Evening Primrose Oil (Oenothera biennis)
Evening primrose oil comes from a small wild flower, Oenothera biennis, which is native to North American land. It can be found along roadsides but grows best under dry conditions. In earlier centuries, Native Indians and European settlers used the whole plant to cure a variety of conditions such as asthma, stomach pain, and bruises. Now the small wild flower is being used because of its production of primrose seeds containing linoleic acid, which is an essential fatty acid. “Essential” means that the body does not synthesize the nutrient but needs it to function properly. Therefore, it has to be obtained from the diet.
Evening primrose oil contains another fatty acid called gamma-linolenic acid (GLA), but GLA is considered “conditionally essential” since it can be synthesized in the body from linoleic acid. Although we can synthesize GLA, it is thought that the body does not make enough of it. Certain diseases such as cancer, diabetes, and multiple sclerosis can also decrease the body’s ability to make GLA. Certain symptoms associated with rheumatoid arthritis and some skin diseases have been shown to decrease because of GLA. GLA is also a precursor of prostaglandin E1 (PGE1). PGE1 has been shown to be deficient in women who suffer from severe premenstrual syndrome (PMS) and breast pain. PGE1 has also been shown to decrease inflammation, help thin blood, and decrease blood pressure.
Claimed Health Benefits
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Reduces (PMS) and breast pain during the menstrual cycle
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Decreases hot flashes associated with menopause
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Helps those with coronary artery disease
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Helps in weight loss
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Improves dermatitis and eczema
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Helps with rheumatoid arthritis
Food Sources
None
Dose
1-4 grams per day, and the supplement should contain 10% GLA
Can sometimes be sold in combination with Vitamin E
Evidence for Health Benefits
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Most of the studies involving women using evening primrose oil to decrease symptoms associated with severe PMS or menopause showed effects similar to a placebo (sugar pill). Most of the PMS and menopausal symptoms are highly subjective and result in such studies being non-conclusive.
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In studies looking at menstrual cycle breast pain, evening primrose oil was shown to be more effective than a placebo pill (44% verses 19% effective, respectively.)
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Ten patients with high cholesterol were assigned to take 3.6 grams of evening primrose oil for 8 weeks. The results showed that they significantly decreased their LDL (“bad”) cholesterol by 9%. However, in patients with high cholesterol and triglyceride levels, no significant reductions occurred.
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A study of men taking a combination of fish oil and evening primrose oil, they experienced a 12% decrease in cholesterol levels compared to men who were taking only fish oil who experienced a 6% decrease.
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No significant changes were seen in 58 children who received evening primrose oil for 6 weeks to treat skin diseases.
Cautions
Most of the claims for evening primrose oil can be ignored because proposed benefits of the supplements are unproven. However, the Arthritis Foundation believes it is worth trying to help alleviate symptoms of rheumatoid arthritis.
Evening primrose oil appears to be safe but can cause stomach and intestinal upset. It can also cause excessive bleeding if taken with anticoagulant drugs such as warfarin. Women who are pregnant or lactating should avoid taking evening primrose oil.
References
1. SupplementWatch, Inc. (2002) Supplement Decisions Made Easy. http://www.supplementwatch.com/supatoz/supplement.asp?supplementId=117 Accessed June 3, 2003.
2. Tyler VE. The Honest Herbal: A Sensible Guide to the Use of Herbs and Related Remedies. 3rd ed. Binghamton, NY: The Haworth Press, Inc.; 1993.
3. UC Berkeley Wellness Letter (2003) The Newsletter of Nutrition, Fitness and Self-Care
http://www.berkeleywellness.com/html/ds/dsEveningPrimrose.php Accessed October 16, 2003.