Honey’s anti-bacterial properties found?

By Grant Jacobs 14/07/2010 10


New research suggests that (some of) the secrets to honey’s anti-bacterial properties may have been revealed.

A Dutch team of microbiologists propose that the anti-bacterial properties of the honey they tested come down to four chemicals and one general property:

Honey comb; near the top-centre bees can be seen entering the combs (Source: Wikimedia Commons.)
Honey comb; near the top-right bees can be seen entering the combs (Source: Wikimedia Commons.)

Sugars High concentrations of sugars have long been known to have anti-bacterial properties and are used in preserving food.

The best known effect is by soaking up water. Bacteria, like most living things, need water. Soak up the water and they’ll dehydrate.

Ever tried to clean up a wine spill in the carpet by dribbling some water over the stain, then sprinkling salt over the water? You’ll know how the salt sucks up the water from the carpet.

In a similar way, high concentrations of sugar outside cells, can suck water out of the cells or absorb other moisture that’s around. This works through creating an osmotic gradient, where the moveable part – water – moves to balance the low concentration of water outside the cell, dehydrating the cell.

H2O2 Hydrogen peroxide is a bleach used in making paper among other things. Household bleach kills bacteria, so does hydrogen peroxide.

Methylglyoxal (MGO) This is known to be cytotoxic (kills cells). There is evidence that this is created from dihydroxyacetone in manuka honey stored at warm temperatures. Something similar might be happening in the honey the Dutch scientists tested.

Defensin-1 One of several anti-bacterial peptides (small protein) found in bees, defensin-1 is part of the bee’s defence against bacterial infection. It’s also found in royal jelly, what queen bees are fed by their worker bees. (Royal jelly also has an epigenetic effect: it causes the larvae to become a queen bee, rather than a worker bee.) A wider range of anti-bacterial peptides are present in Asian honeybees than found in the domesticated Western honeybee; it would be interesting to know if honey from different types of bees have different anti-bacterial peptides.

Acidity The acidity of honey had a small effect too. Honey is acidic, neutralising this to neutral pH (not acidic or alkaline) removed this effect.

Source: WIkimedia Commons.
Source: Wikimedia Commons.

None of the individual compounds identified are new and their anti-bacterial actions are already known.

What is news is that these are the particular compounds giving the honey tested it’s anti-bacterial properties and seem to account for all the anti-bacterial properties against the bacteria tested.

Rather than extracting compounds from the original honey, they neutralised each candidate compound in turn, noting the loss of anti-bacterial properties.

By varying the neutralisations applied, they could work out which combination of compounds was effective in killing which bacteria.

Different combinations had different effects on different bacteria. Some factors had overlapping contributions, requiring the presence of one of the other factors for full effect. The overall combination was effective against all the bacteria tested, giving a broad spectrum antibiotic effect against the bacteria tested.

Several of the bacteria tested had known antibiotic resistance.

References

ResearchBlogging.org

Kwakman, P., te Velde, A., de Boer, L., Speijer, D., Vandenbroucke-Grauls, C., & Zaat, S. (2010). How honey kills bacteria The FASEB Journal, 24 (7), 2576-2582 DOI: 10.1096/fj.09-150789

Xu, P., Shi, M., & Chen, X. (2009). Antimicrobial Peptide Evolution in the Asiatic Honey Bee Apis cerana PLoS ONE, 4 (1) DOI: 10.1371/journal.pone.0004239

Adams, C., Manley-Harris, M., & Molan, P. (2009). The origin of methylglyoxal in New Zealand manuka (Leptospermum scoparium) honey Carbohydrate Research, 344 (8), 1050-1053 DOI: 10.1016/j.carres.2009.03.020

Press release (via EurekaAlert)

For a soft introduction to bees, this gives an overview suitable for kids. (Or those who are lazy! – it’s short and well-written.)


Other articles in Code for life:

Temperature-induced hearing loss Some people go temporarily deaf if their body temperature rises

The scale of cellular life and compacting chromosomes A interactive infographic, video and introduction to two ideas about chromosome structure

Science bite: Longevity gene study has flaws? Hmm, not so fast…

Boney lumps, linkage analysis and whole genome sequencing Locating a gene that causes genetically-inherited bone spurs.


10 Responses to “Honey’s anti-bacterial properties found?”

  • This “research” is more than a little misleading. What they don’t tell you is that hydrogen peroxide (present in all honeys) is quickly broken down by body enzymes and therefore has no reliable antibacterial activity.
    They also don’t tell you that methylglyoxal is found in sufficient quantity to kill bacteria ONLY in manuka honey – and only in some manuka honey (not all). The other factors are minor.
    Prof Thomas Henle, the German food scientist who identified methylglyoxal as the dominant antibacterial constituent in manuka honey in 2006, did later research which found a minimum of 150 mg/kg was required to kill most common bacteria. Ordinary honey has about 30 mg/kg at best.
    Can I add another online reference where there are more details (and a layman’s summary) of the science involved:
    http://www.mgomanuka.com/the_science.cfm

  • Brent,

    Hydrogen peroxide is broken down within the body, but I’d like to think that doesn’t mean it has no use as a topical anti-bacterial agent (i.e. used on the surface of the skin). It’s widely known as an antiseptic for cleaning wounds. (Whatever your position on the merits of using it.)

    Regards your statements about there not being enough MGO (etc.) I am left wondering if you have read the paper. Have you?

    For example, from their discussion:

    “In other situations, bactericidal activity depended on the combined presence of different factors. Thus, the activity of honey against E. coli and P. aeruginosa was markedly reduced by neutralization of either H2O2 or MGO.”

    (Note the issue of combinations of factors.)

    Finally, I note the link you provide is to a commercial website that promotes a commercial product, in their words “a trademarked system for testing the level of Methylglyoxal.” (i.e. MGO.) I generally think it’s wiser to use independent sources of information.

  • Grant
    For sure, hydrogen peroxide is effective topically short term. However, for treatment over several hours or days only manuka honey with a sufficiently high level of methylglyoxal would have the stable antibacterial activity required.
    I referred readers to the mgomanuka.com site because the original research can be downloaded (Prof Henle’s full paper).
    Yes, I have read the papers you refer to. Nowhere do I see an explanation that the level of methyglyoxal sufficient to kill common bacteria (Henle put that at 150 mg/kg) occurs ONLY in manuka honey.
    Henle was quite clear, demonstrating that methylglyoxal is “the dominant antibacterial constituent” of manuka honey.
    The paper reported here refers to “honey” generally. This misleads the reader to think any honey will do, when ordinary honey has an MGO level of 30 to 40 mg/kg at best.

  • Brent,

    “ only manuka honey …”

    This seems to be your theme.

    It seems to me (and I would like to think other readers) that you have a vested interest in manuka honey.

    You might want to consider that whatever the findings of this work, the paper I wrote about will take nothing away from whatever properties manuka honey might or might not have because it’s independent of it.

    It is not my business to have to “defend” a paper I present — that’s for the researchers who did the work to do — but I do object others misrepresenting research, even if unintentionally (e.g. perhaps or because their ideological or business-driven interests have them “reading meanings” into what was written or because they are not familiar with how to read a scientific paper).

    The paper reported here refers to “honey” generally.

    Research papers usually have a ‘materials’ section that explains what was used in the study. The paper‘s ‘Materials and Methods’ section explains what particular honey was used:

    “Unprocessed Revamil source (RS) honey was kindly provided
    by Bfactory Health Products (Rhenen, The Netherlands). RS
    honey has a density of 1.4 kg/L and contains 333 g/kg
    glucose, 385 g/kg fructose, 73 g/kg sucrose, and 62 g/kg
    maltose.”

    The paper is about this particular honey, as they are making clear. (For my part, I pointedly referred to “the honey tested”.)

    Furthermore, they clearly state in their final sentences that they intend to go to test other honeys, i.e. it is clear they are not generalising their work past the honey they tested:

    “We presently use
    the same approach to assess the contribution of these
    factors to activity of other honeys, and simultaneously
    to screen for novel bactericidal factors. Such honeys, or
    isolated components thereof, may serve as novel agents
    to prevent or treat infections, in particular those caused
    by antibiotic-resistant bacteria.”

    Whatever faults or not that paper has, it would be misrepresenting the paper to say that they try make it about all honeys in the way you seem to think that they do. (An editor might have asked them to pedantically refer to ‘RS honey’ throughout, as they do in places, but it is already clear to anyone that reads the complete paper what they mean by ‘honey’.)

    Nowhere do I see an explanation that the level of methyglyoxal sufficient to kill common bacteria (Henle put that at 150 mg/kg) occurs ONLY in manuka honey.

    This is a moot question, really. They are not testing manuka honey, they are testing the honey they described. They do not have to reaffirm Henle’s findings, they’re free to contradict it if that is what their evidence shows. (It might have be fair to ask that they discuss the disparity in findings in their discussion.)

    I would add that Henle will not have tested the honey at these authors did, and vice versa. You cannot write “ONLY in manuka honey“ unless Henle tested every honey on the planet! 😉

    (You can say that Henle reported not observing that level of MGO in the other honeys he tested. I don’t have time to go through all the possible combinations to explain this fully as I have my own work to do, but sufficient to say this over-generalising in the same general way that you make the Dutch researchers out to have!)

    They do cite Henle’s work in their introduction, see the citation for reference 13:

    “The broad spectrum antibacterial activity of honey is
    multifactorial in nature. Hydrogen peroxide and high
    osmolarity—honey consists of 80% (w/v) of sugars—
    are the only well-characterized antibacterial factors in
    honey (11). Recently, high concentrations of the antibacterial
    compound methylglyoxal (MGO) were found
    specifically in Manuka honey, derived from the Manuka
    tree (Leptospermum scoparium) (12, 13). Until now, no
    honey has ever been fully characterized, which hampers
    clinical application of honey.”

    I’ve cited the full paragraph as the context is important. Their claim — what they say is novel about the research they report — is that it “fully characterises” the antibacterial properties of the honey that they, accounting for the different things that might contribute to anti-bacterial action, and the combinatorial effect of these.

    (My own objections are that the work is actually lead by a series of “likely factors” rather than truly fully characterised in the sense of exploring all fractions. It’s a tricky objection, though, as the approach they take of neutralising by definition has to be lead this way. They claim what they tested accounts for all of the antibacterial activity, but it seems to me that while what they present is (apparently) sufficient to have a strong anti-bacterial effect on the bacteria tested, other factors not examined might also have an effect but effectively be masked by the approach used. Note that I am not saying that what they do test has no effect, but that things not tested might.)

    The paper at several point refers to the loss of antibacterial action on neutralising MGO. I quoted on earlier, which you appear to have “overlooked”. Here is another w.r.t. to B. subtilis:

    “Neutralization of
    MGO or H2O2 alone did not alter bactericidal activity
    of RS honey, but simultaneous neutralization of MGO
    and H2O2 in 10% honey reduced the killing of B. subtilis
    by 4-logs (Fig. 1C).”

  • Good on you Grant for defending this.

    The paper is not misleading and I thought you did a great job at explaining it.

    Brent, you really do miss the point of scientific discovery. This work is innovative in its approach to elucidating the ‘in combination’ antibacterial effects in this honey .

    If you are so fixated on this ‘Manuka Only’ antibacterial properties, why don’t you just go buy a whole heap of methylglyoxal and not stuff around with the honey at all? Sigma Aldrich sell it in a 40% solution.

    From this paper I would suggest adding methylglyoxal to a cheap honey. This would seem significantly cheaper.

    There are many non-manuka honey products worldwide that have proven clinical efficacy. Your ignorant, narrow mindedness is really disturbing.