collard-greens
A calcium- and vitamin K-dense Southern cruciferous green with cardiometabolic and cognitive upside.
Moderate evidence
🥦Vegetables
Evidence tier
Moderate
Research weight
Citations
10 verified / 10
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)
- Sugars 0.2 g0%
- Fibre 1.4 g4%
- Other carbs 0.3 g1%
- Protein 1.1 g3%
- Other 33 g92%
12 kcal1.1 g protein1.4 g fiber0.17 g sugar
| Nutrient | Per serving | % daily value |
|---|---|---|
| Vitamin C | 13 mg | 14% |
| Fiber | 1.4 g | 5% |
| Potassium | 77 mg | 2% |
| Folate | 46 µg | 12% |
| Vitamin A | 90 µg | 10% |
| Vitamin K | 157 µg | 131% |
| Vitamin B6 | 0.06 mg | 3% |
| Manganese | 0.24 mg | 10% |
| Copper | 0.02 mg | 2% |
| Vitamin E | 0.81 mg | 5% |
| Magnesium | 9.7 mg | 2% |
| Calcium | 84 mg | 6% |
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
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 ★ 10 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.
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.