Whenever a family member of mine catches a cold or comes down with a slightly sore throat, we are prescribed a home remedy called honimi the name comes from the German words for honey and milk – Honig and Milch. I always recommend honimi as a solution when any of my friends are struggling with croaky voices and sniffling noses. But unfortunately people are usually quite dismissive of my methods, in spite of my testimonies and enthusiasm. This could be due to a multitude of reasons, the main ones being the taste (which is not everyone’s cup of tea) and general disbelief. I can’t do much about the taste as it is what it is but I may be able to convince you, with science, that a warm mug of honimi can help your body fight off any illnesses and infections it may be hosting.

Why does honey have antimicrobial properties?

• Low Water Potential

• Low pH

• Methylglyoxal

• Bee Defensin-1

• Hydrogen Peroxide

Low Water Potential

Honey has a low water potential due to it’s extremely high concentration of sugar

molecules (mainly glucose and sucrose). The high content of sugar leaves very few water molecules that are free to move because many of them are used up to create hydration shells around the sugar molecules. The water molecules move down the concentration gradient (from a higher water potential to a lower water potential) out of the microorganisms and into the honey causing the microbial cells to crenate and die. Because of this many species of bacteria are inhibited by environments with low water potentials.

Low pH

Honey has a pH which ranges from 3.4 to 6.1 with an average of 3.9. This is because honey contains a large number of organic acids including; acetic, butyric, citric, formic, gluconic, lactic, malic, pyroglutamic and succinic. The major acid found in honey is gluconic acid. This is produced when glucose is oxidised in unripened honey by an enzyme called glucose oxidase.

The low pH affects microbes in two main ways:



cytoplasm they interfere with the ionic bonds in the tertiary structure of proteins and enzymes. This causes the proteins and enzymes to denature (their tertiary structure breaks down) which means that their specific shape changes. The active site of enzymes change shape so that their specific substrate no longer fits into it. This inhibits the metabolic reactions and pathways causing the cells to die. The organic acids dissociate which allows the H+ ions to diffuse freely across the semi-permeable membrane of the bacterial cells. Once the H+ ions are in thecytoplasm they interfere with the ionic bonds in the tertiary structure of proteins and enzymes. This causes the proteins and enzymes to denature (their tertiary structure breaks down) which means that their specific shape changes. The active site of enzymes change shape so that their specific substrate no longer fits into it. This inhibits the metabolic reactions and pathways causing the cells to die.

The organic acids dissociate creating an environment full of H+ ions. These denature the proteins in the membrane. This creates pores in the membrane which can cause the inside of the bacterial cell to leak out. N.B Some bacteria thrive in an environment with a low pH as they have certain adaptations which allow them to survive.

Methylglyoxal – a chemical unique to Manuka honey

Methylglyoxal (MGO) derives from dihydroxyacetone which is only present in Manuka nectar which is specifically from the Manuka tree in New Zealand. MGO is a reactive alpha-ketoaldehyde which can modify both DNA and proteins. MGO reacts with guanine residues in DNA and with Lysine & Cysteine (amino acid) residues in DNA polymerase forming DNA—DNA polymerase crosslinks. The polymerase enzyme becomes covalently bound to DNA and when this crosslink is formed it loses its polymerase activity. Another DNA polymerase may continue the paused DNA synthesis but the DNA polymerase covalently bound to a guanine base causes it to behave as a ‘bulky DNA lesion’ which causes mutations and leads to apotosis.

DNA replication may be severely inhibited when crosslinks are formed between DNA and DNA polymerases. Therefore the accumulation of MGO in cells could be very cytotoxic and could induce apoptosis.

Bee Defensin-1

Defensin-1 is an anti-microbial peptide (AMP) which are key components of humoral immunity in most invertebrates. The humoral immune system is a complex network of intracellular signalling pathways which lead to the activation of a variety of humoral factors. There are four families within the group of AMPs: apidaecins, adaecins, hymenoptaecins and defensins.

Defensin-1 is the only AMP found in honey. Bee defensin-1 is secreted by the hypopharyngeal gland in honey bees and secretions of this gland are used in the production of honey and royal jelly (a honey bee secretion that is used in the nutrition of larvae as well as queens). Defensin-1 has the ability to form pores in bacterial membranes which compromises the membrane integrity and causes cell lysis. Defensin-1 is found in all honey but in varying concentrations.

Hydrogen Peroxide

H 2 O 2 is produced within honey when glucose is oxidised by the enzyme glucose oxidase. The product of this reaction, which is gluconolactone, is hydrolysed in water to form H 2 O 2 and gluconic acid. There is still some mystery surrounding the mechanism behind the biocidal action of H 2 O 2 . However many studies imply that the Fenton reaction occurs which leads to the production of free hydroxyl radicals which oxidize thiol groups (a functional group containing a sulfur atom bonded to a hydrogen atom) in proteins and enzymes. Ribosomes can also be damaged by hydrogen peroxide which prevents and slows protein synthesis inhibiting many metabolic pathways.

Conclusion

We live in a time where superbugs are evolving and bacteria are growing resistant even to last resort antibiotics. New antibiotics are hard to produce and it is a process that won’t happen overnight. As you have read there are several factors that contribute to the antimicrobial effect of honey which make it such an effective tool in fighting infection.

Honey has shown antimicrobial activity against resistant strains of bacteria for example a study (Healing of an MRSA-colonized, hydroxyurea-induced leg ulcer with honey.) shows the effect of honey on an MRSA infection. A patient who was taking immunosuppressive drugs developed a leg ulcer with a MRSA infection; this was treated with a topical application of Manuka honey. The MRSA was eradicated from the ulcer and rapid healing was successfully achieved. This shows how much potential honey has and I hope more clinical trials will be done as many reviews of current studies state the evidence is of low or moderate quality because of a risk of bias and imprecision. So until then, don’t be too quick to reach for antibiotics when suffering from a cold or a cough maybe give honimi a try! P.S remember that if you are using antibiotics you should always finish your antibiotic course.

Studies in which Honey has been used to Treat Infections:

Topical Application of Honey in Treatment of Burns:

read the paper here

read a review here

read a more recent paper here

Effects of Topical Honey on Post Operative Infections Following Caesarean Sections and Hysterectomies

read the paper here

Honey in Treatment of Infantile Gastroenteritis

read the paper here

Effect of Honey on the Common Cold

read a paper here

read a paper here

Bibliography

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Any questions? Feel free to ask me in the comments!

