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I am from Santiago, Chile, and here there has been recently this rumour that smashed flax seed loses its properties in around ~4 hours. Does any one knows something about this?

Basically, the rumors say that the flax seed loses its nutritional properties and it can even be damaging once it is smashed but, if you smash it yourself and eat it right away, its ok.

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What properties is it purported to lose? Flavor? Texture? Nutrition? – SAJ14SAJ Dec 27 '12 at 1:25
@SAJ14SAJ, I edited my question to answer yours, thanks :-). – Néstor Dec 27 '12 at 2:45
up vote 5 down vote accepted

I could not find any credible sources indicating that flax seeds (also known as linseed) loose significant nutritional benefits after been smashed, crushed or ground.

This article from Mayo Clinic in fact indicates that since the seeds tend to pass undigested, it is better to grind them:

Most nutrition experts recommend ground flaxseed because your body is better able to digest it. Whole flaxseed may pass through your intestine undigested, which means you won't get all the health benefits.

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Any seed that has been damaged, cut, smashed, or ground starts to lose flavour, texture, nutrition, and eventually will go rancid due to oxidising oils

Four hours is too short a time for anything noticeable to happen. Some types of nuts and seeds show a noticeable change over a day or two, but most take many days or weeks

Milled flax seed is reasonably tough; it should last for a week or so without a noticeable flavour change, and many weeks before going rancid, see

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Thanks a lot for your answer. However, what about its nutritional properties? How fast does it last with them once it is smashed? Can it be damaging? I find this last claim particularly worrying, although I haven't seen any good arguments to support it. – Néstor Dec 27 '12 at 2:49

I was told by a nutritionist to eat flax seed. If eaten whole, the seeds simply pass through the digestive system without contributing anything; they have to be ground in order to reveal their properties. As ground flax seed has anti-oxidative properties, it goes without saying that exposure to air reduces these properties thus the ground seed should be eaten as soon as possible.

Whilst I buy whole flax seed once every five or six weeks (about a kilo and a half), I grind only enough to be eaten in a week. I've never noticed any taste to the seeds, let alone any rancidity.

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