What is S-allylcysteine (SAC) and why does it matter?

SAC is the water-soluble, stable organosulfur compound that forms during the multi-month aging process used to produce aged garlic extract. Unlike allicin — which is volatile, unstable, and largely undetectable in blood after oral ingestion — SAC can be measured in plasma, making it a reliable compliance and dose marker. A double-blind trial in 23 participants used SAC blood levels as a compliance/bioavailability marker — direct evidence that the AGE form delivers a measurable, standardizable compound (PMID 15475033).

Why is aged garlic extract easier to standardize than other forms?

Because its active marker, SAC, is stable and measurable. Allicin-yielding powders depend on an enzyme (alliinase) that is destroyed by stomach acid unless enteric-coated, and allicin itself is unstable and largely unmeasurable in blood — so how much actually reaches circulation is hard to confirm. AGE is standardized to a defined SAC content per dose, and that content can be verified in plasma, which allicin-based forms cannot reliably match.

Does enteric coating make garlic powder more reliable?

It helps, with caveats. Enteric coating preserves alliinase — the enzyme that converts alliin to allicin — by protecting it from stomach acid. However, allicin itself is unstable and largely unmeasurable in blood, making it difficult to confirm how much actually reaches circulation, so the delivered dose is harder to standardize than AGE's SAC-based standardization.

How is aged garlic extract dosed and standardized?

Standardized AGE products state their SAC content per dose. Common labeling is 240 mg, 480 mg, or 960 mg of AGE daily, standardized to 0.6 mg, 1.2 mg, and 2.4 mg SAC respectively (PMID 23169470). Raw-garlic equivalents are harder to estimate because allicin yield varies significantly with preparation method and individual gastric conditions, so a comparable standardized dose cannot be defined.

Best Garlic Form: Which One Should You Take?

Garlic supplements differ mainly in which active compounds survive processing and digestion — and whether the delivered dose can be standardized. Aged garlic extract is standardized to S-allylcysteine (SAC), a stable, water-soluble compound that can be measured in blood, so its dose can be defined and verified in a way that unstable allicin-yielding forms cannot match.

Updated 2026 · Reviewed by Dr. Brennan Commerford, D.C.

All Forms Ranked by Evidence

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Verification pending
Garlic
Form: standardized_extract
Garlic — Garlic is one form of this compound. Limited direct human-PK evidence for this specific form. We grade forms only where form-specific human pharmacokinetic evidence exists; this form does not yet meet that bar, so we do not assign it a benefit rating.
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Verification pending
Garlic Extract 1% Allicin
Form: Extract
Garlic Extract 1% Allicin — Garlic Extract 1% Allicin is one form of this compound. Limited direct human-PK evidence for this specific form. We grade forms only where form-specific human pharmacokinetic evidence exists; this form does not yet meet that bar, so we do not assign it a benefit rating.
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Verification pending
odor controlled Garlic
Form: Standard
odor controlled Garlic — odor controlled Garlic is one form of this compound. Limited direct human-PK evidence for this specific form. We grade forms only where form-specific human pharmacokinetic evidence exists; this form does not yet meet that bar, so we do not assign it a benefit rating.
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Verification pending
organic Garlic
Form: Standard
organic Garlic — organic Garlic is one form of this compound. Limited direct human-PK evidence for this specific form. We grade forms only where form-specific human pharmacokinetic evidence exists; this form does not yet meet that bar, so we do not assign it a benefit rating.
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Verification pending
organic Garlic juice
Form: Juice
organic Garlic juice — organic Garlic juice is one form of this compound. Limited direct human-PK evidence for this specific form. We grade forms only where form-specific human pharmacokinetic evidence exists; this form does not yet meet that bar, so we do not assign it a benefit rating.

Editorial note

AGE's water/ethanol aging process converts unstable allicin precursors into stable S-allylcysteine (SAC), enabling reliable dose standardization and verified plasma detection. SAC is measurable in blood, so a labeled dose can be tied to a confirmed circulating level and used for compliance verification (PMID 15475033) — advantages that allicin-yielding powders cannot match, because allicin is inherently unstable and largely unmeasurable in blood. Standardized AGE products state their SAC content per dose (for example, 480 mg standardized to 1.2 mg SAC), which allicin-based forms cannot reliably do (PMID 23169470).

All Forms Compared

Aged Garlic Extract (AGE / Kyolic)

Best For

A standardized, dose-verifiable garlic form

Water/ethanol aging converts unstable allicin precursors to stable S-allylcysteine (SAC), the primary standardization biomarker. SAC is measurable in blood, enabling dose standardization and compliance verification — an advantage no other garlic form offers (PMID 15475033).

Enteric-Coated Garlic Powder (allicin-releasing)

Best For

General garlic supplementation

Enteric coating is required to protect alliinase from stomach acid; without it, allicin conversion does not occur. Allicin itself is highly unstable and largely unmeasurable in blood, making dose standardization difficult.

Raw Garlic / Garlic Powder (non-enteric)

Best For

Culinary use

Cooking and gastric acid destroy most allicin before absorption. Raw garlic provides variable active-compound delivery depending on crushing method and transit time, so the delivered dose cannot be reliably standardized.

Garlic Oil (steam-distilled / macerated)

Best For

N/A — not standardized to a measurable biomarker

Steam-distilled garlic oils contain diallyl sulfides rather than SAC or allicin, and are not standardized to a measurable blood biomarker. Macerated garlic oil retains some allicin but with the same instability and non-measurability limitations as non-enteric powder.

Frequently Asked Questions

What is S-allylcysteine (SAC) and why does it matter?: SAC is the water-soluble, stable organosulfur compound that forms during the multi-month aging process used to produce aged garlic extract. Unlike allicin — which is volatile, unstable, and largely undetectable in blood after oral ingestion — SAC can be measured in plasma, making it a reliable compliance and dose marker. A double-blind trial in 23 participants used SAC blood levels as a compliance/bioavailability marker — direct evidence that the AGE form delivers a measurable, standardizable compound (PMID 15475033).
Why is aged garlic extract easier to standardize than other forms?: Because its active marker, SAC, is stable and measurable. Allicin-yielding powders depend on an enzyme (alliinase) that is destroyed by stomach acid unless enteric-coated, and allicin itself is unstable and largely unmeasurable in blood — so how much actually reaches circulation is hard to confirm. AGE is standardized to a defined SAC content per dose, and that content can be verified in plasma, which allicin-based forms cannot reliably match.
Does enteric coating make garlic powder more reliable?: It helps, with caveats. Enteric coating preserves alliinase — the enzyme that converts alliin to allicin — by protecting it from stomach acid. However, allicin itself is unstable and largely unmeasurable in blood, making it difficult to confirm how much actually reaches circulation, so the delivered dose is harder to standardize than AGE's SAC-based standardization.
How is aged garlic extract dosed and standardized?: Standardized AGE products state their SAC content per dose. Common labeling is 240 mg, 480 mg, or 960 mg of AGE daily, standardized to 0.6 mg, 1.2 mg, and 2.4 mg SAC respectively (PMID 23169470). Raw-garlic equivalents are harder to estimate because allicin yield varies significantly with preparation method and individual gastric conditions, so a comparable standardized dose cannot be defined.

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FormulaForge formulates and sells supplements containing the ingredients discussed on this page. Our formulary recommendations are based on peer-reviewed bioavailability research. All cited studies are independently verifiable.