4, 5, 6).
Cooking Affects the Nutritional Value
Raw kale has a bitterness that can be reduced by cooking it.
Still, studies have shown that cooking may reduce its content of nutrients, including antioxidants, vitamin C, and several minerals (2, 7).
One study evaluated the effects of five cooking methods on kale’s antioxidant and nutrient composition (7Trusted Source).
Compared with raw kale, all cooking methods significantly reduced total antioxidants and minerals, including calcium, potassium, iron, zinc, and magnesium (7).
While raw kale may boast the highest nutrient content, the study found that steaming retained the most antioxidants and minerals compared with other cooking methods (7).
As a result, for those who prefer cooked kale, steaming it for a short duration may be the best way to preserve its nutrient levels.
Raw Kale May be High in Goitrin
Raw kale may be more nutritious but also harm your thyroid function.
Kale, along with other cruciferous vegetables, contains a high amount of goitrogens, compounds that can interfere with thyroid function (8).
Specifically, raw kale contains a type of goitrogen called goiters.
There are some concerns about eating raw kale, as goiters can decrease the uptake of iodine, which is essential for producing thyroid hormones (8).
This is worrisome, as thyroid hormones help regulate your metabolism. As a result, thyroid dysfunction can lead to reduced energy levels, weight gain, cold sensitivity, and heart rate irregularities (9).
One review of goitrin concentrations in cruciferous vegetables found that only an excessive intake of 2.2 pounds (1 kg) of kale per day for several months significantly impaired thyroid function in otherwise healthy adults (8).
However, research has shown that a moderate intake of goitrin-rich vegetables, including kale, is likely safe for most individuals.
Additionally, animal and human studies indicate that eating broccoli and Brussels sprouts doesn’t significantly affect thyroid hormone levels or functioning, suggesting that moderate amounts may even be safe for those with thyroid issues (10, 11).
Furthermore, consuming cruciferous vegetables has only been associated with an increased risk of thyroid cancer in women with deficient iodine intake (12, 13).
Still, given that cooking vegetables deactivates the enzyme responsible for releasing goitrin, those with thyroid problems may benefit from cooking kale before eating it, as well as ensuring adequate intake of iodine from foods like seafood and dairy (14, 15).
The Bottom Line
Kale is one of the healthiest foods on the planet due to its high concentration of vitamins, minerals, and antioxidants.
Despite being high in goiters, research shows that a moderate intake of raw kale is unlikely to affect your thyroid health. Plus, raw kale may be more nutritious than cooked varieties.
To reduce your risk of potential side effects from goiters while reaping all the nutritional benefits that kale offers, consider incorporating both raw and cooked kale into your diet.
- Before its dramatic rise to popularity in edible form, kale leaves were most commonly used in restaurants as decorative garnishes.
- Some types of Kale offer white, lavender, blue, pink, or purple leaves used in floral bouquets.
- Thomas Jefferson was a kale lover, growing and recording several varieties of Kale in his garden at Monticello in the early 1800s.
References
- Fuentes F, Paredes-Gonzalez X, Kong AN. Dietary glucosinolates sulforaphane, phenethyl isothiocyanate, indole-3-carbinol/3, 3′-diindolylmethane: Antioxidative stress/inflammation, Nrf2, epigenetics/epigenomics and in vivo cancer chemopreventive efficacy. Curr Pharmacol Rep. 2015 Jun 1;1(3):179-96.
- Tse G, Eslick GD. Cruciferous vegetables and risk of colorectal neoplasms: a systematic review and meta-analysis. Nutr Cancer. 2014 Jan 1;66(1):128-39.
- Fujioka N, Fritz V, Upadhyaya P, Kassie F, Hecht SS. Research on cruciferous vegetables, indole‐3‐carbinol, and cancer prevention: A tribute to Lee W. Wattenberg. Mol Nutr Food Res. 2016 Jun 1;60(6):1228-38.
- Zhang X, Shu XO, Xiang YB, Yang G, Li H, Gao J, Cai H, Gao YT, Zheng W. Cruciferous vegetable consumption is associated with a reduced risk of total and cardiovascular disease mortality–. The Am J Clin Nutr. 2011 May 18;94(1):240-6.
- Joshipura KJ, Hung HC, Li TY, Hu FB, Rimm EB, Stampfer MJ, Colditz G, Willett WC. Intakes of fruits, vegetables and carbohydrate and the risk of CVD. Public Health Nutr. 2009 Jan;12(1):115-21.
- Dietary Guidelines for Americans 2015-2020, Eighth Edition. https://health.gov/dietaryguidelines/2015/guidelines/appendix-3/
- Bajaj JK, Salwan P, Salwan S. Various possible toxicants involved in thyroid dysfunction: A Review. J Clin Diagn Res. 2016 Jan;10(1):FE01.
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