Nutrition & nutraceuticals for sick animals

What falls under this?

Nutrition as a treatment modality encompasses two overlapping categories: therapeutic diets (industrially formulated feed that has been clinically tested for a specific condition) and nutraceuticals (isolated bioactive substances in supplement form, such as omega-3 fatty acids, green-lipped mussel or probiotics). Both are used in addition to — not instead of — regular veterinary care.

What is it used for?

The most researched applications are:

• Joint problems (osteoarthritis) in dogs and cats
• Skin conditions such as atopic dermatitis (FASS in cats)
• Chronic kidney disease (CKD), specifically itching and inflammation
• Acute gastrointestinal complaints (diarrhoea in dogs)

What does the evidence say?

Omega-3 fatty acids (fish oil)

Two RCTs show that omega-3 supplementation in dogs with osteoarthritis significantly improves weight bearing on affected limbs and can lower the required dose of NSAIDs [2][3]. A 2022 meta-analysis confirms this broader effect for enriched therapeutic diets and nutraceuticals in osteoarthritis in dogs and cats [1]. In chronic kidney disease, a narrative review suggests some effect on itching and inflammatory markers, but the evidence base here is thinner [5].

Therapeutic diets

An RCT from 2025 demonstrates that a specific therapeutic diet contributes clinically relevantly to the management of feline atopic skin problems (FASS) [4]. Enriched therapeutic diets are also supported as an adjunct to pain relief in meta-analysis data for osteoarthritis [1].

Green-lipped mussel (Perna canaliculus)

A systematic review from 2021 concludes that some positive evidence exists for osteoarthritis, but explicitly points out methodological limitations of the available studies [6]. A narrative review on non-pharmacological treatments in dogs classifies green-lipped mussel as promising but not yet sufficiently proven [7].

Probiotics

A double-blind, placebo-controlled RCT shows that probiotics are comparably effective to metronidazole in acute diarrhoea in dogs [8]. This provides substantiation for probiotics as a low-threshold, generally safe supplement for mild gastrointestinal complaints.

Levels of evidence per application

Safety points

Omega-3 fatty acids are considered broadly safe, but increase the risk of bleeding when used concomitantly with NSAIDs or anticoagulants — consultation with a veterinary surgeon is necessary for combinations. Therapeutic diets are formulated under veterinary supervision; replacement with arbitrary human supplements is not equivalent and may carry risks. Probiotics are generally safe in healthy animals; caution is advised in severely ill or immunocompromised animals.

Dosages are species-, weight- and condition-dependent and always require alignment with a veterinary surgeon. Never use internet dosages as a guideline.