What MGO Actually Measures

Pick up a jar of manuka honey at any pharmacy and you’ll see one of two numbers stamped on the lid: a UMF rating or an MGO rating. The MGO number is the more direct of the two. It is, quite literally, milligrams of methylglyoxal per kilogram of honey, measured by liquid chromatography.

The chemistry, in one paragraph

Manuka nectar is unusually rich in dihydroxyacetone (DHA), a small sugar derivative. As the honey matures, DHA converts to methylglyoxal (MGO) in a slow, non-enzymatic reaction. MGO is the antibacterial agent. More DHA at harvest means more MGO at maturity.

What MGO does, and what it doesn’t

MGO disrupts bacterial cell walls and interferes with biofilm formation. The dose-response is real: MGO 514+ kills Staphylococcus aureus in vitro at lower concentrations than MGO 100+ does. That part is settled.

What MGO doesn’t tell you:

• Leptosperin content. A separate manuka-specific marker. Authentic-source honey will have it; cheap blends won’t.
• Diastase activity. A freshness proxy. High-MGO honey that’s been heat-treated reads as suspicious.
• Origin. MGO can be elevated in adulterated honey through DHA spiking. Not common, but not zero.

Reading the label

A reasonable consumer rule:

1. Check that the jar lists either UMF (a multi-marker certification) or MGO (a single-marker assay).
2. If it’s MGO-only, look for an independent assay reference or batch number.
3. Anything below MGO 100+ is functionally table honey at a manuka markup.

We’ll cover UMF, KFactor, and the whole grading-system mess in the next dispatch.