Medicinal honey

The medicinal properties of honey have been known for many thousands of years, the oldest records of medicinal use being from a Sumerian clay tablet of 2000 BC.  Indeed, in cultures where other sweeteners were available the main use of honey was in medicine.  For example, there are over 500 treatments listed in ancient Egyptian records in which honey is an important ingredient, it being used in wound dressings, for gut problems and even to cure tooth decay.  It was also used as a preservative in mummification: Alexander the Great (356-323BC) is said to have requested to be covered in honey after his death, to stop putrefaction before mummification, and small corpses have been found in Egyptian tombs preserved in large jars of honey.

Although honey continued to be used medicinally, especially in wound dressings for burns, with the rise of modern medical practices the use of honey became sidelined and it became considered an unsubstantiated folk remedy.  However, recent research has validated many of the originally described benefits of honey.  First, in the 1960s, the enzyme glucose oxidase was discovered in honey.  This is secreted by the bees’ hypopharyngeal gland and catalyses the oxidation of glucose in water, liberating hydrogen peroxide, a mild antiseptic.  Honey, being acidic and a very concentrated sugar solution, is already an inhospitable place for many microbes to grow, and glucose oxidase will further enhance the keeping properties of honey, important in the hive.

More recently, we have come to realise how little we know about the constituents of honey as further compounds with an anti-microbial property have been found in honey in the last 10 years or so.  For example, Bee Defensin 1 (BD1) is also secreted by the honey bees’ hypopharyngeal gland into some honeys; this is a peptide which has anti-microbial properties.  Furthermore, the antimicrobial compound methylglyoxal (MGO) can also be present in honey.

With increasing marketing and use of honey for medicinal purposes it becomes important to try and quantify and standardise their anti-microbial properties, as it is clear that these vary greatly, sometimes even within the same type of honey from the same area.  To this end, Kwakman et al (2010) have investigated the medicinal properties of two widely-available medicinal honeys, Revamil and manuka honey.  Revamil is made from honey produced in controlled conditions in The Netherlands from selected pesticide-free hives, and the honey is gamma-irradiated to ensure that it is sterile.  The honey is made into a soft hydrophilic gel which, their website claims, has beneficial effects in the treatment of burns, stimulating granulation, enabling wound closure, reducing swelling and pain and reducing scar tissue.  Manuka honey is produced by bees foraging on the manuka bush, Leptospermum scoparium, indigenous only in New Zealand and SE Australia.  Manuka honey is very variable in its antimicrobial activity, but some has been found to contain very high concentrations of MGO (this is formed from the high concentrations of dihydroxyacetone found in the nectar from manuka bushes, although we don’t know how or why).  The anti-microbial activity of manuka honey is tested, and only honeys with a high level of activity are able to be sold as active manuka honey, with anti-microbial properties.

Kwakman et al (2010) tested these two honey products against a range of medically-important bacteria, and measured the concentration of anti-microbial compounds.  They found that the two products had quite different properties. Revamil honey contained high concentrations of hydrogen peroxide and BD1 and killed Bacillus subtilis, Escherichia coli and Pseudomonas aeriginosa within 2 hours, and killed methicillinin resistant Staphylococcus aureus (MRSA) within 24 hours.  Manuka honey, on the other hand did not contain hydrogen peroxide or BD1 but did have 44-fold higher concentrations of MGO than Revamil. While it was not so effective as Revamil against some of the bacteria after 2 hours, it was more potent after 24 hours and retained its activity at greater dilutions than Revamil.

There are still unknown anti-microbial compounds in honey:  Kwakman et al (2010) neutralised the MGO activity of the manuka honey and found that it still had a greater anti-microbial activity than an equivalent sugar solution.  As manuka honey hoes not have detectable amounts of BD1, this suggests that it has some other anti-microbial agents.

p.s. those who wish for more information on medicinal honeys might like to check out this link, which I found after writing the above.

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