Natural Products

Flaxseed

Linum usitatissimum

Efficacy

• Indications with proven efficacy:
  Hypercholesterolaemia
  
• Indications with possible, but poorly documented efficacy - the use of this product cannot be recommended:
  Chronic constipation
  Menopause symptoms
  Systemic lupus erythematosus nephritis
• Also used for these other indications, but with no proof of efficacy:
  Colon damage due to laxative abuse
  Diverticulitis
  Gastritis and enteritis
  Irritable bowel syndrome
  Skin inflammation (topical)

Security

• Risk of Drug Interactions: Moderate
• Adverse Effects: Rare

What is it?

Flax is a herbaceous plant that grows around the Mediterranean basin. It is now cultivated widely in temperate and tropical climates. While it is sometimes white, the flower is usually blue. The leaves are grey-green and the plant can reach 1,5m high. Seeds are harvested after flowering, before they ripen and fall to the ground.

Flaxseeds are a good source of fibre and omega-3 fatty acids. They are used to treat several gastrointestinal disorders, to slightly lower cholesterol levels, to prevent or delay the progression of certain types of cancer. They can also be used as a poultice to treat skin inflammation. Apparently, seeds can be placed in eyes to help remove foreign objects.

The seeds can be used to produce flaxseed oil, but usually whole seeds are used.

Warning

In 2004, Canada adopted new regulations that control the manufacturing, packaging, labeling and importing of natural health products. The new regulations also include an adverse reaction reporting system. Products that conform to the regulation's criteria are identified with a natural product number (NPN) or homeopathic medicine number (DIN-HM) and can be legally sold in Canada. This number indicates that the product meets specific criteria for safety and purity, not that it is effective for any indication.

Medicinal plants content varies naturally from plant to plant – just as fruits from the same package may vary in taste and texture. There is no standard to measure the active content of each plant. Thus, efficacy of natural products should be expected to vary from brand to brand as well as from bottle to bottle of the same brand.

For more information about the Natural Health Products Regulations, or to check if a product has been assessed, visit the Health Canada website at http://www.hc-sc.gc.ca/dhp-mps/prodnatur/index-eng.php.

Does it work?

There is evidence that flaxseed can effectively be used for hypercholesterolemia. It is also used in other medical conditions, in which it may be of some benefits:

• Chronic constipation:
  Take 15 ml (10 g) of whole or crushed seeds mixed in a glass of water (at least 150 mL) 2 to 3 times a day. Some sources recommend soaking the seeds until they release their mucilage, while others consider that they should do so in the intestine to be effective. Whole flaxseeds are not advisable for people with intestinal diverticula. It can take 18 to 24 hours before the onset of the laxative effect, so flaxseeds should be taken for 2 to 3 days.
• Hypercholesterolemia:
  Flaxseeds are taken whole or crushed, or mixed in muffin batter. Taking 50 grams daily appears to reduce total cholesterol levels by 5 to 9% and “bad” cholesterol by 8 to 18%.
• Menopause symptoms:
  Taking 40 g of flaxseed per day may reduce mild menopausal symptoms.
• Systemic lupus erythematosus nephritis:
  The suggested dosage for this indication is 15 g of crushed seeds twice a day, mixed with cereals, tomato or orange juice.

There is insufficient reliable information to conclude that this plant is effective in any other indication.

Is it safe?

• When taken with lots of water, flaxseeds are not associated with any serious adverse effects. Nonetheless, doses should be increased gradually. Cases of flatulence and diarrhea have been reported. Taking flaxseeds with an insufficient amount of liquid can result in intestinal blockage.
• Flaxseeds should be avoided in people with intestinal obstruction.
• There is insufficient information about its use during pregnancy and breast-feeding.
• Because flaxseeds can impair the absorption of certain drugs, they should be taken 2 hours before or after taking medications. Before taking flaxseeds, check with your pharmacist to make sure that there are no interactions with your regular medication.

Clinical notes

• For thousands of years, the fibre from the flax stem has been used to make clothing.

References

1. Blumethal M et al. The Complete German Commission E monographs, 1998
2. Natural Medicines Comprehensive Database, Therapeutic Research Faculty, 2007
3. Passeportsanté.net. Lin. http://www.passeportsante.net
4. Herbal Companion to AHFS DI, American Society of Health-System Pharmacists, 2001
5. Taylor J. CE: Phytomedicinals: Uses, precautions, and drug interactions. Drug Topics 2003;1:79