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Kale is a green, cruciferous leafy vegetable. It belongs to the Brassicaceae (mustard) family, which also includes bok choy, cabbage, cauliflower, watercress, radishes, broccoli, arugula, and Brussels sprouts.
Kale is packed with vitamins, minerals, and plant-based compounds. Because of its impressive nutritional profile, it is often called a superfood.
This article discusses kale’s nutritional content, health benefits, and why some people may need to limit their intake.
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Benefits of Kale
Kale is a nutrient-dense leafy green vegetable that provides a variety of fiber, vitamins, minerals, and beneficial plant-based compounds, including glucosinolates, antioxidants such as beta-carotene (beta-carotene), lutein, zeaxanthin and more.
Purple varieties have anthocyanins, which have been linked to improved heart health. Due to its abundant amounts of phytochemicals, kale is a nutrient-dense vegetable that is also low-calorie and non-starchy.
Diets rich in various plant foods are associated with a reduced risk of certain diseases, as well as increased longevity. In addition, using a food-as-medicine approach and eating a diet rich in vegetables such as kale, may help prevent and treat insulin resistance (when cells cannot take up glucose from the blood, which requires the pancreas to make more insulin), inflammation, and more.
Diabetes
A meta-analysis published in the Journal of Diabetes Investigation They found a link between a lower risk of type 2 diabetes and a higher intake of fruit (especially berries), green leafy vegetables, yellow vegetables, and cruciferous vegetables.
Researchers believe this is due to a variety of factors, including a high fiber content (which reduces insulin resistance and promotes satiety), as well as antioxidant compounds (including vitamin C), folate, and potassium .
Heart disease
Consumed kale can support heart health because of the nutrients it contains. Kale contains glucosinolates, a class of plant-based compounds that have anti-inflammatory properties.
Kale is rich in potassium, an important electrolyte (a mineral charged in the blood and body fluids) that helps manage blood pressure by increasing sodium excretion. A study published in 2022 in the New England Journal of Medicine suggests that consuming too little potassium and too much sodium can increase the risk of heart disease.
Many studies have shown a reduced risk of cardiovascular disease with increased intake of green leafy vegetables and cruciferous vegetables.
Cancer
The American Institute for Cancer Research recommends eating kale regularly because of its high amounts of antioxidants, including carotenoids and vitamin C. Various studies have shown that eating cruciferous vegetables daily is associated with a lower risk of cancer, especially colorectal cancer.
Glucosinolates, plant-based compounds found in kale that are activated after cutting, chewing and digesting kale, have been investigated for their role in cancer prevention and treatment. Glucosinolates are broken down into isothiocyanates (such as sulforaphane) and indoles.
In laboratory and animal studies, these compounds have been shown to reduce inflammation that can damage cells, which increases the risk of cancer, and inhibit enzymes that activate carcinogens. They may also inactivate enzymes that induce carcinogens.
However, human research is limited and difficult to analyze because the amount of glucosinolates present depends on various factors, including, growth conditions, plant stage, plant tissue analysis, storage conditions, and preparation methods and cooking.
Several studies have shown the positive effect of specific glucosinolates, such as sulforaphane, and their ability to reduce the side effects of cancer therapies. However, more human studies are needed.
Bone Health
Kale’s effect on bone health is in its vitamin K and plant-based calcium levels. Vitamin K is essential for blood clotting, but it is also important for bone strength, and has a positive effect on bone metabolism (building, remodeling, and bone breakdown). Calcium is essential for building bone, and is a major component of bone and tooth structure.
Although calcium in green leafy vegetables is not always highly absorbable, the calcium in kale is more bioavailable (can be absorbed and used by the body) due to its low oxalate content and high calcium to oxalate ratio compared to vegetables such as spinach. .
Digestion
Adequate amounts of fiber and water can help prevent and treat constipation and keep bowels regular. Kale contains fiber, which adds bulk to stools.
Kale also has prebiotics, which greatly contribute to a diverse microbiome (a healthy mix of gut microbes). Microbial diversity in the gut has been linked to a reduced risk of various diseases, including diabetes, Alzheimer’s disease, and more.
Skin and Hair Health
Rich in water-soluble vitamin C and beta-carotene (precursor of vitamin A), it contains nutrients that support skin and hair. Vitamin C plays an important role in supporting immunity, repairing cells, and slowing down the aging process.
Vitamin C is also important for collagen synthesis. Collagen is found in connective tissues and provides the structural framework for the body, including hair and skin. It also helps with skin elasticity.
Eye Health
Specific nutrients are promoted for eye health. For example, nutrients such as vitamins C and E, carotenoids (lutein, zeaxanthin, beta-carotene), zinc, and omega-3 fatty acids important in vision due to their anti-inflammatory and antioxidant functions.
Kale has a variety of these nutrients. Studies have shown that diets highest in lutein and zeaxanthin are associated with a reduced long-term risk of age-related macular degeneration.
Kale nutrition
Kale is low in calories and rich in vitamins and minerals. By volume, raw kale will have fewer calories and nutrients compared to cooked kale but is still a nutritious food source.
A 1-cup serving of raw kale provides the following nutrients:
- Calories: 7.2
- Fat: 0.3 grams (g)
- Sodium: 11 milligrams (mg)
- Carbohydrate: 0,9 g
- Fiber: 0,8 g
- Sugar: 0.2 g
- Protein: 0.6 g
- Vitamin A: 49.6 micrograms (mcg)
- Vitamin K: 80.3 mcg
- Vitamin C: 19.2 mg
- Potassium: 71.7 mg
- Calcium: 52.3 mg
A 1-cup serving of cooked kale (without added fat) provides the following nutrients:
- calories: 60
- Fat: 2 g
- Saturated fat: 0 g
- Sodium: 235 mg
- Cholesterol: 0 mg
- Carbohydrate: 6 g
- Fiber: 5.7 g
- Calcium: 354 mg
- Iron: 2.2 mg
- Potassium: 485 mg
- Vitamin C: 91 mg
- Vitamin K: 543 mcg
- Choline: 0.65 mcg
- Beta carotene: 3,800 mcg
- Lutein+zeaxanthin: 8,290 mcg
Who Should Avoid Kale?
People taking blood-thinning (anticoagulant) medications need to consume consistent amounts of vitamin K in order for their medication to work as it is supposed to. This is because vitamin K plays a role in blood clotting.
Raw kale also contains goitrogens, a type of anti-nutrient that may prevent iodine from entering the thyroid gland. This is mainly a concern for people with iodine deficiency; cooking or fermenting kale destroys the enzyme responsible for its goitrogenic activity.
What’s the Best Way to Eat Kale?
Eating kale raw or cooked is nutritious. However, when you cook kale, you’re likely to eat more volume, which increases nutrient intake. Some research suggests that steamed kale maximizes glucosinolates.
Eat kale with some heart-healthy fat such as extra-virgin olive oil or avocado oil to aid fat-soluble vitamin absorption.
Some of the more common types of kale you will find in the market include curly kale, Tuscan kale, red or Russian kale, red kale and baby kale. If you have never used this vegetable before, you have plenty of options. Try different types and colors for different nutrients, flavors and textures.
Chop and toss kale with extra virgin olive oil for salads, add it to soups and smoothies, blend it into dips, or steam it and pair it alongside your favorite whole grain, legume, fish or lean protein source . Kale is versatile and can be added to a variety of dishes.
Summary
Kale is a highly nutritious leafy green vegetable packed with a variety of vitamins, minerals and plant-based compounds. Eating kale and other vegetables regularly is beneficial and supports a healthy eating plan.
