Kale is a dark, leafy vegetable that has green or purple leaves (90482,90485). It is similar to cruciferous vegetables such as broccoli, cauliflower, and collard (90480). It is believed to have originated in the eastern Mediterranean and to have been used as a food crop since 2000 BC (90482). There is interest in its use as an antioxidant and for improving overall health.

LIKELY SAFE ...when used in amounts commonly found in foods.

There is insufficient reliable information available about the safety of kale when used orally in medicinal amounts.

PREGNANCY AND LACTATION: LIKELY SAFE ...when used orally in amounts commonly found in foods. There is insufficient reliable information available about the safety of kale when used orally in medicinal amounts; avoid use.

• Adult

  Oral:

  Research is limited; typical dosing is unavailable.

• Standardization & Formulation

  There is insufficient reliable information available about the standardization of kale.

None known.

There is insufficient reliable information available about the presentation or treatment of overdose with kale.

There is insufficient reliable information available about the pharmacokinetics of kale.

General: The applicable parts of kale are the above ground parts. Kale contains carotenoids (including lutein and beta-carotene), vitamin K (phylloquinone), vitamin C, vitamin A, folate, iron, calcium, magnesium, phosphorus, and potassium. It also contains glucosinolates including ascorbigen, terpenoids, indole derivatives, and flavonoid glycosides of quercetin, kaempferol, and isorhamnetin (6790,26497,90480,90483,90484,109905).

Anti-cancer effects: Epidemiological research suggests that cruciferous vegetables such as kale have protective effects against some types of cancer (14145). These vegetables contain about 10 different kinds of glucosinolates (6790). Glucosinolates are usually accompanied by myrosinase, a thioglucosidase enzyme found in plant cells in separate compartments (6792). When the plant cells are damaged by cutting or chewing, the myrosinase is exposed to glucosinolates, catalyzing its hydrolysis to a range of breakdown products, such as indoles, nitriles, and isothiocyanates (ITCs).

ITCs are sulfur-containing phytochemicals present in the form of sulforaphane (SFN), phenylethylisothiocyanate, benzylisothiocyanate, and 3-phenylpropylisothiocyanate. These chemicals are thought to be anticarcinogenic due to their effects on phase I and phase II enzymes (10264,26449,26483,47627,55547). Phase I and phase II enzymes act as the body's first line of defense against cancer by protecting the body from carcinogens that routinely enter the body through the diet and the environment. ITCs generally enhance the activity of phase II enzymes and inhibit phase I enzymes, thus reducing the production of electrophilic intermediates with carcinogenic activity and enhancing the detoxification and clearance of carcinogens. ITCs also act as suppressing agents during the promotion phase of the neoplastic process and induce apoptosis, thereby inhibiting cell growth (26449,26485).

Other products of glucosinolate hydrolysis, indoles, include indole-3-acetonitrile, indole-3-carbinol (I3C), and 3,3'-diindolylmethane (DIM) (47627). Evidence from in vitro research suggests that I3C inhibits carcinogenesis by inducing enzymes such as cytochrome P450-dependent monooxygenases, glutathione S-transferases (GST), or epoxide hydrolases (EH). These enzymes metabolize carcinogens to more polar and excretable forms (26489,26491,47596). Evidence from animal research has shown that indoles and isothiocyanates attenuate the effects of polycyclic aromatic hydrocarbons (PAHs) and nitrosamines and are protective towards heterocyclic amines (51183). The effects on PAH and nitrosamines appear to be via induction of GST and inhibition of cytochrome P450 isoenzymes, respectively.

Indoles and phytoestrogens found in Brassica species may also contribute to the protection of hormone-dependent breast and cervical cancers. Evidence from animal research suggests that I3C inhibits mammary cancers (26469) and that its use may inhibit breast and cervical cancers in women (47627). In women, I3C increases the 2-hydroxylation of estrogen urinary metabolites (47615). Evidence from in vitro research suggests that I3C suppresses the proliferation of various tumor cells, including breast, prostate, endometrial, colon, and leukemic cells (47627).

Metabolic effects: Research in obese animals shows that adding 9% kale to a high -fat diet (45% fat) for 12 weeks lowers serum triglycerides and low-density lipoprotein (LDL) cholesterol levels when compared with the high- fat diet alone. Kale contains compounds which act as bile acid sequestrants, preventing bile acid recirculation and reducing fat absorption. Adding kale to a high -fat diet also prevents increases in endotoxemia and inflammation, but does not reduce body weight, fat accumulation, or insulin resistance when compared with the high- fat diet alone. In adipose tissue, kale increases the expression of genes involved in adipogenesis, downregulates expression of adipose tissue-specific inflammation markers, and reduces gene expression of several chemokines and chemokine receptors (109905).