Teeth in dogs and cats. What a powder can do, and what it cannot

This is the category with the widest gap between what a product can do and what its packaging implies. A powder in the bowl reaches the teeth only by way of the body, and whatever is stuck to a tooth mechanically will not come off through a feed supplement.

First: what actually works

Plaque forms again every day. Mechanical cleaning is what removes it, and the order is clear:

• Brushing is the most effective thing possible at home, and it needs to be daily. A cat or dog that has known it from an early age tolerates it surprisingly well.
• Chews and diets designed for it work through friction. The benefit is smaller than brushing, but it is real.
• A scale and polish at the vet is the only thing that takes hardened deposits off again. No feed supplement dissolves them, and a product hinting otherwise is claiming something it cannot deliver.

Supplements come last in that list. That does not mean they do nothing.

The seaweed, and what has been studied

The one ingredient here with a reference amount is the brown alga Ascophyllum nodosum. It is fed rather than applied, and is said to act on the bacterial film by way of the gut instead of scrubbing at the tooth.

Behind it sits a double-blind, placebo-controlled trial over 90 days with 60 dogs, which found less soft plaque and fewer hardened deposits than placebo. Two things belong with that: a co-author works for the manufacturer, and the trial tested one amount, not an upper limit. Both are stated on the ingredient page, along with the amount itself.

For cats we carry no reference amount. The manufacturer's feline trials are unpublished, and what is unpublished cannot be checked. Cat products with the alga are therefore shown without a rating, and with that reason given.

Why the amount is rarely on the pack

For a powder that is 100 per cent alga, the amount per serving is the weight of a scoop, and that is exactly what many makers leave out. The pack says "one scoop per 10 kg" and nothing else, so whether that is one gram or three stays open. In that case we write "the maker gives no amounts" and do not rate it.

Products that blend the alga with other ingredients state its share as a percentage. That can be worked with, as soon as the weight of a serving is given too.

Iodine is the reason to look twice

Ascophyllum nodosum is naturally high in iodine. If your animal's thyroid is under veterinary supervision, cats in particular, or if it is pregnant, ask your vet before the first serving. The note appears on every product page where the alga occurs.

How to spot a usable product

• The alga's share is given as a percentage, or the weight of a serving is stated.
• The feeding guidance is banded by weight, and for cats it goes below 10 kg.
• The product says it contributes to normal oral hygiene, rather than promising to remove hardened deposits.

That last one is not wordplay. A supplement is not a medicine and cannot treat any condition; a pack that promises more is saying more than it is allowed to.