# Grünkohl (Brassica oleracea var. sabellica)

**Canonical URL:** https://ingredients.hermeticasuperfoods.com/ingredients/gr-nkohl
**Data Source:** Hermetica Superfoods Ingredient Encyclopedia
**Updated:** 2026-03-28
**Evidence Score:** 2 / 10
**Category:** Vegetable
**Also Known As:** Kale, Curly kale, Scotch kale, Winter kale, Borecole, Leaf cabbage, German greens, Brassica oleracea var. acephala, Cow cabbage, Kitchen kale

## Overview

Kale (Grünkohl) contains glucosinolates that metabolize into bioactive isothiocyanates with [antioxidant](/ingredients/condition/antioxidant) properties. The vegetable provides exceptionally high fiber content at 43.9g per 100g in powder form, supporting [digestive health](/ingredients/condition/gut-health) through improved gut microbiota.

## Health Benefits

• Rich source of glucosinolates (2.25-93.90 μmol/g DW) which produce isothiocyanates with potential [antioxidant activity](/ingredients/condition/antioxidant) (compositional analysis only, no clinical trials)
• Contains high dietary fiber content (43.9 g/100 g in powder form) supporting [digestive health](/ingredients/condition/gut-health) (nutritional data only, no clinical evidence)
• Provides carotenoids including β-carotene, lutein, and zeaxanthin important for eye health (compositional data only, no human studies)
• Source of phenolic compounds (7.89 mg/g DW) including quercetin and kaempferol with antioxidant potential (analytical data only, no clinical validation)
• Contains vitamins C and E contributing to antioxidant defense systems (compositional analysis only, no intervention studies)

## Mechanism of Action

Kale's glucosinolates (2.25-93.90 μmol/g dry weight) undergo enzymatic hydrolysis by myrosinase to produce isothiocyanates. These compounds activate the Nrf2 pathway, enhancing cellular [antioxidant](/ingredients/condition/antioxidant) defenses through upregulation of [phase II detox](/ingredients/condition/detox)ification enzymes. The high fiber content promotes beneficial gut bacteria growth and improves intestinal barrier function.

## Clinical Summary

Current evidence for kale is limited to compositional analyses rather than controlled clinical trials. Laboratory studies have quantified glucosinolate content and identified isothiocyanate formation, but human intervention studies are lacking. Nutritional analyses confirm the exceptional fiber content, though clinical validation of [digestive health](/ingredients/condition/gut-health) benefits requires controlled trials. The [antioxidant](/ingredients/condition/antioxidant) potential remains theoretical pending human studies.

## Nutritional Profile

Grünkohl (Brassica oleracea var. sabellica) is a nutrient-dense leafy vegetable with the following approximate composition per 100g fresh weight unless noted: Macronutrients: Energy 35-49 kcal, Protein 2.9-4.3g (containing all essential amino acids, notably lysine and leucine), Carbohydrates 4.4-8.8g, Dietary Fiber 2.0-3.6g fresh weight (43.9g/100g in dried powder form), Fat 0.5-1.5g (including alpha-linolenic acid ~0.18g). Vitamins: Vitamin C 41-120mg (high but significantly reduced by cooking, up to 50-60% loss during boiling), Vitamin K1 389-817μg (exceptionally high; bioavailability enhanced by co-consumption with dietary fat), Vitamin A activity from β-carotene 241-500μg RAE, Folate (B9) 62-141μg, Vitamin B6 0.27-0.34mg, Vitamin E (α-tocopherol) 0.66-1.54mg, Riboflavin (B2) 0.13mg, Thiamine (B1) 0.11mg. Minerals: Calcium 135-254mg (bioavailability partially limited by oxalates, estimated absorption ~49% vs ~32% for spinach), Potassium 228-491mg, Phosphorus 55-92mg, Magnesium 34-47mg, Iron 1.0-1.7mg (non-heme; absorption enhanced by co-ingested vitamin C), Manganese 0.66-0.92mg, Zinc 0.39-0.56mg, Copper 0.29mg, Selenium 0.9-1.3μg. Bioactive Compounds: Glucosinolates 2.25-93.90μmol/g DW (primary compounds: glucoraphanin, sinigrin, glucobrassicin, gluconapin; converted to bioactive isothiocyanates such as sulforaphane and allyl-ITC via myrosinase enzyme activity; cooking reduces myrosinase activity but gut microbiota can partially compensate), Carotenoids total 15-45mg/100g DW including β-carotene 8-18mg, lutein 21-40mg, zeaxanthin ~2mg (fat-soluble; bioavailability significantly increased with lipid co-consumption), Polyphenols total 900-1200mg GAE/100g DW including flavonoids (kaempferol, quercetin glycosides, isorhamnetin ~34-110mg/100g DW), hydroxycinnamic acids (sinapic acid, ferulic acid), Chlorophyll 1.5-3.0mg/g DW. Antinutrients: Oxalic acid ~0.1-0.2g/100g fresh weight (lower than spinach, moderate impact on mineral binding), Phytic acid present at low-moderate levels. Bioavailability Notes: Fat-soluble vitamins (K, A, E) and carotenoids require dietary fat for absorption; steaming is preferred over boiling to preserve water-soluble vitamins and glucosinolates; raw consumption maximizes myrosinase-mediated isothiocyanate conversion; [calcium absorption](/ingredients/condition/bone-health) estimated at ~40-49% due to moderate oxalate content.

## Dosage & Preparation

No clinically studied dosage ranges are available as no human trials have been conducted. Kale powder is commercially available with granulometry >95% through 40 mesh, but no standardization or therapeutic dosing has been established through research. Consult a healthcare provider before starting any new supplement.

## Safety & Drug Interactions

Kale is generally safe for most people when consumed as food. High vitamin K content may interact with warfarin and other anticoagulant medications, requiring monitoring of INR levels. Goitrogenic compounds in raw kale may interfere with [thyroid function](/ingredients/condition/hormonal) in susceptible individuals, particularly those with iodine deficiency. Pregnant and breastfeeding women can safely consume kale as part of a normal diet.

## Scientific Research

No human clinical trials, RCTs, or meta-analyses specifically on kale (Brassica oleracea var. sabellica) or Grünkohl were found in the research results. Available data focus solely on compositional analysis, bioactive compound identification, and plant [stress response](/ingredients/condition/stress) studies examining glucosinolate content under various growing conditions.

## Historical & Cultural Context

Kale has been cultivated in Europe, including Germany where it is known as Grünkohl, as a traditional leafy vegetable in diets for centuries. It belongs to Brassica oleracea cultivars used for edible leaves, though no specific use in formalized traditional medicine systems has been documented.

## Synergistic Combinations

Vitamin D, Selenium, Turmeric, Omega-3 fatty acids, [Probiotic](/ingredients/condition/gut-health)s

## Frequently Asked Questions

### How much glucosinolates are in kale?

Kale contains 2.25-93.90 μmol/g of glucosinolates on a dry weight basis, with significant variation depending on cultivar and growing conditions. These compounds are converted to bioactive isothiocyanates when the plant tissue is damaged during chewing or processing.

### Does kale interfere with blood thinners?

Yes, kale is high in vitamin K which can reduce the effectiveness of warfarin and similar anticoagulant medications. Patients on blood thinners should maintain consistent kale intake and have their INR levels monitored regularly by their healthcare provider.

### Can kale affect thyroid function?

Raw kale contains goitrogenic compounds that may interfere with thyroid hormone production, particularly in people with existing thyroid conditions or iodine deficiency. Cooking kale reduces these compounds, and moderate consumption is typically safe for healthy individuals.

### What is the fiber content of kale powder?

Kale powder contains approximately 43.9g of dietary fiber per 100g, making it an exceptionally concentrated source. This high fiber content supports digestive health by promoting beneficial gut bacteria and improving bowel regularity.

### Are there clinical studies on kale supplements?

Currently, there are no published clinical trials specifically testing kale supplements in humans. The available evidence consists primarily of compositional analyses and laboratory studies identifying bioactive compounds like glucosinolates and their metabolites.

### What is the difference between fresh kale and kale powder supplements?

Fresh kale provides glucosinolates and nutrients in their native form with complete food matrix synergies, while kale powder concentrates these compounds but may lose some heat-sensitive vitamins during processing. Kale powder offers standardized dosing and longer shelf stability, making it more convenient for consistent supplementation. However, fresh kale retains more vitamin C and volatile compounds that may be degraded during drying and powdering.

### Is kale supplementation safe for people taking warfarin or other anticoagulants?

Kale contains high levels of vitamin K, which can reduce the effectiveness of warfarin and similar anticoagulants by promoting blood clotting. People taking anticoagulants should maintain consistent kale intake (whether fresh or supplemental) rather than avoiding it completely, and must work with their healthcare provider to monitor INR levels. Sudden increases in kale supplementation can interfere with medication efficacy and may require dose adjustments.

### Who benefits most from kale supplementation—is it for everyone?

Individuals with limited vegetable intake, those seeking concentrated antioxidant support, and people interested in phytonutrient supplementation are primary candidates for kale supplements. However, people with thyroid conditions, those on anticoagulant therapy, or individuals with kidney disease should consult healthcare providers before supplementing due to kale's iodine content and mineral profile. Healthy adults eating varied diets can typically obtain sufficient kale phytonutrients from whole food sources.

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*Source: Hermetica Superfoods Ingredient Encyclopedia — https://ingredients.hermeticasuperfoods.com*
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