Why Not To Feed Flax

This is an article about Flax and Flaxseed I’m often asked for…

Many people today have turned to the consumption of flax seeds or flax seed oils for supplementing their diets with omega-3 fatty acids, but there are some serious problems with the use of flax seed in the diet. There are some toxins and antinutritional factors found in flax seed.

Flaxseed has been used by humans for four thousand years (Schery, 1972). Although attempts have been made to show flaxseed being used as a staple food, it has never used or even [been] considered as a food by any civilization. However, industrial products such as fiber for clothing and oil for lighting were made from the stalks and seeds, respectively, by a number of ancient cultures such as the Greeks, Romans, Egyptians, and Arabs (Cooley, 1899; Gil, 1965p Crawford, 1979; Palagia, 1984; Mayerson, 1997). Flax is mentioned eighty-nine times in the Bible (Moldenke and Moldenke, 1952); however, it is never referred to as a food but rather as a source of fiber for clothing.

Flax has been questioned as a food because it contains a number of factors that interfere with the normal development of humans and animals. The concern about human use of flax is due mainly to the presence of toxic cianoglicosides (limarin), vitamin B6 antagonist factors (Butler, Bailey, and Kennedy, 1965; Stitt, 1988; Center for Alternative Plant and Animal Products, 1995, Vetter, 2000) and other antinutritional factors, including cyanogenic glycosides, trypsin inhibitors, phytic acid, allergens, and goitrogens (Madhusudhan et al., 1986; Bhatty, 1993; Trevino et al., 2000). All flax varieties contain these antinutritional factors. This includes FP967, a genetically modified variety that has a concentration of cyanogenic compounds (linamarin, linustatin, and neolinustatin) no different from traditional varieties (Canadian Food Inspection Agency, 1998).

The antagonistic factors of the vitamin B group that are found in flaxseeds have been specified as a risk factor for human health. Recent findings show that low blood levels of B vitamins are linked with an increased risk of fatal coronary heart disease and stroke (American Heart Association, 1999). Research on animals has brought to light concerns about the negative influence that flax has on pregnancy and reproductive development. These effects have been attributed to a compound known as diclycoside ecoisolariciresinol (SDG), which through microbial action suppresses the effect of estrogen in mammals. Flax is known to be the richest source of SDG, and therefore special caution is recommended if it is consumed during pregnancy and lactation (Toug, Chen, and Thompson, 1998; Rickard and Thompson, 1998).   Both the complex ester form of SDG and the free form of SDG remain stable when flaxseeds are baked in bread (Muir and Westcott, 2000). Thus, commercially prepared bread, muffins, and cookies containing flax carry the warning of being potentially harmful. In order to safely use flax in animal and human diets the seeds should be detoxified. However, the most efficient processes require the use of solvents, and even in the best case the seeds cannot be completely detoxified (Madhusudhan et al., 1986; Mazza and Oomah, 1996).

Human consumption of flax is banned in France and limited in Germany, Switzerland, and Belgium (Le Conseil d’Etat, 1963; Hunter, 1988; Olivier, 1996). The United States Department of Agriculture put a limit on the amount of flaxseed that can be included in human diets. It is recommended that no more than 12 percent be used as a food ingredient (United States Department of Agriculture, 1999). In Argentina the use of flax oil to prepare dietary supplements, is authorized by the National Administration of Medicines, Food, and Medical Technology, but the use of flaxseed is not (Administracion Nacional de Medicamentos, Alimentos y Tecnologia Medica, 2001).