Health Benefits Of Kale

What is Kale?

Kale (Brassica oleracea) is a leafy green vegetable belonging to the cabbage family (Brassicaceae) that contains a large amount of health-promoting phytochemicals.

Kale is a plant that originates from Asia Minor and it was brought to Europe around 600 BC by a Celtic population, though it was widely used by ancient Greeks and Romans (1).

  • Its green colour originates from chlorophyll that acts as powerful antioxidant.

kale picture

  • Kale contains minimum percentage of fatty acids.
  • Kale is a rich source of vitamins and minerals. It is low in calories, high in fibers. Kale is abundant in iron, folate and magnesium.
  • Iron is essential for various biochemical reactions in human organism such as hemoglobin and enzymatic reactions, transport of oxygen molecules to distant parts of the body and hepatic metabolism.
  • Kale is rich in antioxidants such as lutein, zexanthin and carotenoids.
  • Phytonutrients can act as antioxidants, which help to prevent chronic diseases like cancer and heart disease.
  • Kale is high in vitamin K which is important for the prevention of various types of cancer. It is anticoagulation agent, antidiabetic and antioxidative. K1 (phylloquinone) and K2 (menaquinone) vitamin isoforms are able to act cardio and osteoprotective.(2)
  • In kale, there are nearly 45 types of flavonoids that may lower the risk for brain artery occlusion.
  • Kaempferol (3,5,7-trihydroxy-2-(4-hydroxyphenyl)-4H-1-benzopyran-4-one) is one of a major flavonoids found in kale. It has strong antioxidant, antiinflammatory and chemopreventive attributes. It regulates important enzymes involved in metabolism, oxidation and cancerogenesis (catalase, glutathione peroxidase, glutathioone-S-tranferase).

 

Kaempferol biochemical structureKaempferol biochemical structure (C15H10O6)

The anticancer role of kaempferol is expressed through the apoptosis induction, inhibiting the cancer cell growth, cell-cycle arrest, inhibiting metastasis or angiogenesis reactions, regulation of p53 tumor gene and STAT3.

1.Diabetes

Intake of kale suppresses postprandial increases in plasma glucose (3) therefore its shows hypoglycemic effect. The effect is mostly due to high amount of dietary fibers contained in kale.

reduces diabetes

In recent studies it has been shown that the intake of kale containing food at a dose of 7-14 grams decreases postparandial plasma glucose level.

Due to high concentrations of vitamin K and magnesium kale is able to regulate the glucose levels in the circulation. The sulforaphane acts antiinflammatory and may help in the control of glicemia levels as well as protecting blood vessels from microinjuries.

2.Immune System

Kale is a potent stimulator of human immune system due to high levels of antioxidant metabolites, vitamins (particularly A, C, E, K and B6), carotenoids, folate and phenolic compounds. (4)

3.Bone Metabolism

Kalium is of vital importance for various functions such as physiological bone metabolism and coagulation processes.

4.Anticancer Effects

  1. Kale is rich in antioxidants, mainly carotenoids and flavonoids that may prevent certain types of cancer, especially flavonoid such as kaempferol.
  2. Kale is abundant in phytonutrients that prevent cancer according to their ability to activate certain liver enzymes and neutralize toxic substances.
  3. Sulforaphane is a major stimulator of carcinogen detoxification.(5)
  4. Due to their enhanced plant protection to biotic and abiotic stresses and their preventive effects on several human cancers they have been extensively investigated. (6)
  5. In kales there are two aliphatic glucosinolates. They are SIN and glucoiberin (3-methylsulphinylpropyl,), and one indolic glucosinolates, glucobrassicin (3-indolylmethyl,), are the highly contained in the plant’s leaf. (7)

5.Effect On Lung And Gastrointestinal Cancer

Brassica oleracea may protect against lung cancer and gastrointestinal cancer due to their high amount of glucosinolates secondary metabolites (sulfur-containing glucosides) such as sinigrin, glucoiberin, glucobrassicin, progoitrin, glucoraphanin and gluconapin.

Glucosinolates are inactive prior to reaction with the enzyme myrosinase in the digestive enzyme which releases glucose and final degradation products such as isothiocyanates. Isothiocyanates inhibit apoptosis and enhance apoptosis in human cancer cells, therefore preventing their further growth.

They may be as well decomposed by thermal inactivation of myrosinase in the small intestine or by bacterial myrosinase in the colon. (8)

6.Effect On Lung And Oral Cavity Cancer

Due to kales high concentration of vitamin A, it may prevent lung and oral cancer.

Gastrointestinal Effect

It could show an effect on gastrointestinal microorganism flora. (9)

Kale is rich in fiber and may control the body weight. (10)

The high intake of kale leads to the modification of the concentration of certain bacterial species in the gastrointestinal tract. Kale may lead to the better digestive microbial flora and probiotic effects.

7.Cardiovascular Effect

It lowers cholesterol levels due to its fiber related compounds that bind the bile acids in the intestine. Such reactions is dependant on the activation of the cholesterol deposits, therefore reducing its concentration in the blood.

8.Neurological Effect

Kale is abundant in potassium and vitamin C which could prevent heart and brain artery occlusions. (11)

9.Vision

Kale has high levels of vitamin A, therefore leads to the prevention of vision defects, lung and oral cancers.

It is high in vitamin C (ascorbic acid) which enhances immune system, metabolic reactions and hydratation of the organism.

vision

Lutein and zeaxanthin are carotenoids that are selectively taken up into the macula of the eye, where they are thought to protect against the development of macular degeneration in the older age.

10.Rehydratation

Due to its high levels of vitamins, especially vitamin C, and other coumpounds, it is of great value in the proper hydratation if adequately prepared (juice or raw).

11.Bone Disorders

It is high in calcium which prevent bone loss and osteoporosis. Vitamin C is essential for the quality of cartilage and joint mobility.

12.Antiinflammatory Effect

  1. Arthritis
  2. Asthma
  3. Autoimmune Disorders

Kale contains omega-3 fatty acids that are important in the treatment of arthritis, asthma and various autoimmune impairments.

13.Anticoagulant Effect

Kale is loaded with vitamin K, therefore it shows certain anticoagulant effects.

14.Detox Reactions

It contains sulfur and fibers, therefore it is of value in detoxifying reactions of the liver and overall organism reactions.

It contains high concentrations of sulfur phytonutritients (glucosinolates, methyl cysteine sulfoxides) that are capable to enhance hepatic production of certain enzymes that inhibit toxic substances.

 

Kale is rich in antioxidants such as lutein, zexanthin, kaempferol and carotenoids(12) . Antioxidants are potent anticancer, antiviral, antibacterial, antiinflamatory, antihypertensive and cardioprotective molecules.(13)(14)

Phenolic compounds (flavonoids and hydroxycinnamic acids) are known as the vital components with the highest antioxidant capabilites in Brassica.

They are able to eliminate reactive oxygen molecules through the process of electron addition.

15.Drug Liver Metabolism

The effect of kale intake has been investigated in the field of liver (P450 cytohrome) metabolic reactions, especially on midazolam, caffeine, dextromethorphan, tolbutamide, omeprazole and chlorzoxazone.

It was noted that kale causes an important increase in the concentration of midazolam , caffeine, omeprazol and dextromethorphan catabolic products, therefore individuals must be cautios if combining kale vegetables with CYP metabolized drugs (15)

16.Pregnancy

Kale is particularly recommended in pregnancy due to various and high amounts of nutritive substances.

17.Depression

Due to carotenoids and omega-3-acids, kale are effective in the maintaining positive mood, therefore reducing the symptoms of the depression.

 

It has been shown that kale possesses high levels of proteins, folate and vitamin B6 that are responsible for maintaining serotonin and dopamine levels.

18.Skin Wounds

In a recent study on rats it was shown that a combination of kale extract and a photobiomodulation laser may significantly reduce the dimeter of epithelial wound, its thickness and morphology.

 

The main cause is the stimulated scar tissue maturation due to the activation of colagen I and III fibers. (16)

19.Alzheimer’S Disease

Increased level of vitamin K may lead to the prevention of Alzheimer’s disease.

Side Effects Of Kale High Intake

Thyroid function

Kale is a major source of oxalate which may be of concern to certain individuals that suffer from goitre. (17) Kale itself does not cause the disorder of the thyroid, but its certain molecules that are ‘’goitrogenic’’ may compete with iodine uptake into the thyroid. In healthy individuals, it does not lead to thyroid disorders (18)

Calculosis

Due to oxalats, in certain individuals it may cause the formation of sand/stones in biliary and urinary tract.

Blood disorders

Kale is not recommended in patients on anticoagulant therapy due to high concentrations of vitamin K.

References

  1. http://www.nytimes.com/2013/10/20/magazine/who-made-that-kale.html?_r=0
  2. Spronk et al. Tissue specific utilization of menaquinone-4 results in the prevention of arterial calcification warfarin-treated rats. J Vasc Res 2003;40:531–537
  3. Kondo S et al. Intake of kale suppresses postprandial increases in plasma glucose: A randomized, double-blind, placebo-controlled, crossover study.Biomed Rep. 2016 Nov;5(5):553-558. Epub 2016 Sep 29.
  4. Powers SK et al. Dietary antioxidants and exercise.J Sports Sci. 2004 Jan;22(1):81-94.
  5. Horst MA et al. Water extracts of cabbage and kale inhibit ex vivo H(2)O(2)-induced DNA damage but not rat hepatocarcinogenesis. Braz J Med Biol Res. 2010 Mar;43(3):242-8.
  6. Sotelo T et al. Modification of Leaf Glucosinolate Contents in Brassica oleracea by Divergent Selection and Effect on Expression of Genes Controlling Glucosinolate Pathway.Front Plant Sci. 2016 Jul 15;7:1012. doi: 10.3389/fpls.2016.01012. eCollection 2016.
  7. Johnson IT. Glucosinolates: bioavailability and importance to health. Int J Vitam Nutr Res. 2002 Jan;72(1):26-31.
  8. Uyeno Y et al. Changes in mouse gastrointestinal microbial ecology with ingestion of kale. Benef Microbes. 2014 Sep;5(3):345-9.
  9. Kahlon TS, Chiu MC, Chapman MH. Steam cooking significantly improves in vitro bile acid binding of collard greens, kale, mustard greens, broccoli, green bell pepper, and cabbage. Nutr Res. 2008 Jun;28(6):351-7.
  10. D’Elia L, Barba G, Cappuccio FP, Strazzullo P.Potassium intake, stroke, and cardiovascular disease a meta-analysis of prospective studies. J Am Coll Cardiol. 2011 Mar 8;57(10):1210-9.
  11. Lännenpää M. Heterologous expression of AtMYB12 in kale (Brassica oleracea var. acephala) leads to high flavonol accumulation. Plant Cell Rep. 2014 Aug;33(8):1377-88.
  12. Olsen H, Aaby K, Borge GI.Characterization and quantification of flavonoids and hydroxycinnamic acids in curly kale (Brassica oleracea L. Convar. acephala Var. sabellica) by HPLC-DAD-ESI-MSn. J Agric Food Chem. 2009 Apr 8;57(7):2816-25.
  13. Rajendran P, Rengarajan T, Nandakumar N, Palaniswami R, Nishigaki Y, Nishigaki I.Kaempferol, a potential cytostatic and cure for inflammatory disorders.Eur J Med Chem. 2014 Oct 30;86:103-12. doi: 10.1016/j.ejmech.2014.08.011. Epub 2014 Aug 5.
  14. Yamasaki I, Yamada M, Uotsu N, Teramoto S, Takayanagi R, Yamada Y. Inhibitory effects of kale ingestion on metabolism by cytochrome P450 enzymes in rats. Biomed Res. 2012;33(4):235-42.
  15. Gonçalves RV, Sarandy MM, da Matta SL, Novaes RD, Pinto MV. Comparative study of the effects of laser photobiomodulation and extract of Brassica oleracea on skin wounds in wistar rats: A histomorphometric study. Pathol Res Pract. 2013 Oct;209(10):648-53.
  16. Knowles SO, Grace ND.Serum total iodine concentrations in pasture-fed pregnant ewes and newborn lambs challenged by iodine supplementation and goitrogenic kale. J Anim Sci. 2015 Jan;93(1):425-32.
  17. Dal Maso L, Bosetti C, La Vecchia C, Franceschi S.Risk factors for thyroid cancer: an epidemiological review focused on nutritional factors. Cancer Causes Control. 2009 Feb;20(1):75-86.
  18. Kris Etherton PM (2002) Bioactive compounds in foods: Their role in the prevention of cardiovascular disease and cancer. The American journal of medicine 113: 71S–88S
  19. Vinson JA, Dabbagh YA, Yang J, Serry MM (1995) Pure polyphenols and beverages with an emphasis on tea as antioxidants (aox) for the prevention of heart-disease in vitro and in vivo studies. Abstracts of papers – American chemical society210: 242–AGFD