Linseed or flaxseed (Linum usitatissimum L.) is obtained from flax plant. This plant is an annual herb. This plant belongs to the Linaceae family. Temperate regions of Europe and Asia are the native places of this plant. Flour, seed and oil, are the various forms in which it is used. Due to the presence of various bioactive compounds in flaxseed and flaxseed oil, it is considered as healthy. In many countries, it has been used as medicine and food.
Common Flax, Toadflax, Flax weed, Lint Bells, and Linseed are the various names by which it is commonly known. Because of its nutritional properties and good flavor, it has been consumed for centuries. Dietary fiber, fat, and protein are enriched in linseed. It contains 6% moisture, 4%ash, 20% protein, 30%fibre, and 40% oil. A very healthy fatty-acid profile is found in linseed which consists of high concentrations (73%) of polyunsaturated fatty acids (PUFAs), moderate levels (18%) of monounsaturated fat, and low levels (approximately 9%) of saturated fat. The PUFA content consists of about 16% omega-6 fatty acids, primarily linoleic acid (LA), and 57% alpha-linolenic acid (ALA C18:3n-3), an omega-3 fatty acid.
Bioactive Constituents
Bioactive constituents in flaxseed: Alpha-linolenic acid (ALA), lignans (secoisolariciresinol diglycoside (SDG)), soluble flaxseed fiber mucilage (d-Xylose, d-galacturonic acid, LRhamnose , and L-Galactose), unsaturated fatty acids (linolenic acid, linoleic acid, oleic acid), monoglycerides, triglycerides, hydrocarbons (protein), free sterols, sterol esters, blast, phenylpropane derivatives. Monounsaturated fatty acids (MUFAs), such as oleic acid are also present in flaxseed. ALA and linoleic acid are both essential fatty acids (EFA) i.e. must be derived from the diet and cannot be synthesized in the human body.
“Wherever flaxseeds become a regular food item among the people, there will be better health.”- Mahatma Gandhi
Flaxseed as a functional food
Due to the presence of three main bioactive compounds - alpha-linolenic acid, lignans, and dietary fiber, it is considered a functional food.
1. Alpha-linolenic acid: The main functional component of flaxseed is alpha-linolenic acid. In vegetarian diets, it functions as an exclusive source of omega-3 fatty acids (Riediger et al., 2009). Omega-3 and omega-6 fatty acids are the two main groups of omega fats. The three types of omega-3 fatty acids which are nutritionally important are Linolenic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).
The risk of cardiovascular diseases (Hurteau, 2004) has been shown to be reduced by all three fatty acids. The body needs these two polyunsaturated fatty acids and hence they are vital for humans. A positive effect on blood lipids is exerted by ALA from flaxseed.
Total plasma cholesterol, very-low-density lipoprotein cholesterol, and low-density lipoprotein cholesterol in old healthy men aged 20-34 years old were observed to be reduced by ALA and were found to be as effective as oleic acid (18:2η-6) and linoleic acid (18:2η-6) (Chan et al., 1993).
Blends of flaxseed oil and sunflower oil or flaxseed oil promoted cholesterol reduction in hypercholesterolemic rats compared to diets formulated with hard facts as noted by Ranhotra et al. (1992). An omega-3 fatty acid is high in ground flaxseed which has been shown to reduce cholesterol, triglyceride level , and hypertension (Oomah and Maza, 1998). Colon carcinogenesis in multiple intestinal neoplasias (Min) mice may also be prevented by flaxseed oil as reported by Oikarinen et al. (2005).
This finding was also supported by Dwivedi et al. (2005) who showed that flaxseed oil prevented colon tumor development in rats. Breast cancer risk was inversely related to the presence of ALA in breast adipose tissue (Maillard et al., 2002). Since ALA is an essential fatty acid, intake of flaxseed products can only fulfill its requirement.
2. Lignans: The richest source of plant lignans is flaxseed (Thompson et al., 1991). Lignans are phytoestrogens, which are in abundance in alcoholic beverages, fiber-rich plants, vegetables (broccoli, garlic, asparagus, and carrots), cereals (wheat, barley, and oats), fruits, berries, and legumes (bean, lentil, and soybean). Flaxseed contains about 75- 800 times more lignans than cereal grains, legumes, fruits, and vegetables. The anticancer activity of flaxseed may be contributed by the antioxidant activity of lignans.
3. Dietary Fiber (Mucilage or Gum): A variety of plant substances that are not easily digested by the enzymes responsible for digestion in humans are described by a communal word called dietary fiber (Eastwood and Passmore, 1983). Flaxseed meal is reached in total fibers (cellulose, lignin, and hemicellulose), crude, acid detergent, and neutral detergent.
A direct relationship was found in health specifically in body weight regulation through both hunger suppression and diminished nutrient absorption with dietary fibers from flaxseed (Kristensen et al., 2012). In general, gel when mixed with water forms a soluble fiber. The emptying of the stomach is slowed down by this gel potentially lowering blood glucose levels. Cholesterol is also lowered as it is surrounded by the gel, which inhibits its absorption and leads to more cholesterol being excreted.
Since cholesterol is surrounded by gel, it is also lowered inhibiting its absorption. This leads to the excretion of more cholesterol. Hull of flaxseed mucilage associated with flaxseed mucilage is a gum-like material that consists of neutral and acidic polysaccharides. An important role is played by flaxseed fiber in lowering blood glucose levels. Various researches revealed that insoluble fiber reduces the release of sugar in the blood and therefore aid in decreasing blood glucose levels to great extent (Thakur et al., 2009). Research revealed that the high consumption of dietary fibers is helpful for the prevention of obesity in both men and women (Du, 2010).
Health benefits of linseed
1. Prevention of cardiovascular diseases
Mandasescu et al. reported that cardiovascular risk is altered by antioxidant and lipid-lowering properties of phytoestrogens i.e. ALA and dietary lignans which are exclusively found in flaxseed. If consumed with a regular diet, the flaxseed level is increased in serum because it is a good source of ALA. Another study by Bloedon on flaxseed showed improved insulin sensitivity in hyperlipidemic adults and a reduction effect of modest low-density lipoprotein cholesterol (LDL-C).
Continuous consumption for a period of 5 weeks resulted in lowering the levels of LDL-C by ~14% compared to wheat as reported in the study. The above-mentioned findings were supported by the research conducted by Dodin et al that significant reduction in the levels of HDL cholesterol in the blood serum of menopausal women by the ingestion of ~ 40g of flaxseed powder. Blood cholesterol reduction results in improved heart function eicosanoids present in flaxseed which are derived from omega-3-fatty acids.
Diets that consist of high levels of flaxseeds show a balanced effect on low-density lipoprotein fraction and blood cholesterol concentration signifying a larger decrease in LDL protein, liver cholesterol, and serum. Useful effects of flaxseed on the functioning of the heart as reported by various reports signifying ingestion of 40g of whole yellow omega flaxseed ground into powder and added in baked products controls several risk markers of CVD.
2. Prevention of diabetes
Ineffectiveness of the insulin produced or deficiency in insulin production causes diabetes, a chronic disorder. High levels of blood glucose caused due to diabetes results in damage to body systems, particularly in nerves and blood vessels. Eating flaxseeds result in a reduction of glucose and insulin level in hypercholesterolaemic postmenopausal women. The fasting plasma glucose level was reduced by the phenolic complex in a different set of hypercholesterolaemic subjects.
Small improvements in long-term glycaemic control were found in hypercholesterolaemic postmenopausal women diagnosed with type II diabetes but no outcome on insulin sensitivity and fasting glucose was observed after eating small quantities of the phenolic complex for eight weeks. The development of type I and II diabetes in diabetes-prone rats has been observed to be prevented or delayed by SDG by probably decreasing oxidative stress in body tissues. Insulin sensitivity is diminished by a 4-week diet high in alpha-linolenic acid (ALA (20g from margarine products based on flax oil)) as reported in a case study comprising 15 obese patients, Nestel et al.
3. Prevention of cancer
Power and Thompson (2011) have reported in a study especially centering the decrease in the course of cancer advancement relative to the ingestion of flaxseed and its antioxidant, estrogenic, antiestrogenic, estrogenic, and antioxidant effects that guide the prostate cellular proliferation. Enterolactone and enterodiol which are mammalian metabolites of flaxseed lignans can function as a protective method to deal with pre-cancer cellular variations.
Flaxseed lignans like phytoestrogens can metabolize estrogens which are thought to aid in breast and prostate cancer deterrence approaches as an adjuvant in hormone replacement therapy. Progression of chemically induced tumors in laboratory animals was significantly inhibited by fats with natural or enriched higher concentrations from corn oil and flaxseed oil which consists of omega-6-fatty acids and omega-3-fatty acids.
4. Other Beneficial Physiological Effects of Flaxseed
The immune system can be modulated by the positive effects of ALA which inhibits unnecessary inflammatory responses. Allergic responses are also benefited by ALA. Antiviral, antibacterial, and cytotoxic activities are also exercised by lignans. Inflammatory responses and obese individuals can be benefitted from bioactive compounds of flaxseed by lowering the CRP levels as well as serum amyloid A along with low-grade inflammation. Studies on animals demonstrate the antioxidant effect of flaxseed along with its effects against diseases of the gastrointestinal tract.
Consequently, antiulcer effects may be exerted by the mucilage obtained from flaxseed. Constructive effects were also found in patients with irritable bowel syndrome who received 17 g of flaxseed per day for 3 months, demonstrating a reduction in constipation and in other abdominal symptoms. A reduction in constipation and in other abdominal symptoms was demonstrated by patients suffering from bowel syndrome who received 17 g of flaxseed per day for 3 months showing its positive effects. In summary, the studies in humans demonstrate that the ingestion of 30 g of flaxseed per day provides a sufficient quantity of bioactive compounds.
Authors
Mahin Haque, Sapna, Rashmi Yadav, Vikender Kaur, Renu Singh1, Rakesh Bhardwaj & Ashok Kumar
ICAR-National Bureau of Plant Genetic Resources, Pusa Campus, New Delhi-110012
1ICAR-Indian Agricultural Research Institute, Pusa Campus, New Delhi-110012
