Eating fish is more superior to flax seed oil

Fish like salmon, tuna, mackerel, sardines, etc are natural sources of Omega-3 fatty acids which is essential for healthy body.
Omega-3 fatty acids has 3 group or  derivatives :
ALA( found in plant oils like flax seed oil),  
EPA(found in marine oils) and 
DHA(found in marine oils).

 

Benefits of Omega-3 fatty acids include :

  • Contribution to neurological development, brain function and cognitive function
  • Low risk of cardiovascular disease
  • Regulate blood pressure and dilate blood vessels
  • Beneficial in  rheumatoid arthritis
  • Helpful in cases of depression or bipolar disorder 
  • Prevent colon cancer
  • Are anti-inflammatory
  • Improve insulin sensitivity and glucose toleranace
Flax seed oil is high in Omega-3s but requires several chemical conversion process involving enzymes o convert EPA/DHA.
This EPA/DHA conversion process is highly inefficient in the human body because of which very little of actual benefits are obtained. So, it’s better to intake a direct source of EPA/DHA and that is eat fish.

 

 
Flax seed oil are stored in black bottles( to keep it away from light) and advised to store in refrigerator. The reason for all this is refined polyunsaturated fats are highly unstable and susceptible to oxidation. If the oil  is not processed, packaged, and stored  right then we end up having rancid oil.
 
Furthermore, flax seed oil contain certain  compounds which has estrogen-like properties in the human body called as phytoestrogens. Excess of estrogen in human body leads to storage of fat and risk towards several cancer.
 
Dosage : The acceptable intake levels for omega−3 is 1.6 grams/day for men and 1.1 grams/day for women.
The FDA has advised that adults can safely consume a total of 3 grams per day of combined DHA and EPA, with no more than 2 g per day coming from dietary supplements.
 
Caution : Should not be consumed more than 3 grams per day. If  consumed in excess of 3 grams per day then it may cause
  • Increased incidence of bleeding
  • Hemorrhagic stroke
  • Oxidation of omega-3 fatty acids, forming biologically active oxidation products
  • Increased levels of low-density lipoproteins (LDL) cholesterol or apoproteins associated with LDL cholesterol among diabetics and hyperlipidemics
  • Reduced glycemic control among diabetics
Sources:
http://www.ncbi.nlm.nih.gov/pubmed/17144568
http://en.wikipedia.org/wiki/Omega-3_fatty_acid#Daily_values