I am from Santiago, Chile. Here, there's a rumour that smashed (ground) flax seed loses its properties in around 4 hours. Do you know anything about this?  Basically, the rumors say that the flax seed loses its nutritional properties, and that it can even be unhealthy once it is ground — but, if you grind it yourself and eat it right away, it's OK. 
I could not find any credible sources indicating that flax seeds (also known as linseed) lose significant nutritional benefits after they've 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.  