Flaxseed and Cholesterol

Nutritional Value and Health Benefits of Flax Seed

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 dates back to ancient Egypt.

The flax plant has multiple uses. In fact, its Latin name means “most useful”.

Besides its use in the making of flax fiber for clothing, flax is also grown as an ornamental, food and medicinal crop. The most important part of the 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 flaxseed are edible and the seeds themselves are powdered to make a traditional Indian delicacy.

Flaxseed 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, flaxseed 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 tumors. Studies also indicate that flaxseed may be useful in the treatment of breast cancer.

Of particular note is the lignan content of flaxseed. It is estimated that flaxseed contains 800 times more lignans than other food plants. These lignans are phytoestrogens and also have antioxidant properties.

Because of its high fiber content, flaxseed 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 levels.

Lastly, studies have also confirmed that flaxseed can reduce cholesterol levels.

The Effects of Flax Seed Supplementation on Cholesterol

Different studies investigating the benefits of flaxseed for improving lipid profiles all confirm that this medicinal plant can lower LDL (low-density lipoproteins) or “bad” cholesterol levels while increasing HDL (high-density lipoprotein) or “good” cholesterol level.

On average, these studies show that flaxseed can lower LDL levels by 14 – 18%.

A few studies concluded that the hypolipidemic benefits of flaxseed only affected men. However, the results of most studies investigating the cholesterol-lowering effect of flaxseed showed that the herbal remedy can lower total cholesterol in both genders.

In fact, there are studies that have found specific hypolipidemic benefits of flaxseed for post-menopausal women.

So, what are the active ingredients of flaxseed that are responsible for lowering cholesterol levels? Experts have identified dietary fiber, lignans, and omega-3 fatty acids as the bioactive constituents of flaxseed responsible for its effects on cholesterol.

Dietary Fiber

The dietary fiber in flaxseed is chiefly responsible for the seed’s medicinal use as a laxative. Once it absorbs water, flaxseed fiber forms into a gelatinous mass that speeds up bowel movement.

This laxative property of flaxseed is also useful for lowering cholesterol levels. By increasing bowel movement and fecal excretion, flaxseed fiber can reduce the absorption of cholesterol and all fats.

The gelatinous mass formed when flaxseed fiber absorbs water binds to fats in the intestine and prevents digestive enzymes from breaking them down for absorption.

Because flaxseed fiber removes cholesterol before it is absorbed from the intestine, the amount of cholesterol reaching the blood is significantly lowered. Even when flaxseed 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 flaxseed fiber to promote the clearance of cholesterol, it must be taken with sufficient water. Without water, flaxseed 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 the systemic circulation.

Lignan

Lignans are known for their antioxidant and estrogenic properties. Studies have specifically identified the lignan content of flaxseed 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 levels. 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 an effect has been conclusively proven.

Omega-3 Fatty Acid

The omega-3 fatty acid in flaxseed 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 such benefit is the improvement of the lipid profile.

Omega-3 fatty acids can increase the levels of HDL cholesterol while lowering the total cholesterol and LDL cholesterol levels.

How to Lower Cholesterol with Flax Seed

Ground flaxseed is recommended over whole flaxseed. This is because it is easier for the body to digest ground flaxseed. Whole seed, on the other hand, may pass through the gastrointestinal tract undigested.

Both whole flaxseed and ground flaxseed are commonly sold in grocery stores. Although the whole seed is more stable than ground flaxseed, the latter can still be kept for months if it is stored in an airtight container.

To make your own ground flaxseed, use a coffee grinder to crush whole flax seed before it is used or stored.

On average, each tablespoon of ground flaxseed 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 flaxseed. Because it is heat-stable, it can even be mixed with baked goods. Generally, a tablespoon of ground flaxseed should be mixed with your breakfast cereal or yogurt. Use only one teaspoon when adding flaxseed to mustard or mayonnaise.

Studies on Flaxseed and Cholesterol

Benefits of Different Flax Seed Extracts

A 2008 study published in the British Journal of Nutrition investigated the effects of the lignan extract of flaxseed 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 flaxseed 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 flaxseed 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 levels.

This study confirms that the lignan in flaxseed contributes significantly to its cholesterol-lowering property. In addition, flaxseed 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 flaxseed rich in alpha-linolenic acid for lowering cholesterol levels.

The researchers gave a group of rats fed with high-fat diets this extract of flaxseed. The result showed that flaxseed 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.

Flax Seed vs. Sunflower Seed

In a double-blind, cross-over study published in the journal, Nutritional Research, in 1998, researchers compared the effects of flaxseed 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 bread prepared with 38 g of either flaxseed or sunflower seed.

A 2-week washout period was allowed before each of the women was switched from flaxseed 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 flaxseed and sunflower seed lowered total cholesterol levels. However, flaxseed produced a better result.

The results of the study also showed that only flaxseed significantly lowered LDL cholesterol while neither seeds significantly raised HDL cholesterol.

Hamster Studies

A 2009 study published in the journal, Food Chemistry, compared the effects of flaxseed 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 flaxseed oil had any hypocholesterolemic activity.

More specifically, flaxseed oil increased the excretion of cholesterol and triacylglycerol.

The researchers also demonstrated that another mechanism (besides reducing the absorption of cholesterol) by which flaxseed 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 raising cholesterol levels following the removal of the ovaries. The results of the study showed that flaxseed can reduce plasma cholesterol levels even after ovarian hormone production falls. In addition, flaxseed also reduced plaque formation in the hamsters.

This study suggests possible benefits for flaxseed supplementation in postmenopausal women.

The Cardiovascular Benefits of Flax Seed

A group of researchers investigated the benefits of flaxseed 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 flaxseed 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 in arteries) by 73%.

This study proved that the lignan fraction of flaxseed can improve cardiovascular health by improving lipid profile and by its antioxidant effect.

An earlier study also confirmed this cardiovascular benefit of flaxseed in rabbits. This study was published in the journal, Atherosclerosis, in 1997.

This study linked the cardiovascular benefit of flaxseed with its omega-3 fatty acid and lignan content.

The researchers identified that flaxseed 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 flaxseed can improve cardiovascular health by their anti-platelet and antioxidant properties.

This study indicates that flaxseed 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 flaxseed 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 flaxseed can indeed reduce the risk of cardiovascular problems in humans.