NutriDex

The Supplement Research Compendium
🥬

kale

Vitamin-K-dense cruciferous leafy green with cardiometabolic, ocular, and cognitive signals

Moderate evidence 🥦Vegetables

✚ Updated · How we grade evidence

Evidence tier
Moderate
Research weight
Citations
9 verified / 9
Classification
Vegetables
❝
What the evidence says. Several controlled trials; effects real but modest or context-dependent.

Nutrition per serving 1 cup chopped, raw (67 g)

67gSERVING
  • Sugars 0.7 g1%
  • Fibre 2.7 g4%
  • Protein 1.9 g3%
  • Other 61.7 g92%
What's in one serving, by weight — average composition (USDA).
Vitamin C69%Fiber10%Potassium5%Folate10%Vitamin A18%Vitamin K100%+Vitamin B66%Manganese27%
One serving as % of the adult daily requirement (FDA Daily Values). The bold outer ring = 100% of a day's needs.
23 kcal1.9 g protein2.7 g fiber0.7 g sugar
NutrientPer serving% daily value
Vitamin C62 mg69%
Fiber2.7 g10%
Potassium233 mg5%
Folate42 µg10%
Vitamin A161 µg18%
Vitamin K261 µg217%
Vitamin B60.1 mg6%
Manganese0.62 mg27%
Copper0.03 mg4%
Vitamin E0.45 mg3%
Magnesium22 mg5%
Calcium170 mg13%

Composition data: USDA FoodData Central ↗

What is kale?

kale is a vegetable used for kale juice raised hdl and lowered ldl cholesterol in a 12-week rct in hypercholesterolemic men. NutriDex grades the human evidence as Moderate. Direct randomized human evidence for kale itself is limited but supportive: a 12-week RCT in hypercholesterolemic men found 150 mL/day of kale juice raised HDL-cholesterol ~27% and lowered LDL ~10%. The bulk of strong evidence comes from kale's food family and signature bioactives—cruciferous-vegetable cohorts and meta-analyses link higher intake to lower cardiovascular disease, total mortality, and colorectal cancer risk, while green-leafy intake tracks with markedly slower cognitive decline. Kale is one of the richest dietary sources of vitamin K, lutein/zeaxanthin (eye-protective in the AREDS2 trial), and glucosinolate precursors of sulforaphane. Most outcome data are observational and confounded by overall healthy lifestyle, so effects on hard endpoints remain associational rather than proven causal.

Purported Benefits

✓Kale juice raised HDL and lowered LDL cholesterol in a 12-week RCT in hypercholesterolemic men
✓Higher cruciferous/leafy-green intake associated with lower cardiovascular disease incidence and mortality
✓Cruciferous intake linked to reduced colorectal cancer risk in dose-response meta-analyses
✓Daily green-leafy intake tied to substantially slower age-related cognitive decline
✓Rich source of lutein/zeaxanthin, supporting macular health (AREDS2)
✓Exceptional vitamin K, vitamin C, and provitamin-A carotenoid density at very low calories

Dosing & Compounds

Typical Dose
Standard serving: 1 cup chopped, raw (67 g). Eat whole (with skin where edible); favour whole fruit over juice.
Active Compounds
Glucosinolates (glucoraphanin, glucobrassicin)Sulforaphane (isothiocyanate)Indole-3-carbinolLutein and zeaxanthin (xanthophyll carotenoids)Beta-caroteneQuercetin and kaempferol (flavonols)Vitamin K1 (phylloquinone)Vitamin C (ascorbic acid)

Safety & Cautions

Very high vitamin K1 can destabilize INR in patients on warfarin—keep intake consistent and coordinate with anticoagulation monitoring. As a raw cruciferous vegetable, kale contains goitrogenic glucosinolates that may modestly affect thyroid iodine uptake when consumed raw in very large amounts (cooking reduces this); relevant mainly with marginal iodine status. Contains moderate oxalate (caution with calcium-oxalate kidney stones) and FODMAPs that can cause gas/bloating in sensitive individuals. Generally very safe within normal dietary amounts. Educational only — always check with your doctor or pharmacist before combining kale with any medicine.

Key Studies

Meta-analysis Li Q 2025 ✓ Full text
Dose-response meta-analysis found a nonlinear inverse association between cruciferous vegetable intake and colorectal/colon cancer risk, with significant risk reduction emerging at >=20 g/day.
Meta-analysis Sulforaphane-broccoli sprout meta-analysis 2022 ✓ Full text
Meta-analysis of 10 clinical trials found broccoli-sprout (sulforaphane) intake significantly reduced systolic blood pressure (-10.9 mmHg, 95% CI -17.0 to -4.86) and improved other cardiometabolic markers.
Meta-analysis Pollock 2016 ✓ Full text
Meta-analysis of 8 prospective studies (>540,000 participants, 26,173 CVD cases) found highest vs lowest green-leafy/cruciferous vegetable intake associated with a 15.8% lower CVD incidence (RR 0.842, 95% CI 0.753-0.941).
RCT Bjornshave 2024 ✓ PubMed
In a 12-week double-blind RCT (n=30 type 2 diabetes patients), three daily bars of freeze-dried kale (26.25 g each) significantly reduced HbA1c, HOMA-IR, body weight and caloric intake versus placebo, with a non-significant downward trend in LDL-cholesterol.
RCT Al-Daghri 2024 ✓ PubMed
In a cross-over RCT of 124 Saudi women with obesity, 3 g freeze-dried kale thrice daily produced significant weight reduction (p=0.02) and favorable metabolic/anthropometric changes, though freeze-dried pea was superior for acute glycemic control.
RCT AREDS2 Research Group (Chew) 2013 ✓ Source
In 4,203 participants at risk of advanced AMD, lutein/zeaxanthin supplementation reduced progression to late AMD versus no lutein/zeaxanthin (HR 0.90, 95% CI 0.82-0.99 in those with lowest dietary intake).
RCT Kim SY 2008 ✓ PubMed
In 32 hypercholesterolemic men, 150 mL/day kale juice for 12 weeks raised HDL-cholesterol by 27% (P<0.0001) and lowered LDL-cholesterol by 10% (P=0.0007).
Prospective cohort Morris MC 2018 ✓ Source
In 960 older adults followed ~5 years, the highest green-leafy-vegetable intake (median 1.3 servings/day) was associated with slower cognitive decline (beta=0.05 standardized units/year; P=0.0001), equivalent to being 11 years younger.
Prospective cohort Zhang X 2011 ✓ PubMed
In 134,796 Chinese adults, cruciferous vegetable intake was inversely associated with total mortality (highest vs lowest quintile HR ~0.86 men, ~0.89 women) and cardiovascular mortality.
9 sources cited · 9 verified Search all studies on PubMed ↗

Common questions about kale

What is kale used for?

kale is most often taken for Kale juice raised HDL and lowered LDL cholesterol in a 12-week RCT in hypercholesterolemic men, Higher cruciferous/leafy-green intake associated with lower cardiovascular disease incidence and mortality, Cruciferous intake linked to reduced colorectal cancer risk in dose-response meta-analyses, Daily green-leafy intake tied to substantially slower age-related cognitive decline. Vitamin-K-dense cruciferous leafy green with cardiometabolic, ocular, and cognitive signals

Does kale work — what does the evidence say?

Moderate evidence. Several controlled trials; effects real but modest or context-dependent. Direct randomized human evidence for kale itself is limited but supportive: a 12-week RCT in hypercholesterolemic men found 150 mL/day of kale juice raised HDL-cholesterol ~27% and lowered LDL ~10%. The bulk of strong evidence comes from kale's food family and signature bioactives—cruciferous-vegetable cohorts and meta-analyses link higher intake to lower cardiovascular disease, total mortality, and colorectal cancer risk, while green-leafy intake tracks with markedly slower cognitive decline. Kale is one of the richest dietary sources of vitamin K, lutein/zeaxanthin (eye-protective in the AREDS2 trial), and glucosinolate precursors of sulforaphane. Most outcome data are observational and confounded by overall healthy lifestyle, so effects on hard endpoints remain associational rather than proven causal.

What is the typical dose of kale?

Standard serving: 1 cup chopped, raw (67 g). Eat whole (with skin where edible); favour whole fruit over juice.

Is kale safe? Any cautions or side effects?

Very high vitamin K1 can destabilize INR in patients on warfarin—keep intake consistent and coordinate with anticoagulation monitoring. As a raw cruciferous vegetable, kale contains goitrogenic glucosinolates that may modestly affect thyroid iodine uptake when consumed raw in very large amounts (cooking reduces this); relevant mainly with marginal iodine status. Contains moderate oxalate (caution with calcium-oxalate kidney stones) and FODMAPs that can cause gas/bloating in sensitive individuals. Generally very safe within normal dietary amounts.

How many studies support kale?

NutriDex cites 9 sources for kale, graded "Moderate".

Cite this page
APA

Peh, D. (2026). kale: Benefits, Dosage, Side Effects & Evidence. NutriDex — The Supplement Research Compendium. Retrieved 26 Jun 2026, from https://nutridex.info/s/kale

BibTeX
@misc{nutridex_kale,
  author       = {Peh, Daryl},
  title        = {kale: Benefits, Dosage, Side Effects \& Evidence},
  year         = {2026},
  howpublished = {NutriDex --- The Supplement Research Compendium},
  url          = {https://nutridex.info/s/kale},
  note         = {Reviewed by Dr Daryl Peh, MBBS Singapore, MMed FM. Accessed 2026-06-26}
}

For medical claims, citing the underlying primary studies linked above is preferred. NutriDex is an educational reference, not medical advice.

← Back to the full dex · All substances