Demystifying Manuka Honey Ratings: Part 1

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 19th century but it has been known anecdotally since ancient times, even being mentioned by Aristotle in the 4th 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 honeys 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 honeys have a pH of 3 – 4.5, which is acidic enough to inhibit the growth of a number of common pathogens.
  • Immunomodulatory properties: Certain honeys 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 honeys 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 a 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: Honeys 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 honeys 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 honeys have antimicrobial constituents beyond hydrogen peroxide. Manuka honey fits into this category. Non-peroxide activity can be measured by adding catalase, an enzyme which 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:
  • Bee Defensin-1: A peptide identified in Remavil, a particular type of medical-grade honey (more on that later). It is unknown how many other types of honey also contain this compound, but it has not yet been identified as a constituent of manuka honey. Interestingly, this peptide originates as a part of the immune system of the honey bees themselves.
  • Methylglyoxal (MGO): This has been identified as a major component of manuka honey’s activity. Although MGO is a key player in manuka’s effectiveness, it is not the only component at work, since when MGO is neutralized manuka still displays some non-peroxide antibacterial activity (more on this as well in Part 2).
  • Other factors: The rigorous, systematic examination of many honeys has yet to be performed. Numerous factors may not yet be identified, and it also remains to be investigated how active constituents in isolation differ from the synergistic effect that they may have when combined with others compounds naturally found in the same honey.

In the second installation to this series, we’ll take a closer look at manuka honey itself and its various labelling conventions.  Stay tuned...