leek
Mild allium with vitamin K and folate, riding the broader garlic/onion evidence base.
Moderate evidence
🥦Vegetables
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 (89 g)
- Sugars 3.5 g4%
- Fibre 1.6 g2%
- Other carbs 7.5 g8%
- Protein 1.3 g1%
- Other 75.1 g84%
54 kcal1.3 g protein1.6 g fiber3.5 g sugar
| Nutrient | Per serving | % daily value |
|---|---|---|
| Vitamin C | 11 mg | 12% |
| Fiber | 1.6 g | 6% |
| Potassium | 160 mg | 3% |
| Folate | 57 µg | 14% |
| Vitamin A | 74 µg | 8% |
| Vitamin K | 42 µg | 35% |
| Vitamin B6 | 0.2 mg | 12% |
| Manganese | 0.43 mg | 19% |
| Copper | 0.11 mg | 12% |
| Vitamin E | 0.82 mg | 5% |
| Magnesium | 25 mg | 6% |
| Calcium | 53 mg | 4% |
Composition data: USDA FoodData Central ↗
What is leek?
leek is a vegetable used for allium-rich diets linked to markedly lower gastric cancer risk in pooled analyses. NutriDex grades the human evidence as Moderate. Leeks are a member of the Allium genus alongside garlic and onion, and most human evidence is generated by those better-studied relatives rather than by leeks directly. Pooled data show allium-rich diets are associated with substantially lower gastric cancer risk (umbrella review RR 0.78, 95% CI 0.67-0.91), and randomized trials of concentrated garlic preparations lower systolic blood pressure by roughly 3.8-8.4 mmHg and LDL/total cholesterol modestly, with the largest effects in hypertensive or dyslipidemic patients. Evidence specific to leek-level dietary intake is largely observational and confounded; the cardiometabolic signals come from supplement-dose garlic, so culinary leek portions should be viewed as part of a healthy vegetable-rich pattern rather than a proven therapeutic.
Purported Benefits
✓Allium-rich diets linked to markedly lower gastric cancer risk in pooled analyses
✓Concentrated allium (garlic) lowers blood pressure in hypertensive adults in RCTs
✓Garlic-class allium modestly reduces total and LDL cholesterol
✓Good source of vitamin K and folate for a low-calorie vegetable
✓Contributes prebiotic inulin-type fibre and flavonols to a vegetable-rich diet
Dosing & Compounds
Typical Dose
Standard serving: 1 cup chopped, raw (89 g). Eat whole (with skin where edible); favour whole fruit over juice.
Active Compounds
Safety & Cautions
Generally very safe as food. The inulin-type fructans make leeks high-FODMAP, so they can trigger bloating, gas, or diarrhea in people with IBS. The vitamin K content (about 42 ug per cup) can interfere with warfarin dosing, so intake should be kept consistent. Concentrated garlic/allium supplements (not culinary leeks) can increase bleeding risk and should be paused before surgery. Rare allium contact or IgE allergy occurs. Educational only — always check with your doctor or pharmacist before combining leek with any medicine.
Key Studies ★ 11 studies
updated meta-analysis and review
Halsted CH 2023
✓ Source
Updated pooled analysis confirmed garlic lowers blood pressure in hypertensive individuals and modestly improves serum cholesterol, supporting an adjunct cardioprotective role for allium.
Meta-analysis
Wan 2022 (Front Nutr)
✓ PubMed
Systematic review and meta-analysis of 22 studies found no significant association between high allium vegetable intake and overall cancer risk (RR 0.97; 95% CI 0.92-1.03), with no linear or nonlinear dose-response relationship.
umbrella review of meta-analyses
Wan Q 2019
✓ Full text
Across 16 meta-analyses (50 outcomes), high allium vegetable intake was associated with lower gastric cancer risk (RR 0.78, 95% CI 0.67-0.91) and garlic lowered total cholesterol by 17.2 mg/dL after >8 weeks.
meta-analysis of RCTs
Wang J 2015
✓ Full text
In 17 randomized trials, garlic supplementation reduced systolic BP by 3.75 mmHg (95% CI -5.04 to -2.45) and diastolic BP by 3.39 mmHg (95% CI -4.14 to -2.65) versus control, with larger effects in hypertensive patients.
meta-analysis of RCTs
Sun YE 2018
✓ PubMed
Pooled analysis of 39 trials found garlic reduced total cholesterol by about 17 mg/dL and LDL-C by about 9 mg/dL in adults with elevated baseline cholesterol over at least 2 months.
systematic review and meta-analysis
Turati F 2015
✓ Source
Higher allium vegetable consumption was inversely associated with gastric cancer risk, with a pooled case-control odds ratio of 0.54 (95% CI 0.43-0.65) comparing highest versus lowest intake.
meta-analysis of prospective studies
Wu X 2015
✓ PubMed
Pooled prospective-cohort data found no significant association between allium vegetable intake and colorectal cancer risk, tempering claims from case-control data.
meta-analysis of prospective cohorts
Wang PY 2016
✓ Source
Each additional serving per day of vegetables was associated with a ~10% lower type 2 diabetes risk (RR 0.90, 95% CI 0.80-1.01), with green/leafy and allium-type vegetables contributing to the protective pattern.
RCT
Bordbar 2023
✓ Full text
In a double-blind RCT of 97 children with chemotherapy-induced febrile neutropenia, Allium ampeloprasum (leek) capsules (500 mg twice daily) achieved neutrophil recovery within 7 days in 83.6% vs 54.2% of placebo controls (P<0.001) and earlier discharge (67.3% vs 48%, P=0.028).
RCT
Li 2023 (AJCN)
✓ PubMed
In a 22.3-year continuous follow-up of the randomized Shandong Intervention Trial (3229 subjects, 144 incident gastric cancers), garlic-allium vegetable intake was associated with lower gastric cancer risk (OR 0.83; 95% CI 0.70-0.98 per 1 kg/y increment; P-trend=0.02), while scallion intake showed no association.
Observational
Ferro 2022 (StoP Project)
✓ Full text
Pooled analysis of the Stomach cancer Pooling (StoP) Project found non-significant inverse associations for any vs no consumption of allium vegetables (OR 0.84; 95% CI 0.66-1.08), onions (OR 0.88; 95% CI 0.77-1.01), and garlic (OR 0.92; 95% CI 0.80-1.06).