TRYPTOPHAN…A helpful or harmful calmer for horses?

Tryptophan is a common ingredient in ‘calming’ products for horses. It is an amino acid which is a precursor to serotonin. This means that tryptophan is one of the building blocks our horses need to make the neurotransmitter (chemical messenger) serotonin. Serotonin plays important roles in helping regulate mood, pain perception, arousal state and digestive function. We know that a lack of serotonin in the body can be associated with a variety of symptoms including anxiety, aggression, low pain tolerance, colic and a dull mood.

What we know from current research is that simply giving our horses tryptophan as a supplement doesn’t help promote calm behaviour- in fact, it may do the very opposite. Low doses of tryptophan given to horses actually promotes excitement, whilst high doses have been shown to reduce endurance capacity and cause haemolytic anaemia. In either case, hardly helping with overall health and performance.

The reasons for the effects of tryptophan supplementation on horses are likely multifaceted. We know that responses to tryptophan are species dependent- whilst it can be helpful in humans and some animal species, the same cannot be said for horses.

It is important to remember that very few nutrients act in isolation. For tryptophan to be converted to serotonin, it has to go through several metabolic processes. Each of these processes requires key nutrients to facilitate the conversion. Without sufficient nutrient levels and good gastrointestinal health to facilitate this, the conversion and metabolism of tryptophan are effected.

We also need to remember, like many facets of health- there is a sweet spot between not too little and not too much. The same is true for serotonin- too little, and our horses can be anxious, too much and they can become agitated.

The take-home message is that whilst some supplements can be incredibly useful, not all are. We can better promote healthy neurotransmitter levels (such as serotonin) by ensuring our horses are receiving a balanced diet providing all key nutrients in appropriate quantities and forms. Additionally, we want to ensure that we’re promoting optimal gastrointestinal health, as this in turn helps to facilitate both healthy nutrient production and neurotransmitter levels.

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