Scallion (Allium fistulosum)

Scallion (Allium fistulosum) contains bioactive compounds including flavonoids, vitamin C, and organosulfur compounds that demonstrate anti-inflammatory and antioxidant properties. The primary mechanisms involve modulation of IL-10/CD163 and IFN-γ/iNOS inflammatory pathways.

Origin & History

Scallion (Allium fistulosum) is a perennial herbaceous plant native to Siberia, Mongolia, and parts of China, cultivated worldwide as a vegetable known as Welsh onion, green onion, or spring onion. It is sourced from the entire plant, particularly leaves and bulbs, containing sulfur-containing organosulfur compounds, flavonoids, and phenolic acids.

Historical & Cultural Context

Allium fistulosum has been used as an important spice worldwide with implied historical roles in traditional medicine due to its phytochemicals. Pharmacological evidence builds on its long-standing use for potential anti-obesity, anti-viral, and anti-inflammatory benefits, though specific traditional medicine systems or indications are not detailed.

Health Benefits

• Anti-inflammatory effects demonstrated through modulation of IL-10/CD163 and IFN-γ/iNOS pathways (in vitro evidence only)
• Antioxidant activity from flavonoids (465.87 mg/g), vitamin C (0.161 mg/g), and carotenoids (2.87 mg/g) in leaf extracts (in vitro studies)
• Antimicrobial properties attributed to allicin and polysulfides formed upon tissue damage (in vitro evidence)
• Potential anti-obesity effects reported in animal studies (preliminary evidence)
• Immunomodulatory activity with Onionin A1 inhibiting IL-10-induced CD163 expression in cell lines (in vitro only)

How It Works

Scallion's bioactive compounds modulate inflammatory responses through the IL-10/CD163 anti-inflammatory pathway while suppressing IFN-γ/iNOS pro-inflammatory signaling. The flavonoids (465.87 mg/g) and vitamin C (0.161 mg/g) in leaf extracts provide antioxidant protection by scavenging free radicals. Organosulfur compounds contribute to antimicrobial activity through cell membrane disruption mechanisms.

Scientific Research

No human clinical trials, RCTs, or meta-analyses on Allium fistulosum were found in the available research. Evidence is limited to in vitro and animal studies showing anti-obesity, anti-viral, antimicrobial, anti-tumor, anti-oxidant, anti-inflammatory, and immunomodulatory effects.

Clinical Summary

Current evidence for scallion's health benefits comes primarily from in vitro laboratory studies rather than human clinical trials. Research has quantified specific bioactive compound concentrations including 465.87 mg/g flavonoids, 0.161 mg/g vitamin C, and 2.87 mg/g carotenoids in leaf extracts. The anti-inflammatory and antimicrobial properties demonstrated in cell culture studies require validation through controlled human studies. No large-scale clinical trials have been conducted to establish therapeutic dosages or clinical efficacy.

Nutritional Profile

Per 100 g raw scallion (green onion, Allium fistulosum): Energy ~32 kcal; Water ~89.8 g; Protein ~1.83 g; Total fat ~0.19 g; Carbohydrates ~7.34 g (including ~2.33 g sugars, primarily fructose and glucose); Dietary fiber ~2.6 g (mix of soluble fructans/inulin-type fructooligosaccharides and insoluble cellulose/hemicellulose). VITAMINS: Vitamin K1 (phylloquinone) ~207 µg (173% DV, high bioavailability from lipid-soluble matrix when consumed with fat); Vitamin C (ascorbic acid) ~18.8 mg (21% DV, degrades significantly with cooking — ~30–50% loss upon boiling); Folate (B9) ~64 µg (16% DV); Vitamin A as provitamin A carotenoids (primarily β-carotene ~598 µg, equivalent to ~997 IU; bioavailability enhanced by fat co-ingestion and thermal processing); Riboflavin (B2) ~0.08 mg; Thiamine (B1) ~0.055 mg; Vitamin B6 (pyridoxine) ~0.061 mg; Vitamin E (α-tocopherol) ~0.55 mg; Niacin ~0.525 mg. MINERALS: Potassium ~276 mg; Calcium ~72 mg (moderate bioavailability ~20–30%, partially limited by oxalate content); Iron ~1.48 mg (non-heme form, bioavailability ~5–12%, enhanced by concurrent vitamin C intake); Manganese ~0.16 mg; Magnesium ~20 mg; Phosphorus ~37 mg; Zinc ~0.39 mg; Copper ~0.083 mg; Selenium ~0.6 µg. BIOACTIVE COMPOUNDS: Organosulfur compounds — alliin (S-allyl-L-cysteine sulfoxide) converted to allicin and further to diallyl disulfide (DADS), diallyl trisulfide (DATS), and methyl allyl disulfide upon tissue disruption by alliinase enzyme (estimated total thiosulfinates ~0.5–1.5 mg/g fresh weight in green leaves, higher ~2–5 mg/g in white bulb portion); Flavonoids — quercetin (primarily as quercetin-3,4'-diglucoside and quercetin-4'-glucoside, total quercetin glycosides ~10–50 mg/100 g in green leaves; bioavailability of glucoside forms is relatively high at ~50% absorption compared to aglycone); kaempferol glycosides present in lower concentrations (~2–10 mg/100 g); Phenolic acids — ferulic acid, caffeic acid, and p-coumaric acid (~5–20 mg GAE/100 g total phenolics); Fructooligosaccharides (FOS)/inulin-type fructans ~0.5–1.5 g/100 g (prebiotic activity, resistant to upper GI digestion, fermented by colonic Bifidobacterium and Lactobacillus spp. producing short-chain fatty acids); Carotenoids — lutein + zeaxanthin ~1137 µg/100 g (bioavailability improved with dietary fat; relevant to macular health); Chlorophyll present in green portions (~15–30 mg/100 g); Saponins — trace to low levels in bulb tissue; Pectin and arabinogalactans contributing to soluble fiber fraction. NOTE: Green leaf portions are significantly richer in vitamins A, C, K, and flavonoids compared to the white sheath/bulb portion, which is richer in organosulfur compounds and fructans. Nutrient density is high relative to caloric content, making scallions a micronutrient-dense low-calorie food.

Preparation & Dosage

No clinically studied dosage ranges are reported for extracts, powders, or standardized forms of Allium fistulosum. Studies do not specify standardization levels used. Consult a healthcare provider before starting any new supplement.

Synergy & Pairings

Garlic, Turmeric, Ginger, Quercetin, Vitamin C

Safety & Interactions

Scallion is generally recognized as safe when consumed as food, with minimal reported adverse effects in healthy individuals. Individuals with allium allergies may experience allergic reactions including skin irritation or digestive upset. No significant drug interactions have been documented, though individuals taking anticoagulant medications should monitor intake due to potential vitamin K content. Safety during pregnancy and lactation is presumed safe at food levels, but therapeutic doses have not been studied in these populations.