NutriDex

The Supplement Research Compendium
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Collard Greens

A calcium- and vitamin K-dense Southern cruciferous green with cardiometabolic and cognitive upside.

Moderate evidence 🥦Vegetables

✚ Updated · How we grade evidence

Evidence tier
Moderate
Research weight
Citations
11 verified / 11
Classification
Vegetables
❝
What the evidence says. Several controlled trials; effects real but modest or context-dependent.

Nutrition per serving 1 cup chopped, raw (36 g)

36gSERVING
  • Sugars 0.2 g0%
  • Fibre 1.4 g4%
  • Other carbs 0.3 g1%
  • Protein 1.1 g3%
  • Other 33 g92%
What's in one serving, by weight — average composition (USDA).
Vitamin C14%Fiber5%Potassium2%Folate12%Vitamin A10%Vitamin K100%+Vitamin B63%Manganese10%
One serving as % of the adult daily requirement (FDA Daily Values). The bold outer ring = 100% of a day's needs.
12 kcal1.1 g protein1.4 g fiber0.17 g sugar
NutrientPer serving% daily value
Vitamin C13 mg14%
Fiber1.4 g5%
Potassium77 mg2%
Folate46 µg12%
Vitamin A90 µg10%
Vitamin K157 µg131%
Vitamin B60.06 mg3%
Manganese0.24 mg10%
Copper0.02 mg2%
Vitamin E0.81 mg5%
Magnesium9.7 mg2%
Calcium84 mg6%

Composition data: USDA FoodData Central ↗

What is Collard Greens?

Collard Greens is a vegetable used for lowers blood pressure (rct evidence). NutriDex grades the human evidence as Moderate. Collard greens are a glucosinolate-rich cruciferous vegetable and one of the densest plant sources of vitamin K and bioavailable calcium. Human evidence for the cruciferous family is robust: randomized crossover trials show cruciferous vegetables lower blood pressure, while large meta-analyses and prospective cohorts link higher intake to reduced cardiovascular and colorectal-cancer risk. Green leafy vegetables specifically are associated with markedly slower cognitive decline in older adults.

Purported Benefits

✓Lowers blood pressure (RCT evidence)
✓Associated with reduced cardiovascular mortality
✓Linked to lower colorectal cancer risk
✓Supports slower cognitive decline
✓Rich in vitamin K and calcium for bone health

Dosing & Compounds

Typical Dose
Standard serving: 1 cup chopped, raw (36 g). Eat whole (with skin where edible); favour whole fruit over juice.
Active Compounds
glucosinolates (glucobrassicin)sulforaphane / isothiocyanateslutein & zeaxanthinvitamin K1 (phylloquinone)kaempferolbeta-carotenenitrate

Safety & Cautions

Very high vitamin K (~157 ug per cup raw, far more when cooked-concentrated) can antagonize warfarin — keep intake consistent if anticoagulated. Raw cruciferous goitrogens may modestly affect thyroid in iodine-deficient individuals; cooking reduces this. Contains moderate oxalate and some FODMAPs. Generally very safe as food. Educational only — always check with your doctor or pharmacist before combining Collard Greens with any medicine.

Key Studies ★ 11 studies

Meta-analysis Nutrition Journal dose-response MA (2025) ✓ Full text
GRADE-assessed dose-response meta-analysis of 75 RCTs (n=1823) found each mmol increase in dietary nitrate lowered diastolic BP (WMD -0.12 mmHg; 95% CI -0.21, -0.03) and improved flow-mediated dilation and pulse wave velocity.
Meta-analysis Pollock 2016 (meta-analysis) ✓ Full text
Meta-analysis of prospective studies: green leafy and cruciferous vegetable intake inversely associated with incident cardiovascular disease.
Meta-analysis Mishra et al. 2018 (Singapore + meta-analysis) ✓ PubMed
Meta-analysis of prospective cohorts (754,729 participants): higher cruciferous vegetable intake associated with borderline lower type 2 diabetes risk (RR ~0.87; 95% CI 0.76–1.00).
Meta-analysis Wu et al. 2013 (meta-analysis) ✓ PubMed
Meta-analysis of observational studies: highest vs lowest cruciferous vegetable intake associated with lower colorectal cancer risk (RR 0.82; 95% CI 0.75–0.90).
RCT (crossover) Connolly et al. 2024 (VESSEL) ✓ Full text
Randomized controlled crossover trial: ~300 g/day cruciferous vegetables for 2 weeks reduced 24-h systolic blood pressure by 2.5 mmHg vs root/squash vegetables in adults with mildly elevated BP.
RCT VESSEL Study (Connolly 2024) ✓ Source
In a randomized crossover trial of 18 adults with mildly elevated BP, ~300 g/day of cruciferous vegetables (Brassica) for 2 weeks lowered 24-hour systolic BP by 2.5 mmHg versus root/squash vegetables.
RCT Jackson AJCN RCT (2020) ✓ Full text
Randomized trial in 243 adults (50-70 y, SBP 130-159 mmHg) comparing leafy green vegetables (~300 mg nitrate/day) vs nitrate pills vs low-nitrate placebo over 5 weeks assessing blood pressure effects.
RCT Axelsson et al. 2017 ✓ Source
12-week RCT in type 2 diabetes with obesity: concentrated broccoli sprout extract (sulforaphane) reduced HbA1c and fasting glucose vs placebo.
Review Gill 2026 ✓ PubMed
Integrating multiomic resources and gene expression studies to identify candidates for engineering climate-resilient Brassica
Prospective cohort Morris et al. 2018 ✓ Full text
Prospective study (n=960, mean 4.7 y): highest vs lowest green leafy vegetable intake (median ~1.3 servings/d) associated with slower cognitive decline equivalent to being ~11 years younger.
Prospective cohort Zhang et al. 2011 ✓ Full text
Prospective cohort of 134,796 Chinese adults: higher cruciferous vegetable intake associated with reduced total mortality (HR ~0.78–0.84) and cardiovascular mortality.
11 sources cited · 11 verified Search all studies on PubMed ↗

Common questions about Collard Greens

What is Collard Greens used for?

Collard Greens is most often taken for Lowers blood pressure (RCT evidence), Associated with reduced cardiovascular mortality, Linked to lower colorectal cancer risk, Supports slower cognitive decline. A calcium- and vitamin K-dense Southern cruciferous green with cardiometabolic and cognitive upside.

Does Collard Greens work — what does the evidence say?

Moderate evidence. Several controlled trials; effects real but modest or context-dependent. Collard greens are a glucosinolate-rich cruciferous vegetable and one of the densest plant sources of vitamin K and bioavailable calcium. Human evidence for the cruciferous family is robust: randomized crossover trials show cruciferous vegetables lower blood pressure, while large meta-analyses and prospective cohorts link higher intake to reduced cardiovascular and colorectal-cancer risk. Green leafy vegetables specifically are associated with markedly slower cognitive decline in older adults.

What is the typical dose of Collard Greens?

Standard serving: 1 cup chopped, raw (36 g). Eat whole (with skin where edible); favour whole fruit over juice.

Is Collard Greens safe? Any cautions or side effects?

Very high vitamin K (~157 ug per cup raw, far more when cooked-concentrated) can antagonize warfarin — keep intake consistent if anticoagulated. Raw cruciferous goitrogens may modestly affect thyroid in iodine-deficient individuals; cooking reduces this. Contains moderate oxalate and some FODMAPs. Generally very safe as food.

How many studies support Collard Greens?

NutriDex cites 11 sources for Collard Greens, graded "Moderate".

Cite this page
APA

Peh, D. (2026). Collard Greens: Benefits, Dosage, Side Effects & Evidence. NutriDex — The Supplement Research Compendium. Retrieved 16 Sept 2026, from https://nutridex.info/s/collard-greens

BibTeX
@misc{nutridex_collard_greens,
  author       = {Peh, Daryl},
  title        = {Collard Greens: Benefits, Dosage, Side Effects \& Evidence},
  year         = {2026},
  howpublished = {NutriDex --- The Supplement Research Compendium},
  url          = {https://nutridex.info/s/collard-greens},
  note         = {Reviewed by Dr Daryl Peh, MBBS Singapore, MMed FM. Accessed 2026-09-16}
}

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

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