Let your food be your medicine, and your medicine be your food. ...Hippocrates
Flax (Linum usitatissimum L.) is an annual plant, 18 -36 inches tall, with small and thin leaves, blue flowers, and brown and golden colored seeds. It is an ancient plant with a variety of uses: the stem is a source of fiber for textile fabric (linen), the oil is an ingredient in paint and varnish, the meal is an ingridient in animal feed. Whole flaxseed, as ground (meal), powder and intact seed and oil capsule, is a source of essential fatty acids and fiber for humans. There is growing evidence that flax seed is beneficial for improving general health and preventing diseases.
Whole flax seed (ground meal, powder or intact seed) contains 40% fat (73% of it being polyunsaturated fatty acids), 28% dietary fiber, (7 – 10% soluble fiber, 11 - 18% insoluble fiber), and 21% protein. Unlike the ground meal and powder, flax seed oil contains no dietary fiber. Flax seed is also a good source of other vitamines and minerals: vitamins E and B, calcium, iron, and potassium.
More than 50% of the fat in flax seed is an essential omega-3 fatty acid called alpha-linolenic acid (ALA), which makes flax seed the richest plant source of dietary omega-3 fatty acids.
More on nutritional profile of flax seed.
Flax seed, with all the nutrients mentioned above, has beneficial effects on human health. The high dietary fiber, due to its high water-holding capacity and low digestibility, increases the bulkiness and gastric emptying of stool. This in effect helps relieve constipation and other irritable bowel syndrome. Lignans, which are antioxidants and phytoetrogens, may help reduce oxidative damage to cells and cellular molecules from free radicals. The alpha-linolenic acid is associated with decreased blood pressure in patients with peripheral arterial disease.
Flax seed may also lower blood glucose and improve insulin tolerance (diabetes). Whole flaxseed (powder and ground meal) may also reduce serum total cholesterol and low-density lipoprotein cholesterol. Flaxseed can also reduce some markers of inflammation, and raise serum levels of the omega-3 fatty acids, ALA.
Studies suggest that consumption of ground flaxseed meal, at a dosage of 15 - 50 gram per day, can help reduce serum total and LDL cholesterol with out meaningful change in HDL cholesterol and tryglyceride levels. No similar benefits are reported for flaxseed oil, though.
Flax seed can be consumed as a dietary supplement in various forms: whole seed, powder, ground (flax seed meal), or oil capsule. Flax seed taken as oil capsule lacks the fiber and lignan components. Flaxseed is used also as an ingredient in muffin, bread, or yogurt. Flaxseed meal can be prepared easily at home or bought in the market.
There are no recorded flax seed oil side effects that inflicted harm on humans. Nevertheless, moderation is necessary. As the Dutch proverb goes “everything preceeded by the word ‘too’ is not good ”. Flaxseed may have side effects when consumed in large quantities, especially if it is uncooked. Flaxseed contains cynogenic glycosides; and uncooked flaxseed intakes amounting to more than 10 tablespoons may elevate the cynide level to toxic levels. Large intakes of flaxseed may upset hormonal balance. Studies on animals have reported birth defects. However, in humans, there is no reported danger of flaxseed on pregnancy or children.
Most human studies on health benefits of flaxseed used 5 – 10 g/day dose.
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Bloedon, Leanne T., Szapary, Philippe O. 2004. Flaxseed and Cardiovascular Risk. Nutrition Reviews, 62(1): 18-27
Singh KK, Mridula D, Rehal J, Barnwal P. (2011). Flaxseed: a potential source of food, feed and fiber. Crit Rev Food Sci Nutr. 51(3):210-22.
Caligiuri SP, Aukema HM, Ravandi A, Guzman R, Dibrov E, Pierce GN. 2014. Flaxseed consumption reduces blood pressure in patients with hypertension by altering circulating oxylipins via an α-linolenic acid-induced inhibition of soluble epoxide hydrolase. Hypertension. 64(1):53-9.