Presented by: Conner Brown MD
Hadassah Medical Center

Introduction

Mankind likely started harvesting honey from the European honey bee, Apis mellifera, at least 10,000 years ago while domestication of this species has been in effect for at least 5,000 years. Due to the crop pollination services these insects provide throughout North America, a great deal of research has gone into their greatest known threat to date: Varroa destructor. Varroa mites are a major pest affecting honeybees, leading to up to 80% losses in some apiaries when first introduced to North America in 1987. Oxalic acid treatment has been widely used to control the infestation of varroa mites in honeybee colonies. The treatment involves the application of oxalic acid by vaporization, dusting, or evaporation. It has been found to be an effective method for controlling varroa mite infestation in honeybee colonies, while having almost no impact on the overall health of the honeybees. It is reasonable to be concerned that the use of oxalic acid treatment and its potential contribution to dietary oxalate levels. Oxalate is a naturally occurring compound found in many plants and is known to form kidney stones when consumed in excess.

Materials

A PubMed and Google Scholar search was performed with the keywords, “varroa”, varroa destructor”, “oxalic acid treatment”, “per capita honey consumption” between the years of 1990 and 2021. The resulting papers and publications were analyzed for relevant data.

Results

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If and to what degree oxalic acid treatments contribute to oxalate levels in honey is somewhat contested, however some sources clam it is between 68mg/kg and 119mg/kg. The 2021 per capita honey consumption was 0.87 kg in the USA, 1.55 kg in Greece, and 2.03 kg in New Zeeland. Respective annual oxalic acid intake per capita in these countries may be as high as 103.5mg, 184.5 mg, and 241.6 mg.

Conclusion

Although the potential impact of oxalic acid treatment on dietary oxalate levels is a concern, it should be noted that the contribution of honey to overall oxalate intake is generally low. With the average recommended oxalate intake levels for stone formers with known hyperoxaluria being 100mg or less, the levels found in honey are negligible. Although oxalate is metabolized differently in insects than in vertebrates, there is enough concern that the US Food and Drug Administration banned the use of oxalic acid treatment on hives in which honey gathering “supers” have been added for the season. Overall, the use of oxalic acid treatment remains an important tool for controlling varroa mite infestation in honeybee colonies and its contribution to human oxalate consumption is of little impact.

Funding

None

Co-Authors

Zvi Ben-Yitzhak, MD
Hadassah Medical Center

Mordechai Duvdevani, MD
Hadassah Medical Center