Leek (Allium ampeloprasum var. porrum)

Leek (Allium ampeloprasum var. porrum) contains organosulfur compounds like allicin and diallyl disulfide that may reduce cancer risk through enhanced detoxification enzyme activity. The polyphenols in leeks provide antioxidant protection with ABTS radical scavenging activity of 31-37 mg TE/100g.

Origin & History

Leek (Allium ampeloprasum var. porrum) is a vegetable from the Allium genus cultivated outdoors, particularly in regions like Belgium, grown for its edible green leaves and white shaft. It originates from cultivated varieties of wild Allium species and contains bioactive compounds including S-alk(en)yl-L-cysteine sulfoxides (ACSOs), polyphenols, and vitamins, with green leaves richer in antioxidants and white shafts higher in ACSOs and fructans.

Historical & Cultural Context

Leek has historical use in traditional medicine similar to other Allium species for anti-asthma, antiseptic, diuretic, antibacterial, antioxidant, antifungal, and gastrointestinal protection applications. Modern epidemiology supports its traditional role in cancer risk reduction, building on its longstanding dietary importance.

Health Benefits

• May reduce cancer risk - Epidemiologic studies link consumption to reduced prostate, colorectal, stomach, and breast cancer risk (preliminary evidence)
• Antioxidant activity - Polyphenol extracts show ABTS radical scavenging (31-37 mg TE/100g ww) and FRAP activity (5-7 mg Fe(II)/100g ww) in vitro
• Potential blood pressure support - Animal studies show anti-hypertensive effects from oral alcoholic extract at 250-500 mg/kg (no human data)
• Radical scavenging properties - Leaf oil demonstrates DPPH inhibition (28%) and H2O2 scavenging (12%) in laboratory tests
• Traditional antimicrobial uses - Historical applications include antiseptic and antibacterial properties (traditional use only)

How It Works

Leek's organosulfur compounds, including allicin and diallyl disulfide, enhance phase II detoxification enzymes like glutathione S-transferase and quinone reductase, promoting carcinogen elimination. The polyphenolic compounds provide antioxidant activity through direct radical scavenging and metal chelation. These mechanisms work synergistically to reduce oxidative DNA damage and support cellular protection pathways.

Scientific Research

No human clinical trials, RCTs, or meta-analyses specific to leek were identified in the research. Evidence is limited to epidemiologic observations linking consumption to cancer risk reduction and preclinical studies showing antioxidant activity in optimized polyphenol extracts.

Clinical Summary

Epidemiologic studies suggest leek consumption is associated with reduced risk of prostate, colorectal, stomach, and breast cancers, though most evidence comes from observational dietary surveys rather than controlled trials. In vitro studies demonstrate antioxidant activity with ABTS radical scavenging of 31-37 mg trolox equivalents per 100g wet weight and FRAP activity of 5-7 mg Fe(II) per 100g. Current evidence is preliminary and primarily from population studies, with limited randomized controlled trials specifically examining leek supplementation. More rigorous clinical research is needed to establish definitive therapeutic benefits.

Nutritional Profile

Leek (Allium ampeloprasum var. porrum) per 100g fresh weight (raw, edible portion): Macronutrients - Energy ~61 kcal, Carbohydrates ~14.2g (of which sugars ~3.9g), Dietary fiber ~1.8g (predominantly fructooligosaccharides and inulin-type fructans acting as prebiotics), Protein ~1.5g (containing sulfur-containing amino acids including alliin precursors), Fat ~0.3g, Water ~83g. Key Vitamins - Vitamin K1 (phylloquinone) ~47µg (39% DV, highest micronutrient by DV contribution), Vitamin C ~12mg (13% DV, bioavailability moderate, losses significant with boiling ~30-50%), Folate (B9) ~64µg (16% DV), Vitamin B6 ~0.23mg (14% DV), Vitamin A (as carotenoids) ~83µg RAE primarily from beta-carotene (~1000µg) and lutein+zeaxanthin (~1900µg, concentrated in dark green leaves). Key Minerals - Manganese ~0.48mg (21% DV), Iron ~2.1mg (12% DV, non-heme form, bioavailability enhanced by co-consumed Vitamin C), Copper ~0.12mg, Potassium ~180mg, Calcium ~59mg, Magnesium ~28mg, Phosphorus ~35mg. Bioactive Organosulfur Compounds - Alliin, allicin precursors, kaempferol glycosides (~5-10mg/100g, predominantly kaempferol-3-glucoside and kaempferol-3,7-diglucoside), quercetin derivatives present at lower concentrations than onion (~1-3mg/100g). Polyphenol total content ~30-50mg GAE/100g fresh weight. Thiosulfinates formed upon tissue damage via alliinase activity. Fructans (inulin-type) ~3-10g/100g dry weight supporting gut microbiota. Bioavailability notes: Fat-soluble carotenoids (beta-carotene, lutein) require dietary fat for absorption; cooking increases carotenoid bioaccessibility but reduces Vitamin C and water-soluble polyphenols; the white shaft portion is lower in carotenoids and polyphenols compared to dark green leaf portions.

Preparation & Dosage

No clinically studied dosage ranges exist for leek extracts, powders, or standardized forms as human trials are absent. Animal studies used alcoholic extract at 250-500 mg/kg orally, but this cannot be translated to human doses. Consult a healthcare provider before starting any new supplement.

Synergy & Pairings

Garlic, Onion, Quercetin, Vitamin C, Green Tea Extract

Safety & Interactions

Leek is generally recognized as safe when consumed as food, with minimal reported adverse effects in healthy individuals. High consumption may cause gastrointestinal upset, bloating, or breath odor due to sulfur compounds. Individuals taking anticoagulant medications should exercise caution as alliums may have mild blood-thinning properties. Pregnant and breastfeeding women can safely consume leeks as part of a normal diet, though concentrated supplements should be avoided without medical supervision.