The seeds of most plants are rich in nutrients and can provide us with health benefits. Yet flaxseeds are also nutritionally unique and offer us health benefits not found across the board within the seeds food group. The nutritional uniqueness of flaxseeds features three nutrient aspects, and all three play a key role in the outstanding health benefits of this food.
The first unique feature of flax is its high omega-3 fatty acid content. Among all 127 World's Healthiest Foods, flaxseeds comes out number one as a source of omega-3s! The primary omega-3 fatty acid found in flaxseeds is alpha-linolenic acid, or ALA. The ALA in flaxseed has found to be stable for at least 3 hours of cooking at oven temperatures (approximately 300F/150C), which makes it available after ground flaxseeds have been added to baked goods like muffins or breads.
The second unique feature of flaxseed is its lignans. Lignans are fiber-like compounds, but in addition to their fiber-like benefits, they also provide antioxidant protection due to their structure as polyphenols. The unique structure of lignans gives them a further health-supportive role to play, however, in the form of phytoestrogens. Along with isoflavones, lignans are one of the few naturally occurring compounds in food that function as weak or moderate estrogens when consumed by humans. Among all foods commonly eaten by humans, researchers rank flaxseeds as the number one source of lignans. Sesame seeds come in second, but contain only one-seventh of the total lignans as flaxseeds. To give a few further examples, sunflower seeds contain about 1/350th as many lignans, and cashews nuts contain about 1/475th as many lignans as flaxseeds.
A third unique feature of flaxseeds is their mucilage (gum) content. "Mucilage" refers to water-soluble, gel-forming fiber that can provide special support to the intestinal tract. For example, gums can help prevent the rapid emptying of the stomach contents into the small intestine, thereby improving absorption of certain nutrients in the small intestine. Arabinoxylans and galactoxylans are included within the mucilage gums found in flaxseeds.
This combination of features—omega-3 fatty acids, high-lignan content, and mucilage gums—helps to explain the unique health benefits of flaxseeds. The specific areas of health benefit described below all draw in some way from this unique combination of nutrients not found in other commonly eaten nuts or seeds.
The primary omega-3 fatty acid in flaxseeds—alpha-linolenic acid, or ALA—can be helpful to the cardiovascular system in and of itself. As the building block for other messaging molecules that help prevent excessive inflammation, ALA can help protect the blood vessels from inflammatory damage. Numerous studies have shown the ability of dietary flaxseeds to increase our blood levels of ALA, even when those flaxseeds have been ground and incorporated into baked goods like breads or muffins. When flaxseeds are consumed, two other omega-3 fatty acids have also been shown to increase in the bloodstream, namely, eicosapentaenoic acid (EPA) and docosapentaenoic acid (DPA). Increases in EPA and DPA also help provide inflammatory protection.
Protection of our blood vessels from inflammatory damage can also be provided by the lignans in flaxseeds. These lignans can inhibit formation of platelet activating factor (PAF), which increases risk of inflammation when produced in excessive amounts. The overall anti-inflammatory benefits of ALA and lignans in flaxseeds has been further corroborated by studies in which flaxseed-enriched baked goods (like muffins) lead to decreases of 10-15% in C-reactive protein (CRP) levels. CRP levels are a commonly used indicator of inflammatory status in the whole body.
Risk of oxidative stress in the blood vessels can also be lowered by flaxseed intake. In addition to being a very good source of the mineral antioxidant manganese, polyphenols in flaxseed—including flaxseed lignans—provide measurable antioxidant benefits. The antioxidant benefits of one particular flaxseed lignan, secoisolariciresinol, have been especially well-documented. Decreased lipid peroxidation and decreased presence of reactive oxygen species (ROS) in the bloodstream have both been associated with flaxseed intake in amounts of approximately 2 tablespoons per day.
Intake of flaxseeds has also been shown to decrease the ratio of LDL-to-HDL cholesterol in several human studies and to increase the level of apolipoprotein A1, which is the major protein found in HDL cholesterol (the "good" cholesterol). This HDL-related benefit may be partly due to the simple fiber content of flaxseeds, since 2 tablespoons of ground flaxseed provide about 4 grams of dietary fiber.
Although direct studies on flaxseed and blood pressure are limited (and mostly confined to flaxseed oil versus ground flaxseed), numerous studies have shown the ability of increased omega-3 fatty acid intake to help regulate blood pressure and to help reduce blood pressure in persons who have been diagnosed with hypertension. With its excellent content of the omega-3 fatty acid alpha-linolenic acid (ALA), flaxseed can help us increase our overall omega-3 intake and, by doing so, at least potentially decrease our risk of high blood pressure.
There is one area of concern that we want to note involving flaxseeds and the cardiovascular system. We've seen one very small-scale study from Canada involving 30 children and teens (ages 8-18), all previously diagnosed with hypercholesterolemia (high cholesterol) and given added flaxseed in their diets over a period of 4 weeks. The flaxseed amount was 2 tablespoons, and the form was ground flaxseeds incorporated into breads and muffins. In this study, blood levels of total cholesterol and LDL cholesterol did not significantly change, but blood fat levels (in the form of triglycerides) increased and HDL cholesterol (the "good" cholesterol) decreased. Since we would consider these changes in blood lipids to be unwanted, we believe this study raises some preliminary questions about the role of daily flaxseeds in amounts of 2 tablespoons or above in the diet of children and teenagers who are already known to have high cholesterol. Much more research is needed in this area, but if you are the parent of a child or teen who is already diagnosed with high cholesterol, we recommend that you consult with your healthcare provider about the pros and cons of incorporating flaxseeds into your child's meal plan on a daily basis in any substantial amount.
It is important to realize that the antioxidant and anti-inflammatory benefits of flaxseed do not apply only to the cardiovascular system. Oxidative stress (which is often related to deficient intake of antioxidant nutrients) and excessive inflammation (which can also be related to deficient intake of anti-inflammatory nutrients) are common risk factors for a wide variety of health problems. These problems include development of insulin resistance, type 2 diabetes, asthma, obesity, and metabolic syndrome. There is preliminary evidence that either whole flaxseed intake or its constituents can decrease risk of all the problems above by increasing our anti-inflammatory and antioxidant protection.
The antioxidant and anti-inflammatory benefits of flaxseeds also make them a logical candidate for risk reduction with certain types of cancer. That's because chronic inflammation (even low-level inflammation) and chronic oxidative stress are theoretical risk factors for cancer development. In the case of flaxseeds, basic science research is strongest for breast cancer, prostate cancer, and colon cancer. We have started to see small clinical trials adding flaxseeds to meal plans for cancer survivors, but to date, they have only focused on short-term outcomes like treatment-related symptoms.
Three of the lignans found in flaxseeds—secoisolariciresinol, matairecinol, and pinoresinol—can be converted by intestinal bacteria into enterolactone (ENL) and enterodiol (END). ENL and END have direct effects on our hormonal balance and in this way may play an especially important role in hormone-related cancer. The relationship between flaxseed intake and cancer risk is complicated, furthermore, by the important and variable role of gut bacteria in converting secoisolariciresinol and other lignans in flax into enterolactone and enterodiol. This conversion process involves many different enzyme-related steps provided by a complicated mix of gut bacteria including Bacteriodes, Bifidobacterium, Butyribacterium, Eubacterium and others.
Benefits of flaxseed for the digestive tract—although mentioned earlier throughout this food profile—are worth repeating here. The strong fiber content of flaxseeds—including their mucilaginous fiber—help to delay gastric emptying and can improve intestinal absorption of nutrients. Flaxseed fibers also help to steady the passage of food through our intestines. Finally, the lignans in flaxseed have been of interest to researchers for their potential to reduce cellular changes that could increase risk of colon cancer. This impressive group of digestive tract benefits is likely to receive more attention in future research studies.
We've seen mixed findings regarding the post-menopausal benefits (such as reduction of hot flashes) associated with flaxseed intake, with some studies showing significant benefits and other studies showing a lack of significant benefits. However, there continues to be strong interest in flaxseeds and their components (including enterolactone and secoisolariciresinol diglucoside) as potential aids during management of perimenopausal and postmenopausal symptoms as well as during hormone replacement therapy (HRT).
This area of flaxseed research is admittedly complex. For example, enterolactone made from flaxseed lignans has been shown to be pro-estrogenic (promoting estrogen production, through increased formation of transcription factors like ER-alpha and ER-beta), as well as anti-estrogenic (working against estrogen production, through inhibition of enzymes like estrogen synthetase). It's also known to lower the activity of 5-alpha-reductase (an enzyme that converts testosterone into dihydrotestosterone) and 17-beta hydroxysteroid dehydrogenase (an enzyme that converts estrone into estradiol). Given this complicated set of circumstances that may vary from one woman to another, it may turn out that flaxseed intake is simply of inconsistent benefit based on individual variation.
Although we've already mentioned decreased risk of insulin resistance in relationship to flaxseed intake, we think it is likely we will see more research studies in this area. The strong fiber content, antioxidant content, and anti-inflammatory content of flaxseeds make them a natural here.
One final note about the health benefits of flaxseeds involves their feeding to animals. We've seen repeated studies on the content of beef, chicken, and eggs that reflect significantly increased omega-3 content in these foods when flaxseed meal and/or flaxseed oil are added to the diets of cows and chickens. For persons who enjoy these foods in their meal plan on a regular basis, this increased omega-3 content can really add up. Some manufacturers of beef, chicken, and eggs provide omega-3 information on their product packaging. Consumption of certified organic animal foods in which flaxseed was added to the animals' feed can be an effective way of increasing your omega-3 intake.
The scientific name for flax—Linum usitatissimum— reveals a lot about our human relationship to this plant. The "linum" part of this name sounds a lot like "linen," which is a fabric that has been made from flax for over 3,000 years. The "usitatissimum" part of its name means "of greatest use" in Latin, and that quality also rings true in our relationship to flax. This plant has served not only as a food source and source of linen, but also for the creation of sails on sailing ships, bowstrings, and body armor. Flaxseed is known in many parts of the world as "linseed," although most of the linseed oil sold in the United States is not food grade and is sold instead for use as a wood finish and preservative.
Brown flax and golden flax (sometimes called yellow flax) are the two basic varieties of flax, and they are similar in their nutritional composition. Both can be excellent sources of omega-3 fatty acids (in the form of alpha-linolenic acid) and very good sources of fiber. As with all foods, however, growing conditions and other factors play a key role in determining the quality of harvested flaxseeds, including their nutrient composition. You can find detailed and practical information for selecting high-quality flaxseeds in the "how to select" section in this chapter.
One additional clarification about varieties of flax is also important. New Zealand flax, even though it bears the same name, is not related to the flax plant Linum usitatissimum whose flaxseeds we recommend as a World's Healthiest Food. New Zealand flax also has a rich history of use for its fiber content, however, as well as traditional medicinal uses as developed by the Maori peoples of New Zealand.
In their raw form, flaxseeds usually range from amber/yellow/gold in color to tan/brown/reddish brown. White or green flaxseeds have typically been harvested before full maturity, and black flaxseeds have typically been harvested long after full maturity.
Sometime between 4000 and 2000 BC, flax cultivation became a common practice in countries bordering the Mediterranean Sea and in regions of the Middle East, and there is some evidence that flax cultivation may have started even thousands of years earlier, during the Neolithic Era of approximately 10,000 BC. From the very beginning, the value of flax was both culinary and domestic, since flax fibers could be spun into linen to provide clothing and other textile-related products.
To this day, flax cultivation has remained both culinary and domestic, although crop production has become more specialized and wide scale. In the United States and Canada, most commercial flax production involves oilseed varieties of flax, in which the seeds will eventually be dried and crushed and used to produce different grades of oil. Non-food grade flaxseed/linseed oil is used in wood finishes, paints, coatings, and other industrial supplies. Food grade flaxseed/linseed oil can as be used in livestock feed, or as a culinary oil. (It is much more common, however, for livestock feed to contain flaxseed meal versus flaxseed oil.) Oilseed varieties of flax are typically classified as oilseed crops along with soybeans, rapeseed, cottonseed, sunflower seed, and peanuts. Canada is the world's largest producer of oilseed flax, followed by Russia, France, and Argentina.
Fiber flax is the other major variety of flax in terms of commercial production. In Europe, France and Belgium are especially large producers of fiber flax. While cotton, wool and silk remain the most popular natural fibers in the global textile market, the global flax market has grown in recent years following increased production of linen products in China.
Alongside of these other flax markets, however, has developed a gradually expanding consumer market for flaxseeds themselves, to be considered as uniquely nourishing food. We expect to see food interest in flaxseeds increase, primarily because of their unique nutrient combinations and health benefits.
Flaxseeds can be purchased either whole or already ground. The two different forms offer distinct benefits. Because flaxseeds can be very difficult to chew, grinding of the seeds prior to consumption can usually increase their digestibility. However, grinding takes time, and pre-ground flaxseeds can have great convenience. On the other side of the coin, pre-ground flaxseeds—while more convenient—also come with a shorter shelf life than whole flaxseeds.
Whole flaxseeds are generally available in prepackaged containers as well as bulk bins. Just as with any other food that you may purchase in the bulk section, make sure that the bins containing the flaxseeds are covered and that the store has a good product turnover so as to ensure their maximal freshness. Whether purchasing flaxseeds in bulk or in a packaged container, make sure that there is no evidence of moisture.
At WHFoods, we encourage the purchase of certified organically grown foods, and flaxseeds are no exception. Repeated research studies on organic foods as a group show that your likelihood of exposure to contaminants such as pesticides and heavy metals can be greatly reduced through the purchased of certified organic foods, including flaxseeds.
If you purchase whole flaxseeds, either store them in an airtight container in a dark, dry and cool place or place their airtight container directly in the refrigerator.
Ground flaxseeds are usually available both refrigerated and non-refrigerated. If you are purchasing ground flaxseed that is sitting on the store shelf at room temperature, we recommend that the flaxseed be packaged in a gas-flushed, vacuum-sealed bag. If you are purchasing ground flaxseed that is found in the refrigerator section, it's not essential that vacuum-sealed packaging be used, but it can still be helpful from a food quality standpoint.
The best way for you to store flaxseeds depends on the form in which you have purchased them. For this reason, we've divided up our "how to store" section into the three categories below:
Storage of ground flaxseeds:
Regardless of the form in which you purchase your ground flaxseeds (in vacuum-sealed packaging on the store shelf at room temperature or from a refrigerated case), you should keep them in your home refrigerator after opening. The reason for this precaution is simple: once flaxseeds are ground, they are much more prone to oxidation and spoilage. Similarly, if you are grinding whole flaxseeds on your own at home (for example, in a small spice or coffee grinder), you will want to store them in the refrigerator in an airtight container. If using glass, you may also want to use a darkened glass as that will lessen exposure of the ground flaxseeds to light.
Just to reiterate: even when carefully packaged in a gas-flushed, light-protective pouch, ground flaxseeds should be refrigerated after opening. They will typically store safely for about 6-16 weeks.
Storage of whole flaxseeds:
Whole flaxseeds can typically be stored for 6-12 months if placed in an airtight container in a dark, cool dry spot. They can also be refrigerated, and may safely store for a year or longer using this approach.
Storage of flaxseed oil:
Flaxseed oil is especially perishable and should always be purchased in opaque bottles that have been kept refrigerated.
Flaxseeds, ground, raw
GI: very low
|omega-3 fats||3.19 g||133||32.0||excellent|
|vitamin B1||0.23 mg||19||4.6||very good|
|copper||0.17 mg||19||4.5||very good|
|manganese||0.35 mg||15||3.7||very good|
Density>=7.6 AND DRI/DV>=10%
Density>=3.4 AND DRI/DV>=5%
Density>=1.5 AND DRI/DV>=2.5%