Is Kale Good for You?

Kale is a hearty leafy green, cruciferous 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. Due to its impressive nutrition profile, it is often referred to as a superfood.

This article discusses kale's nutrition content, health benefits, and why some people may need to limit their intake.

Kale Benefits

Kale is a nutrient-dense leafy green vegetable that provides a variety of fiber, vitamins, minerals, and beneficial plant-based compounds, including glucosinolates, antioxidants like beta carotene (beta-carotene), lutein, zeaxanthin and more.

Purple varieties have anthocyanins, which are linked to improved heart health. The numerous amounts of phytochemicals in it make kale a nutrient-dense vegetable that is also low-calorie and non-starchy.

Diets rich in a variety of plant-based foods are associated with reduced risk of certain diseases, as well an increase in longevity. In addition, using a food-as-medicine approach and eating a diet rich in vegetables like kale, may help prevent and treat insulin resistance (when cells can’t take up glucose from the blood, requiring the pancreas to make more insulin), inflammation, and more.

Diabetes

A meta-analysis published in the Journal of Diabetes Investigation found a link between a lower risk of type 2 diabetes and higher intakes of fruits (especially berries), leafy green vegetables, yellow vegetables, and cruciferous vegetables.

Researchers believe this is due to a variety of factors, including high fiber content (which reduces insulin resistance and promotes satiety), as well as antioxidant compounds (including vitamin C), folate, and potassium.

Heart Disease

Consuming kale can support heart health because of the nutrients it contains. Kale contains, glucosinolates, a class of plant-based compounds that has anti-inflammatory properties.

Kale is rich in potassium, an important electrolyte (charged mineral in the blood and body fluids) that can help 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 leafy green vegetables and cruciferous vegetables.

Cancer

The American Institute for Cancer Research recommends eating kale regularly due to 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, particularly 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 preventing and treating cancer. Glucosinolates are broken down into isothiocyanates (such as sulforaphane) and indoles.

In laboratory and animal studies, these compounds have been shown to decrease inflammation that can damage cells, which increases cancer risk, and inhibit enzymes that activate carcinogens. They may also stimulate enzymes that deactivate carcinogens.

Yet, human research is limited and analyzing it is difficult because the amount of glucosinolates present depends on a variety of factors, including, growth conditions, plant stage, plant tissue analyzed, storage conditions, and preparation and cooking methods.

Some studies have shown a positive impact of specific glucosinolates, like sulforaphane, and their ability to lessen the side effects of cancer therapies. However, more human studies are needed.

Bone Health

Kale's impact on bone health resides in its levels of vitamin K and plant-based calcium. Vitamin K is essential for blood clotting, but also important for bone strength, and has a positive impact on bone metabolism (building, remodeling, and breaking down bone). Calcium is essential for building bone, and it makes up much of the structure of bone and teeth.

While calcium in leafy green vegetables isn't always highly absorbable, the calcium in kale is more bioavailable (able to be absorbed and used by the body) due to its low oxalate content and high ratio of calcium to oxalate compared with vegetables such as spinach.

Digestion

Adequate amounts of fiber and water can help to prevent and treat constipation and keep bowels regular. Kale contains fiber, which adds bulk to stools.

Kale also contains prebiotics, key contributors to a diverse microbiome (a healthy combination of gut microbes). Microbial diversity in the gut is 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 to vitamin A), kale contains nutrients that support skin and hair. Vitamin C plays an important role in supporting immunity, repairing cells, and slowing 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 aids in 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 are important in vision due to their anti-inflammatory and antioxidant functions.

Kale contains a variety of these nutrients. Studies have shown that diets highest in lutein and zeaxanthin are associated with a long-term reduced risk of age-related macular degeneration.

Kale Nutrition

Kale is low in calories and rich in vitamins and minerals. By volume, raw kale as opposed to cooked kale will have fewer calories and nutrients 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 who take blood-thinning medications (anticoagulants) need to eat consistent amounts of vitamin K so that their medication works as it's supposed to. This is because vitamin K plays a role in blood clotting.

Raw kale also contains goitrogens, a type of antinutrient that can prevent iodine from entering the thyroid gland. This is mostly 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 either raw or cooked is nutritious. However, when you cook kale, you are likely to eat more volume, which increases the nutrient intake. Some research suggests that steaming kale maximizes glucosinolates.

Consume kale with some heart-healthy fat like extra-virgin olive oil or avocado oil to assist in fat-soluble vitamin absorption.

Some of the most popular types of kale you will find in the market include curly kale, Tuscan kale, red or red Russian kale, Redbor kale, and baby kale. If you have never used this vegetable before, you have plenty of options. Try different types and colors for a variety of 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 an extremely nutrient-dense, leafy green vegetable packed with a variety of vitamins, minerals, and plant-based compounds. Eating kale and other vegetables regularly is advantageous and supports a healthy eating plan.