How to Know When Flax Is Rancid

Discard flaxseed if you are unsure about its safety.

Discard flaxseed if you are unsure about its safety.

Flaxseed meal and oil are rich in omega-3 fatty acids, fiber, protein and lignans -- phytoestrogens that may help normalize hormone levels in your body. However, the oils in flaxseed turn rancid rapidly, and for this reason, flaxseed should be refrigerated. Whole flaxseeds can last up to seven years from time of harvesting. Flaxseed meal can last up to two years after milling if it is kept tightly sealed and away from heat. Flaxseed oil may turn rancid within six weeks of milling, even if kept cool.

Check the expiration or use-by date on your flaxseed if you still have the packaging. Discard any flaxseed that is out of date.

Inspect flaxseed for any visible sign of mold or fungal growth. This may appear as white, green or black clumps or wisps.

Smell your flaxseed for any hint of a bitter or sour smell. Flaxseed has a natural nutty smell. You should smell flaxseed when it is fresh, as well, so you'll have a basis for comparison.

Taste a small amount of the flaxseed in question for any sour, bitter or otherwise "off" taste if the smell test was indeterminate. Fresh flaxseed will not leave a significant aftertaste in your mouth.


  • Store flaxseed tightly sealed in the refrigerator.

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Chris Daniels covers advances in nutrition and fitness online. Daniels has numerous certifications and degrees covering human health, nutritional requirements and sports performance. An avid cyclist, weightlifter and swimmer, Daniels has experienced the journey of fitness in the role of both an athlete and coach.

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