Kale

Kale (Brassica oleracea var. acephala)

1. Identity: Botanical Classification, Names, and Common Forms

Kale (Brassica oleracea var. acephala) is a non-heading leafy vegetable of the Brassicaceae family, widely recognized for its dense nutritional profile and diverse phytochemical composition. The botanical name literally means "cabbage of the vegetable garden without a head." The plant belongs to the Brassica oleracea (acephala group) and is in the same botanical family as broccoli, cauliflower, and Brussels sprouts.

Kale is known by several common names across cultures. In Scotland, kale provided such a basis for a traditional diet that the word in some Scots dialects became synonymous with food. The ancient Norse called it "kal" (the same as Swedish), while in Scotland it was "Kail," and the Danish term was "kaal." In English, the alternate name "borecole" has also been recorded historically.

Major cultivars and forms include:

• Curly kale (Brassica oleracea var. sabellica or acephala, cv. Reflex and others): the most commercially familiar form with tightly frilled, dark-green leaves.
• Lacinato / Tuscan / Cavolo Nero kale: dark, bumpy-surfaced, narrow leaves; an Italian heirloom type.
• Siberian kale: broader, flatter leaves; cold-tolerant; introduced to North America via Canada in the early 19th century.
• Red Russian kale: flat, oak-shaped reddish-purple leaves with a sweeter flavor.

Common preparations and commercial forms:

• Fresh/whole leaf: the primary culinary form, used raw in salads, braised, sautéed, or in soups.
• Kale juice / cold-pressed juice: used in several clinical studies at doses of approximately 300 ml/day.
• Freeze-dried kale powder: concentrated form used in studies and as a dietary supplement ingredient; described in clinical research as kale powder for metabolic syndrome evaluation.
• Kale chips: baked or dehydrated kale, a processed snack form.
• Kale bars / fortified food products: used in randomized controlled trials where participants consumed bars each containing 26.25 g of freeze-dried kale, corresponding to approximately 341 g fresh kale/day.
• Isolated phytochemical supplements: kale is a source plant for commercial indole-3-carbinol (I3C) and diindolylmethane (DIM) supplements. I3C is available without a prescription as a dietary supplement, alone or in combination products.

The chemical composition of kale and its nutrient content is characterized by a rather high variability depending on the region of study or the material itself (fresh, freeze-dried).

2. Historical and Traditional Use

Origins and Ancient Cultivation

Kale originated in the eastern Mediterranean and Anatolia, where it was cultivated for food beginning by 2000 BCE at the latest. Curly-leaved varieties of cabbage already existed along with flat-leaved varieties in Greece in the 4th century BC. Domesticated around 400 BCE, it was widely cultivated in Ancient Greece and Rome. Ancient Greeks and Romans were familiar with and consumed members of the Brassica oleracea family, including kale; they valued it not only for its culinary uses but also for its perceived medicinal properties.

Medieval Europe

Kale thrived in colder climates and spread across Europe and Asia, becoming a staple by the Middle Ages. Because of its cold tolerance, it was an important winter famine food throughout Northern Europe during the Middle Ages and, hence, is still commonly consumed in Scotland, Ireland, Germany, Denmark, and Sweden. During the Middle Ages, kale became so popular in England and Scotland that the word "kale" actually meant "dinner."

Cultural and Folk Uses by Region

• Scotland and Ireland: Kale was a significant part of Scottish heritage and folklore during the 18th and 19th centuries. It wasn't just a staple crop—it was deeply woven into cultural traditions; for example, during Samhain, kale was used as a divination tool to predict future lovers. In Ireland, kale is mixed with mashed potatoes to make the traditional dish colcannon.
• Netherlands: A traditional winter dish called "boerenkoolstamppot" is a mix of curly kale and mashed potatoes, sometimes with fried bacon and smoked sausage.
• Northern Germany: There is a winter tradition known as "Kohlfahrt" ("kale trip"), where a group of people hike through the woods before gathering for a meal of kale with bacon and kale sausage. Kale is considered a Northern German staple and comfort food.
• Italy: In Italy, cavolo nero kale is an ingredient of the Tuscan soup ribollita.
• Portugal: A traditional Portuguese soup, caldo verde, combines puréed potatoes, very finely sliced kale, olive oil, and salt.
• Sri Lanka: Known as kola gova or ela gova in Sri Lanka, a dish called "kale mallung" is served almost everywhere on the island, along with rice.
• United Kingdom (World War II): In the United Kingdom, the cultivation of kale was encouraged during World War II via the "Dig for Victory" campaign.

Perceived Medicinal Use (Historical)

During Roman times (about 2,000 years ago), forms of cabbage such as kale were thought to keep Romans so healthy that they did not even need doctors. These uses were rooted in folk and empirical tradition rather than systematic scientific inquiry. The historical medicinal reputation of kale and related brassicas centered on digestive complaints and general fortification, though no formal pharmacopeial monograph exists for kale specifically.

Modern Revival

For most of the 20th century, kale was primarily used in the U.S. for decorative purposes; it became more commonly consumed starting in the 1990s, mainly due to its nutritional value. After falling out of favor, kale was revived globally by farmers' markets and health trends, gaining popularity in the United States starting around 2007.

3. Key Constituents and Active Compounds

3.1 Macronutrients and Vitamins

Kale is particularly rich in vitamins (A, C, K), minerals (Ca, Fe, K), dietary fiber, glucosinolates, polyphenols, carotenoids, flavonoids, and chlorophylls. Noteworthy is the realistically high protein content and amino acid composition for plants of the Brassicaceae family. Kale is widely consumed as a green leafy vegetable worldwide; it provides high bioavailability of calcium, better than milk, and good concentrations of iron.

3.2 Glucosinolates and Their Hydrolysis Products

Glucosinolates constitute the most pharmacologically significant class of compounds in kale. When kale or related crucifers are damaged — for example, by chewing or chopping resulting in cellular fragmentation — endogenous enzymes (myrosinase) hydrolyze glucosinolates and convert them to bioactive isothiocyanates such as sulforaphane.

Major glucosinolate-derived compounds:

• Sulforaphane (SFN): SFN is a low-molecular-weight aliphatic isothiocyanate generated from the glucosinolate precursor glucoraphanin that is abundant in broccoli, Brussels sprouts, kale, and other cruciferous vegetables. Early studies show that SFN scavenges oxygen radicals by increasing cellular defenses against oxidative damage, mainly through the induction of phase II detoxification enzymes by nuclear factor erythroid 2-related factor 2 (Nrf2). The anticancer mechanism of SFN also includes induction of apoptotic pathways in tumor cells, inhibition of cell cycle progression, and suppression of tumor stem cells.
• Indole-3-Carbinol (I3C) and Diindolylmethane (DIM): Glucobrassicin, the glucosinolate precursor of I3C, is found in a number of cruciferous vegetables, including kale. Ingested glucobrassicin is catalysed via the enzyme myrosinase and turns into indole-3-carbinol, which is rapidly digested into both DIM and various other metabolites in the human stomach via acid-mediated condensation reactions. DIM has multiple mechanisms of action, the most well-characterized being modulation of aryl hydrocarbon receptor (AHR) signaling.
• Other isothiocyanates (ITCs): Evidence suggests that isothiocyanates exert their effects through a variety of distinct but interconnected signaling pathways important for inhibiting carcinogenesis, including those involved in detoxification, inflammation, apoptosis, and cell cycle and epigenetic regulation.

3.3 Flavonoids and Polyphenols

Flavonoids such as quercetin and kaempferol have antioxidant, anti-inflammatory, antimutagenic, anti-edematous, antiallergic, antiatherosclerotic, gastroprotective, neuroprotective, normotensive, vasodilatory, and antiproliferative effects. One study reported that kale has 204 mg of hydroxycinnamic acids per 100 g fresh weight. Sinapic acid inhibits NF-κB, which regulates inflammation and plays a role in the response to infections, and also has antiproliferative effects on breast cancer cell lines. Ferulic acid has antioxidant, anti-inflammatory, antidiabetic, antihypertensive, antimicrobial, and antiviral effects.

3.4 Carotenoids

Beta-carotene, zeaxanthin, and lutein present in kale are converted in the body into vitamin A, which is essential for vision processes. Vitamin A prevents problems with vision in low light (night blindness). Lutein and zeaxanthin protect the retina from the effects of free radicals because they are components of the macula.

3.5 Vitamins and Minerals

One cup of cooked kale contains 544 micrograms (mcg) of vitamin K. Kale also contains substantial amounts of vitamins C, A (as beta-carotene), B vitamins, calcium, iron, and potassium. Research has shown that consuming kale leaves in winter would meet part of the requirement for omega-3 fatty acids.

3.6 Chlorophylls and Organic Acids

Kale has been reported to contain better concentrations of prebiotic carbohydrates, organic acids, unsaturated fatty acids, carotenoids, phenolic acids, and different vitamins. Fructose, glucose, and sucrose are the major soluble sugars; citric and malic acids are the major organic acids.

3.7 Anti-Nutritional Factors

Kale also contains prebiotic carbohydrates and unsaturated fatty acids, while anti-nutritional factors such as oxalates, tannins, and phytate are present in higher concentrations. These compounds can reduce bioavailability of certain minerals if intake is very high or if dietary variety is limited.

3.8 Effects of Processing on Phytochemical Content

In kale, steaming preserves 87–92% of phenolic compounds and antioxidant activity. In contrast, frying causes the most substantial nutrient degradation, with losses of 71% for chlorophylls, 28.2% for carotenoids, and 80–81% for flavanols. Ascorbic acid is particularly heat-sensitive, decreasing by 53.1% during boiling and 54.9% during frying.

4. Scientific Evidence by Area of Use

4.1 Cardiovascular Health

Recent in vivo and clinical studies demonstrate kale's potential in reducing the risk of chronic diseases such as cardiovascular disorders.

Human/Clinical Evidence:

A prospective single-arm clinical study published in the Journal of Hypertension and Cardiology (2016) examined the effects of kale powder consumption in subjects with potential metabolic syndrome. The prospective intervention study was conducted to investigate the effects of kale powder consumption on metabolic syndrome in subjects with potential metabolic syndrome, measuring effects on blood pressure, HbA1c, BMI, abdominal circumference, and blood triglycerides, LDL-C, HDL-C, and fasting blood sugar levels. After eight weeks of kale powder intake, a significant decrease was observed in laboratory and home test-based blood pressure, abdominal circumference, and levels of LDL-C, HDL-C, and fasting blood sugar. A hypotensive effect was also observed in patients with blood pressure-related diseases when stratified. No safety concerns were identified regarding kale powder.

A separate study in South Korean patients examined GST genetic polymorphism effects. Eighty-four subclinical hypertensive patients showing systolic BP over 130 mmHg or diastolic BP over 85 mmHg received 300 ml/day of kale juice for 6 weeks. Systolic and diastolic blood pressure was significantly decreased in all patients regardless of their GSTM1 or GSTT1 polymorphisms after kale juice supplementation. Blood glucose level was decreased only in the GSTM1-present genotype, and plasma lipid profiles showed no difference in both GSTM1-null and GSTM1-present genotypes.

Overall, findings suggest that supplementation of kale juice affected blood pressure, blood glucose, and lipid profiles in subclinical hypertensive patients depending on their GST genetic polymorphisms. The improvement of lipid profiles was mainly greater in the GSTT1-present genotype, although the strength of this finding is limited by the sample size. Much larger studies are required to accurately measure the modest effects of genes and to identify the extent of gene-diet interactions.

With respect to cholesterol-lowering mechanisms, kale (Brassica oleracea ssp. acephala) can favourably affect serum lipid profiles in hypercholesterolemic and hypertensive patients. Research compared kale with dill for cholesterol-lowering potential, focusing on quercetin glycosides as representative bioactive compounds.

Evidence Strength: Preliminary. Human trials to date are small (n = 30–84), lack robust placebo controls in some cases, and do not consistently isolate kale from overall dietary changes. Results are biologically plausible but insufficient to establish causal efficacy for cardiovascular endpoints.

4.2 Glycemic Control and Type 2 Diabetes

A 2024 randomized, double-blinded, placebo-controlled clinical trial published in PMC/Nutrients investigated freeze-dried kale in 30 type 2 diabetes (T2D) patients. The study was designed as a 12-week, blinded, randomized, controlled trial. Thirty T2D patients were randomly assigned to either a placebo bar or a kale bar, with participants in the intervention group instructed to consume three bars per day, each containing 26.25 g of freeze-dried kale, corresponding to approximately 341 g fresh kale per day. Results showed a significant reduction in HbA1c, insulin resistance, body weight, and calorie intake in the intervention group compared to control. Positive trends were detected in fasted blood glucose and LDL-cholesterol for those in the kale intervention group. No significant differences were found in total body fat mass and area under the curve glucose during OGTT. Further research with a larger sample size is needed to better understand the health benefits.

A 2018 study concluded that people who consumed higher amounts of dietary fiber appeared to have a lower risk of developing type 2 diabetes, and consuming dietary fiber might also lower blood glucose levels. Kale is a notable source of dietary fiber, supporting this dietary pathway.

Evidence Strength: Promising but limited. The pivotal 2024 RCT was small (n = 30). Larger, multi-center trials are needed before dietary or clinical recommendations can be based on this evidence alone.

4.3 Cancer Chemoprevention

This is the most extensively studied mechanistic area for kale's bioactive compounds, though human clinical trial evidence remains largely indirect.

Higher consumption of cruciferous vegetables (including kale) is associated with a reduced risk of several cancers, particularly cancers of the gastrointestinal tract, lung, and prostate, based on epidemiological studies. Evidence suggests that isothiocyanates exert their effects through a variety of distinct but interconnected signaling pathways important for inhibiting carcinogenesis, including those involved in detoxification, inflammation, apoptosis, and cell cycle and epigenetic regulation.

SFN has been shown to play a cancer chemopreventive role by inducing phase II detoxification and antioxidant enzymes through the Nrf2/ARE signaling pathway. At the same time, SFN can inhibit phase I enzymes that activate procarcinogens, thereby interfering with the initiation stage of cancer.

Recent research has discovered novel mechanisms of action for the effects of isothiocyanates including the modulation of tumor microenvironment, the inhibition of the self-renewal of stem cells, the rearrangement of multiple pathways of energy metabolism, the modulation of microbiota, and protection against Helicobacter pylori.

For indole compounds specifically, indole-3-carbinol (I3C) is thought to possess properties against cancer by facilitating the conversion of estrogen to a less cancer-promoting form, partially blocking the effects of estrogen on cells, directly killing or inhibiting cancer cells, and reducing levels of free radicals which can promote cancer by damaging DNA. A four-week, double-blind, placebo-controlled trial of fifty-seven women found that a minimum dose of 300 mg of I3C daily may be necessary to reduce the risk of estrogen-promoted cancers.

In humans, much of the focus has been on chemoprevention of breast and prostate cancer. Alteration of cytochrome P450-dependent estrogen metabolism is hypothesized to be an important driver of DIM-dependent breast cancer prevention. The few studies comparing glucobrassicin-rich crucifers with I3C/DIM supplements have shown the greater impact of the latter is due to dose: daily ingestion of kilogram quantities of Brussels sprouts is required to produce in vivo levels of DIM achievable by supplementation.

Epidemiological studies have demonstrated that intake of cruciferous vegetables such as broccoli, kale, and cabbage reduces the risk of advanced prostate cancer.

Evidence Strength: Mechanistic evidence from in vitro and animal studies is robust. Epidemiological associations are consistent for several cancer types. Direct human intervention trials on kale itself are limited; most clinical evidence derives from broccoli-sprout or purified SFN/I3C/DIM studies, which are extrapolated to kale. Isothiocyanates possess potent anti-cancer activities based on up-to-date evidence from in vitro and in vivo studies, but the nature of hormesis suggests that the benefits or risks of isothiocyanates largely depend on the dose and endpoint of interest.

4.4 Antioxidant Activity

Kale is exceptionally rich in antioxidants, including lutein, zeaxanthin, beta-carotene, and flavonoids, which collectively help protect cells from oxidative stress — a key factor in aging and chronic disease development. These plant compounds support the body's defense against free radicals that can damage tissues over time.

Regarding flavonoid bioavailability and antioxidant mechanisms, fermentation of kale juice increased quercetin and kaempferol content, and the fermented juice exhibited notable antioxidant activity and suppressed nitric oxide (NO) production, revealing anti-inflammatory potential.

Evidence Strength: Well-documented in vitro and animal studies; consistent with established phytochemistry. Direct human trials measuring kale-specific antioxidant endpoints are limited but supported by extensive research on individual constituents (quercetin, kaempferol, lutein).

4.5 Eye Health (Age-Related Macular Degeneration, Cataracts)

A large body of evidence shows that lutein has several beneficial effects, especially on eye health. In particular, lutein is known to improve or even prevent age-related macular disease, which is the leading cause of blindness and vision impairment. Many studies have also reported that lutein may have positive effects in different clinical conditions, including decreasing the risk of cancer and improving measures of cardiovascular health.

Lutein exerts an extremely potent antioxidant action by quenching singlet oxygen and scavenging free radicals. Another protective effect consists in the ability to filter blue light, thus reducing phototoxic damage to photoreceptor cells.

Lutein and zeaxanthin protect the retina from the effects of free radicals because they are components of the macula. Kale contains lutein and zeaxanthin, an antioxidant combination that may help reduce the risk of age-related macular degeneration.

Evidence Strength: Strong for the constituent compounds (lutein and zeaxanthin) based on multiple human trials, including the AREDS2 study on macular degeneration supplements. The research supporting the use of lutein and zeaxanthin in eye health is promising, but more research is needed before conclusions can be drawn about their applications. Lutein and zeaxanthin may help improve or reduce the progression of many eye conditions, but research in this area is limited. Kale itself has not been the subject of dedicated ophthalmic clinical trials.

4.6 Gut Microbiome and Gastrointestinal Health

The effects of kale on the composition of the gut microbiome, glycemic control, and cholesterol metabolism have been investigated in scientific reviews.

Animal model evidence shows relevant microbiome effects: compared to a high-fat diet, kale supplementation enhanced several bacterial metabolic functions, including glycan degradation, thiamine metabolism, and xenobiotic metabolism. Findings provide evidence that kale is a functional food that modulates the microbiota and changes in inflammation phenotype.

The benefits of kale are attributed to its abundant glucosinolates, polyphenols, carotenoids, terpenoids, and various indole derivatives. In an acute inflammation mouse model, one key finding was the ability of kale to protect against typical histological markers of inflammation in the mucosa and submucosa; granuloma was markedly absent in the histology samples from mice supplemented with kale before a damaging agent was administered.

Compounds such as sulforaphane and flavonoids (kaempferol, quercetin) not only strengthen the intestinal barrier by regulating the expression of tight junction proteins but also exhibit gastroprotective effects by reducing NSAID-induced gastric mucosal damage.

Evidence Strength: Predominantly preclinical (animal models). Human clinical data on kale's specific impact on gut microbiome composition and function remain sparse.

4.7 Anti-Inflammatory Effects

Research studies have reported different health-beneficial activities of kale, including anti-inflammatory activity, antigenotoxic ability, and gastroprotective activity.

Several studies have observed that lutein (abundant in kale) inhibits both the pro-inflammatory cytokine cascade and the transcription factor NF-κB. There is also compelling evidence that lutein reduces reactive oxygen species (ROS) production, the expression of inducible nitric oxide synthase (iNOS), and the activation of the complement system.

Evidence Strength: Mechanistically well-documented for kale's individual phytochemicals (quercetin, kaempferol, lutein, sulforaphane), primarily from in vitro and animal studies. Human interventional data specifically for kale are limited.

5. Body Systems Associated with Kale

• Cardiovascular system: Blood pressure modulation, LDL/HDL cholesterol improvement, antioxidant protection of vascular endothelium.
• Endocrine/Metabolic system: Blood glucose regulation, insulin resistance reduction, HbA1c improvement in T2D populations.
• Oncological/Chemoprevention: Hormone-related cancers (breast, prostate), gastrointestinal cancers (colon), lung cancer risk reduction (epidemiological data for cruciferous intake).
• Ocular system: Age-related macular degeneration protection, cataract risk reduction via lutein/zeaxanthin accumulation in the macula.
• Gastrointestinal system: Gut microbiome modulation, intestinal barrier integrity, prebiotic fiber effects, gastroprotection.
• Skeletal system: Vitamin K1 (phylloquinone) plays a role in osteocalcin carboxylation and bone mineralization; kale is among the richest dietary sources of vitamin K1.
• Immune system: Anti-inflammatory phytochemicals modulate NF-κB, COX-2, and cytokine cascades.
• Integumentary system (skin): Vitamin C and carotenoids support collagen synthesis and photoprotection.

6. Dosage Forms and Reported Dosages in Clinical Studies

No universal recommended daily intake or pharmacopeial dose has been established for kale as a medicinal agent. The following dosages are drawn from published clinical and research sources:

• Kale juice: 84 subclinical hypertensive patients received 300 ml/day of kale juice for 6 weeks in a Korean clinical study.
• Kale powder (metabolic syndrome study): 80 male and female participants aged 30–74 were studied over 12 weeks; for the first 4 weeks they did not ingest kale powder, and for the final 8 weeks they ingested 14 g of fujiKale per day, typically by mixing the powder into water.
• Freeze-dried kale (T2D RCT): Participants in the intervention group consumed three bars per day, each containing 26.25 g of freeze-dried kale, corresponding to approximately 341 g fresh kale per day, over 12 weeks.
• Isolated I3C (clinical trials): A four-week, double-blind, placebo-controlled trial found that a minimum dose of 300 mg of I3C daily may be necessary to reduce the risk of estrogen-promoted cancers. No official recommended daily allowance (RDA) or daily value has been established for I3C by the FDA or EFSA.
• Dietary I3C (population reference): A typical Japanese diet provides the equivalent of about 112 milligrams (mg) of I3C daily; intake in Western diets is lower.

7. Safety Considerations and Drug Interactions

7.1 Vitamin K and Anticoagulant Medications (Warfarin)

Vitamin K, which plants use in the process of photosynthesis, is found largely in green leafy vegetables — most notably kale, spinach, broccoli, lettuce, and Brussels sprouts. It is an essential cofactor used by the liver to "activate" the clotting factors it releases into the blood.

Vitamin K opposes warfarin's anticoagulant effect, so dramatic changes in kale intake can affect INR levels. Sudden large increases in kale intake can lower INR (less anticoagulation); sudden decreases can raise it. People taking these medicines can safely eat these vegetables with a general precaution: eating a relatively consistent amount from day to day can allow one's physician to adjust the dose of medication to balance the dietary intake of vitamin K, and should not interfere with the anticoagulant medication's effectiveness.

A systematic review of literature (to October 2015) including two dietary interventional trials and nine observational studies found conflicting evidence on the effect of dietary intake of vitamin K on coagulation response. Some studies found a negative correlation between vitamin K intake and INR changes, while others suggested that a minimum amount of vitamin K is required to maintain adequate anticoagulation. An effect on coagulation may be detected only for high vitamin K intake (>150 μg/day).

Newer anticoagulants (DOACs such as apixaban and rivaroxaban) are not affected by vitamin K and have no kale interaction.

7.2 Goitrogens and Thyroid Function

A concern has been the goitrogen content of kale and other cruciferous vegetables. Goitrogens are naturally occurring substances, sometimes referred to as "anti-nutrients," that can block iodine from being used by the thyroid. Iodine is a trace mineral needed by the body to make thyroid hormones that promote normal metabolism; a deficiency of iodine can lead to goiter or enlargement of the thyroid.

Raw kale contains goitrogens, which can interfere with iodine absorption, but cooking the kale substantially reduces this effect. This is primarily a concern in individuals with existing thyroid conditions or those consuming very large daily quantities of raw kale.

7.3 Oxalates and Kidney Stone Risk

People with a history of calcium-oxalate kidney stones should consume modest amounts; pairing with calcium-rich foods can mitigate oxalate absorption. Anti-nutritional factors such as oxalates, tannins, and phytate are present in higher concentrations in kale and may impair mineral absorption in high-intake scenarios.

7.4 Potassium and ACE Inhibitor / ARB Interactions

The high potassium content in kale could be a concern for individuals taking certain blood pressure medications (such as ACE inhibitors) that can increase potassium levels. This is relevant for patients with chronic kidney disease or those on potassium-sparing agents.

7.5 General Tolerability

In the 8-week kale powder intervention study, no safety concerns were identified regarding kale powder. In clinical trials of I3C/DIM supplements derived from cruciferous sources, these supplement doses have elicited few if any adverse effects. High-fiber intake in individuals not accustomed to it may cause transient gastrointestinal symptoms.

7.6 Bioavailability Considerations

Isothiocyanates are about six times more bioavailable than glucosinolates, which must first be hydrolyzed. Thorough chewing of fresh vegetables exposes glucosinolates to plant myrosinase and significantly increases bioavailable dithiocarbamate excretion. Cooking, particularly boiling, inactivates myrosinase and reduces isothiocyanate generation, though gut bacteria can partially compensate.

References

• Nutritional, Therapeutic, and Functional Food Perspectives of Kale (Brassica oleracea var. acephala): An Integrative Review — PMC/Molecules (2025)
• Kale: Review on nutritional composition, bio-active compounds, anti-nutritional factors, health beneficial properties and value-added products — Cogent Food & Agriculture (2020)
• Kale — Wikipedia
• Sulforaphane in Cancer Prevention and Therapy: A State-of-the-Art Review — PMC (2025)
• Potential mechanisms of cancer prevention and treatment by sulforaphane — Molecular Medicine, Springer (2024)
• Mechanisms of Action of Isothiocyanates in Cancer Chemoprevention: An Update — PMC (2011)
• Dietary Isothiocyanates: Novel Insights into the Potential for Cancer Prevention and Therapy — PubMed (2023)
• Analysis of Effects of Kale Powder Consumption among Subjects with Potential Metabolic Syndrome: A Prospective Single-Arm Clinical Study — Journal of Hypertension and Cardiology (2016)
• The effect of glutathione S-transferase M1 and T1 polymorphisms on blood pressure, blood glucose, and lipid profiles following kale juice supplementation in South Korean subclinical hypertensive patients — PubMed (2015)
• The molecular mechanism of the cholesterol-lowering effect of dill and kale — PMC (2017)
• Beneficial Effects of a Freeze-Dried Kale Bar on Type 2 Diabetes Patients: A Randomized, Double-Blinded, Placebo-Controlled Clinical Trial — PMC/Nutrients (2024)
• The Effect of Lutein on Eye and Extra-Eye Health — PMC (2018)
• Kale Attenuates Inflammation and Modulates Gut Microbial Composition and Function in C57BL/6J Mice with Diet-Induced Obesity — PMC (2021)
• The Vegetable 'Kale' Protects against DSS-Induced Acute Inflammation through Moderating LPS-Producing Bacterial Taxa — PMC (2023)
• Synergistic Antioxidant and Anti-Inflammatory Activities of Kale Juice Fermented with Limosilactobacillus — PMC (2023)
• Interaction Between Dietary Vitamin K Intake and Anticoagulation by Vitamin K Antagonists: Is It Really True? A Systematic Review — PMC (2016)
• Attenuation of Carcinogenesis by the Influence of Indole-3-carbinol and Its Metabolite 3,3′-Diindolylmethane — PMC (2014)
• Indoles Derived From Glucobrassicin: Cancer Chemoprevention by I3C and DIM — PMC (2021)
• Indole-3-Carbinol — Linus Pauling Institute, Oregon State University
• Kale — The Nutrition Source, Harvard T.H. Chan School of Public Health
• Anticancer Activity of Sulforaphane: The Epigenetic Mechanisms and the Nrf2 Signaling Pathway — PMC (2018)