Attributes

• Flax, in the form of seeds or oil, is one of the best known nutritional sources of omega-3 fatty acids. Regular consumption of foods rich in omega-3 fatty acids is closely linked to a decreased risk of cancer and heart disease. In its seed form, flax contains large amounts of essential vitamins and minerals, soluble fiber and the phytonutrient lignin, a compound thought to prevent certain types of cancer. Regularly consuming flax, in any form, is also thought to aid in lowering and stabilizing blood-sugar levels and promoting the development of the brain.
  
  

Digestive System Side-Effects

• The amount of flaxseed oil or ground seeds recommended for an individual to experience health benefits is one tablespoon of flax oil or two tablespoons of ground flax seeds. Consuming significantly more than this amount is linked to unpleasant digestive system side-effects, including flatulence; loose, frequent stools; diarrhea; constipation; abdominal pain; heartburn; or nausea.
  
  

Possible Risks

• Research published in 2004 in the American Journal of Clinical Nutrition found that large amounts of omega-3 fatty acids in the diet of men can possibly increase the risk of prostate cancer and can exacerbate preexisting prostate tumor problems. (See Reference 1.) Since flax, especially flaxseed oil, provides a large amount of omega 3 fatty acids, it is possible that regular, long-term flax use, combined with the omega-3 fats contained in dairy and meat sources, could inadvertently increase the risk of prostate tumors.
  
  In addition, eating large amounts of raw flax seeds can contribute to the development of goiter. Goiter is a condition in which the thyroid gland lacks the iodine it requires to function properly and swells, creating a protuberance in the neck. Raw flax seeds contain cyanogenic glycosides, a compound that can prevent the thyroid from taking in iodine. Cooking the seeds, or being certain to include iodine in the diet from other sources, can prevent this problem. (See reference 2.)
  
  

Serious Side-Effects

• While it is extremely uncommon, it is possible for flax use to cause serious medical problems. These problems are usually caused by a severe allergic reaction to flax or taking large amounts of flaxseed without consuming enough water. Serious side-effects include a sudden difficulty in breathing or swallowing; severe constipation; stools that are black or red with blood; headaches; possible weakness in a limb; and vomiting blood.
  
  

Other Drawbacks

• Flaxseed oil becomes rancid quickly; it must be refrigerated and used within several weeks of purchase in order to keep it from going bad too soon. Flaxseed oil also cannot be used in cooking, because the addition of heat to the fatty acids contained in the oil can convert the compounds into potentially harmful substances. (See Reference 3.)