A preliminary investigation into prevalence of garlic supplements in the United Kingdom

Background: Garlic is anecdotally considered as one of the most commonly fed herbal supplements in the equine industry, despite limited equine specific research to support its use. There are no current recommendations regarding safe dosage of garlic for horses in UK, even though certain preparations of garlic have been linked to negative side effects such as Heinz body anaemia1.Objectives: The aim of this study was to investigate the prevalence of garlic supplementation in the UK, the main reasons for garlic supplementation, the most common dosage, and identify knowledge on side effects within the UK horse population.Methods: An online questionnaire was created and distributed via social media. A range of closed questions were used to obtain information on the most common preparation of garlic used and relevant dosage, the most common reason(s) for supplementing garlic, and to establish knowledge of any side effects associated with garlic supplementation. Descriptive statistics were used to analyse the data.Results: Responses from 359 horse owners / carers were analysed. Garlic was supplemented by 39% of respondents, with the majority (53%) supplementing garlic all year round. A further 38% of owners only supplemented garlic between April – September. The most common reasons for garlic supplementation was as a fly repellent (44%), boosting of the immune system (15%) and respiratory health (12%). Garlic was mainly supplemented to the feed in granule form (57%) or powder form (35%). NAF horse feeds (28.5%) was identified as the most popular brand for garlic supplementation, although 22.8% of respondents reported they would select any garlic supplement with cost being the main reason to change brands. Responses on added dosage were variable in response and units, with the most common dosages including the use of a scoop according to manufacturer’s guidelines (13%) or 10 gram (11.7%). However, 13.4% of respondents could not remember how much garlic they supplemented. The majority of participants (90%) were unaware of any side effects associated to garlic supplementation, although 14% of respondents were aware of the potential development of anaemia.Conclusions: As this is the first study to identify the prevalence of garlic supplementation in horses, it confirms the existing anecdotal evidence of the use of garlic as a popular supplement within the equine industry. The variation in supplementation form and dosage requires further research as human research has assigned the majority of therapeutic effect of garlic supplementation to garlic’s main biological active compound, allicin2. As allicin content has been suggested to vary according to the preparation of the garlic, it is suggested that further research is undertaken on the impact of garlic supplementation in granule or powder format on allicin levels within the supplement.