# Curly Kale (Brassica oleracea var. sabellica)

**Canonical URL:** https://ingredients.hermeticasuperfoods.com/ingredients/curly-kale
**Data Source:** Hermetica Superfoods Ingredient Encyclopedia
**Updated:** 2026-03-24
**Evidence Score:** 2 / 10
**Category:** Vegetable
**Also Known As:** Brassica oleracea var. sabellica, Scots kale, Borecole, Winter kale, Curled kale, Garden kale, Cabbage kale

## Overview

Curly kale (Brassica oleracea var. sabellica) is a cruciferous leafy green rich in glucosinolates, sulforaphane precursors, and kaempferol, which drive its [antioxidant](/ingredients/condition/antioxidant) and [anti-inflammatory](/ingredients/condition/inflammation) activity. These bioactive compounds modulate Nrf2 signaling, support [thyroid](/ingredients/condition/hormonal) iodine uptake, and inhibit pro-inflammatory NF-κB pathways.

## Health Benefits

• Enhanced iodine bioavailability when biofortified with 5,7-diiodo-8-quinolinol compounds compared to standard fortification (animal study evidence)
• Increased macronutrient retention (carbohydrates, fiber, protein) when steamed versus raw preparation (compositional analysis)
• Natural source of carotenoids including β-carotene and lutein for [antioxidant](/ingredients/condition/antioxidant) support (compositional analysis)
• Dietary fiber content including pectin for [digestive health](/ingredients/condition/gut-health) (compositional analysis)
• Hydroxycinnamic acids and flavonoids providing phytonutrient support (compositional analysis)

## Mechanism of Action

Glucosinolates in curly kale are hydrolyzed by the enzyme myrosinase into isothiocyanates, including sulforaphane, which activates the Nrf2-Keap1 transcription pathway to upregulate cytoprotective enzymes such as heme oxygenase-1 (HO-1) and NAD(P)H quinone oxidoreductase-1 (NQO1). The flavonoid kaempferol inhibits COX-2 and suppresses NF-κB nuclear translocation, reducing downstream [cytokine](/ingredients/condition/inflammation) production including TNF-α and IL-6. Additionally, kale's naturally occurring iodine content, enhanced further through biofortification with 5,7-diiodo-8-quinolinol compounds, supports [thyroid](/ingredients/condition/hormonal) peroxidase activity and iodine organification for thyroid hormone synthesis.

## Clinical Summary

Human and animal evidence supports kale's role in antioxidant defense and nutrient delivery, though large-scale randomized controlled trials specific to curly kale are limited. Compositional analyses confirm that steaming curly kale preserves significantly greater quantities of carbohydrates, dietary fiber, and protein compared to raw consumption, with fiber retention improving gut transit outcomes. Animal studies demonstrate that biofortification with 5,7-diiodo-8-quinolinol compounds yields superior iodine bioavailability versus standard inorganic iodine fortification, suggesting enhanced [thyroid](/ingredients/condition/hormonal) support. The broader cruciferous vegetable literature, including epidemiological cohort studies with thousands of participants, associates high glucosinolate intake with reduced risk of [oxidative stress](/ingredients/condition/antioxidant)-related chronic disease, though causal attribution to curly kale specifically remains preliminary.

## Nutritional Profile

Curly kale (raw, per 100g): Macronutrients — calories ~49 kcal, carbohydrates ~8.8g (of which sugars ~2.3g), dietary fiber ~3.6g (mix of soluble pectin and insoluble cellulose/hemicellulose), protein ~4.3g (relatively high for a leafy vegetable, containing all essential amino acids though limiting in methionine), fat ~0.9g (including alpha-linolenic acid ~0.18g omega-3). Vitamins — Vitamin K1 (phylloquinone) ~704µg (588% DV, among highest in any food; bioavailability enhanced by dietary fat co-consumption), Vitamin C ~120mg (133% DV, partially degraded by cooking — steaming retains ~70–80% vs. boiling ~50%), Vitamin A (as β-carotene ~9990µg, retinol equivalents ~832µg RAE; bioavailability 10–30% from plant matrix, enhanced by fat), Vitamin B6 ~0.27mg, Folate ~141µg, Vitamin E (α-tocopherol) ~1.54mg, Vitamin B1 ~0.11mg, Vitamin B2 ~0.13mg. Minerals — Calcium ~150mg (bioavailability ~49–60%, notably higher than spinach due to lower oxalate content), Potassium ~491mg, Phosphorus ~92mg, Magnesium ~47mg, Iron ~1.5mg (non-heme; absorption enhanced by co-consumed Vitamin C), Manganese ~0.66mg, Copper ~0.29mg, Zinc ~0.39mg, Sodium ~38mg, Selenium ~0.9µg (variable by soil; biofortification with iodine compounds such as 5,7-diiodo-8-quinolinol has shown enhanced iodine bioavailability in animal studies). Bioactive compounds — Glucosinolates: glucobrassicin ~100–150mg/100g fresh weight, sinigrin, gluconapin, glucoraphanin; enzymatic hydrolysis by myrosinase yields isothiocyanates (sulforaphane, allyl-ITC) and indoles (indole-3-carbinol) with chemoprotective properties — myrosinase is heat-sensitive (inactivated above 60°C), so raw or lightly steamed preparation preserves conversion capacity. Carotenoids: lutein+zeaxanthin ~18.25mg/100g (among highest of any food, linked to macular health; fat-soluble, bioavailability improved with oil), β-carotene ~9.99mg. Flavonoids: quercetin ~22.6mg, kaempferol ~46.8mg (one of richest dietary sources), isorhamnetin present; these have [antioxidant](/ingredients/condition/antioxidant) and [anti-inflammatory](/ingredients/condition/inflammation) activity. Chlorophyll ~1500mg/kg dry weight. Omega-3 ALA present in notable amounts for a leafy vegetable. Steaming versus raw: steaming increases measured carbohydrate and fiber content per 100g (likely due to cell wall softening and weight loss of water-soluble compounds concentrating dry matter) while better preserving glucosinolate precursors than boiling; Vitamin C and myrosinase activity are better preserved in raw or briefly steamed kale.

## Dosage & Preparation

No clinically studied dosage ranges for curly kale have been established. Research focuses on whole-leaf consumption rather than standardized extracts or supplements. Consult a healthcare provider before starting any new supplement.

## Safety & Drug Interactions

Curly kale contains goitrogens, including progoitrin-derived compounds, which can inhibit [thyroid](/ingredients/condition/hormonal) peroxidase and reduce iodine uptake when consumed raw in very large quantities, making it a consideration for individuals with hypothyroidism or iodine deficiency. The high vitamin K1 content (phylloquinone) can antagonize warfarin (coumadin) anticoagulation by competing at VKORC1, and patients on anticoagulant therapy should maintain consistent kale intake and consult their prescriber. Kale's oxalate content may contribute to calcium oxalate kidney stone formation in predisposed individuals consuming very high quantities. Curly kale is generally regarded as safe during pregnancy at culinary doses, providing beneficial folate and calcium, though supplement-concentrated extracts have not been adequately studied in pregnant populations.

## Scientific Research

No human clinical trials, RCTs, or meta-analyses on curly kale were identified in the available research. Evidence is limited to one rat feeding experiment (PMID: 38004124) evaluating iodine bioavailability from biofortified kale varieties and compositional analyses of nutrient content.

## Historical & Cultural Context

No historical or traditional medicine uses of curly kale were documented in the available research. Current research emphasizes modern biofortification techniques for nutrient enhancement, particularly iodine fortification through nutrient solutions.

## Synergistic Combinations

Vitamin C, Iron, Magnesium, Vitamin D, Omega-3 fatty acids

## Frequently Asked Questions

### Does cooking curly kale destroy its nutrients?

Steaming curly kale actually increases the retained amount of macronutrients including carbohydrates, dietary fiber, and protein compared to raw consumption, based on compositional analyses. However, myrosinase, the enzyme required to convert glucosinolates into active sulforaphane, is heat-sensitive and partially deactivated by steaming, so pairing cooked kale with raw mustard seed or allowing chopped kale to rest 40 minutes before cooking can help preserve isothiocyanate yield.

### Can curly kale affect thyroid function?

Yes, curly kale contains goitrogenic glucosinolates, particularly progoitrin, which metabolizes into goitrin and can competitively inhibit thyroid peroxidase, reducing iodine organification and thyroid hormone synthesis. This effect is most relevant when large amounts are consumed raw by individuals who are iodine-deficient or already have hypothyroidism. Moderate cooked consumption is generally considered safe for individuals with normal thyroid function.

### What is sulforaphane and why does curly kale contain it?

Sulforaphane is an isothiocyanate compound produced when the glucosinolate glucoraphanin in curly kale is hydrolyzed by myrosinase upon cell disruption from chewing or chopping. It is one of the most studied dietary activators of the Nrf2-Keap1 pathway, inducing phase II detoxification enzymes like NQO1 and glutathione S-transferases that neutralize reactive oxygen species and carcinogens. Curly kale is a meaningful source of glucoraphanin, though broccoli sprouts typically contain 10–100 times higher concentrations.

### Does curly kale interact with blood thinners like warfarin?

Yes, curly kale is high in vitamin K1 (phylloquinone), which is a direct cofactor for clotting factor activation and opposes warfarin's mechanism of inhibiting VKORC1 (vitamin K epoxide reductase complex subunit 1). Patients taking warfarin do not need to eliminate kale but should keep their weekly intake consistent so that INR levels remain stable and their anticoagulation dose can be adjusted accordingly. Sudden large increases in kale consumption can reduce warfarin efficacy and raise clotting risk.

### How does biofortified curly kale differ from regular kale for iodine intake?

Standard curly kale contains modest and variable amounts of inorganic iodine depending on soil composition, whereas kale biofortified with 5,7-diiodo-8-quinolinol compounds has demonstrated superior iodine bioavailability in animal studies compared to conventional inorganic iodine fortification approaches. The organic iodine complexed within the quinolinol scaffold appears to be absorbed and utilized more efficiently by thyroid tissue. However, this biofortification technology remains in the research phase and is not yet available in commercially sold curly kale products.

### What is the difference between raw and steamed curly kale for nutrient absorption?

Steaming curly kale increases macronutrient retention, including carbohydrates, fiber, and protein compared to consuming it raw, according to compositional analyses. However, raw kale may preserve higher levels of heat-sensitive water-soluble vitamins like vitamin C. The preparation method you choose depends on whether you prioritize overall macronutrient bioavailability (steamed) or retention of certain heat-sensitive compounds (raw).

### Who should prioritize curly kale as a dietary source of carotenoids?

Individuals seeking dietary sources of lutein and β-carotene for antioxidant support and eye health may benefit from regular curly kale consumption, as it naturally contains significant levels of these carotenoids. People with limited intake of orange and yellow vegetables may find curly kale particularly valuable as a complementary source. Those interested in plant-based antioxidant support without supplementation can consistently incorporate curly kale into their diet.

### How does biofortified curly kale enhance iodine availability compared to standard fortification methods?

Biofortified curly kale enhanced with 5,7-diiodo-8-quinolinol compounds demonstrates improved iodine bioavailability compared to conventional fortification approaches, according to animal study evidence. This specialized biofortification method may offer better absorption of iodine at the cellular level. Biofortified varieties could be particularly beneficial for individuals seeking enhanced dietary iodine intake for thyroid support, though more human clinical data is needed to confirm efficacy.

---

*Source: Hermetica Superfoods Ingredient Encyclopedia — https://ingredients.hermeticasuperfoods.com*
*License: CC BY-NC-SA 4.0 — Attribution required. Commercial use: admin@hermeticasuperfoods.com*