The Bog Bilberry Enigma

The bog bilberry (Vaccinium uliginosum L.) is a species of wild-growing berry native to most countries of central and northern Europe and to the arctic vegetation of the entire northern hemisphere. While in some countries it is regularly eaten, collected and processed into jams and beverages, elsewhere (especially in central Europe) there are mentions of its peculiar toxicity in the oral tradition. This is particularly visible in the local names: in Germany Rauschbeere intoxicating berry, in Slovakia "šialenica" - "mad berry", Czech Republic "blinkavka" - "vomit berry", Poland "opilki" "drunken berry". These folk tales sometimes vary even in the same area, from one village to another. To this day there has been no systematic attempt at scientifically addressing this mystery. One theory claims that the toxic effects are a result of a parasitic fungus Monilinia megalospora that colonizes the plant, infects the berries and releases its toxic metabolic products into the fruits. However, this theory hasnt been researched yet either. The aim of this project is to address this enigma for the first time in a controlled, detailed way. Multiple samples of bog bilberry fruits will be gathered from all over central Europe, as well as from Scandinavia and Alaska in cooperation with local institutes. The locations are chosen both from regions where its considered safe to eat and where its avoided as poisonous. These berries will be processed into exctracts, separated and analyzed for the presence of potentially toxic substances such as alkaloids or terpenoids. Any newly discovered compounds will be isolated and their chemical structure will be identified using Nuclear Magnetic Resonance (NMR). The samples from different locations will also be compared to each other to see if there are any regional differences in the content of the active constituents and if this can be somehow traced to the presence of Monilinia mold. The extracts, their fractions and all potentially isolated pure compounds will be tested for toxicity on an animal model using nematodes Caenorhabditis elegans. Any compound that significantly shortens the lifespan of this microscopic worm can be considered potentially harmful. These compounds will be investigated further using molecular modeling and computer simulations to predict their effects on human body. When put all together, these results should give us an answer to the question of bog bilberrys toxicity; whether it is safe to eat or potentially harmful and should be avoided.

The aim of this project was to answer a century-old question: are bog bilberries (Vaccinium uliginosum L.) edible, or do they cause poisoning and hallucinations? To address the topic in detail, a literature review was performed first, critically analyzing the reports of the bog bilberry toxicity and going back to the primary sources (in some cases centuries back), translating from multiple languages. We compared the opinions of locals from all around the world and proposed possible explanations for this phenomenon. This was published in Vanekov et al., 2024 (10.3389/ftox.2024.1358840). The first step of the experimental part was a collection of bog bilberry fruits as the material used for analysis. The sample collection spanned two continents and seven countries, thanks to the help of our collaborators in Finland, Norway and Alaska. This allowed for a thorough comparison of the phytochemical makeup of the fruits. The fruit samples were thoroughly chemically analyzed in order to detect possible toxic compounds, such as alkaloids, sesquiterpenes or diterpenes. During this analysis, several triterpenes were isolated from the fruits which are not considered toxic, but nevertheless are a novel finding for the species and for the family Ericaceae. The full analysis of these triterpenes is currently under review. The main outcomes of this project are summarized in Vanekov et al. 2025 (10.3390/plants14172645). In this publication, we explore the theories proposed in the above mentioned review and answer them using state-of-the-art methods: There were no toxic compounds found in any of the berry samples from anywhere in the world There were no negative effects observed in the toxicity screening on cells and Caenorhabditis elegans. The parasitic fungus theory did not appear likely either, as the infected sample did not differ toxicologically from the healthy berries The most likely explanation is that the berries ferment rapidly, creating alcohol content which is then responsible for the inebriation. We tested the ability of the berries to ferment under different conditions, which resulted each time in measurable alcohol percentages. We conclude that the reports about the toxic effects of the bog bilberries could not be confirmed using modern scientific methods. Alternative explanations are possible, for example miscommunication, accidental ingestion of a different plant/berry or individual intolerances. In addition, during the sample collection we identified two genetically distinct populations of bog bilberries in Central Europe. A study mapping their occurrence in Central Western Carpathians is currently under review. Other important project outcomes include multiple congress presentations, media outreach and several Master's and Bachelor's degree theses, some of which are still ongoing or under development.