Is Caffeine Beneficial for Equine Endurance?
CAFFEINE IN ENDURANCE by Dr David Marlin
Anyone who follows endurance will probably by now be aware of the positive tests for caffeine and its breakdown products (metabolites) in horses in Group VII recently. A number of people have asked me why this might be used. This isn’t a judgemental post as I don’t have the full details; this is factual.
Most of us are familiar with the effects of caffeine. Its a stimulant and can pick us up if we are feeling a little sluggish or slow. It can help us stay awake on a long drive. Physiologically and pharmacologically caffeine and or its major metabolite theobromine have many effects, including but not limited to: It causes an increase in heart rate, it increases glycogen breakdown, it can open the airways (its a bronchodilator), it increases urine production (it is a diuretic), it can improve vascular function, it can make you feel exercise is “easier”, it can increase blood lactate, it can act as an analgesic, it can reverse feelings of fatigue, it enhances both short term high intensity AND ENDURANCE performance. It may have cognitive/mood/behavioural/concentration effects but this can depend on whether you are a regular “user” or a one off “user”.
The effect varies between individuals. Some people can smell coffee and be awake for days. Others can drink three strong cups an hour before bedtime and get an uninterrupted quality nights sleep. The same will be true in horses. So yes, ingestion of the correct dose of caffeine at the right time can increase endurance performance in people and may have the same effect in horses.
The sensitivity of horses to caffeine is not known although there is at least one report of poisoning (Delfiol et al. 2012). If caffeine was given intentionally to the endurance horses racing in Group VII recently then we can possibly at least partly blame Ferraz et al. (2008) who showed that IV (intravenous) administration of caffeine at 5 mg/kg bodyweight 30 minutes before exercise allowed Arabian horses to run faster at the same heart rate compared with when not given caffeine. They also had higher blood lactate, higher plasma insulin, higher plasma glucose and lower plasma cortisol when given caffeine. In short, the IV administration of caffeine at 5 mg/kg improved the performance of Arabian horses during intense exercise of SHORT duration. However, 2.5mg/kg IV had no effect on performance or response of fit TB horses in a short term high-intensity run to fatigue in a different study (Savage et al. 2005). Previous studies showed that 5mg/kg IV but not 2.5mg/kg IV increased plasma adrenaline in horses during exercise (Kurosawa et al. 1999), hence the doses used in subsequent studies.
There exist two possibilities. One, caffeine was given deliberately either IV or orally, potentially, but less likely, even intramuscularlly or by inhalation or per rectum. The levels of metabolites in the urine would potentially help differentiate accidental from intentional administration. Two, the presence of caffeine and or its metabolites was accidental. Caffeine and theobromine contamination are EXTREMELY common contaminants in many equine feed and supplement raw materials. If companies buy from reputable ingredient sources and undertake thorough testing then the risk of a positive in a horse due to accidental ingestion of a contaminated feed or supplement is very very low. Different companies have different standards. Even those belonging to the BETA NOPS scheme (UK scheme for reducing the risk of accidental positives). This scheme is good but companies are still only required to ASSESS THE RISK of contamination and then put a plan in place. If the risk is classified by an individual company as low they are not required to undertake regular or extensive testing of ingredients or finished products for common NOPS (naturally occurring prohibited substances), of which CAFFEINE and its metabolite THEOBROMINE are two of the most commonly occurring.
In summary, if the presence of caffeine and or theobromine was accidental this will likely be traced to a poorly controlled feed or supplement. If the administration was deliberate then it’s use was extremely ill-informed; caffeine and theobromine are so simple and basic to identify in horse urine or blood that anyone with a little chemistry knowledge could setup the tests within a few weeks. Furthermore, a recent publication in 2016 by Machnik et al. in Drug Testing and Analysis should also have had alarm bells ringing for anyone informed enough to have looked into the possible benefits of giving caffeine to endurance horses.