Nutrition

Supplements for pets and horses: which are worth it?

The supplement aisle is full of promises. We looked at the research behind the most popular ones, so you can spend your money where the evidence is.

By The Animal Physio Co 7 min read

A happy dog beside the words "Which supplements are worth it?"

Joint chews, calming drops, gut powders, coat oils: there's a supplement for almost everything, and most come with confident claims. Some are backed by good research. Many aren't. Here's what the studies actually show for the most popular supplements, and how to choose one safely.

Key points

  • Omega-3 from fish oil has the best evidence of any joint supplement for dogs.1,2
  • Glucosamine and chondroitin, the most common joint ingredients, didn't beat a placebo in the better-quality trials.1,3
  • If your animal eats a complete and balanced food, it rarely needs extra vitamins or minerals, and too much calcium or vitamin D can do harm.4,5,6
  • In South Africa, check the label for an Act 36 registration number, and ask your vet before starting anything new.7,8

Why it's hard to know what works

Supplement research has some common weaknesses: many trials are small and short, some have no placebo group, and many are funded by the company selling the product. There's also a strong placebo effect, on owners rather than animals. In one well-run trial of a joint supplement, dogs on the placebo improved just as much as dogs on the real thing, according to both their owners and activity monitors.3 The authors called it a "caregiver placebo effect": when we expect our animal to feel better, we tend to see it.

So we've given the most weight to randomised, placebo-controlled trials and systematic reviews, and we've flagged where the evidence is thin.

At a glance

Supplement What the research shows
Omega-3 (fish, krill or algal oil) Best evidence for arthritis pain in dogs; smaller but encouraging studies in cats
Green-lipped mussel Modest benefit in some trials, less than an anti-inflammatory painkiller
Glucosamine and chondroitin No benefit over placebo in better-quality trials
Collagen (including UC-II) Small, low-quality studies
Turmeric (curcumin) Mixed results; no measurable change in weight bearing
CBD Mixed results; no CBD product is registered for animals in South Africa
Probiotics for diarrhoea May shorten simple diarrhoea slightly
Multivitamins and minerals Rarely needed on a complete and balanced diet

Omega-3

Omega-3 fats from marine sources have the strongest evidence of any joint supplement. In a randomised trial of 127 arthritic dogs, those fed a fish-oil-rich food got up and played more easily within six weeks.9 In a force-plate study of 38 dogs, 82% on the fish-oil food put more weight on the sore leg, compared with 38% on the control food.10 Two systematic reviews rate omega-3 the best-supported option.1,2

What matters is the amount of EPA per dose, and that it comes from a marine source rather than flax or chia. We cover this in detail in Omega-3 for dogs and cats: why EPA matters.

Glucosamine and chondroitin

These are in most joint supplements, but the evidence is disappointing.

  • In a placebo-controlled trial of 60 dogs, there was no difference between the supplement and placebo on activity monitors or owner scores.3
  • An earlier trial of 35 dogs found improvement over 70 days, slower than with an anti-inflammatory painkiller, but it had no placebo group.11
  • A 2012 systematic review rated the evidence as low for every supplement except omega-3 in dogs,2 and a 2022 meta-analysis concluded glucosamine and chondroitin "should no longer be recommended" for arthritis pain in dogs and cats.1

Green-lipped mussel

Green-lipped mussel comes from New Zealand and contains its own omega-3s.

  • In a randomised, double-blind trial of 45 dogs, more dogs improved on green-lipped mussel than on placebo, but it was less effective than the anti-inflammatory carprofen.12
  • In 23 dogs, weight bearing on a force plate improved after two months on a mussel-enriched diet, but there was no separate control group.13

It may help some dogs, but don't expect it to replace pain relief your vet prescribes.

Collagen

Undenatured type II collagen (UC-II) is popular, but the studies are small. One had just five dogs per group,14 and another, of 60 dogs, compared it with an anti-inflammatory but had no placebo group and owners knew which treatment their dog was getting.15 The 2022 meta-analysis rated collagen's effect as weak and the trials as poor quality.1

Turmeric (curcumin)

In a placebo-controlled trial of 54 dogs analysed, a turmeric extract made no difference to weight bearing on a force plate. Vets' overall assessment favoured turmeric, but owners' assessment didn't reach significance.16 A diet combining turmeric extract, collagen and green tea also showed no difference on the force plate, with improvement in only a few pain measures.17

CBD

The research on CBD is mixed. The 2022 meta-analysis couldn't reach a definitive conclusion.1 In South Africa, no CBD product is registered for use in animals,18 and under FEI rules CBD is a controlled medication, so it mustn't be in a horse's system when it competes.19 If you're considering it, talk to your vet first, especially if your animal is on other medication.

Probiotics

Probiotics are mostly used for diarrhoea, where the evidence suggests a small benefit at best.

  • In 36 dogs with sudden diarrhoea, those given a probiotic recovered slightly faster (1.3 vs 2.2 days).20
  • In 148 dogs, diarrhoea lasted a median of 32 hours with a probiotic paste and 47 hours with placebo. That trial was funded by the manufacturer.21
  • In 60 dogs, there was no significant difference between a probiotic, an antibiotic and placebo.22
  • A systematic review of 17 studies found a "very limited and possibly clinically unimportant" effect in sudden diarrhoea.23

Diarrhoea that's severe, bloody, or lasts more than a day or two needs a vet, not a supplement.

Vitamins and minerals: when more is worse

Animals on a commercial complete and balanced food rarely need extra vitamins or minerals, except with certain medical conditions.4 Adding them can cause harm:

  • Calcium: Great Dane puppies fed three times the recommended calcium developed abnormal cartilage and bone development.5 Don't add calcium to a large-breed puppy's diet unless your vet tells you to.
  • Vitamin D: too much can cause kidney failure. In 2018, the US Food and Drug Administration warned about dry dog foods containing up to about 70 times the intended amount of vitamin D.6

Horses

The research on horse joint supplements is generally poor. A review of 15 studies of glucosamine-based products found only three met minimum quality standards.24 Oral hyaluronic acid reduced joint swelling after surgery in yearlings in one study,25 but made no difference in a smaller trial in young horses.26 If your horse competes, check every product against the competition rules before using it.

How to choose a supplement safely

  1. Talk to your vet first. Some supplements interact with medicines or aren't suitable for certain conditions.
  2. Check it's registered. In South Africa, pet foods and feeds must show "Reg. No. V…, Act 36 of 1947" on the label,8 and it's illegal to sell one that isn't registered.7
  3. Be wary of big claims. The South African advertising code for pet food doesn't allow claims that a product cures, treats or prevents disease.27
  4. Look for amounts, not just ingredients, such as the mg of EPA per dose for omega-3.
  5. Change one thing at a time and give it a fair trial. Judge it by things you can measure, like how far your dog happily walks or how easily it gets up.

Where physiotherapy fits

Even the best-supported supplement is a supporting act. Veterinary pain-management guidelines rank exercise and weight management among the first-line treatments for long-term pain, with therapeutic exercise and rehabilitation next, while they place supplements other than omega-3 in the lowest tier.28 Keeping a healthy weight, the right exercise and pain relief from your vet do the most for joints, and that's where physiotherapy comes in. If your animal is stiff, slowing down or recovering from an injury, book an assessment and we'll come to you.

References

  1. Barbeau-Grégoire M, Otis C, Cournoyer A, et al. A 2022 systematic review and meta-analysis of enriched therapeutic diets and nutraceuticals in canine and feline osteoarthritis. International Journal of Molecular Sciences. 2022;23(18):10384.
  2. Vandeweerd JM, Coisnon C, Clegg P, et al. Systematic review of efficacy of nutraceuticals to alleviate clinical signs of osteoarthritis. Journal of Veterinary Internal Medicine. 2012;26(3):448–456.
  3. Scott RM, Evans R, Conzemius MG. Efficacy of an oral nutraceutical for the treatment of canine osteoarthritis: a double-blind, randomized, placebo-controlled prospective clinical trial. Veterinary and Comparative Orthopaedics and Traumatology. 2017;30(5):318–323.
  4. Shmalberg J. ACVN nutrition notes: surveying supplements: current trends, research and recommendations. Today's Veterinary Practice. 2014.
  5. Goedegebuure SA, Hazewinkel HA. Morphological findings in young dogs chronically fed a diet containing excess calcium. Veterinary Pathology. 1986;23(5):594–605.
  6. US Food and Drug Administration. FDA alerts pet owners about potentially toxic levels of vitamin D in several dry pet foods. 2018.
  7. Fertilizers, Farm Feeds, Agricultural Remedies and Stock Remedies Act 36 of 1947, section 7.
  8. Department of Agriculture. Regulations relating to farm feeds (R.1087 of 2006), regulation 22.
  9. Roush JK, Dodd CE, Fritsch DA, et al. Multicenter veterinary practice assessment of the effects of omega-3 fatty acids on osteoarthritis in dogs. Journal of the American Veterinary Medical Association. 2010;236(1):59–66.
  10. Roush JK, Cross AR, Renberg WC, et al. Evaluation of the effects of dietary supplementation with fish oil omega-3 fatty acids on weight bearing in dogs with osteoarthritis. Journal of the American Veterinary Medical Association. 2010;236(1):67–73.
  11. McCarthy G, O'Donovan J, Jones B, et al. Randomised double-blind, positive-controlled trial to assess the efficacy of glucosamine/chondroitin sulfate for the treatment of dogs with osteoarthritis. The Veterinary Journal. 2007;174(1):54–61.
  12. Hielm-Björkman A, Tulamo RM, Salonen H, et al. Evaluating complementary therapies for canine osteoarthritis part I: green-lipped mussel (Perna canaliculus). Evidence-Based Complementary and Alternative Medicine. 2009;6(3):365–373.
  13. Rialland P, Bichot S, Lussier B, et al. Effect of a diet enriched with green-lipped mussel on pain behavior and functioning in dogs with clinical osteoarthritis. Canadian Journal of Veterinary Research. 2013;77(1):66–74.
  14. Deparle LA, Gupta RC, Canerdy TD, et al. Efficacy and safety of glycosylated undenatured type-II collagen (UC-II) in therapy of arthritic dogs. Journal of Veterinary Pharmacology and Therapeutics. 2005;28(4):385–390.
  15. Stabile M, Samarelli R, Trerotoli P, et al. Evaluation of the effects of undenatured type II collagen (UC-II) as compared to robenacoxib on the mobility impairment induced by osteoarthritis in dogs. Veterinary Sciences. 2019;6(3):72.
  16. Innes JF, Fuller CJ, Grover ER, et al. Randomised, double-blind, placebo-controlled parallel group study of P54FP for the treatment of dogs with osteoarthritis. Veterinary Record. 2003;152(15):457–460.
  17. Comblain F, Barthélémy N, Lefèbvre M, et al. A randomized, double-blind, prospective, placebo-controlled study of the efficacy of a diet supplemented with curcuminoids extract, hydrolyzed collagen and green tea extract in owner's dogs with osteoarthritis. BMC Veterinary Research. 2017;13(1):395.
  18. Cottage Vet Clinic. Cannabis oil for pets: what you should know. 2021.
  19. Fédération Equestre Internationale. 2026 Equine Prohibited Substances List.
  20. Herstad HK, Nesheim BB, L'Abée-Lund T, et al. Effects of a probiotic intervention in acute canine gastroenteritis: a controlled clinical trial. Journal of Small Animal Practice. 2010;51(1):34–38.
  21. Nixon SL, Rose L, Muller AT. Efficacy of an orally administered anti-diarrheal probiotic paste (Pro-Kolin Advanced) in dogs with acute diarrhea: a randomized, placebo-controlled, double-blinded clinical study. Journal of Veterinary Internal Medicine. 2019;33(3):1286–1294.
  22. Shmalberg J, Montalbano C, Morelli G, et al. A randomized double blinded placebo-controlled clinical trial of a probiotic or metronidazole for acute canine diarrhea. Frontiers in Veterinary Science. 2019;6:163.
  23. Jensen AP, Bjørnvad CR. Clinical effect of probiotics in prevention or treatment of gastrointestinal disease in dogs: a systematic review. Journal of Veterinary Internal Medicine. 2019;33(5):1849–1864.
  24. Pearson W, Lindinger M. Low quality of evidence for glucosamine-based nutraceuticals in equine joint disease: review of in vivo studies. Equine Veterinary Journal. 2009;41(7):706–712.
  25. Bergin BJ, Pierce SW, Bramlage LR, et al. Oral hyaluronan gel reduces post operative tarsocrural effusion in the yearling Thoroughbred. Equine Veterinary Journal. 2006;38(4):375–378.
  26. Carmona JU, Argüelles D, Deulofeu R, et al. Effect of the administration of an oral hyaluronan formulation on clinical and biochemical parameters in young horses with osteochondrosis. Veterinary and Comparative Orthopaedics and Traumatology. 2009;22(6):455–459.
  27. Advertising Regulatory Board. Code of Advertising Practice: Appendix on pet food.
  28. Gruen ME, Lascelles BDX, Colleran E, et al. 2022 AAHA pain management guidelines for dogs and cats. Journal of the American Animal Hospital Association. 2022;58(2):55–76.

This article is general information, not veterinary advice. Speak to your vet before starting any supplement or treatment, and ask a qualified animal physiotherapist to assess your animal individually.