Supplements

Calming Supplements: The Most Marketing, the Least Evidence

Updated July 30, 2026

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By Morgan Reyes

The Short Answer

The calming ingredient with the least evidence behind it is also the one you're most likely to have already been sold on.

That table comes from a direct read of a clinical review by veterinary behaviourist Dr. Lorella Notari, not from a product review site. The ingredient with the most marketing spend behind it (CBD) and the ingredient with the most controlled-study support (L-theanine) are not the same one.

What each ingredient actually has behind it

L-theanine has real controlled-study support, in both dogs and cats. It's a structural analogue of glutamate, an excitatory brain neurotransmitter, and is thought to work by binding to glutamate receptors and reducing that excitatory signal. Controlled studies (Araujo et al., 2010, and Dramard et al., 2018) found it improved signs of anxiety-related behavior in dogs, and a separate open-label field trial found reduced stress-related emotional signs specifically in cats. Among commercial products, it's studied under names including Anxitane and Nutracalm, though the ingredient itself, not any specific brand, is what the controlled studies actually tested.

L-tryptophan is in most calming blends and has weaker, more mixed support. As a precursor to serotonin, the reasoning behind including it is sound: tryptophan crosses the blood-brain barrier and serotonin doesn't, so raising tryptophan intake is a real route to raising CNS serotonin. But a study feeding dogs three different dietary tryptophan percentages found no difference in behavior between them, and products aren't consistent in how much tryptophan they actually contain per dose. Real mechanism, inconsistent real-world result.

Melatonin sits in an honest middle ground. There's evidence it reduces stress and anxiety in rats, and it's anecdotally reported to have anxiolytic and sleep-regulating effects in dogs. But per the same clinical review, the optimal dose, best route of administration, treatment duration, and best time to start treatment are all still unknown for behavioral use in dogs and cats. The dose studied for an unrelated use (a dermatological condition, seasonal alopecia) was 3 mg for an average medium-to-large dog, which is a data point from a different indication, not an established behavioral dose.

CBD has essentially no supporting evidence for anxiety, despite being the most heavily marketed of the four. The clinical review states it directly: "the anxiolytic effect of CBD oil are not supported by evidence so far and more studies are required to investigate both efficacy and safety of these products in dogs and cats." What CBD does have evidence for is a different use entirely: it was reported effective for arthritis-related pain in dogs at 2 mg/kg twice daily. That's a real finding, for a different problem than anxiety.

And there's a real, species-specific safety signal worth knowing. A 2019 safety study (Deabold et al.) gave a hemp-based CBD product at that same 2 mg/kg twice-daily dose to eight dogs and eight cats for 12 weeks. The dogs showed no abnormal biochemistry or side effects. The cats showed a persistent increase in ALT, a liver enzyme, above the normal range, along with excessive licking and head shaking. That's not a reason to panic about a single missed dose, but it's a real, checkable finding that a "CBD is basically harmless" assumption glosses over, specifically for cats.

Why CBD is everywhere anyway

Popularity and evidence are answering two different questions, and it's worth being plain about which one a shelf full of CBD products is actually answering. CBD's rise in pet products tracks its broader consumer popularity generally, not a growing body of pet-specific anxiety research. That's not a conspiracy, and it doesn't mean every CBD product is useless for every purpose. It does mean that "everyone's using it" and "it's been shown to work for this" are two separate claims, and the marketing on a calming-product shelf usually only makes the first one explicit.

Bottom line: the four most common calming-supplement ingredients don't share the same evidence base, and the gap runs opposite to what marketing spend would suggest. L-theanine has real controlled-study support in dogs and cats. L-tryptophan and melatonin sit in honest middle ground, with real mechanisms but unresolved dosing questions. CBD, the most heavily marketed of the four, has no supporting evidence for anxiety specifically, and carries a documented liver-enzyme and behavioral safety signal in cats at a commonly-used dose.

FAQ

Does CBD actually calm an anxious dog or cat?

No supporting evidence exists for that specific use, per a veterinary behaviourist's clinical review. See the full evidence table above.

Does L-theanine actually work for pet anxiety?

Yes, with real controlled-study support in both dogs and cats, more than any of the other three common calming ingredients.

Is CBD safe for cats?

A 2019 safety study found a persistent liver-enzyme elevation and excessive licking/head-shaking in cats given a hemp-based CBD product at 2 mg/kg twice daily for 12 weeks, with no equivalent issue found in dogs at the same dose.

Keep reading

• The Pet Supplement Label Decoder. Whether the bottle contains what the label claims, a separate question from whether the ingredient itself works.
• Omega-3s for Pets: The Supplement With the Most Consistent Evidence. The opposite end of this site's own evidence spectrum from CBD.

A guide on separation anxiety specifically, as distinct from general or noise-related anxiety, is planned and not yet built.

A Note on Scope

This guide summarizes published evidence on calming-supplement ingredients generally. It is not veterinary advice and does not recommend a specific product. A supplement or medication plan for an anxious pet, especially alongside any other medication, is a conversation with your vet.

Sources

• Notari, "Overview of Behaviour Supplements for Dogs and Cats". Fetched and extracted 30 July 2026. Source for every ingredient-level finding in this guide, including the L-theanine studies (Araujo et al., 2010; Dramard et al., 2018), the L-tryptophan dietary-percentage study, the melatonin dosing gap, and the CBD evidence statement and safety data (Gamble et al., 2018; Deabold et al., 2019).