Prudent Use of Flax

Small brown flax seeds and flax meal signal goodness and add a nutty flavour to your foods. Flax seed offers plenty of health benefits for vegans, but is it safe to eat? Can you overdo a good thing?

Cooking or baking with flax is a perfectly safe practice. However, when raw flax is added in large quantities to diets that do not contain a healthy mix of foods, health problems can develop. Adopt the following strategies to ensure health problems do not arise:

Balance your diet - Be sure you eat uncooked flax as part of a balanced diet. For healthy people, who consume raw ground flax seed daily in a balanced diet, no health problems are likely. 1 You must be diligent about eating a varied diet in order to supply the body with enzymes. Enzymes supplied by other foods protect against the buildup in the body of unhealthy compounds. 

Illness from eating too much uncooked flax seed, in a diet with little variety, can arise because flax seeds are among 12,000 plant seeds 2(cited in 1) , such as almonds and cassava, which contain moderate amounts of natural compounds called cyanogenic glucosides. These glucosides occur naturally in many plants. A 1993 study by Cunanne 3(cited in 1) of healthy, female subjects eating 50 grams (1/4 cup equals 45 grams) of flax daily, showed no increase in glucoside buildup.

In an unbalanced diet, one which is based mainly on a plant containing cyanogens, a concentration of the cyanogenic compounds can build up in the body, leading to unpleasant and, on occasion, life-threatening reactions. Such a buildup has been documented in populations relying solely on a staple such as cassava in their diet. In these cases, the illness-causing deposits were not blocked by enzymes supplied by other foods in the diet.

Cook a portion of your flax seed - Cyanogenic compounds are made harmless by cooking. Thus, eating cooked foods, such as muffins that contain flax seed, is quite safe.

An analysis of muffins containing 25 grams of flax each, showed no detectable levels of cyanogenic glucosides after baking for 15 to 18 minutes at 230°C (400°F). 4(cited in 1)

Be careful about your iodine intake - Vegans must also be alert to another potential health problem that can occur. The cyanogenic glucosides found in flax can interfere with the way the body uses iodine. Lack of iodine can lead to goiter. Your concern should be greatest when the level of iodine in your diet is low. 5(cited in 6) Iodine requires an Adequate Intake of 150 mcg/day 7 , and availability varies. In Canada, 1/4 tsp. of iodized salt provides 67 mcg of iodine. In the United States, only some table salt is iodized. In Britain, no salt is iodized. (7)


  1. Morris D, Vaisey-Genser M. Flaxseed: Health, nutrition and functionality. Winnipeg: Flax Council of Canada; 1997.pp 57-9.
  2. McMahon JM, White WLB and Sayre RT. Cyanogenesis in cassava. J.Exp.Botany 1995. 46:731-41.
  3. Dieken HA. Use of flaxseed as a source of omega-3 fatty acids in human nutrition. Proc. Flax Inst. 1992; 54:1-4.
  4. Cunnane SC, Ganguli S, Menard C, Liede AC, Hamadeh MJ, Chen Z-Y, Wolever TMS and Jenkins DJA. High alpha-linolenic acid flaxseed ( Linum usitatissimum ): Some nutritional properties in humans. Br.J.Nutr.1993:69:443-53.
  5. Institute of Medicine. Dietary reference intakes for vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington: National Academy Press. pp 290-393 (iron); 258-89 (iodine).
  6. Morris D. Flax: A health and nutrition primer. Winnipeg: Flax Council of Canada; 2003. p 79.
  7. Davis B, Melina V. Becoming vegan. Summertown: Book Publishing Co; 2000. p 116.