What’s New and Beneficial About Kale
- Kale can provide you with some special cholesterol-lowering benefits if you will cook it by steaming. The fiber-related components in kale do a better job of binding together with bile acids in your digestive tract when they’ve been steamed. When this binding process takes place, it’s easier for bile acids to be excreted, and the result is a lowering of your cholesterol levels. Raw kale still has cholesterol-lowering ability—just not as much.
- Kale’s risk-lowering benefits for cancer have recently been extended to at least five different types of cancer. These types include cancer of the bladder, breast, colon, ovary, and prostate. Isothiocyanates (ITCs) made from glucosinolates in kale play a primary role in achieving these risk-lowering benefits.
- Kale is now recognized as providing comprehensive support for the body’s detoxification system. New research has shown that the ITCs made from kale’s glucosinolates can help regulate detox at a genetic level.
- Researchers can now identify over 45 different flavonoids in kale. With kaempferol and quercetin heading the list, kale’s flavonoids combine both antioxidant and anti-inflammatory benefits in way that gives kale a leading dietary role with respect to avoidance of chronic inflammation and oxidative stress.
You’ll want to include kale as one of the cruciferous vegetables you eat on a regular basis if you want to receive the fantastic health benefits provided by the cruciferous vegetable family. At a minimum, we recommend 3/4 cup of cruciferous vegetables on a daily basis. This amount is equivalent to approximately 5 cups per week. A more optimal intake amount would be 1-1/2 cups per day, or about 10 cups per week. You can use our Veggie Advisorfor help in figuring out your best cruciferous vegetable options.
Kale is one of the healthiest vegetables around and one way to be sure to enjoy the maximum nutrition and flavor from kale is to cook it properly. We recommend Healthy Steaming kale for 5 minutes. To ensure quick and even cooking cut the leaves into 1/2″ slices and the stems into 1/4″ lengths. Let them sit for at least 5 minutes to enhance their health-promoting qualities before steaming. See our Healthiest Way of Cooking Kale in the How to Enjoy section below.
GI: very low
This chart graphically details the %DV that a serving of Kale provides for each of the nutrients of which it is a good, very good, or excellent source according to our Food Rating System. Additional information about the amount of these nutrients provided by Kale can be found in the Food Rating System Chart. A link that takes you to the In-Depth Nutritional Profile for Kale, featuring information over 80 nutrients, can be found under the Food Rating System Chart.
- Health Benefits
- How to Select and Store
- Tips for Preparing and Cooking
- How to Enjoy
- Individual Concerns
- Nutritional Profile
While not as well researched as some of its fellow cruciferous vegetables like broccoli or cabbage, kale is a food that you can count on for some unsurpassed health benefits, if for no other reason than its exceptional nutrient richness. In our own website food rating system, kale scored 4 “excellents,” 6 “very goods,” and 10 “goods”—for a total of 20 standout categories of nutrient richness! That achievement is difficult for most foods to match.
Antioxidant-Related Health Benefits
Like most of its fellow cruciferous vegetables, kale has been studied more extensively in relationship to cancer than any other health condition. This research focus makes perfect sense. Kale’s nutrient richness stands out in three particular areas: (1) antioxidant nutrients, (2) anti-inflammatory nutrients, and (3) anti-cancer nutrients in the form of glucosinolates. Without sufficient intake of antioxidants, our oxygen metabolism can become compromised, and we can experience a metabolic problem called “oxidative stress.” Without sufficient intake of anti-inflammatory nutrients, regulation of our inflammatory system can become compromised, and we can experience the problem of chronic inflammation. Oxidative stress and chronic inflammation—and the combination of these metabolic problems—are risk factors for development of cancer. We’ve seen research studies on 5 specific types of cancer—including bladder cancer, breast cancer, colon cancer, ovarian cancer, and prostate cancer—and intake of cruciferous vegetables (specifically including kale). As a group, these studies definitely show cancer preventive benefits from kale intake, and in some cases, treatment benefits as well.
Kale’s cancer preventive benefits have been clearly linked to its unusual concentration of two types of antioxidants, namely, carotenoids and flavonoids. Within the carotenoids, lutein and beta-carotene are standout antioxidants in kale. Researchers have actually followed the passage of these two carotenoids in kale from the human digestive tract up into the blood stream, and they have demonstrated the ability of kale to raise blood levels of these carotenoid nutrients. That finding is important because lutein and beta-carotene are key nutrients in the protection of our body from oxidative stress and health problems related to oxidative stress. Increased risk of cataracts, atherosclerosis, and chronic obstructive pulmonary disease (COPD) are three such problems. Also among these chronic health problems is cancer since our overall risk of cells becoming cancerous is partly related to oxidative stress.
Within the flavonoids, kaempferol is a spotlight antioxidant in kale, followed by a flavonoid called quercitin. But recent research has also made it clear that at least 45 different antioxidant flavonoids are provided in measurable amounts by kale. This broad spectrum of flavonoid antioxidants is likely to be a key to kale’s cancer-preventive benefits and benefits that we expect to be documented for other health problems stemming from oxidative stress.
Anti-Inflammatory Health Benefits
We have yet to see research on kale’s omega-3 content and inflammation, but we would expect this kind of research to show the omega-3s in kale to be an important part of kale’s anti-inflammatory benefits. It only takes 100 calories of kale to provide over 350 milligrams for the most basic omega-3 fatty acid (alpha-linolenic acid, or ALA). We suspect that this amount will be plenty to show direct anti-inflammatory benefits from routine kale intake.
We also have yet to see specific research on inflammation and kale’s vitamin K content. But we know that kale is a spectacular source of vitamin K (one cup of kale provides far more micrograms of vitamin K than any of our World’s Healthiest foods) and we also know that vitamin K is a key nutrient for helping regulate our body’s inflammatory process. Taken in combination, we expect these two facts about vitamin K to eventually get tied together in health research that shows kale to be an exceptional food for lowering our risk of chronic inflammation and associated health problems.
Glucosinolates and Cancer-Preventive Benefits
What we have already seen in the health research on kale is ample evidence that its glucosinolates provide cancer-preventive benefits. Kale is a top food source for at least four glucosinolates, and once kale is eaten and digested, these glucosinolates can be converted by the body into cancer preventive compounds. Kale’s glucosinolates and the ITCs made from them have well-documented cancer preventive properties, and in some cases, cancer treatment properties as well. At the top of the cancer-related research for kale are colon cancer and breast cancer, but risk of bladder cancer, prostate cancer, and ovarian cancer have all been found to decrease in relationship to routine intake of kale. The chart below presents a summary of the unusual glucosinlate phytonutrients found in kale, and the anti-cancer ITCs made from them inside the body
Glucosinolates in kale and their detox-activating isothiocyanates
|Glucosinolate||Derived Isothiocyanate||Isothiocyanate Abbreviation|
* Indole-3-carbinol (I3C) is not an isothiocyanate. It’s a benzopyrrole, and it is only formed when isothiocyanates made from glucobrassicin are further broken down into non-sulfur containing compounds.
You can count on kale to provide valuable cardiovascular support in terms of its cholesterol-lowering ability. Researchers now understand exactly how this support process works. Our liver uses cholesterol as a basic building block to product bile acids. Bile acids are specialized molecules that aid in the digestion and absorption of fat through a process called emulsification. These molecules are typically stored in fluid form in our gall bladder, and when we eat a fat-containing meal, they get released into the intestine where they help ready the fat for interaction with enzymes and eventual absorption up into the body. When we eat kale, fiber-related nutrients in this cruciferous vegetable bind together with some of the bile acids in the intestine in such a way that they simply stay inside the intestine and pass out of our body in a bowel movement, rather than getting absorbed along with the fat they have emulsified. When this happens, our liver needs to replace the lost bile acids by drawing upon our existing supply of cholesterol, and, as a result, our cholesterol level drops down. Kale provides us with this cholesterol-lowering benefit whether it is raw or cooked. However, a recent study has shown that the cholesterol-lowering ability of raw kale improves significantly when it is steamed. In fact, when the cholesterol-lowering ability of steamed kale was compared with the cholesterol-lowering ability of the prescription drug cholestyramine (a medication that is taken for the purpose of lowering cholesterol), kale bound 42% as many bile acids (based on a standard of comparison involving total dietary fiber). Amongst all of the cruciferous vegetables, only collard greens scored higher at 46%.
Other Health-Related Benefits
Kale has a definite role to play in support of the body’s detoxification processes. The isothiocyanates (ITCs) made from kale’s glucosinolates have been shown to help regulate detox activities in our cells. Most toxins that pose a risk to our body must be detoxified by our cells using a two-step process. The two steps in the process are called Phase I detoxification and Phase II detoxification. The ITCs made from kale’s glucosinolates have been shown to favorably modify both detox steps (Phase I and Phase II). In addition, the unusually large numbers of sulfur compounds in kale have been shown to help support aspects of Phase II detoxification that require the presence of sulfur. By supporting both aspects of our cellular detox process (Phase I and Phase II), nutrients in kale can give our body an “edge up” in dealing with toxic exposure, whether from our environment or from our food.
We have yet to see studies that look directly at kale and its support for our digestive system. However, we have seen studies for kale’s fellow cruciferous vegetable—broccoli—in this regard, and we definitely expect to see future research that looks directly at kale and our digestive function. We predict that one area of digestive support provided by kale will turn out to involve fiber. We feel that 7 grams of fiber per 100 calories of kale is just too much fiber to fail in the digestive benefits category. We predict that a second area of digestive benefits will involve kale’s glucosinolates. The ITCs make from kale’s glucosinolates should help protect our stomach lining from bacterial overgrowth of Helicobacter pylori and should help avoid too much clinging by this bacterium to our stomach wall.
The beautiful leaves of the kale plant provide an earthy flavor and more nutritional value for fewer calories than almost any other food around. Although it can be found in markets throughout the year, it is in season from the middle of winter through the beginning of spring when it has a sweeter taste and is more widely available.
Kale is a leafy green vegetable that belongs to the Brassica family, a group of vegetables including cabbage, collards, and Brussels sprouts that have gained recent widespread attention due to their health-promoting, sulfur-containing phytonutrients. It is easy to grow and can grow in colder temperatures where a light frost will produce especially sweet kale leaves. There are several varieties of kale; these include curly kale, ornamental kale, and dinosaur (or Lacinato or Tuscan) kale, all of which differ in taste, texture, and appearance. The scientific name for kale is Brassica oleracea.
Curly kale has ruffled leaves and a fibrous stalk and is usually deep green in color. It has a lively pungent flavor with delicious bitter peppery qualities.
Ornamental kale is a more recently cultivated species that is oftentimes referred to as salad savoy. Its leaves may either be green, white, or purple and its stalks coalesce to form a loosely knit head. Ornamental kale has a more mellow flavor and tender texture.
Dinosaur kale is the common name for the kale variety known as Lacinato or Tuscan kale. It features dark blue-green leaves that have an embossed texture. It has a slightly sweeter and more delicate taste than curly kale.
Like broccoli, cauliflower, and collards, kale is a descendent of the wild cabbage, a plant thought to have originated in Asia Minor and to have been brought to Europe around 600 B.C. by groups of Celtic wanderers. Curly kale played an important role in early European foodways, having been a significant crop during ancient Roman times and a popular vegetable eaten by peasants in the Middle Ages. English settlers brought kale to the United States in the 17th century.
Both ornamental and dinosaur kale are much more recent varieties. Dinosaur kale was discovered in Italy in the late 19th century. Ornamental kale, originally a decorative garden plant, was first cultivated commercially as in the 1980s in California. Ornamental kale is now better known by the name salad savoy.
How to Select and Store
Look for kale with firm, deeply colored leaves and moist hardy stems. Kale should be displayed in a cool environment since warm temperatures will cause it to wilt and will negatively affect its flavor. The leaves should look fresh, be unwilted, and be free from signs of browning, yellowing, and small holes. Choose kale with smaller-sized leaves since these will be more tender and have a more mild flavor than those with larger leaves. Kale is available throughout the year, although it is more widely available, and at its peak, from the middle of winter through the beginning of spring.
To store, place kale in a plastic storage bag removing as much of the air from the bag as possible. Store in the refrigerator where it will keep for 5 days. The longer it is stored, the more bitter its flavor becomes. Do not wash kale before storing because exposure to water encourages spoilage. Loss of some nutrients in kale—for example, its vitamin C content—is likely to be slowed down through refrigeration.
Tips for Preparing and Cooking
Tips for Preparing Kale
Rinse kale leaves under cold running water. Chop leaf portion into 1/2″ slices and the stems into 1/4″ lengths for quick and even cooking.
The Healthiest Way of Cooking Kale
We recommend Healthy Steaming kale. We have developed our Healthy Steaming method as a way to minimize duration of cooking, degree of heat exposure, and extent of food surface contact with cooking liquids. These three cooking guidelines are often associated with better nutrient retention in research studies. We also feel that Healthy Steaming kale gives it maximum flavor.
Fill the bottom of a steamer pot with 2 inches of water. While waiting for the water to come to a rapid boil chop greens. Steam for 5 minutes and toss with our Mediterranean Dressing and top with your favorite optional ingredients. For details see 5-Minute Kale.
How to Enjoy
A Few Quick Serving Ideas
- Braise chopped kale and apples. Before serving, sprinkle with balsamic vinegar and chopped walnuts.
- Combine chopped kale, pine nuts, and feta cheese with whole grain pasta drizzled with olive oil.
WHFoods Recipes That Feature Kale
- Healthy Breakfast Frittata
- Italian Tofu Frittata
- Poached Eggs Over Sauteed Greens
- Minestrone Surprise
- Spicy Posole Soup
- Super Energy Kale Soup
- Turkey and Vegetable Chili Verde
- Sesame Braised Chicken & Cabbage
- Indian Style Lamb with Sweet Potatoes
- 5-Minute Kale
- 5-Minute Kale with Sea Vegetables
Kale and Pesticide Residues
According to the Environmental Working Group (EWG) in their 2016 report, Shopper’s Guide to Pesticides in Produce, conventionally grown kale are contaminated with concentrations of organophosphate insecticides, which are considered to be highly toxic to the nervous system. While they were not among the 12 varieties of produce most concentrated in overall pesticide residues (and therefore not part of the EWG’s traditional “Dirty Dozen”), the EWG felt that this organophosphate concentration was relevant enough to bring attention to kale. They actually renamed their produce category of concern from “Dirty Dozen” to “Dirty Dozen Plus” with kale, collard greens, and hot peppers being the “Plus” conventionally grown produce. Therefore, individuals wanting to avoid pesticide-associated health risks may want to avoid consumption of kale unless it is grown organically.
Kale and Goitrogens
You may sometimes hear kale being described as a food that contains “goitrogens,” or as a food that is “goitrogenic.” For helpful information in this area—including our WHFoods Recommendations—please see our article What is meant by the term “goitrogen” and what is the connection between goitrogens, food, and health?.
Kale is a nutritional standout in three basic areas: (1) antioxidant and anti-inflammatory nutrients, (2) much-needed micronutrients (in which the average U.S. adult is currently deficient), and (3) cancer-preventive nutrients called glucosinolates.
Antioxidant and Anti-inflammatory Nutrients
Kale’s antioxidants are both traditional as well as recently discovered.
In addition to conventional antioxidants like vitamin C, beta-carotene, and manganese, kale also provides us with at least 45 different recently discovered flavonoids, including kaempferol and quercetin. Many of the flavonoids in kale are also now known to function not only as antioxidants, but also as anti-inflammatory compounds.
Fiber and Anti-Inflammatory Omega-3 Fatty Acids
Fiber and omega-3s are two macronutrients largely deficient in the U.S. diet and provided by kale in impressive amounts. It only takes 200 calories’ worth of kale to provide 14 grams of fiber — substantially more than the average U.S. adult gets in an entire day after a diet of 2,000 calories. And while kale is not as concentrated in omega-3s as some of the other cruciferous vegetables—and certainly not in the same category as walnuts or salmon—it still provides us with a significant amount of alpha-linolenic acid (ALA), the basic building block for all omega-3 fats. From less than 100 calories’ worth of kale, we can get over 350 milligrams.
Kale and its Cancer-Preventing Phytonutrients
Kale’s special mix of cancer-preventing glucosinolates has been the hottest area of research on this cruciferous vegetable. Kale is an especially rich source of glucosinolates, and once kale is eaten and digested, these glucosinolates can be converted by the body into cancer preventive compounds. Some of this conversion process can also take place in the food itself, prior to consumption.
Also worth noting in kale’s nutritional profile is its vitamin K content. Kale contains nearly twice the amount of vitamin K as most of its fellow cruciferous vegetables.
In addition to the above-cited nutrients, according to our Food Rating System, kale is an excellent source of vitamin A (in the form of carotenoids), vitamin C, vitamin K, copper and manganese. It is a very good source of vitamin B6, dietary fiber, calcium, potassium, vitamin E, vitamin B2, iron, magnesium, vitamin B1, omega-3 fatty acids phosphorus, protein, folate and niacin.
Introduction to Food Rating System Chart
In order to better help you identify foods that feature a high concentration of nutrients for the calories they contain, we created a Food Rating System. This system allows us to highlight the foods that are especially rich in particular nutrients. The following chart shows the nutrients for which this food is either an excellent, very good, or good source (below the chart you will find a table that explains these qualifications). If a nutrient is not listed in the chart, it does not necessarily mean that the food doesn’t contain it. It simply means that the nutrient is not provided in a sufficient amount or concentration to meet our rating criteria. (To view this food’s in-depth nutritional profile that includes values for dozens of nutrients – not just the ones rated as excellent, very good, or good – please use the link below the chart.) To read this chart accurately, you’ll need to glance up in the top left corner where you will find the name of the food and the serving size we used to calculate the food’s nutrient composition. This serving size will tell you how much of the food you need to eat to obtain the amount of nutrients found in the chart. Now, returning to the chart itself, you can look next to the nutrient name in order to find the nutrient amount it offers, the percent Daily Value (DV%) that this amount represents, the nutrient density that we calculated for this food and nutrient, and the rating we established in our rating system. For most of our nutrient ratings, we adopted the government standards for food labeling that are found in the U.S. Food and Drug Administration’s “Reference Values for Nutrition Labeling.” Read more background information and details of our rating system.
GI: very low
|vitamin K||1062.10 mcg||1180||583.6||excellent|
|vitamin A||885.36 mcg RAE||98||48.6||excellent|
|vitamin C||53.30 mg||71||35.1||excellent|
|vitamin B6||0.18 mg||11||5.2||very good|
|fiber||2.60 g||10||5.1||very good|
|calcium||93.60 mg||9||4.6||very good|
|potassium||296.40 mg||8||4.2||very good|
|vitamin E||1.11 mg (ATE)||7||3.7||very good|
|vitamin B2||0.09 mg||7||3.4||very good|
|vitamin B1||0.07 mg||6||2.9||good|
|omega-3 fats||0.13 g||5||2.7||good|
|vitamin B3||0.65 mg||4||2.0||good|
Density>=7.6 AND DRI/DV>=10%
|very good||DRI/DV>=50% OR
Density>=3.4 AND DRI/DV>=5%
Density>=1.5 AND DRI/DV>=2.5%
In-Depth Nutritional Profile
In addition to the nutrients highlighted in our ratings chart, here is an in-depth nutritional profile for Kale. This profile includes information on a full array of nutrients, including carbohydrates, sugar, soluble and insoluble fiber, sodium, vitamins, minerals, fatty acids, amino acids and more.
(Note: “–” indicates data unavailable)
|GI: very low|
|BASIC MACRONUTRIENTS AND CALORIES|
|Fat – total||0.52 g||—|
|Dietary Fiber||2.60 g||10|
|MACRONUTRIENT AND CALORIE DETAIL|
|Total Sugars||1.62 g|
|Soluble Fiber||1.17 g|
|Insoluble Fiber||1.43 g|
|Other Carbohydrates||3.09 g|
|Monounsaturated Fat||0.04 g|
|Polyunsaturated Fat||0.25 g|
|Saturated Fat||0.07 g|
|Trans Fat||0.00 g|
|Calories from Fat||4.68|
|Calories from Saturated Fat||0.61|
|Calories from Trans Fat||0.00|
|Vitamin B1||0.07 mg||6|
|Vitamin B2||0.09 mg||7|
|Vitamin B3||0.65 mg||4|
|Vitamin B3 (Niacin Equivalents)||1.15 mg|
|Vitamin B6||0.18 mg||11|
|Vitamin B12||0.00 mcg||0|
|Folate (DFE)||16.90 mcg|
|Folate (food)||16.90 mcg|
|Pantothenic Acid||0.06 mg||1|
|Vitamin C||53.30 mg||71|
|Vitamin A (Retinoids and Carotenoids)|
|Vitamin A International Units (IU)||17707.30 IU|
|Vitamin A mcg Retinol Activity Equivalents (RAE)||885.36 mcg (RAE)||98|
|Vitamin A mcg Retinol Equivalents (RE)||1770.73 mcg (RE)|
|Retinol mcg Retinol Equivalents (RE)||0.00 mcg (RE)|
|Carotenoid mcg Retinol Equivalents (RE)||1770.73 mcg (RE)|
|Beta-Carotene Equivalents||10624.90 mcg|
|Lutein and Zeaxanthin||23719.80 mcg|
|Vitamin D International Units (IU)||0.00 IU||0|
|Vitamin D mcg||0.00 mcg|
|Vitamin E mg Alpha-Tocopherol Equivalents (ATE)||1.11 mg (ATE)||7|
|Vitamin E International Units (IU)||1.65 IU|
|Vitamin E mg||1.11 mg|
|Vitamin K||1062.10 mcg||1180|
|INDIVIDUAL FATTY ACIDS|
|Omega-3 Fatty Acids||0.13 g||5|
|Omega-6 Fatty Acids||0.10 g|
|14:1 Myristoleic||— g|
|15:1 Pentadecenoic||— g|
|16:1 Palmitol||— g|
|17:1 Heptadecenoic||— g|
|18:1 Oleic||0.04 g|
|20:1 Eicosenoic||— g|
|22:1 Erucic||— g|
|24:1 Nervonic||— g|
|Polyunsaturated Fatty Acids|
|18:2 Linoleic||0.10 g|
|18:2 Conjugated Linoleic (CLA)||— g|
|18:3 Linolenic||0.13 g|
|18:4 Stearidonic||— g|
|20:3 Eicosatrienoic||— g|
|20:4 Arachidonic||0.00 g|
|20:5 Eicosapentaenoic (EPA)||— g|
|22:5 Docosapentaenoic (DPA)||— g|
|22:6 Docosahexaenoic (DHA)||— g|
|Saturated Fatty Acids|
|4:0 Butyric||— g|
|6:0 Caproic||— g|
|8:0 Caprylic||— g|
|10:0 Capric||— g|
|12:0 Lauric||0.00 g|
|14:0 Myristic||0.00 g|
|15:0 Pentadecanoic||— g|
|16:0 Palmitic||0.06 g|
|17:0 Margaric||— g|
|18:0 Stearic||0.00 g|
|20:0 Arachidic||— g|
|22:0 Behenate||— g|
|24:0 Lignoceric||— g|
|INDIVIDUAL AMINO ACIDS|
|Aspartic Acid||0.22 g|
|Glutamic Acid||0.28 g|
|Organic Acids (Total)||— g|
|Acetic Acid||— g|
|Citric Acid||— g|
|Lactic Acid||— g|
|Malic Acid||— g|
|Sugar Alcohols (Total)||— g|
|Artificial Sweeteners (Total)||— mg|
The nutrient profiles provided in this website are derived from The Food Processor, Version 10.12.0, ESHA Research, Salem, Oregon, USA. Among the 50,000+ food items in the master database and 163 nutritional components per item, specific nutrient values were frequently missing from any particular food item. We chose the designation “–” to represent those nutrients for which no value was included in this version of the database.