Natural Products

Evening Primrose - Oil

Oenothera biennis

Efficacy

• Indications with proven efficacy:
  None
• Indications with possible, but poorly documented efficacy - the use of this product cannot be recommended:
  Atopic eczema
  Diabetic neuropathy
  Endometriosis
  Mastalgia
  Osteoporosis
  Raynaud's disease
  Rheumatoid arthritis
  Sjögren's syndrome
• Also used for these other indications, but with no proof of efficacy:
  Alzheimer's disease
  Asthma
  Cancer
  Chronic fatigue syndrome
  Flushing associated with menopause
  Hyperactivity in children
  Hypercholesterolemia
  Multiple sclerosis
  Post-viral fatigue syndrome
  Premenstrual syndrome
  Psoriasis
  Weight loss (to enhance)

Security

• Risk of Drug Interactions: Low
• Adverse Effects: Not Frequent

What is it?

Evening primrose oil is obtained from the seeds of the evening primrose plant. It contains essential fatty acids: gamma linoleic acid (GLA) and linoleic acid. GLA appears to inhibit production of inflammatory metabolites. Low levels of GLA are associated with some diseases.

The body can naturally produce small quantities of gamma linoleic acid. Taking GLA supplements can significantly increase blood levels.

Evening primrose oil is usually available in oral capsules standardized to 8% GLA.

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 evening primrose oil may be useful in the treatment of many conditions but available data are limited. It is administer 2 or 3 times daily with meals and use should last at least 3 to 6 months.

• Atopic eczema:
  Improvement of atopic eczema symptoms, especially itching, allowing the patient to decrease his need for other prescribed drugs (topical or oral corticosteroids, antihistamines).In children less than 12 years of age, a typical dose is 160 to 320 mg of GLA, while in adults it is 320 to 640 mg daily. It may take up to 3 months to observe results.
• Diabetic neuropathy:
  Diabetes appears to be associated with low blood GLA levels, which could result in neuronal anomalies. In animals, GLA supplements can prevent or reverse diabetic neuropathy. This effect has not been established in humans. Doses from 320 to 480 mg of GLA daily have been used.
• Endometriosis:
  Available data are still limited. In one study, 90% of women with endometriosis experienced a reduction of their symptoms when taking GLA combined with another product (eicosapentaenoic acid).
• Mastalgia:
  Women take 160 to 320 mg of GLA daily for this indication. Cyclical mastalgia responds better than non-cyclical to treatment.
• Osteoporosis:
  GLA and fish oils with calcium supplements seems to be more effective then calcium to increase bone mineral density.
• Raynaud's disease:
  Evening primrose oil could attenuate extremity excessive sensitivity to cold temperature.
• Rheumatoid arthritis:
  A few studies have shown improvement of subjective symptoms when compared to placebo. Data are still limited. It may be necessary to take 240 to 540 mg of GLA daily for at least 6 to 12 months before results are observed.
• Sjögren's syndrome:
  Controlled studies have shown modest results. In this disease, the gland's ability to produce secretions is markedly reduced. Lacrymal and salivary glands are especially affected.

There is insufficient reliable information to conclude that evening primrose is effective in any other indication.

Is it safe?

• Evening primrose oil is not associated with severe toxicity. It is usually well tolerated. On occasions, people may suffer from upset stomach, nausea, soft stools or headaches. Large doses may be associated with abdominal pain.
• Evening primrose oil might increase the risk for delivery complications. Pregnant women should not take this product. High levels of GLA are naturally excreted in breast milk. It is reasonable to assume that evening primrose oil may be taken while breast feeding.
• It is believed that patients taking drugs that affect the nervous system (phenothiazines) may be more at risk for seizures. Evening primrose oil apparently interacts with oral anticoagulants, such as Coumadin, and increase the effects of antiplatelet agents. Bleeding risks may be increased. Before taking evening primrose, check with your pharmacist to make sure that there are no interactions with your regular medication.

Clinical notes

• Evening primrose oil is approved in the United Kingdom as a prescription product for the treatment of atopic eczema and mastalgia. In Europe, doctors use it to treat diabetic neuropathy. In Canada, it is approved as a dietary supplement to increase the intake of essential fatty acids.

References

1. Pharmacist's Letter, CE Booklet: Therapeutic Uses of Herbs Part. 2, Spring 1998
2. Natural Medicines Comprehensive Database, Therapeutic Research Faculty, 2007
3. Lininger S. et Al. The Natural Pharmacy, Prima Health, 1998
4. Barnes J. et Al. Herbal Medicines, 2nd edition, Pharmaceutical Press, 2002
5. Passeportsanté.net. Huile d'onagre. http://www.passeportsante.net
6. Rotblatt M. et Ziment I. Evidence-Based Herbal Medicine, Hanley & Belfus, 2002