Walk through any tack shop or scroll through equestrian social media and you’ll find a tidal wave of trending supplements promising to soothe joints, support the gut, brighten coats, or ‘boost the immune system.’ From golden turmeric to kelp, mushrooms to magnesium, the modern supplement aisle is bursting with natural-sounding solutions.
But how many of these work? Which are safe, and which could actually cause harm? And how can horse owners separate genuine benefit from marketing spin?
In this article, we unpack some of the most popular equine add-ons and what the science (or lack thereof) actually reveals. We’ll also highlight why it’s essential to consult with your vet or nutritionist before adding anything to the bucket.
Turmeric: The golden cure-all?
Turmeric (and its active compound curcumin) is touted as a natural anti-inflammatory, often used for joint issues or general wellness.
The science:
- Curcumin has anti-inflammatory properties in lab settings, but it has low oral bioavailability, meaning very little is absorbed through the gut unless combined with other ingredients (like piperine from black pepper or formulated delivery systems).
- In horses, limited studies show minor improvements in inflammation markers, but the evidence is far from conclusive.
Risks:
- Turmeric may interfere with iron absorption, which could be an issue in young or anaemic horses.
- It can affect blood clotting, so caution is advised pre-surgery.
- May worsen gastric ulcers in sensitive horses due to its bitter, spicy profile.
Verdict:MAYBE WORTH TRYING in some arthritic or older horses, but not a magic bullet, and not ideal for every gut.
Seaweed/kelp: A natural mineral booster or iodine overload?
Seaweed, especially kelp, is often marketed as a rich source of trace minerals, especially iodine, zinc, and copper.
The science:
- Kelp does contain iodine, which is essential for thyroid function, but horses only need tiny amounts.
- Many seaweed products have extremely high iodine levels, far exceeding NRC recommendations.
Risks:
- Excess iodine can cause thyroid dysfunction, hair loss, poor coat, and reproductive issues.
- Can also interfere with the balance of other trace minerals (e.g. zinc and copper).
Verdict: NOT WORTH IT unless specifically advised by a nutritionist to correct a known deficiency, as it is too easy to overdose.
Magnesium: The calmative?
Magnesium supplements are popular for anxious, spooky, or tense horses, often under the label of ‘calming support.’
The science:
- Magnesium is essential for muscle function and nerve transmission.
- Deficiencies can cause tension and excitability, but true deficiencies are uncommon on a balanced diet.
- Some anecdotal support exists for magnesium as a mild calming agent, but studies are inconsistent.
Risks:
- Oversupplementation can lead to diarrhoea or electrolyte imbalances.
- Magnesium oxide is the most common form but has low bioavailability.
- Often sold with no actual dosage guidance, making it hard to compare products.
Verdict: POSSIBLY WORTH IT in specific cases, but overuse is common and not all horses need it.
Medicinal mushrooms: Trendy or transformative?
Blends containing reishi, cordyceps, or lion’s mane are marketed as immune boosters, stress relievers, and even tumour preventatives.
The science:
- Research in humans and lab animals shows anti-inflammatory and immune-modulating effects, but equine studies are lacking.
- No conclusive equine data on bioavailability, effective dose, or long-term safety.
Risks:
- Expensive and largely unregulated.
- May interact with other medications or supplements.
- Could suppress the immune response if not used appropriately.
Verdict: INSUFFICIENT EVIDENCE, so use with caution and only under professional guidance.
Apple cider vinegar: Old-school ‘detox’ or digestive disruptor?
A favourite of natural horse care forums, apple cider vinegar (ACV) is often claimed to aid digestion, repel flies, and balance pH.
The science:
- No solid evidence of benefit in horses.
- ACV acidifies the stomach which is not ideal for horses already prone to ulcers.
- Fly-repellent effect is anecdotal at best.
Risks:
- May aggravate gastric ulcers or reduce the palatability of feed.
- Can lower potassium levels if overused.
Verdict: NOT WORTH IT, especially in ulcer-prone horses.
Spirulina: Immune support and allergy aid?
Spirulina is a type of blue-green algae often promoted for respiratory support, skin health, and general immunity.
The science:
- A small 2012 study showed reduced allergic reactivity in horses with insect bite hypersensitivity (sweet itch).
- Spirulina is high in protein and antioxidants which may help in recovery from skin or allergy issues.
Risks:
- Expensive and unproven in most horses.
- May have a strong taste and be rejected by picky eaters.
Verdict: POTENTIALLY WORTH IT for horses with skin or allergy issues, but not needed for all.
Joint supplements with Glucosamine, MSM, Chondroitin
Still a staple in most supplement cupboards, joint supplements often contain glucosamine, chondroitin sulphate, MSM, and hyaluronic acid.
Science:
- Mixed evidence, with some horses responding well and others not at all.
- May work best preventatively or in mild osteoarthritis.
- Bioavailability of ingredients varies widely by brand and formulation.
Verdict: WORTH TRYING, especially if your vet supports it, but quality and dosing matter hugely.
Before your scoop
Important questions to ask before adding any supplement:
- Does my horse have a specific deficiency or need that this addresses?
- Could this interfere with existing feed, medications, or conditions?
- What is the evidence for its use specifically in horses?
- Is the dose clear, appropriate, and backed by third-party testing?
Bottom line
Supplements should fill specific gaps, not replace good nutrition, training, or veterinary care. The best ‘add-ons’ are those that:
- Are evidence-informed
- Match the horse’s individual needs
- Are used with clarity and purpose, not because they’re ‘in’
Let us know if there are any supplements you’d like us to review in future issues.