Flax seed has many documented benefits. WebMD has a good entry 
- Cardiovascular disease
- Hot flashes
Flax seed’s active compounds are
- Omega-3 fatty acids
- Dietary fiber
- Phytoestrogens, or plant estrogens
An added benefit could be appetite control: The main conclusion from  is :
“A small dose of flax seed fiber significantly suppresses appetite and energy intake. Furthermore, flax seed fibers administered as drinks or tablets produce similar responses.”
- The Wikipedia entry asserts that flax seed contains : “…neurotoxic cyanogen glycosides and immunosuppressive cyclic nonapeptides”. No citation is given, but we found a Korean patent for processes to remove the possibly toxic components.
- The benefits or risks or phyto estrogen for men are still debated, particularly regarding male fertility and prostate cancer.
 WebMD ; “The Benefits of Flaxseed”
 Appetite ; “Flaxseed dietary fiber supplements for suppression of appetite and food intake
 Wipo ; Korean patent “EDIBLE FLAXSEED OIL WHICH SATURATED FATTY ACID AND TOXIC COMPONENTS WERE REMOVED THEREFROM AND PREPARATIVE PROCESS THEREOF”