Honey, Manuka and the gut: what MGO means and what the research says

Manuka honey carries a number on the jar. This article explains what it means, why honey from Australian Leptospermum trees is legitimately Manuka, and what the research on honey and gut bacteria actually shows.

What MGO means

Methylglyoxal (MGO) forms in Manuka honey from dihydroxyacetone in the nectar of Leptospermum flowers. The MGO number is milligrams of methylglyoxal per kilogram of honey. Across 29 commercial Manuka honeys from Australia and New Zealand, measured MGO matched the label with mostly minor differences (Green et al., PLoS One, 2022, PMID 35901185). Australia has more than 80 Leptospermum species; a study of 80 Australian Leptospermum honeys found levels up to 1,100 mg/kg in honey from the Northern Rivers and Byfield, stable over seven years of storage (Cokcetin et al., PLoS One, 2016, PMID 28030589). Industry conversion tables put the grade many people know as UMF 10+ at about MGO 263.

Australian Manuka is Manuka

New Zealand producers tried to register "Manuka honey" as a certification mark. The UK Intellectual Property Office refused in December 2021, the Intellectual Property Office of New Zealand upheld the Australian Manuka Honey Association's opposition in May 2023, and the New Zealand applicants then withdrew their UK appeal and EU application. The word has been in Australian use since the 1800s.

Honey and gut bacteria

Honey contains small amounts of non-digestible oligosaccharides. In a laboratory fermentation with human gut bacteria, honey oligosaccharides increased bifidobacteria and lactobacilli, though less than the reference prebiotic FOS (Sanz et al., Journal of Agricultural and Food Chemistry, 2005, PMID 15826039). In another study, honey grew Lactobacillus acidophilus and L. plantarum 10- to 100-fold more than sucrose in the lab, and rats fed honey had significantly more lactic acid bacteria than rats fed sucrose (Shamala et al., Letters in Applied Microbiology, 2000, PMID 10849275). A 2022 review from Sydney summarised in vitro, animal and pilot human evidence that some honeys have prebiotic activity, and noted honey's long history of use for digestive complaints (Schell et al., Frontiers in Nutrition, 2022, PMID 35967810). A 2026 review was blunter about the gap: most evidence is from the lab and animals, with a shortage of good human trials (Yang et al., Foods, 2026, PMID 42587978).

Manuka specifically

The one human trial is a safety study: 20 healthy adults aged 42 to 64 took 20 g a day of UMF 20+ Manuka or ordinary multiflora honey for four weeks each. Neither honey changed IgE, advanced glycation end products or the gut microbial profile, and neither increased beneficial gut bacteria (Wallace et al., British Journal of Nutrition, 2010, PMID 20064284). In mice, UMF 20+ Manuka did not disturb the gut microbiota, including Bifidobacteria (Rosendale et al., PeerJ, 2016, PMID 28028466). In food science, 10% Manuka honey significantly enhanced Bifidobacterium bifidum growth in probiotic milk without harming yoghurt starter cultures (Ibrahim et al., Food Microbiology, 2026, PMID 41722988).

The honest summary

Honey's sugars feed people; its oligosaccharides feed some gut bacteria in the lab; Manuka is safe and gentle on the gut's bacteria in the one human trial and did not boost them. Manuka's famous research is about wound care, and that has nothing to do with eating it.

This article reports published research for parents and adults who want to read it for themselves. It is not medical advice, it does not describe or recommend any product, and it never replaces a conversation with your GP or your child's clinicians.