Are all herbs compatible with
EquiFeast's approach to brain food?

Back in 2011 we ran our first horse blood trials and one of the key things they showed us was that, if magnesium levels in diets and blood were too high, our chelated calcium technology didn’t work as well as we would like. Since then we have monitored over 30,000 horses and refined our conclusions, redesigned our products and modified our advice to start all new recruit horses on WHOLE DIETS with no artificial added magnesium in them. In the UK this has turned us from a pure supplements company into a feed company. Unfortunately we can't do that here in North America but there are feed ingredients readily available to you to make our sort of diets quite easily.

We also dug deep into both the human science (neuroscience, physiology, biochemistry etc) and the limited equine science and all of that supports our thesis. Of course the world isn’t perfect and we and our customers still experienced unexplained failures.

In 2014 we won the FSB/WorldPay Business Innovation Award for the way we leverage our close customer relationships into our R&D. And we continue to work closely with customers to further refine our understanding. As time went on it became clear that one cause of failure to improve behaviour involved horses on products that contained herbs. By blocking or downregulating brain function some herbs are capable of working against our approach so increasing our failure rate.

Let me make this clear – we are not saying herbal products are bad. If your horse sedates nicely on them and you are happy and feel safe – please use them. The same applies to magnesium. But we do think you should be aware how these products are affecting your horse so you can make an informed decision.

For ourselves we have a company policy that we will not knowingly sell something that will impair the horse’s brain function. Our philosophy is that good behaviour comes when a horse can evaluate the risks in its world properly – clearly things that impair brain function are not compatible with that. So everything we are going to say about herbs here is aimed at those people that want to try our brain supporting approach. If you are happy sedating your horse – read no further and buy your feeds and supplements from other firms.


The development of our products and supporting advice are largely influenced by two sources of information:

  1. The feedback we get from our customers.
  2. The published science – limited though that is. Sometimes this is equine science but more often it is from the broader fields of biochemistry, neuroscience and physiology.

The first, the one that really drives things, is the information provided by our customers. They are the people that know their horses and can see the changes in them. Yes they can be wrong, yes they can be influenced by the placebo effect but their observations are “evidence” that deserves further investigation. Contrary to the proposals of some, this is the first plank in the scientific process. Darwin didn’t reject his theories of evolution because the academics that published literature before him hadn’t looked at it. He looked at the evidence, determined that it didn’t fit the prevailing paradigm (that God had created the world in six days) and developed a new hypothesis. This is what we do. It is also what our competitors do – including those who claim the scientific high ground. For example there are no double blind placebo controlled trials supporting the efficacy of any horse calmers that we are aware of. Nor trials of that nature in horses on any of the individual ingredients. That doesn’t make the calmers on the market useless but it does make them “scientifically unproven”.

The first herb that came to our attention proved to be one of the hardest to explain – simply because the experiments carried out on many herbs haven’t been done on it. That herb was Fenugreek. Our products seemed to struggle when used in conjunction with Fenugreek containing feeds. I don’t think I could find it now but about 4-5 years ago there was a Facebook thread where the OP asked people’s opinions about a particular feed product, marketed as “calming” and that we were regularly recommending (because it had no added magnesium). The replies (and there were a lot) split almost 50:50 between those people who loved the product and those whose horses had gone loopy on it. There didn’t seem to be much middle ground. So we looked at the product and the only unusual ingredient was Fenugreek. I have no idea if this herb was added for its calming properties or as a flavouring but it seemed to be the most likely ingredient to be causing the problem. When we want to see if a herb might cause a problem we generally Google the herb name and “GABA”. A huge number of herbs have been tested for their effect on the GABA receptor in the brain (also known as the benzodiazepene receptor (BDZ)). But Fenugreek hasn’t so we were none the wiser about what it’s mode of action is.

For quite a while we couldn’t explain how Fenugreek caused a problem so our advice to avoid it tended to be fairly gently put. But we had a breakthrough recently when we were investigating a GABA agonist that is listed on the United States Equestrian Federation banned list and that was Eugenol. Eugenol is the active chemical in licorice, aniseed, fennel, ginger, nutmeg and a whole pile of other plants. It turns out that when you Google fenugreek and “eugenol” you find the link. So is it the eugenol in Fenugreek that causes a problem or some or many of the other biologically active chemicals it contains? We don’t know but at least we now have some sort of explanation for the problem.

So now let’s combine that desk research with the real world. Here is a story that came in to us in early 2021 that is just another nail in the coffin for Fenugreek. Though it is possible from this feedback that the problem is Mint!:

“William, my 11 year old Irish Draft, had two issues:

  • If he wasn’t the first out to the field he would barge out of his stable like a bull in a china shop! It isn’t fun when you’ve got a really big horse coming at you.

  • In Early Sept 2020 his arthritis meant he was just starting on daily Bute - which didn’t seem like a good long term plan for a horse that young.

That is when we tried EquiFeast’s FlexEasi, and what can I say? A simple diet of FlexEasi, MORE Fibre, and a handful of a basic High Fibre chaff worked an absolute treat. It doesn’t seem a lot but it made a remarkable difference. His movements were a lot better and his stable manners were absolutely impeccable. FlexEasi’s “brain food” component allowed William to process what was going on and increased his concentration in his ridden work which made hacking and schooling feel a lot safer.

This fabulous behaviour didn’t last long. In mid-December the horrible, bolshy, boisterous William was back - but worse! He was being more reactive to small things – like leaves rustling in the hedge. He pushed my husband to the ground a few times when turning out. Hacking and schooling soon became far from a pleasure and more a dread.

What had happened? It turns out we had changed that tiny bit of chaff to a Molasses Free version of the same brand. You would think that less molasses would be a good thing but it turns out it isn’t if it is replaced with Mint and Fenugreek! Within a few days of removing the chaff and reverting to the original (no herbs and no magnesium) the gentlemanly behaviour returned. From being a bull, to being a gentle giant within a week was astonishing. Now he is a saint.

Sue, E. Yorks.”

You can find another story that illustrates how the GABA agonist Devil's Claw prevented our supplement working properly on a PSSM horse in America (Jesse, owned by Tamra Young):

So our advice is this. If your horse sedates nicely on GABA agonist herbal products and you are happy to ride a horse knowing what you are doing to its brain – please stick with it – you don’t need EquiFeast. But if your horse goes loopy on GABA agonists or you would rather not use a brain impairing herbal drug then please speak to us. Be prepared to change the diet to avoid any ingredients that work against our products though.


How are GABA agonists identified?

For a large number of herbs with a history of being used for behavioural issues in humans there are some simple experiments. Firstly they test for their chosen characteristic on the control diet and then they repeat the experiment using the trial herb (or chemical). If they get an effect from the test product they know it is affecting the animal but not how.

So they repeat the experiment having firstly blocked the GABA receptors (BDZ) with a BDZ antagonist. If they get the same result the GABA receptors were not involved. But if the observed effect is gone they conclude that the herb was acting on the GABA receptors.

The benefit of this test is that the researcher doesn’t have to know what active chemical inside the plant is that causes the GABA receptor to be triggered. Below we will list herbs that have been identified as GABA agonists this way. But before that ……..


Chemical components of herbs known to be GABA agonists or allosteric modulators

1. We have already mentioned Eugenol. This chemical is listed on the USEF list of substances for which they will not grant authorisation for use in competition. So that counts Fenugreek out as an ingredient in American feeds or supplements except for recreational horses. It isn’t on the FEI list of prohibited substances but see below for a discussion of whether or not that matters. Here is one paper that discusses how eugenol affects GABA receptors.

2. The next chemical we need to consider is GABA itself. This is an amino acid but one that isn’t incorporated into proteins. Instead it operates as a neurotransmitter. Back in 2012 the USEF persuaded the FEI to rush through the incorporation of GABA and many GABA agonists onto the Prohibited Substances list. This was in response to what they regarded as the dangerous use of a product called Carolina Gold which contained pure GABA mixed with some other things.

GABA is not only an animal neurotransmitter. Quite a lot of plants use GABA. So any herbal ingredient that actually contains GABA is not legal under FEI rules. Passionflower is an example. Here is a paper that describes GABA as a “prominent ingredient” in Passionflower. This paper also demonstrates that Passionflower is capable of producing anxiogenic effects – that means that it causes anxiety!

We had a well-known calmer with Passionflower in it tested and, sure enough, we found what is most likely GABA. If we can find it so can a WADA accredited laboratory - if they were told to look for it.

3. Menthol

At this stage (2021) we are not sure if this is a major problem or not. So we are tending to recommend that people avoid it when using our products. It is an incredibly well known chemical is an analgesic (painkiller). It also tells the body that it is cold. https://europepmc.org/article/med/18593637

There is some evidence that menthol acts as GABAA receptor positive allosteric modulator and increases Gaba-ergic transmission.


4. Alpha-casozepine

This polypeptide is derived from milk and is a GABA agonist. It is on the FEI prohibited list.

5. Valerenic Acid

The active ingredient in Valerian. Is a GABA receptor allosteric modulator. It is an FEI Controlled Substance.


6. Camphor

This is on the USEF Prohibited list. It is a GABA receptor modulator.

7. Taurine and Beta Alanine

These are both non-protein amino acids. They are both capable of activating GABA receptors. Taurine containing “calmers” are heavily promoted in the USA as FEI/USEF legal. I would question that:

8. Serine

An amino acid that has GABA agonist properties.


9. Others

There are dozens of chemicals in plants that have significant biological effects when ingested by animals. This article concentrates on those that have been demonstrated to work on the GABA receptors. There will be lots more of these that we have not yet identified from the literature or that have not been identified by the limited scientific resources committed to understanding herbal medicine.

There are also many other ways that various natural chemicals can influence the GABAercic system. For example L-Theanine (another non-protein amino acid) works synergistically with GABA and enhances its effect:


Herbs known to have an effect on GABA receptors

This table includes both plants whose active chemical has been identified as one of those we have listed above and those where the GABA agonist effect has been demonstrated but the active chemical isn’t yet known or isn’t on our “watch list”. This is not intended to be a comprehensive list. And it doesn’t include many herbs whose Mode of Action does not involve GABA but that still negatively impact on brain function.

Click here to enlarge the below table. 


What is the FEI status of these herbs?

We are not going to propose an opinion about the FEI compliance of the individual herbal and amino acid ingredients mentioned in this article. We are interested in them because we think they are incompatible with our “brain supporting” approach to good, safe behaviour. Here are two extracts from the FEI Cleansport web site for readers to consider:

"The EPSL lists all substances that are prohibited for use during FEI events. Substances that are not listed on the EPSL are not prohibited provided that they do not have a similar chemical structure or biological effect to a substance listed on the EPSL."

Riders need to take specialist advice about what constitutes “similar biological effect”. Are all GABA agonists prohibited?


"Athletes and their support teams are strongly encouraged to work closely with their veterinarians when administering substances to horses. The FEI has published a warning regarding the use of supplements (including herbal supplements) and products of which the ingredients are unknown. Any substances which affects the performance of a horse in a calming (tranquillising) or an energising (stimulant) manner and which contain a Prohibited Substance are forbidden. Athletes should also be aware that the use of a calming product during competition may also have important safety consequences."


Australia and the USA both spell out their policies somewhat more clearly than the FEI. The list of prohibited herbal ingredients on the Equestrian Australia web site contains a lot not listed in this article and not specifically listed on the FEI database:

And here is the list for the USEF. Again it has many herbs and ingredients of herbs that are not on the FEI list. See pp 4-5: