Is Manuka Honey Safe? The Active Ingredient in Honey from New Zealand's Tea Tree is Toxic

Manuka honey is produced by bees that collect pollen and nectar from the New Zealand tea tree (Leptospermum scoparium). This plant has been used among the Maori people for generations for its purported health benefits.

An entire industry has developed around Manuka honey and its varied uses. Advocates claim beneficial effects ranging from clearing of skin structure infections (including methicillin-resistant staphylococcus), to treatment of Helicobacter pylori-related peptic ulcer disease, to curing cancer.

For years, Manuka honey was marketed with labels attesting to its “unique manuka factor” (UMF). Manuka honeys were graded on the basis of UMF activity—the degree of inhibition of bacterial growth when compared to a phenol standard.

Manuka’s Active Ingredient Identified

In January 2008, Professor Thomas Henle, Head of the Institute of Food Chemistry at the Technical University of Dresden, demonstrated that methylglyoxal is the active ingredient that endows Manuka honey with its unique antibacterial properties...that is, its UMF. (Identification and quantification of methylglyoxal as the dominant antibacterial constituent of Manuka (Leptospermum scoparium) honeys from New Zealand. Molecular Nutrition and Food Research 2008;52(4):483-489)

Unfortunately, methylglyoxal is considered by most cellular biologists to be a genotoxin (i.e., toxic to genes and chromosomes), and it has been “linked to several diverse biological processes including mutagenesis, aging, carcinogenesis, and diabetic complications.” (Kang J. Oxidative damage of DNA induced by methylglyoxal in vitro. Toxicology Letters 2003;145(2):181-187)

What is Methylglyoxal?

Methylglyoxal is a normal byproduct of sugar metabolism. It is also present in many foods and beverages (particularly foods cooked at high heat), and it is produced by bacteria in the gut (IARC Summaries and Evaluations 1991;51:443). Normally, human cells possess an efficient means for dealing with this molecule and the cellular damage it causes.

Individuals with diabetes, whose ability to metabolize sugar is impaired, may be subject to enhanced cellular damage secondary to increased tissue levels of methylglyoxal. Indeed, metformin—a drug commonly prescribed for diabetics—was designed to ameliorate the effects of methylglyoxal in the tissues of diabetic patients.

Why is Manuka Antibacterial?

Undoubtedly, it is methylglyoxal’s toxic properties that make it an effective antibacterial agent. The molecule has demonstrated activity against MRSA, Streptococcus species, E. coli, H. pylori, and other bacteria. Honeys in general, and Manuka honeys in particular, have shown clinical benefit in wound management, including those infected with resistant organisms.

Animal studies have shown no toxicity from oral administration of physiologic doses of methlglyoxal—in fact, one study showed that pretreatment with methylglyoxal prevented gastric damage in rats that were subsequently administered caustic agents (Al-Shabanah O. Inhibition of gastric mucosal damage by methylglyoxal pretreatment in rats. Food and Chemical Toxicology 2000;38(7):577-84). For better or worse, methylglyoxal from Manuka honey is unlikely to enter the bloodstream in significant quantities. Cellular defense mechanisms (glyoxlyases) would break down a significant portion of orally-administered doses.

So How Should I Use Manuka Honey?

Manuka’s “natural” properties notwithstanding, claims regarding the honey’s usefulness for many chronic medical conditions, cancer, or acute systemic illness should probably be viewed with caution. Manuka honey’s primary role, if it has one, will probably be in the arena of topical treatment. This might include the following:

Though Manuka honey is surrounded by history and promise, insufficient evidence currently exists to support its use in many of the conditions advocated by its proponents.

Nov 16, 2008 3:18 PM

Albert Burchsted :

It would seem methylglyoxal acts as a natural homeopathic substance that kills bacteria, and, since it is toxic, stimulates the body to fight off illness. Scientists have recently become aware of the beneficial properties of poisons in small amounts in promoting a healthier state in individuals who are ill.

I would like to see an expansion of this idea for myself and for other suite101 readers.

Nov 16, 2008 4:07 PM

Stephen Allen Christensen :

Albert,
Homeopathy, as you have implied, is the practice of administering small amounts of substances that, in larger quantities, would produce symptoms identical to the condition that is being treated. For example, if a person complained of nausea and vomiting, a homeopathic physician might give him or her a minute dose of, say, nux vomica, which is prepared from the Poison Nut tree (a source of strychnine).
Although many Western physicians decry homeopathy as a baseless science(some even call it quackery), they themselves practice a form of the art: the subcutaneous administration of very small doses of allergens in an attempt to "desensitize" allergic subjects seems to mirror the philosophies of homeopathy quite nicely.
It's interesting that you would think of methylglyoxal in this sense. I must admit that my limited knowledge of homeopathy prevents me from speaking authoritatively about whether an endogenously-produced molecule can be considered homeopathic. I've worked with homeopaths before; some of their remedies, I guess, could be called "metabolites" (calcarea carbonica, sulphur, etc.). Someone else will have to come to my rescue. Any homeopathic physicians out there?

Nov 17, 2008 9:41 AM

Guest :

I am a certified classical homeopath, so I'll add my 2 cents to the discussion.
A bit of homeopathic philosophy: homeopathic remedies do not act directly on pathogens, rather they stimulate the body's own defense systems to do the work. Most homeopathic remedies are so dilute that not a single molecule of the original substance remains, which is the major bone of contention among the orthodox medical community, although there is research suggesting possible modes of action (including the work of Prof Rustum Roy of Penn State University).
It seems to me from reading the article above that methylglyoxal acts in a direct physiological way, and so is not strictly speaking working homeopathically.
There are over 3000 remedies used by homeopaths, and they will only heal someone if they are chosen to match the symptoms that person exhibits. Homeopaths have been conducting clinical trials (called "provings") for over 200 years to discover the healing properties of the remedies we use. If a remedy can cause a certain pattern of symptoms in a healthy test subject, it is capable of relieving the same symptoms in a sick person. So whether remedies are metabolites or not is interesting, but not strictly relevant. However, it might be interesting to do a proving on Manuka honey or on methylglyoxal.

Nov 17, 2008 10:19 AM

Stephen Allen Christensen :

Thanks for your input!

Mar 2, 2009 7:53 AM

Guest :

Can you specifiy the difference between Mehtylglyoxal and "Dietary Methylglyoxal"? Manuka Honey has been identified to have "Dietary Methylglyoxal" which is different than the compound you are discussing, right?

Mar 2, 2009 8:27 AM

Stephen Allen Christensen :

Dietary methylglyoxal is simply methylglyoxal (MGO) that is found in the diet. They're the same molecule. MGO is a toxic byproduct of glycolysis, which is a necessary process that takes place in cells as they metabolize glucose. Most cells are equipped with enzymes that rapidly deal with MGO, but high levels of MGO lead to oxidative damage. Interestingly, diabetics have higher serum levels of MGO than do non-diabetics.
MGO is also formed in the manufacture of many foods and beverages via the Maillard reaction, a complex series of interactions between reducing sugars and amino compounds (proteins, etc.). The presence of MGO in various food products--particularly those containing high fructose corn syrup-- is a cause for concern, but there is a great deal of debate about the significance of low levels of MGO in manufactured products. A 2008 study done at Rutgers University demonstrated extremely high levels of MGO in some commercial beverages, and the study's authors noted that the toxic effects of dietary MGO on humans needed to be explored.
So I guess that's where it stands. Manuka honey contains MGO. It has been consumed by humans for a long time without any KNOWN ill effects. I use it myself, as a matter of fact, placing my trust in that efficient cellular machinery that has carried me through more than a half century (so far).

May 23, 2009 1:12 PM

Guest :

Camelyn, which is an extract of honey produced primarily from the nectar of acacia trees in the Caucasus region, has no such toxicity and is a much better broad spectrum antibacterial agent than tea tree honey. The extraction process removes all sugar and water, leaving only the concentrated, active ingredients.