Benefits (and Risks) of Juicing Kale

Kale is a cruciferous vegetable in the same family as broccoli and brussel sprouts, though most tend to think of it more as a dark leafy green.

Kale is packed with vitamins, minerals, and other phytonutrients, making it one of the most nutrient-dense foods around.

Juicing kale may be a good way to deliver many of the nutrients and antioxidants from the popular vegetable to the body quickly while protecting some of the important compounds when compared to cooking. Juicing kale may be a helpful part of many healthy diet and lifestyle routines.

Benefits of juicing kale

Nutrient-dense

Kale has become one of the most popular vegetables for both eating and juicing in recent years, thanks to its impressive nutrient composition. Kale is a low-calorie food that delivers many key nutrients.

The U.S.D.A FoodData Central note the nutrition profile of 100g of raw kale is as follows:

Calories: 49
Protein: 4.3g
Carbohydrate: 8.8g
Sugars 2.3g
Dietary fiber: 3.6g

Kale is low in calories and sugars and contains easily digestible proteins that appear in the juice as well as the leaf.

Kale also contains important minerals, including:

Calcium: 150mg
Iron: 1.5mg
Magnesium: 47mg
Potassium: 491mg
Phosphorous: 92mg

Antioxidants

The same amount of kale also provides the body with important nutrients and antioxidants such as:

Vitamin A (as beta carotene): 5927µg
Vitamin C: 120mg
Vitamin E: 1.5mg
Lutein & zeaxanthin: 8198µg

A review posted to Critical Reviews in Food Science and Nutrition also notes kale contains other antioxidant compounds such as the flavonoids quercetin and kaempferol.

Antioxidants are undoubtedly important in the diet, as oxidation and oxidative damage have links to numerous chronic disorders.

Increasing antioxidant intake in the diet, such as by juicing kale, may have an impact in a number of disorders, including:

Macular degeneration (eye health)
Aging
Degenerative diseases
Cancer
Obesity
Metabolic syndrome
Type 2 diabetes
Atherosclerosis
Cardiovascular disease

This is not to say that antioxidants will prevent or treat these diseases. Antioxidants empower the body’s defenses and help protect cells from damage.

Raw

Kale juice is also a raw form of kale. This is important, especially when it comes to antioxidant activity. A study posted to Acta Scientiarum Polonorum Technologia Alimentaria notes that cooking kale results in a significant reduction in the amount of antioxidants. Cooked kale only has about 38% of the antioxidant activity as raw kale.

Juicing raw kale protects this antioxidant capacity.

May protect against bone loss

Like other leafy greens, kale is high in calcium. Yet as a review posted to Critical Reviews in Food Science and Nutrition notes, the type of calcium in kale is highly bioavailable, meaning the body can quickly and easily use it. This makes kale a great source of calcium, even in populations that do not get other simple calcium sources.

The availability of this calcium, coupled with other important minerals such as vitamin K, may help build stronger bones and protect these bones from becoming weaker.

Convenience

When looking at the nutrient profile, consider the numbers are for 100g of raw kale. This is about twice the serving size of the average kale salad.

So while a very large kale salad would make someone full trying to capture these nutrients, juicing kale can provide many of the same nutrients in a much smaller, more convenient form.

Risks of juicing kale

Juicing itself may not be right for everyone, and people with certain conditions should check with a doctor before doing a juice fast.

Prediabetes

People with prediabetes may need to be careful about which foods they juice, as high sugar juices may cause spikes in blood sugar.

Juicing removes many of the fibers from the fruits and vegetables while retaining the natural nectar and sugars of the plant.

Fiber helps slow the absorption of sugars into the body. This slow absorption leads to a slower rise in insulin levels. While kale is relatively low in sugar, other common ingredients in juice blends may not be.

Kidney disease

Kale juice and other juices are potent sources of phytonutrients and minerals. This is great for the body as a whole but may take a toll on the kidneys in people with kidney disease.

People with chronic kidney disease may have trouble filtering the extra minerals from these fresh juices, especially potassium. People on a potassium-restricted diet should talk to their doctor before choosing a juicing program.

Drug interactions

Many fruit and vegetable juices contain high levels of antioxidants and other compounds that could potentially interact with some forms of medication. Anyone taking prescription medications should talk to their doctor before starting a juicing program to check for any possible interactions.

Summary

There are a number of benefits to juicing kale, thanks to an impressive nutrient and antioxidant profile. Juicing kale can help a person get these nutrients in a quick and simple way.

With this said, juicing is not a replacement for a healthy diet and lifestyle choices. Juicing nutrient-dense foods such as kale may not be right for everyone, and people taking prescription medications or those with digestive conditions should talk to their doctor before starting a regular juicing program.

References

Kale, Raw. (2020). https://fdc.nal.usda.gov/fdc-app.html#/food-details/787307/nutrients

Šamec, D., Urlić, B., & Salopek-Sondi, B. (2019). Kale (Brassica oleracea var. acephala) as a superfood: Review of the scientific evidence behind the statement. Critical Reviews in Food Science and Nutrition, 59(15), 2411-2422. https://www.essentialnutrition.com.br/media/artigos/aminogreens/14.pdf

Sikora, E., & Bodziarczyk, I. (2012). Composition and antioxidant activity of kale (Brassica oleracea L. var. acephala) raw and cooked. Acta Scientiarum Polonorum Technologia Alimentaria, 11(3), 239-248. https://pubmed.ncbi.nlm.nih.gov/22744944/

Stübler, A. S., Lesmes, U., Heinz, V., Rauh, C., Shpigelman, A., & Aganovic, K. (2019). Digestibility, antioxidative activity and stability of plant protein-rich products after processing and formulation with polyphenol-rich juices: Kale and kale–strawberry as a model[Abstract]. European Food Research and Technology, 245(11), 2499-2514. https://link.springer.com/article/10.1007/s00217-019-03362-5

Yan, L. (2016). Dark Green Leafy Vegetables. https://www.ars.usda.gov/plains-area/gfnd/gfhnrc/docs/news-2013/dark-green-leafy-vegetables/