Demystifying Manuka Honey Ratings: Part 1

This is part one of a two-part blog series that sets out to shed some light on that curious and enigmatic substance known as manuka honey: specifically, we aim to walk you through what it is, how it works, and what the labels mean when you see it on a retailer’s shelf.

To begin, we must start at the beginning: Honey 101.

What is honey?

Honey is a sugar solution produced by bees from the nectar of flowers. Comprised of roughly 80% fructose/glucose and 18% water, it also contains proteins, amino acids, vitamins, enzymes, minerals, and other miscellanea that differentiate it from a pure sugar solution. 

The antibacterial activity of honey has been officially documented in Western culture since the 19^th century but it has been known anecdotally since ancient times, even being mentioned by Aristotle in the 4^th century BC as “a salve for sore eyes and wounds.” It has a history of use for a prolific amount of applications, including culinary, cosmetic, and wound-remediation purposes.

The therapeutic use of honey (generally for digestive issues or wound care) has fallen out of favor in modern medicine, but interest has resurfaced in recent years. Today, a branch of alternative medicine called apitherapy studies the therapeutic benefits of honey and other bee-derived products. 

How does honey ‘work’?

All kinds of honey are antimicrobial, primarily due to the enzymatic release of hydrogen peroxide. When bees collect nectar from flowers, they add an enzyme called glucose oxidase. When oxidized, this enzyme splits the glucose in honey into H₂0₂ and gluconic acid, with antiseptic results.

In addition to peroxide, honey has several other characteristics that contribute to its antibacterial qualities: 

• High sugar content: The high sugar-to-moisture ratio in honey makes it hygroscopic, meaning that it can draw moisture out if its environment. This creates an osmotic effect that can dehydrate bacteria that come into direct contact with it. Its viscosity can also create a physical barrier to infection and help maintain a moist wound environment while drawing out lymph from the wound, encouraging healing of the tissue.

• Low pH: Many kinds of honey have a pH of 3 – 4.5, which is acidic enough to inhibit the growth of a number of common pathogens.

• Immunomodulatory properties: Certain kinds of honey have been shown to stimulate the activities of monocytes, precursors to macrophages, helping the immune system encourage wound regeneration.

What factors affect the potency of honey?

Not all kinds of honey are equal. Some of the factors that can influence its activity are: 

• Excessive heat and/or light: These conditions can inactivate the enzyme that produces hydrogen peroxide. If honey relies solely on H₂O₂ activity for its antimicrobial action, this can denature it entirely. Processing, storage and shipping conditions are key here. Purchasing raw, local honey is your best bet for the least adulterated peroxide activity.

• Nectar source: Kinds of honey inherit their properties from the plant nectars that they are derived from. Certain nectars are naturally imbued with different compounds than others, and thus some kinds of honey are more antiseptic than others. As with any agricultural product (or in this case apicultural), variations in the source material (nectar) can be triggered by seasonal or geographical considerations, in addition to the species of plant.  

• Non-peroxide activity: Certain kinds of honey have antimicrobial constituents beyond hydrogen peroxide. Manuka honey fits into this category. The non-peroxide activity can be measured by adding catalase, an enzyme that inactivates H₂O₂ activity. Unlike the H₂O₂ activity that can be denatured by heat and light, non-peroxide constituents tend to be more stable, and can include compounds like:

In the second installation of this series, we’ll take a closer look at manuka honey itself and its various labeling conventions.  

Part two of Demystifying Manuka Honey Ratings 

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