Antibacterial effect of honey

Honey found during an excavation in Egyptian tombs older than 3.000 years was still completely safe to eat! What is it that gives this by-product of floral nectar metabolism from the queen's digestive system such longevity and resistance to the natural spoilage process caused by microorganisms?

There are several factors, and some of them are also used in human medicine.

Lots of sugar

Technically speaking, honey is a supersaturated solution of sugar in water, with a small but significant amount of other bioactive substances. But the two most abundant components are sugars (glucose and fructose, and some fructo-oligosaccharides) and water, with water making up only 17% of the total volume of honey.

Hence the phenomenon - typical of (over)saturated solutions - that the dissolved substance, here sugar, tends to come out of the solution, which is what happens during the natural crystallization of honey.

This low moisture content and high sugar content make honey a physically and chemically unfavorable environment for the survival of bacteria. Through the process of diffusion, when the bacterium is found in honey (it is similar with fungi and molds), it loses intracellular water and dies.

It can therefore be said that honey, a medium with a lower water content, "extracts" water from the bacterial cells, where it is present in a higher percentage than in the same volume of honey.

But apart from pure physical chemistry, honey exhibits its antimicrobial properties through biochemical reactions, primarily through the action of the enzyme glucose oxidase.

Glucose oxidase

Glucose oxidase in honey catalyzes (enhances and accelerates the reaction) the conversion of glucose into gluconic acid and hydrogen peroxide. Hydrogen peroxide, as is commonly known - has a disinfecting effect (destroys the wall of bacterial cells, among other things) and this is one of the reasons why honey was, and still is, used under appropriate conditions to dress wounds in order to prevent or suppress infection in them. .

Gluconic acid, on the other hand, is the reason why honey has a pH between 3.2-4.5, which makes it an acidic environment, which is unsuitable for the development of the largest number of pathogenic microbes. However, for optimal activity, glucose oxidase requires a higher percentage of moisture than that typical for honey, so this enzyme has a higher rate of activity in honey solutions, e.g. aqueous solution of honey.

For example, upon contact with a wound, where there is more moisture than in honey, the rate of glucose oxidase activity increases with honey, and therefore the production of hydrogen peroxide, which has an antiseptic effect.

Honey has an antimicrobial effect also thanks to antimicrobial biomolecules, which we can freely call natural antibiotics.

Natural antibiotics

The antibacterial peptide created by the immune system of bees, the so-called defensin-1, which varies in concentration in different types of honey, greatly contributes to wound healing by stimulating the migration of keratinocytes, and the production of matrix metalloproteases 9 in them, concludes a study from "Scientific reports" published in August 2017.

The presence of this molecule in honey is another factor that contributes to the fact that honey essentially has an unlimited shelf life.

There is another organic molecule with an extremely strong antimicrobial effect in honey - methylglyoxal, a derivative of pyruvic acid. This molecule occurs naturally in the human body, and in increased concentrations is strongly cytotoxic, interacts with LDL cholesterol in diabetic patients, thus increasing their risk of atherosclerosis, and mediates the formation of very harmful advanced glycation end products (AGE).

However, glyoxylase systems, with the participation of glutathione, detoxify methylglyoxal efficiently in healthy individuals, converting it into D-lactate. Moreover, a series of studies, one of which was published in the "British Journal of Nutrition" in 2010, (Wallace A. et al) showed that methylglyoxal from honey does not lead to increased production of advanced glycation end products (AGE) in healthy individuals.

But that's why it shows strong antimicrobial activity against microbes like Escherichia coli, Staphyloccus aureus and can also prevent the formation of biofilm by Pseudomonas aeurginosa.

Manuka honey, superbugs and wound therapy

Although every honey has an antimicrobial effect, the effects of the so-called honey are especially astonishing. manuka honey, which bees in New Zealand and Australia make by collecting nectar from the flowers of manuka species (Leptospermum spp.).

A study from August 2020, published in "Scientific reports", even describes how it is possible to make self-dissolving microneedles from manuka honey, which prevent post-surgical infections with methylicin-resistant staphylococcus aureus, the so-called. MRSA, which is resistant to most or all antibiotics, as the case may be.

In addition, according to the study, needles prepared in this way contributed to faster healing of postoperative wounds! All types of honey, especially those with a lower concentration of water, contribute to faster healing of wounds.

Thanks to the high osmolarity of honey, when it is applied to a wound it "draws out" the water that is at the base of the wound, which then encourages increased circulation under the wound itself to replace the lost fluid.

This osmotic effect then results in greater lymph flow, cleaning of bacteria from the wound and faster healing. In a way, this kind of wound treatment with honey imitates the treatment of wounds with negative pressure. In the treatment of burns, honey has been shown to be more effective than silver-sulfodazine in some studies, reducing the recovery time many times over.

Indirect antimicrobial action

Honey can act on microbes inside the body indirectly, even though most of the antimicrobial compounds are lost in the human digestive tract.

In vitro studies with cell cultures have shown that honey has an immunomodulatory effect, which contributes to its overall antibacterial effect. Namely, honey stimulates the activity of human monocytes, which then synthesize certain pro-inflammatory cytokines, interleukins and tumor-necrotic factors, strengthening the weakened immune response.

Additionally, honey is considered a potential prebiotic food. It contains oligosaccharides that promote the growth of lactobacilli and bifidobacteria, which act synergistically with antimicrobial and immunomodulatory substances to suppress pathogenic microorganisms.

Practical examples

In a 2007 study, different varieties of honey showed an inhibitory effect on Helicobacter pylori similar to that shown by clarithromycin (in vitro).

So, for example, as an auxiliary therapy in the treatment of infection caused by this microorganism, a smoothie of half a cup of cabbage leaves, half a cup of apple, half a cup of water, 2 grams of inulin powder and a spoonful of honey can be taken. Provided that there is no hypersensitivity to any of the ingredients, this drink can be taken daily with regular therapy.

Since it has proven to be very effective in treating burns and shortening their healing time, honey diluted in an equal volume of water, with a few drops of lavender essential oil and a teaspoon of apple cider vinegar added, can be used to relieve redness and pain in burns.

A spoonful of manuka honey, mixed with a little aloe gel, to which 1-2 drops of clove or sage essential oil have been added, can be applied every day in a very thin layer to inflamed gums in case of gingivitis or for the treatment of stomatitis.

Who should not use honey?

People who, for any reason, need to control (reduce) the daily amount of sugar they consume, must remember that a teaspoon of honey contains 6 grams of sugar, which is ¼ of the recommended daily intake of sugar for women, according to the American Heart Association (AHA).

At the same time, the same teaspoon of honey has 0 grams of fiber, which would alleviate a sudden spike in blood sugar, as is the case, for example, with fruit. Then again, honey has a significantly lower glycemic index than sugar, so it is definitely a better choice as a sweetener.

Although honey is naturally resistant to spoilage and invasion by microorganisms, it can contain minor amounts of inactive spores of Clostridium botulinum. This happens in about 10% of cases.

For adults, this is not a problem - since spores cannot grow and produce toxins in honey, and the average adult's immune system easily destroys them before they have a chance to develop and grow in the body.

In contrast, the immune system of newborns is not always able to destroy these spores, so it is not recommended to give honey to children under 1 year of age.

Milorad Vlaović, graduate biologist