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Flax Seeds and Cholesterol
Flax seed has been shown to significantly lower total cholesterol and LDL cholesterol. Some studies even found that it can raise HDL cholesterol. Researchers have identified lignans, omega-3 fatty acids and dietary fiber as the cholesterol-lowering constituents of flax seed. Read on to find out how these 3 flax seed ingredients affect cholesterol levels and how you can use flax seed to improve your lipid profile and reduce the risks of atherosclerosis.
by Brad Chase
Flax or linseed is an annual plant native to the Mediterranean region and India. It is one of the oldest fiber crops and its use in manufacturing linen garments date back to ancient Egypt.
Flax plant has multiple uses. In fact, its Latin name means “most useful”.
Besides its use in the making flax fiber for clothing, flax is also grown as an ornamental, food and medicinal crop. The most important part of flax plant is its seed.
Flax seeds come in two varieties: brown and yellow/golden. Both variants of the seeds are nutritionally equivalent. The shoots of flax seed are edible and the seeds themselves are powdered to make a traditional Indian delicacy.
Flax seed contains a high proportion of dietary fiber as well as short-chain omega-3 fatty acids especially alpha-linolenic acid (ALA). Its constituents also include carbohydrates and proteins as well as essential micronutrients such as B vitamins (except vitamin B12), vitamin C, iron, magnesium, calcium, potassium, manganese, copper and zinc.
Besides these nutrients, flax seed also contains bioactive phytochemicals such as lignans and phenolic glucosides.
One of these glucosides, ferulic acid glucoside, is partly (along with lignans) responsible for the medicinal use of the seed extract in the treatment of prostate tumor. Studies also indicate that flax seed may be useful in the treatment of breast cancer.
Of particular note is the lignan content of flax seed. It is estimated that flax seed contains 800 times more lignans than other food plants. These lignans are phytoestrogens and also have antioxidant properties.
Because of its high fiber content, flax seed can be used as a laxative. In addition, the fiber content is useful in the management of diabetes as fibers slow down the absorption of carbohydrates and can, therefore, help stabilize blood sugar level.
Lastly, studies have also confirmed that flax seed can reduce cholesterol levels.
Different studies investigating the benefits of flax seed for improving lipid profile all confirm that this medicinal plant can lower LDL (low-density lipoproteins) or “bad” cholesterol level while increasing HDL (high-density lipoprotein) or “good” cholesterol level.
On average, these studies show that flax seed can lower LDL level by 14 – 18%.
A few studies concluded that the hypolipidemic benefits of flax seed only affected men. However, the results of most studies investigating the cholesterol-lowering effect of flax seed showed that the herbal remedy can lower total cholesterol in both genders.
In fact, there are studies that have found specific hypolipidemic benefits of flax seed for post-menopausal women.
So, what are the active ingredients of flax seed that are responsible for lowering cholesterol level? Experts have identified dietary fiber, lignans and omega-3 fatty acid as the bioactive constituents of flax seed responsible for its effects on cholesterol.
The dietary fiber in flax seed is chiefly responsible for the seed’s medicinal use as a laxative. Once it absorbs water, flax seed fiber forms into a gelatinous mass that speeds up bowel movement.
This laxative property of flax seed is also useful for lowering cholesterol level. By increasing bowel movement and fecal excretion, flax seed fiber can reduce the absorption of cholesterol and all fats.
The gelatinous mass formed when flax seed fiber absorbs water binds to fats in the intestine and prevents digestive enzymes from breaking them down for absorption.
Because flax seed fiber removes cholesterol before it is absorbed from the intestine, the amount of cholesterol reaching the blood is significantly lowered. Even when flax seed does not act as a full laxative, its effect on bowel movement can still be significant enough to promote gastrointestinal emptying and reduce the absorption of cholesterol.
However, for flax seed fiber to promote the clearance of cholesterol, it must be taken with sufficient water. Without water, flax seed fiber actually blocks the gastrointestinal tract and can cause constipation. This may have the opposite effect as food sources of cholesterol spend more time in the intestine waiting to be absorbed into systemic circulation.
Lignans are known for their antioxidant and estrogenic properties. Studies have specifically identified the lignan content of flax seed to be important to its cholesterol-lowering properties.
There is also strong evidence to suggest that other sources of phytoestrogens, such as soy isoflavones, can lower plasma cholesterol level. As a phytoestrogen, lignans binds to estrogen receptors and may mimic or block the actions of estrogen.
The actual mechanism of action by which lignans lower cholesterol remains unclear even though such effect has been conclusively proven.
The omega-3 fatty acid in flax seed is alpha linolenic acid or ALA. ALA is converted to the more active omega-3 fatty acids, EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). However, this conversion only produces limited amounts of EPA and DHA.
Different studies have confirmed the benefits of omega-3 fatty acids on cardiovascular health. One of such benefits is the improvement of lipid profile.
Omega-3 fatty acids can increase the levels of HDL cholesterol while lowering the total cholesterol and LDL cholesterol levels.
Ground flax seed is recommended over whole flax seed. This is because it is easier for the body to digest ground flax seed. Whole seed, on the other hand, may pass through the gastrointestinal tract undigested.
Both whole flax seed and ground flax seed are commonly sold in grocery stores. Although whole ground seed is more stable than ground flax seed, the latter can still be kept for months if it is stored in an airtight container.
To make your own ground flax seed, use a coffee grinder to crush whole flax seed before it is used or stored.
On the average, each tablespoon of ground flax seed contains 2 g of polyunsaturated fatty acids including omega-3 fatty acids and 2 g of dietary fiber. It will only add 37 calories to the food you are mixing it with.
There are different ways of taking ground flax seed. Because it is heat-stable, it can even be mixed with baked goods. Generally, a tablespoon of ground flax seed should be mixed with your breakfast cereal or yogurt. Use only one teaspoon when adding flax seed to mustard or mayonnaise.
A 2008 study published in the British Journal of Nutrition investigated the effects of the lignan extract of flax seed on plasma cholesterol and glucose.
For this study, 55 participants suffering from hypercholesterolemia were recruited. They were randomly given one of placebo, 300 mg or 600 mg dietary flax seed lignan extract for 8 weeks.
The results of the study showed that both doses of lignan extract reduced total and LDL cholesterol levels. Those receiving the 600 mg dose experienced the cholesterol-lowering benefits of flax seed lignan as early as week 6. In addition, the higher dose reduced total and LDL cholesterols by over 20%.
Lastly, the results also showed that only the higher dose of lignan extract lowered plasma glucose level.
This study confirms that the lignan in flax seed contributes significantly to its cholesterol-lowering property. In addition, flax seed lignan can also be used to improve blood sugar control at high doses.
A 2006 study published in the journal, Life Sciences, investigated the benefits of an extract of flax seed rich in alpha linolenic acid for lowering cholesterol levels.
The researchers gave a group of rats fed with high-fat diets this extract of flax seed. The result showed that flax seed ALA can reduce weight gain due to the fatty diet and also lower LDL cholesterol and VLDL (very low-density lipoprotein) cholesterol as well as total plasma cholesterol and free fatty acids.
The study also showed that ALA lowers cholesterol by speeding up lipid metabolism in the liver.
In a double-blind, cross-over study published in the journal, Nutritional Research, in 1998, researchers compared the effects of flax seed and sunflower seed on cholesterol levels in a group of post-menopausal women.
Thirty eight such women with hypercholesterolemia were recruited for this study. For the first 6 weeks of the study, each of the women was given muffins and breads prepared with 38 g of either flax seed or sunflower seed.
A 2-week washout period was allowed before each of the women was switched from flax seed to sunflower seed or vice versa for another 6 weeks.
By analyzing the blood samples collected at the beginning of the study and also at weeks 6, 8 and 14, the researchers were able to determine that both flax seed and sunflower seed lowered total cholesterol levels. However, flax seed produced the better result.
The results of the study also showed that only flax seed significantly lowered LDL cholesterol while neither seeds significantly raised HDL cholesterol.
A 2009 study published in the journal, Food Chemistry, compared the effects of flax seed oil against coconut oil and butter (two other fats used in food preparation) on cholesterol levels.
By feeding a group of hamsters with diets prepared with these oils and fats, the researchers determined that only flax seed oil had any hypocholesterolemic activity.
More specifically, flax seed oil increased the excretion of cholesterol and triacylglycerol.
The researchers also demonstrated that another mechanism (besides reducing the absorption of cholesterol) by which flax seed oil lowers cholesterol level is increasing LDL receptor mRNA expression.
Another flax seed study involving hamsters was published in the journal, Atherosclerosis, in 2004.
This study investigated the effects of flaxseed on rising cholesterol levels following the removal of the ovaries. The results of the study showed that flax seed can reduce plasma cholesterol level even after ovarian hormone production falls. In addition, flax seed also reduced plaque formation in the hamsters.
This study suggests possible benefits for flax seed supplementation in post-menopausal women.
A group of researchers investigated the benefits of flax seed lignan extract for reducing serum cholesterol and preventing blockage of arteries by fatty deposits in rabbits. This study was published in the journal, Circulation, in 1999.
The results of the study showed that the lignan extract of flax seed can reduce total serum cholesterol as well as LDL cholesterol levels. In addition, this flax extract increased HDL cholesterol and provided antioxidant protection to inhibit the oxidation of LDL cholesterol.
The combination of these effects reduced atherosclerosis (fat deposition on arteries) by 73%.
This study proved that the lignan fraction of flax seed can improve cardiovascular health by improving lipid profile and by its antioxidant effect.
An earlier study also confirmed this cardiovascular benefit of flax seed in rabbits. This study was published in the journal, Atherosclerosis, in 1997.
This study linked the cardiovascular benefit of flax seed with its omega-3 fatty acid and lignan content.
The researchers identified that flax seed omega-3 fatty acids can inhibit the production of pro-inflammatory cytokines such as interleukin-1, leukotriene B4 and tumor necrosis factor. Furthermore, the lignans in flax seed can improve cardiovascular health by their anti-platelet and antioxidant properties.
This study indicates that flax seed supplementation can help prevent heart attack and other cardiovascular diseases caused by high cholesterol levels.
An even earlier study had confirmed the cardiovascular benefit of flax seed in humans. This study was published in the Journal of the American College of Nutrition in 1993. The results of this study showed that the antioxidant and anti-platelet properties of flax seed can indeed reduce the risk of cardiovascular problems in humans.
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Resterol is a natural cholesterol remedy that helps lower bad cholesterol (LDL) and raise good cholesterol (HDL). Works best when used in conjuction with a healthy diet such as the Paleo Diet.