Alliin
The stable sulfoxide stored in intact garlic cloves. By itself, alliin has no clinical activity — its job is to wait for cellular damage to bring it into contact with the enzyme alliinase, which converts it to allicin in seconds. Almost all 'garlic / allicin / alliin' supplement evidence is really about whether the product successfully generates allicin in the GI tract. Pair this page with the Allicin and Garlic pages for the full picture.
Quick decision guide
May help most
Understanding what the 'alliin yield' or 'allicin potential' on a garlic supplement label means. Adults using garlic supplements for modest BP or cholesterol benefit should focus on standardized garlic powder (enteric-coated) or aged garlic extract rather than pure alliin.
Common dosing range
Most clinical-trial garlic-powder products provide ~3,600–7,200 µg (3.6–7.2 mg) 'allicin yield' per day — derived from alliin + alliinase activity. Pure alliin alone is not a typical supplement form.
When to expect effects
8–12 weeks for blood pressure or cholesterol effects (from the alliin → allicin system).
Watch out for
Alliin per se is benign; the clinical effects (and risks — bleeding, drug interactions) come from allicin and downstream sulfur compounds. See the Allicin and Garlic pages for safety detail.
Evidence snapshot
What is it
Alliin is the odorless sulfur-containing amino acid stored in intact garlic cloves; when garlic is crushed, the enzyme alliinase converts it to allicin, the pungent compound responsible for garlic's smell and most biological activity.
Is it worth it for you?
Use this as a quick fit check, not a diagnosis.
Worth considering if…
Probably skip if…
Evidence at a glance
| Goal | Effect | Best fit | Time |
|---|---|---|---|
Alliin → allicin generation (the bioactive system) Strong Evidence | Essentially complete conversion within seconds when alliinase is active and substrate is available | Universal — this is how garlic works biochemically | Seconds in vitro; depends on GI conditions in vivo |
Blood pressure reduction in hypertension (via alliin+alliinase → allicin) Good Evidence | Systolic BP ~−8 mmHg, diastolic ~−5 mmHg in hypertensives over 8–12 weeks (garlic preparations) | Adults with stage 1 hypertension wanting a food-derived adjunct to lifestyle change | 8–12 weeks |
Total / LDL cholesterol (via the alliin+alliinase → allicin system) Good Evidence | Total cholesterol ~−17 mg/dL; LDL ~−9 mg/dL over 8+ weeks (garlic preparations) | Adults with borderline-elevated cholesterol who aren't yet on a statin | 8+ weeks |
Alliin → allicin generation (the bioactive system)
- Effect
- Essentially complete conversion within seconds when alliinase is active and substrate is available
- Best fit
- Universal — this is how garlic works biochemically
- Time
- Seconds in vitro; depends on GI conditions in vivo
Blood pressure reduction in hypertension (via alliin+alliinase → allicin)
- Effect
- Systolic BP ~−8 mmHg, diastolic ~−5 mmHg in hypertensives over 8–12 weeks (garlic preparations)
- Best fit
- Adults with stage 1 hypertension wanting a food-derived adjunct to lifestyle change
- Time
- 8–12 weeks
Total / LDL cholesterol (via the alliin+alliinase → allicin system)
- Effect
- Total cholesterol ~−17 mg/dL; LDL ~−9 mg/dL over 8+ weeks (garlic preparations)
- Best fit
- Adults with borderline-elevated cholesterol who aren't yet on a statin
- Time
- 8+ weeks
Evidence for 3 uses
AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.
Alliin → allicin generation (the bioactive system)
Mechanism onlyAlliin (S-allyl-L-cysteine sulfoxide) and the enzyme alliinase are stored in separate compartments of intact garlic cells. When the clove is crushed, chewed, or cut, cellular disruption brings them together and alliinase converts alliin to allicin (allyl 2-propenethiosulfinate) within seconds. Allicin is the unstable thiosulfinate that gives crushed garlic its characteristic odour and accounts for most of garlic's in-vitro pharmacology. This is established biochemistry, well-described since Stoll & Seebeck 1947 and reviewed many times since.
Bottom line: Alliin is the substrate, alliinase is the enzyme, allicin is the product. The clinical question is whether commercial products preserve both alliin and alliinase activity until they meet in the right place.
Blood pressure reduction in hypertension (via alliin+alliinase → allicin)
Supplement benefitStandardized garlic-powder products (which deliver clinical effect by generating allicin from alliin in the small intestine) consistently lower blood pressure in hypertensive patients across meta-analyses. The 2020 Ried meta-analysis (12 RCTs, n=553) found ~8 mmHg systolic and ~5 mmHg diastolic reductions, similar to a single first-line antihypertensive at low dose. Effects are smaller in normotensives. Aged garlic extract (no alliin remaining, but other stable sulfur compounds) shows similar BP benefit. Isolated pure alliin has not been tested in BP trials because it doesn't work without alliinase.
Bottom line: Real modest BP benefit at studied doses. Choose enteric-coated standardized garlic powder (or aged garlic extract) for evidence-aligned delivery.
Evidence is mixed
EFSA rejected the Article 13.1 health claim that garlic 'maintains normal blood pressure' in 2009, citing trial heterogeneity. Meta-analyses since (Ried 2020) have strengthened the picture.
Total / LDL cholesterol (via the alliin+alliinase → allicin system)
Supplement benefitRied et al. 2013 meta-analysis of 39 primary trials found garlic preparations reduced total cholesterol ~17 mg/dL and LDL ~9 mg/dL in subjects with baseline total cholesterol >200 mg/dL over ≥8 weeks. Most trial preparations were standardized dried garlic powder; aged garlic extract showed similar modest magnitude. Pure isolated alliin has not been tested for cholesterol because it isn't pharmacologically active without alliinase.
Bottom line: Modest cholesterol-lowering effect via the alliin+alliinase → allicin system. Don't expect pure alliin or alliin-only products to deliver.
How it works
How to take it
What to track
Bottom line: Pick an enteric-coated standardized garlic powder (or aged garlic extract) at 600–1,200 mg/day for 8–12 weeks. Pure alliin alone is not the right purchase.
5 commercial forms
Compare the main delivery options and what they’re best suited for.
Alliin in intact garlic clove
BiologyAlliin (S-allyl-L-cysteine sulfoxide) is stored in the cytoplasm of intact garlic cells; the enzyme alliinase is sequestered in vacuoles. Cellular disruption (crushing, chewing) brings them together, generating allicin in seconds.
Not consumed as 'alliin' per se; the alliin → allicin conversion is what delivers activity.
Standardized garlic powder (enteric-coated)
Best evidenceDried, powdered garlic standardized to allicin yield (typically 1.3% alliin equivalent to ~5,000 µg allicin per 600 mg tablet). Enteric coating preserves alliinase activity past stomach acid so allicin generates in the small intestine. Used in most BP and cholesterol RCTs.
Allicin yield 60–80% under good manufacturing; tablet quality varies (Lawson 2018).
Aged garlic extract (Kyolic-type)
No alliin remainingGarlic aged in dilute alcohol for 18+ months. Converts alliin to stable water-soluble S-allyl cysteine and S-allyl mercaptocysteine; no allicin remains. Distinct evidence base with very low odour and good tolerability.
Active compounds stable and orally bioavailable; not the same molecules as the alliin → allicin system.
Pure alliin (research chemical)
Inert without alliinaseIsolated alliin is available as a research chemical or analytical reference standard. Has no clinical activity on its own — without alliinase to convert it, alliin is biologically inert. Not a meaningful consumer supplement form.
Reaches the gut intact but is not converted in vivo without alliinase activity.
Fresh crushed raw garlic
Food sourceCrush and let stand 10 minutes before use — alliinase converts alliin to allicin during the rest. Cooking destroys alliinase, so heat-then-add-garlic dishes deliver mostly residual alliin without allicin. One large clove (~4 g) generates clinically meaningful allicin if eaten promptly.
Best in-vivo allicin delivery, with the highest breath/GI cost.
Safety
Know the common side effects, key cautions, and who should avoid it.
Common side effects
Serious risks
Bleeding risk — garlic preparations inhibit platelet aggregation. Case reports of spontaneous spinal epidural hematoma and excess surgical bleeding. Stop garlic supplements 1–2 weeks before any procedure.
Hypoglycemia risk in people with diabetes — modest glucose-lowering effect; monitor closely with insulin or sulfonylureas.
Topical raw garlic causes chemical burns — never apply concentrated raw garlic to skin or ear as a home remedy.
Who should avoid it
- Anyone on warfarin, DOACs, or antiplatelets without clinician oversight — additive bleeding risk.
- Anyone taking saquinavir (HIV protease inhibitor) — garlic reduced saquinavir AUC ~50%; risk of treatment failure. See the Allicin / Garlic page for detail.
- Anyone within 2 weeks of scheduled surgery or dental procedures — stop garlic supplements.
- People with active gastritis, peptic ulcer disease, or GERD — garlic can aggravate symptoms.
Pregnancy & breastfeeding
Garlic in normal culinary amounts is considered safe in pregnancy and breastfeeding. Therapeutic doses (600+ mg/day) have not been adequately studied in pregnancy and should be avoided given the bleeding risk. Discuss with your obstetrician.
Bottom line: Alliin per se is inert. Safety considerations for any 'alliin' supplement are really about garlic / allicin downstream effects — see the Garlic and Allicin pages.
Interactions
Additive bleeding risk; case reports of elevated INR with garlic supplements. Avoid or monitor INR closely.
Additive bleeding risk via antiplatelet effect of garlic. Avoid supplemental garlic.
Garlic inhibits platelet aggregation; additive bleeding risk.
Garlic reduced saquinavir AUC by ~51% in healthy volunteers — risk of treatment failure. Avoid combination.
Garlic may modestly lower glucose; monitor for additive hypoglycemia.
Garlic adds small BP-lowering effect — generally helpful, but monitor for symptomatic hypotension when starting or stopping.
Food sources
| Food | Amount | %DV |
|---|---|---|
| Fresh garlic clove (intact) | 1 large clove / ~4 g (contains ~12 mg alliin) | — |
| Garlic powder (dried) | 1 tsp / ~3 g (alliin content varies with processing; alliinase often inactive) | — |
| Onions (Allium cepa) | Contain a different but related sulfoxide (isoalliin / propenyl cysteine sulfoxide), not alliin per se | — |
| Leeks, shallots, scallions | Trace allium sulfoxides; not alliin in meaningful amounts | — |
Fresh garlic clove (intact)
- Amount
- 1 large clove / ~4 g (contains ~12 mg alliin)
- %DV
- —
Garlic powder (dried)
- Amount
- 1 tsp / ~3 g (alliin content varies with processing; alliinase often inactive)
- %DV
- —
Onions (Allium cepa)
- Amount
- Contain a different but related sulfoxide (isoalliin / propenyl cysteine sulfoxide), not alliin per se
- %DV
- —
Leeks, shallots, scallions
- Amount
- Trace allium sulfoxides; not alliin in meaningful amounts
- %DV
- —
Choosing a product
What to look for on the label — and what to be skeptical of.
Look for…
Be skeptical of…
Frequently asked questions
Is alliin or allicin in my supplement?⌄
Most quality garlic supplements list alliin yield or allicin potential; allicin forms when the tablet dissolves in the small intestine.
References by claim
Blood pressure reduction in hypertension (via alliin+alliinase → allicin)
Safety
NCCIH — Garlic — NIH National Center for Complementary and Integrative Health (2024) link
Alliin → allicin generation (the bioactive system)
Total / LDL cholesterol (via the alliin+alliinase → allicin system)
Ried et al., 2013 — Nutrition Reviews (2013) link
Track Alliin with Pilora
Set up dose reminders, check interactions, and join the community in the Pilora iPhone app.
Coming to App StoreDisclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.