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The truth about tryptophan...

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If you've read a recent Facebook post recently, you may be pondering about the use of tryptopahan in calmers. It was nice to see at least one comment on said post, from an individual who was curious to hear a response from those that do use tryptophan, so here it goes!

The problem we have when tryptophan is concerned is that the science that has been done all suffers from a simple fundamental flaw and that is that is assumes that anything marketed as a calmer will “calm” all and any horses. In other words they make the assumption that calming and sedation are the same thing. That means the tests that have been developed actually test sedation. As tryptophan doesn’t sedate (which is a good thing) it will always fail these flawed experiments.

Some of the papers referred to in this post use the “Reaction Speed Test”. That measures the instantaneous flight response to a scare for just a distance of two metres (about half a second). In those tests “control” (untreated) animals canter away at about 5 metres per second. Sedated horses trot away at about 3.5 metres per second. Give horses sedative drugs like Acepromazine (ACP, ACE, Sedalin) and they trot away. Magnesium, in quite small doses, also slows the reaction response to a trot which is to be expected as its sedative effects are well understood by the biochemists and neuroscientists – though many equine nutritionists seem to be in denial.

Sedatives impair brain function. They are drugs as the body is being forced to do something unnatural when they are used. In my view good nutrition does not work that way. Good nutrition should enable the body to work normally not it force it. That is what tryptophan does.

To understand this we have to consider the role of a chemical messenger (hormone and neurotransmitter) called serotonin. Serotonin is important in this discussion because it is made from tryptophan. Serotonin has two major and completely different jobs in the body. Unfortunately the equine science I have seen completely ignores one of these. That makes all the science fundamentally flawed. Let’s look at these two roles:

  •  Inside the brain serotonin is used as a neurotransmitter. That is a chemical message sent from one nerve cell to another. It is only used in a relatively small part of the brain and that is involved in our and our horse’s sense of wellbeing and relaxation.
  • If there is enough tryptophan to make serotonin this part of the brain will function normally and the horse will have this ability to remain calm. This is about 10% of the serotonin in the body.
  • Serotonin cannot cross from the main part of the body into the brain. What is called the “blood brain barrier” has evolved to protect the brain from toxic waste products but it also enables the brain to use some chemicals for completely different jobs to those the same chemicals do elsewhere. 80-90% of the serotonin in the body is actually used in the gut. When an animal is stressed it produces serotonin and that tells the gut muscles to contract, empty the gut, make the animal lighter and so facilitate flight or fight.

This understanding gives a simple explanation of how a horse’s tryptophan reserves may be depleted – STRESS.

So stressed horses may become tryptophan deficient. And tryptophan deficient horses will benefit from tryptophan supplementation. Hence the ONLY horses that will benefit from tryptophan will be those that stress a lot.

This brings us to the quality of the science employed. I don’t think that any of the papers quoted by this recent Facebook post, pre-stressed the horses, and then the only response they tested for was a sedative response.

Since only stressed horses will benefit and even they will not be sedated the experiments employed were designed for tryptophan to fail. This isn't good science because it has deviated so too from the real world.

Let me take the example of the 2016 research that is used as a headline (Noble et al 2016 The Veterinary Journal). I have exchanged emails with the author on this matter because (can you believe it?) this is a piece of nutrition research that didn’t even publish any diet information!! So how can anyone assess it rationally let alone peer review it.

So let me list my criticisms of this work:

- The subject horses were not selected for any behavioural criteria. They were the University’s laboratory animals living in a quiet, herd environment and occasionally brought in to be poked and prodded experimentally. They would never be the sorts of horses that riders would buy a calmer for.

- These horses were not stressed as part of the experiment. Without testing a stressed group against an unstressed group this experimental methodology is never going to see an impact from tryptophan supplementation.

- When quizzed about the diet it became clear that no attempt had been made to control the magnesium content of the diet. These horses were getting somewhere between 23 and 30+ grams of magnesium a day. The RDA is 7.5 grams or less.

A PhD student at the same university had used the same experimental method to evaluate magnesium as a calmer and found that on only 13.7 grams of magnesium reduced the flight speed from a canter (5.3 m/s) to a trot (about 3.7 m/s). So sedated horses respond to a scare at about 3.7 m/s.

The control horses in the 2016 study fled at between 3.33 and 3.57 m/s. IN OTHER WORDS THEY WERE ALREADY MAGNESIUM SEDATED BEFORE THE EXPERIMENT STARTED!

All is not lost from this research because it makes it very clear that tryptophan did not sedate these horses. That is good news because it supports our experience that providing tryptophan to a horse that doesn’t need it has no negative effects except to the wallet of the rider. And in the case of EquiFeast we normally supply a FREE tester pack to people to try before they buy.

So having rather trashed the science what are the things that many years of experience and careful monitoring of outcomes in the real world tells us.

- Tryptophan either helps or it doesn’t there isn’t much of a grey area. It will work in the situations described above but only if other issues are not impacting negatively on behaviour. This is why we nearly always work to get chelated calcium and magnesium right before using tryptophan to fix specific, stress related issues.

- When we first investigated tryptophan we were aware of the claims that it could affect stamina. So we gave a gram or two very carefully. Then one of our sponsored riders gave a 3* event horse (with a history of stress in big dressage arenas) 40 grams! The horse completed all three phases perfectly – no stamina issues on XC at all. Since then we have often started horses on 10g or 20g and never had any stamina issue reported in any horse (including endurance horses).

- As horses gain in confidence their need for tryptophan diminishes. The horse mentioned above ended the season on just 3 grams a day and later dropped to no tryptophan at all at which level it qualified for a senior British team.

The eventing anecdote quoted above took place in 2011. We have been selling tryptophan since then and, based on customer feedback, refined the advice we give and the circumstances in which we use it. In the right circumstances it is a really powerful nutritional tool with no downsides that we have identified in normal use.

I hope this helps!


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