Kale is a nutrient-rich green, leafy, cruciferous vegetable. For the whole body, it can provide a variety of health benefits.
Like cabbage and Brussels sprouts, it is a member of the mustard, or Brassicaceae, family.
Possible advantages include helping to reduce blood pressure, enhancing digestive health, and defending against cancer and diabetes type 2.
This article looks at kale’s nutrient value and health effects, how to use it in the diet, and why certain individuals should not consume so much of it.
Health benefits
Kale provides fiber, antioxidants, calcium, C and K vitamins, iron, and a wide variety of other nutrients that can help avoid different health issues.
The body is supported by antioxidants to destroy unwanted contaminants arising from natural activities and environmental pressures.
These toxins, known as free radicals, are molecules which are unstable. If too many build up in the body, they can lead to cell damage. This can result in health problems such as diseases and inflammation. Experts believe that, for example, free radicals may play a role in cancer growth.
Read more about foods containing antioxidants here.
Diabetes
Eating foods that are high in vitamins, nutrients, fiber, and antioxidants is recommended by the American Diabetes Association. There is proof that some of these can provide diabetes protection.
Fiber: A 2018 study showed that there appears to be a reduced chance of developing type 2 diabetes for individuals who eat the highest levels of dietary fiber. Consuming dietary fibre, the authors say, may also reduce blood glucose levels.
Antioxidants: Authors of a 2012 article mention that high levels of blood sugar will allow free radicals to be developed. They note that antioxidants can help mitigate problems that may arise with diabetes, such as vitamin C and alpha-linolenic acid (ALA). Kale contains all of these antioxidants.
Heart disease
Heart health can be helped by different nutrients in kale.
Potassium: The American Heart Association (AHA) advises that potassium intake should be increased, while additional salt or sodium consumption should be decreased. This will decrease the risk of elevated blood pressure and cardiovascular disease, according to the AHA. A cup of cooked kale contains 3.6 per cent of the daily potassium requirements of an adult.
Fiber: A 2016 Cochrane review found a correlation between fiber intake and lower levels of blood lipids (fat) and blood pressure. It’s more likely that those who ate more fiber had lower levels of total cholesterol and low-density lipoprotein (LDL) or “bad” cholesterol.
Cancer
Chlorophyll: Kale and other chlorophyll-containing green vegetables may help protect heterocyclic amines from being consumed by the body. When people grill animal-derived foods at a high temperature, these chemicals occur. They have been linked by experts to cancer.
A lot of chlorophyll can not be consumed by the human body, but chlorophyll binds to these carcinogens and keeps the body from absorbing them. Kale will lower the chance of cancer in this way, and mixing a chargrilled steak with green vegetables will help decrease the negative effects.
Antioxidants: Cancer prevention can be improved by vitamin C, beta carotene, selenium and other antioxidants in kale. Studies have not shown that antioxidants have the same effect, although there seems to be a reduced chance of contracting different cancers in people who have a high consumption of fruits and vegetables. This may be due to the antioxidants found in these foods.
Fiber: According to a 2015 report, a high fiber intake can help reduce the risk of colorectal cancer.
Health of the bone
For good bone growth, calcium and phosphorus are essential.
A high intake of vitamin K may help reduce the risk of bone fractures, some research has shown.
A cup of cooked kale contains about five times the daily need for vitamin K for an adult, about 15-18 percent of its calcium requirement, and about 7 percent of the daily need for phosphorus.
Digestion
Kale is rich in fiber and water, all of which help reduce constipation and encourage a balanced digestive tract and regularity.
Skin and hair
Kale is a good source of beta-carotene, the carotenoid that is converted as required by the body into vitamin A.
For the growth and maintenance of all body tissues, including skin and hair, beta-carotene and vitamin A are required.
To build and preserve collagen, the body uses vitamin C, a protein that provides structure for the skin, hair, and bones. Vitamin C is also present in kale.
At least 20 percent of a person’s daily need for vitamin A and over 23 percent of the daily need for vitamin C is provided by a cup of cooked kale.
Eye health
Kale contains lutein and zeaxanthin, a combination of antioxidants which can help reduce the risk of macular degeneration associated with age.
For eye protection, vitamin C, vitamin E, beta-carotene, and zinc also play a part. These are all found in kale.
Nutrition
The amount of each nutrient in a cup of boiled kale, weighing about 118 grams (g), without added salt, is shown in the table below.
It also indicates, according to the 2015-2020 Dietary Guidelines for Americans, how much an adult requires for each nutrient. Requirements differ according to the sex and age of the person.
| Nutrient | Amount in 1 cup | Daily adult requirement |
| Energy (calories) | 42.5 | 1,800–3,000 |
| Carbohydrate in grams (g) | 6.3, including 1.4 g of sugar | 130 |
| Fiber (g) | 4.7 | 22.4–33.6 |
| Protein (g) | 3.5 | 46–56 |
| Calcium in milligrams (mg) | 177 | 1,000–1,200 |
| Iron (mg) | 1.0 | 8–18 |
| Magnesium (mg) | 29.5 | 320–420 |
| Phosphorus (mg) | 49.6 | 700 |
| Potassium (mg) | 170 | 4,700 |
| Sodium (mg) | 18.9 | 2,300 |
| Zinc (mg) | 0.3 | 8–11 |
| Copper (mg) | 0.8 | 900 |
| Manganese (mg) | 0.6 | 1.8–2.3 |
| Selenium in micrograms (mcg) | 1.1 | 55 |
| Vitamin C (mg) | 21 | 75–90 |
| Folate (mcg DFE) | 76.7 | 400 |
| Betaine (mg) | 0.4 | No data |
| Beta carotene (mcg) | 2,040 | No data |
| Lutein + zeaxanthin (mcg) | 5,880 | No data |
| Vitamin E (mg) | 1.9 | 15 |
| Vitamin K (mcg) | 494 | 90–120 |
| Vitamin A (mcg RAE) | 172 | 700–900 |
A variety of antioxidants and B vitamins are also given by Kale.
Find out more about the value of another green, leafy vegetable, which is spinach.
Dietary tips
With a hint of earthiness, Kale is a crisp and hearty vegetable. The flavors and quality of nutrition can differ between types. Younger leaves tend to be less bitter and fibrous, compared with summer leaves.
Curly kale: This is the kind that is most widely available. It is usually bright green, dark green, or purple, with easy to tear, tight, ruffled leaves. To remove the leaves from the fibrous stalk, run your hand down the stalk in the direction of growth.
Lacinato or dinosaur kale: This dark blue-green variety is firmer and more robust than curly kale. Owing to its scaly appearance, it is known as the dinosaur kale. The leaves tend to be longer and flatter and, after cooking, retain their texture. Dinosaur kale is less bitter than curly kale, and is perfect for producing kale chips.
Red Russian kale: This is a flat-leaf variety that looks a little like oak leaves. The stalks are slightly purple and there is a reddish tinge to the leaves. People may find the stalks too fibrous to eat, but the leaves, with a hint of pepper and lemon, are sweet and delicate, almost like sorrel. People can add them raw, or as a garnish, to salads, sandwiches, and juices.
Kale grows well in the colder winter months, making a good addition when other fruits and vegetables are less readily available. Cooking winter kale is best, as colder weather will transform the kale sugars into starch, raising the bitterness and fiber quality.
Serving suggestions
Kale may be consumed raw, or steamed, braised, boiled, or sautéed, or added to soups and casseroles.
Raw: Scrunching the leaves briefly in the hands can make them easier to digest. Add to salads, sandwiches, wraps, or smoothies.
As a side dish: Sauté fresh garlic and onions in olive oil until soft. Add kale and continue to sauté until desired tenderness. Alternatively, steam for 5 minutes, then drain and stir in a dash of soy sauce and tahini.
Kale chipsRemove the ribs from the kale and sprinkle with olive oil or lightly spray with a mixture of cumin, curry powder, chili powder, red pepper flakes or garlic powder. Bake to the perfect crispness for 15-30 minutes at 275 ° F.
Smoothies: For your favourite smoothie, add a handful of kale. It will add nutrients without changing the flavor very much.
Risks
The Environmental Working Group, which reviews a number of items each year, placed kale third on its 2019 list of fruits and vegetables most at risk of pesticide contamination. Before using it, people should wash kale thoroughly.
For the following reasons, certain people should stop eating too much kale:
Beta-blockers: This type of drug is often recommended for heart disease by doctors. It can increase blood levels of potassium. High potassium foods, such as kale, can be eaten cautiously by those who use beta-blockers.
Kidney disease: It can be dangerous for people whose kidneys are not completely functioning to absorb so much potassium. If excess potassium will not be eliminated from the blood by the kidneys, it may be fatal to consume extra potassium.
Blood thinners: Kale is a rich source of vitamin K, which helps to coagulate the blood. This could interact with blood thinner activity, such as warfarin (Coumadin).
Anyone on any of these drugs should discuss foods to avoid with their doctor.
Conclusion
Kale is a leafy, green vegetable which provides a wide variety of nutrients. It is a balanced addition to a diverse diet, and it can be used in numerous ways by people.
Sources
- A primer on potassium. (2018).
(LINK) - Antioxidants and cancer prevention. (2017).
(LINK) - Appendix 7. Nutritional goals for age-sex groups based on dietary reference intakes and Dietary Guidelines recommendations. (2015).
(LINK) - Bone health for life: Health information basics for you and your family. (2018).
(LINK) - Diabetes superfoods. (n.d.).
(LINK) - Forrest, K. Y., & Stuhldreher, W. L. (2011). Prevalence and correlates of vitamin D deficiency in US adults [Abstract].
(LINK) - Full list: EWG’s 2019 shopper’s guide to pesticides in produce. (2019).
(LINK) - Hao, G., et al. (2017). Vitamin K intake and the risk of fractures.
(LINK) - Kale, cooked, boiled, drained, without salt. (2019).
(LINK) - Kunzmann, A. T., et al. (2015). Dietary fiber intake and risk of colorectal cancer and incident and recurrent adenoma in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial.
(LINK) - Liu, R., et al. (2015). Lutein and zeaxanthin supplementation and association with visual function in age-related macular degeneration.
(LINK) - May, H. L., et al. (2016). Dietary fiber to prevent cardiovascular disease.
(LINK) - What are the health benefits of kale? (LINK)
- McRae, M. P. (2018). Dietary fiber intake and type 2 diabetes mellitus: An umbrella review of meta-analyses.
(LINK) - Rasmussen, H. M., & Johnson, E. J. (2013). Nutrients for the aging eye.
(LINK) - Woziwodzka, A., et al. (2013). Heterocyclic aromatic amines heterocomplexation with biologically active aromatic compounds and its possible role in chemoprevention.
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