How should I store flax seeds to keep them fresh, and how long do they last?

Flax seeds contain natural oils, including the omega-3 alpha-linolenic acid, which can oxidize and become rancid if exposed to heat, light, and air over time. To maintain freshness and nutritional quality, store them in a cool, dark place. An airtight container in a pantry or cupboard is ideal for whole seeds. For longer storage, you can keep the sealed package or container in the refrigerator or even freezer; this significantly slows oil degradation.

Whole flax seeds in their intact shells have a longer shelf life, typically staying good for up to a year when stored properly. Once ground, the surface area exposed to air increases, so they should be used more quickly—within a few weeks to a couple of months. It's best to grind only what you need for immediate use or store pre-ground flax in an airtight container in the refrigerator and use it within a month. A simple smell check is useful: fresh flax seeds have a mild, slightly nutty aroma. If they smell bitter, sharp, or like old paint, they have likely gone rancid and should be discarded.