For horses · Sep 30, 2021
Your horse’s calming supplement needs better biochemistry behind it
From magnesium’s role in HPA axis regulation to vitamin D3’s control over serotonin synthesis, the science of equine calm is more precise than most formulas admit.
Natural calming supplements can meaningfully reduce anxiety and neuronal hyperexcitability in horses through several complementary mechanisms. Magnesium supplementation alone reduced headshaking behaviour, a condition rooted in neuronal hyperexcitability, by 52% in horses, rising to 64% when combined with boron. Vitamin D3 potently upregulates TPH2, the rate-limiting enzyme in brain serotonin synthesis. Ginkgo biloba (EGb 761) reduced anxiety symptoms in a randomised controlled trial, and Centella asiatica significantly reduced acoustic startle response compared to placebo.
Common misconception: Calming supplements work by sedating your horse
I hear this constantly, and I understand why people think it. The word “calming” conjures images of a drowsy, rubber-legged horse that’s been chemically blunted. Some products on the market do exactly that, which hasn’t helped the reputation of the category.
But the supplements I formulate work through entirely different mechanisms, ones rooted in normal neurochemistry and basic nutritional physiology, not sedation.
Take magnesium. A deficient horse isn’t calm because magnesium sits at the centre of neuronal excitability. Research in mammals shows that magnesium deficiency reliably induces anxiety-like behaviour and dysregulates the HPA axis, the very stress-response system you’re trying to quieten [4]. Correcting a deficiency doesn’t sedate; it restores normal function. The same logic applies to thiamine (vitamin B1), which is a cofactor in neuronal energy metabolism, and deficiency of which is associated with genuine neurological dysfunction [6]. You’re not drugging a horse; you’re feeding its nervous system properly.
The herbal actives operate differently again. Ginkgo biloba (Ginkgo biloba) has demonstrated measurable reductions in anxiety scores in randomised controlled trials in humans [7], and the mechanism involves neuroprotection and neurotransmitter modulation across multiple pathways [10], not receptor blockade or CNS depression.
Gotu kola (Centella asiatica) reduced the acoustic startle response significantly versus placebo in a double-blind trial [8], and its active triterpenoids, asiaticoside and madecassoside, work by upregulating BDNF signalling and modulating central monoamines including serotonin [9]. A horse with a lower startle threshold is not a sedated horse; it is a horse whose nervous system is responding proportionately to its environment.
The distinction matters practically. A sedated horse is a liability, dull reactions, compromised proprioception, potentially dangerous under saddle. A horse supported through nutritional and phytochemical pathways stays sharp; it just doesn’t over-react. Those are not the same thing, and conflating them does real harm to owners who dismiss nutritional support because they don’t want a zombie.
How the ingredients work on the anxious horse brain
Vitamin D3 works at the gene level. 1,25-dihydroxyvitamin D3 transcriptionally activates tryptophan hydroxylase 2 (TPH2), the rate-limiting enzyme that converts tryptophan into 5-hydroxytryptophan (5-HTP) and, ultimately, serotonin in the brain. In cultured serotonergic neurones, this activation produced a 47.8-fold increase in TPH2 mRNA expression at just 10 nM.
Niacin sits in the same metabolic neighbourhood. It serves as a cofactor in NAD(P) synthesis, and because tryptophan is the shared substrate for both the serotonin pathway and niacin-dependent NAD production, dietary niacin adequacy matters: without enough niacin, there is a metabolic competition for tryptophan that can compromise either pathway.
Magnesium deficiency has a well-documented effect on the nervous system. In animal studies, insufficient magnesium reliably induces anxiety-like behaviour and disrupts the hypothalamic-pituitary-adrenal (HPA) axis, the stress-response system. Critically, in horses specifically diagnosed with trigeminal-mediated headshaking (a condition driven by neuronal hyperexcitability), magnesium supplementation alone reduced headshaking behaviour by 52% from baseline; magnesium combined with boron reduced it by 64%.
Thiamine (vitamin B1) functions as a cofactor in neuronal energy metabolism. Deficiency is associated with peripheral neuropathy and serious neurological signs. Its role here is foundational: neurones that are energy-depleted cannot regulate excitability normally.
Ginkgo biloba extract (EGb 761) at 480 mg daily reduced anxiety symptoms over four weeks in a randomised, double-blind, placebo-controlled trial in humans with generalised anxiety disorder and adjustment disorder. A separate study in rats showed that ginkgo biloba extract (GbE) ameliorated anxiety and restored serotonin-related behavioural responses, with the proposed mechanism involving neuroprotection and neurotransmitter modulation across multiple pathways rather than a single target.
**Gotu kola (*Centella asiatica*) works through at least two distinct mechanisms the research describes. First, in healthy human subjects, it significantly reduced the acoustic startle response compared to placebo, with the proposed mechanism involving binding at cholecystokinin (CCK) receptors, which modulate fear and startle. Second, its active pentacyclic triterpenoids, asiaticoside and madecassoside, upregulate brain-derived neurotrophic factor (BDNF) signalling and the ERK1/2 pathway in chronically stressed rats, and moderate alterations in central monoamines including serotonin (5-HT)**.
How to use a calming supplement containing these ingredients, what the evidence actually tells us
Duration before expecting results
The most specific equine data in the pool comes from the magnesium and boron trial [5], which measured headshaking behaviour, a condition driven by trigeminal neuronal hyperexcitability, over a supplementation period that produced a 52% reduction with magnesium alone and 64% with magnesium combined with boron. The human Ginkgo biloba (EGb 761) trial ran for four weeks at 480 mg daily and recorded meaningful reductions on the Hamilton anxiety scale [7]. The Centella asiatica (Gotu kola) startle-response study used a single-dose, acute-administration design [8], suggesting some effects on reactivity may be relatively fast-acting, while the BDNF/serotonin pathway effects observed in the chronic stress rat model [9] imply sustained use is needed for neurochemical remodelling.
Taken together, the pool supports expecting some horses to respond within days on the startle-response dimension, with fuller neurochemical and HPA-axis benefits accumulating over weeks of consistent use.
What to watch for
– Reduced startle and spook intensity, the acoustic startle mechanism is what the Centella asiatica evidence directly addresses [8].
– Calmer baseline demeanour over weeks, which aligns with the HPA-axis normalisation seen when magnesium deficiency is corrected [4, 5].
– In horses showing trigeminal-mediated headshaking specifically, the magnesium evidence is the strongest signal in this pool [5].
What we’d recommend
Supports serotonin synthesis and reduces startle response through targeted micronutrient and herbal support.
See the product
Frequently asked questions
Does vitamin D actually increase serotonin levels, or is that just theory?
The mechanism is real at the gene level: 1,25-dihydroxyvitamin D3 activates tryptophan hydroxylase 2 (TPH2), the rate-limiting enzyme in brain serotonin synthesis, inducing its expression 47.8-fold in serotonergic neurons.
Why is magnesium in a calming supplement for horses?
Magnesium deficiency reliably triggers anxiety-like behaviour and dysregulation of the HPA (stress-response) axis, demonstrated in controlled animal studies.
What does niacin have to do with calming a horse?
Niacin is a cofactor in NAD(P) synthesis. When tryptophan is being preferentially channelled towards serotonin production, it competes with the pathway that produces niacin’s metabolic substrate. If dietary niacin is inadequate, that competition creates a bottleneck. Including niacin in the formulation removes that constraint, supporting the serotonin pathway rather than leaving it to compete with NAD-dependent cellular processes.
Is there any real evidence that Ginkgo biloba reduces anxiety?
Yes, a four-week randomised, double-blind, placebo-controlled trial in 107 human patients found that Ginkgo biloba extract (EGb 761) at 480 mg daily reduced anxiety symptoms measured on the Hamilton Anxiety Rating Scale, in both generalised anxiety disorder and adjustment disorder with anxious mood. The mechanism appears to involve multiple pathways including neuroprotection and neurotransmitter modulation, rather than a single target.
How does Gotu kola (Centella asiatica) help a spooky or reactive horse?
In a double-blind, placebo-controlled human study, Centella asiatica significantly reduced the acoustic startle response, the same flinch-and-bolt reflex that makes horses dangerous in traffic or unfamiliar environments. The proposed mechanism involves CCK receptor binding. Animal research also shows its active triterpenoids (asiaticoside and madecassoside) upregulate BDNF signalling and moderate central serotonin alterations under chronic stress.
Why is vitamin B1 (thiamine) included, and is it safe at supplemental levels?
Thiamine is an essential cofactor in neuronal energy metabolism; deficiency is associated with peripheral neuropathy and serious neurological signs. Pharmacokinetic work in horses confirms that even intravenous thiamine at 5-20 mg/kg produced no adverse clinical signs, suggesting a good safety margin. Oral supplemental doses are far lower. If a horse is subtly deficient, supporting this pathway is a straightforward way to underpin normal nervous system function.
Sources
- Niacin Deficiency – StatPearls – NCBI Bookshelf
- 1,25-Dihydroxyvitamin D regulates expression of the tryptophan hydroxylase 2 and leptin genes: implication for behavioral influences of vitamin D
- Does vitamin D supplementation impact serotonin levels? A systematic review and meta‐analysis
- Modulation of magnesium deficiency-induced anxiety and HPA axis dysregulation by therapeutic drug treatment
- Effects of magnesium with or without boron on headshaking behavior in horses with trigeminal‐mediated headshaking
- Pharmacokinetics of thiamine (vitamin B1) in adult horses after administration of three single intravenous doses
- Ginkgo biloba special extract EGb 761 in generalized anxiety disorder and adjustment disorder with anxious mood: a randomized, double-blind, placebo-controlled trial
- A double-blind, placebo-controlled study on the effects of Gotu Kola (Centella asiatica) on acoustic startle response in healthy subjects
- Centella asiatica (Gotu kola) ethanol extract up-regulates hippocampal brain-derived neurotrophic factor (BDNF), tyrosine kinase B (TrkB) and extracellular signal-regulated protein kinase 1/2 (ERK1/2) signaling in chronic electrical stress model in rats
- Ginkgo biloba extract (GbE) attenuates obesity and anxious/depressive-like behaviours induced by ovariectomy