Australasian Science: Australia's authority on science since 1938

How Safe Is Australian Honey?

How Safe Is Australian Honey?

By AusSMC

A study has reported that Australian honey has liver-damaging toxins at levels that exceed European standards. How concerned should we be?

"Plants often use toxic chemicals to stop animals eating them. One class of toxic chemicals are the pyrrolizidine alkaloids, which can cause liver and lung damage. Long-term consumption of pyrrolizidine alkaloids may increase the risk of cancer.

“Pyrrolizidine alkaloids are present in plants ranging from comfrey to Patterson’s curse (Salvation Jane), and small amounts of pyrrolizidine alkaloids may be found in salads, herbal medicines and honey. In many parts of Australia, Patterson’s curse /Salvation Jane is a significant source of nectar for foraging bees. This honey can have high levels of pyrrolizidine alkaloids, and must be diluted with honey from other sources to reduce the levels.

“The recent report (www.tinyurl.com/guq888l) shows that Australian honey has on average four times more pyrrolizidine alkaloids than European honeys. European guidelines are more stringent than Australian guidelines, mostly due to a more conservative estimate of cancer risk. While pyrrolizidine alkaloids are able to produce cancer in rats, evidence for cancer in humans is indirect. However, for most Australian honeys the risk is low.

“For a 70 kg person consuming the average amount of honey (around 3 grams per day, roughly three teaspoons), consumption of most of the Australian honeys would be safe at both European and Australian guidelines. There were a few exceptions, and these are of concern. However, people who are high consumers of honey are at much greater risk, and several honeys exceed both current Australian and European guidelines when consumed at levels seen in 5% of the Australian population.

“While for the average consumer the risk is low, further investigation will be needed to understand the risk to more vulnerable groups.”

Dr Ian Musgrave is a Senior Lecturer in the Faculty of Medicine, School of Medicine Sciences, within the Discipline of Pharmacology at the University of Adelaide.

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“Pyrrolizidine alkaloids (PAs) are naturally occurring compounds found in Patterson's curse and in more than 600 plants that grow across most of the world’s pasture lands. Complete avoidance of PAs is therefore not possible. During the summer months and particularly where other plants are water-stressed, Patterson's curse may be the dominant flowering plant available for beekeepers to use for honey production.

PAs are known to be liver toxins in humans at high intakes, and some have been shown to be carcinogenic in rodents in studies where the animals are administered the compound for their entire lifetime. In humans, liver (or other) cancer has not been associated with high-level PA exposure even where outbreaks of PA-induced liver toxicity have been of sufficient severity to cause multiple deaths due to liver failure. Such outbreaks have only been reported in communities consuming relatively large quantities of PA-containing seeds as contaminants in their grain and where protein intake has been low, impairing normal liver detoxification mechanisms.

“Consumers would be wise to avoid honey produced solely or predominantly from Patterson's curse, which is generally only available from specialist outlets or farmers markets, and honey producers have previously been advised to blend such honey with that produced from other flowering plants to keep levels as low as possible.

“There is unlikely to be a significant human health risk from consuming normal amounts of Australian honey. Those consuming high levels of honey may wish to seek honey produced from other plants.”

Adjunct Professor Andrew Bartholomaeus is from the School of Pharmacy, University of Canberra; and the Therapeutic Research Unit, School of Medicine, University of Queensland.