Definition :
Flaxseed is the seed of the plant Linum usitatissimum. It is a rich source of alpha-linolenic acid (ALA), an essential nutrient in the human diet. Flaxseed has health and possibly medical benefits. Flaxseed oil is a vegetable oil derived from pressed flaxseed. Flaxseed and flaxseed oil have different properties and nutritional values.
Purpose :
Flaxseed is a good source of ALA and is thought to improve health by lowering blood cholesterol. Flaxseeds may also protect against certain cancers. It can also be used as a laxative.
Description :
L. usitatissimum is a slender plant with narrow leaves and blue flowers that grows anywhere from 8– 45 in (20–130 cm) tall. The plant originated in India but has been farmed across the world for thousands of years. Archeologists discovered evidence that flax was cultivated in ancient Babylon as early as 3,000 B.C. Today, in Europe and Asia, a tall variety of flax is grown primarily for its fibers, which are used to make linen. A shorter, bushier variety is grown for its seeds in North America. The Canadian provinces of Alberta, Manitoba, and Saskatchewan are the leading producers of flax in North America. North Dakota produces most of the flax grown in the United States.
Seed flax is grown for both consumption and industrial use. The seed is about 42% oil. Solvent-extracted oil from flax seeds is used for industrial purposes and is often called linseed oil. It is used in manufacturing oil paints, varnishes, and linoleum. The material that remains after oil has been extracted from the seeds is called linseed cake or linseed meal. It is often added to animal feed as a protein and omega-3 fatty acid supplement. Omega-3 enriched eggs, for example, come from chickens fed flax. Omega-3 enriched pork is available in Canada and Japan. The fiber in the stems of seed flax is
used in the production of cigarette papers.
Human consumption of flaxseed and flaxseed oil
has increased substantially since the mid-1990s. Flaxseed oil for human consumption is produced through
solvent-free cold pressing at low temperatures. The oil
is sold in bottles to be used as food or in capsules to be
taken as a dietary supplement.
Flax seeds come in brown, golden, and yellow
varieties and have a slightly nutty flavor. All colors
of seed have the same nutritional value. Seeds are sold
whole or ground (milled flax). Whole seeds can be
stored at room temperature for up to one year.
Ground seeds are easier to digest than whole seeds,
but they spoil and develop an unpleasant taste more
rapidly. Ground seeds can be kept in an airtight container in the refrigerator for up to three months. However, when ground flax is needed, it is preferable to
grind whole seeds in a coffee grinder, blender, or food
processor immediately before use. Flaxseed and flaxseed oil are sold primarily in health food stores or by
mail order.
Nutritional information
Flaxseed is an excellent source of alpha-linolenic
acid. ALA is an essential fatty acid for humans. Essential fatty acids are molecules the body needs but cannot synthesize for itself from other nutrients. Thus,
essential fatty acids, just like essential vitamins, must
be obtained through diet. Eating 1 tbsp (8 g) of ground
flax or 1 tsp (5 g) of flax oil provides enough ALA to
meet daily diet requirements.
According to the Flax Council of Canada, 1 tbsp
ground flaxseed provides about 36 calories, 1.8 g of
ALA, 1.6 g of protein, and 2.2 grams of dietary fiber.
Ground flax is preferred over whole seeds because it is
easier to digest. One teaspoon of flax oil provides 44
calories and 2.8 g of ALA, but contains no protein or
fiber. The oil in flaxseed is very high in polyunsaturated fat (a healthy type of fat) and contains no trans
fat or cholesterol. Flaxseed also provides vitamins C,
E, K, B1 (thiamin), B2 (riboflavin), and B6, along with
the minerals calcium, iron, magnesium, phosphorous,
zinc, copper, manganese, and selenium. Flaxseed is
low in sodium and carbohydrates. The seed, but not
the oil, is also an excellent source of lignin, a nutrient
thought to have anti-cancer properties.
Flaxseed can be added to the diet in several ways.
Ground, a daily serving can be sprinkled on hot or
cold cereal or mixed into yogurt or smoothies. Larger
amounts can be added to pancake or waffle mix or
baked goods such as muffins or cookies. Flax oil can
be added to salad dressings or smoothies. Frying in
flax oil is not recommended. Three tablespoons of
ground flax can replace one tablespoon of butter,
margarine, or vegetable oil in recipes. One tablespoon
of ground flax mixed with three tablespoons of water,
when left to stand for two minutes before use, can
replace one egg in many recipes.
Health claims
Major health claims for flaxseed and flax oil arise
from the fact that these products contain high levels of
ALA. ALA can be converted by the body into two
different long chain omega-3 fatty acids. Long chain
omega-3 fatty acids have been shown to lower the risk
of heart attack in people with heart disease. They
appear to lower the level of cholesterol in the blood,
especially low-density lipoprotein (LDL) or ‘‘bad’’
cholesterol. Other health claims for omega-3 fatty
acids include lowering blood pressure, lowering triglycerides (fats) in the blood, and reducing the tendency
of blood to clot in veins.
Cold-water oily fish such as salmon and fresh tuna
(canned is not a source) are good sources of omega-3
fatty acids. Vegans and vegetarians use flaxseed, along
with walnuts and canola oil, get enough ALA in their
diet, which is then converted into beneficial omega-3
fatty acids. However, many of the health benefits
claimed for omega-3 fatty acids require higher doses
than necessary to meet daily dietary requirements.
Flaxseed and flaxseed oil have been found to lower blood cholesterol levels in animal studies, but few
high-quality human studies have been done using
flax products. Results that do exist have been mixed.
Another health claim for flaxseed (but not flax oil)
is that it has anti-cancer properties. Flaxseed and sesame seed both contain large amounts of lignans.
Lignans are naturally occurring molecules found in
plants that mimic the effect of the female hormone
estrogen. Lignans compete with estrogen for binding
sites on cells. They can either act as antagonists and
lessen the estrogen response where there is continual
estrogen exposure (increasing risk of breast cancer) or
they can mimic estrogen and boost the response where
exposure is limited (post menopause) helping to prevent post menopausal symptoms. Few well-designed,
well-controlled human studies of the effect of lignans
on cancer have been completed. Although the results
of animal studies are encouraging, there is not enough
evidence to say that lignans, or flaxseed, can slow or
prevent cancer.
Researchers generally agree that ground flaxseed
is an effective laxative. Flaxseed provides dietary fiber
and, along with the oil it naturally contains, helps
move material through the bowel. Whole seed may
have the reverse effect, swelling and blocking the
bowel.
Some studies have shown that flaxseed oil supplements can reduce symptoms of attention deficit-hyperactivity disorder (ADHD) in some children.
Other studies claim that flaxseed can lower blood
sugar levels in people with diabetes. Initial results
also suggest that flaxseed may reduce symptoms of
menopause. None of these health claims have been substantiated with large, well-controlled human studies.
Precautions :
ALA, which is found in large quantities in flaxseed, appears to increase the risk of developing prostate cancer. This finding is preliminary and not yet
substantiated. Individuals with prostate cancer or a
history of prostate cancer should consult their oncologist before using flax products.
Although no health risks are known when flaxseed
and flax oil are used in reasonable and moderate quantities, no studies have been done on the safety of flax in
pregnant or breastfeeding women or in children.
Complications :
Complications are unlikely to occur when flax
products are used to meet daily dietary needs. Whole
flaxseed can cause blockage of the intestines when
taken with inadequate amounts of liquids.
Parental concerns :
Parents should be aware that the safe dose of
many herbal supplements has not been established
for children. Accidental overdose may occur if children are given adult dietary supplements.
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