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 and blue flowers. Flax seed is brown but modern varieties with golden seeds are also available. It is an ancient plant with a variety of uses. Flax stem is used as a source of fiber for textile fabric (linen), and its oil is an ingredient in paint and varnish. Besides, flaxseed meal is used as animal feed. Whole flaxseed, as ground (meal), powder, and intact seed, and oil capsule, is a source of essential fatty acids and fiber for human diet. There is growing evidence that flax seed is good for improving general health or preventing diseases.
Whole flax seed (ground meal, powder or intact seed) contains 28% dietary fiber, (7 – 10% soluble fiber, 11 - 18% insoluble fiber), 40% fat (73% of it being polyunsaturated fatty acids), and 21% protein. Other flax seed nutrients include vitamins E and B, phytosterols, and mineral nutrients such as 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. Flax seed is rich in antioxidants, such as lignans (also a phytosterogen) and other phenolic molecules. Unlike the ground meal and powder, flax seed oil contains no dietary fiber.
More on nutritional profile of flax seed.
The above list of nutrients renders flax seed to have beneficial effects on human health. The high dietary fiber in flax seed, 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, are also associated with lower serum cholesterol and may help reduce oxidative damage to cells and cellular molecules from free radicals. 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.
Based on review of literature, it is suggested 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 diet supplement in its whole seed, powder, ground (flax seed meal) or oil capsule form. 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 in uncooked flaxseed intakes amounting to more than 10 table spoons the cyanide level may reach to toxic levels. Large amount intake of flaxseed may upset hormonal balance. Studies on animals have reported birth defects. However, there is no reported danger of flaxseed on pregnancy or children. Most studies that reported health benefit 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.