Flaxseed

Flaxseed supplies alpha-linolenic acid (ALA), a plant omega-3, along with fibre. It’s a common way to raise the omega-3 number on a label.

That number can flatter it. Dogs convert only a small part of ALA into the EPA and DHA that fish oil supplies, and cats less still, so flax isn’t a like-for-like substitute. Whole seeds also pass through partly undigested, which is why many foods use them ground. It adds useful fibre and fat either way.