Evening primrose oil contains gamma-linolenic acid (GLA), an essential fatty acid in the omega-6 family of oils that is metabolized to dihomogammalinolenic acid (DGLA). These fatty acids are precursors to prostaglandins series 1 and 2 (PGE1 and PGE2).  Evening primrose oil contains about 4 to 16 % GLA while borage oil  has about 22% and black currant seed oil has about 17%. EPO has a high concentration of linoleic acid.

Evening Primrose 1300 mg
Jarrow Formulas
Evening Primrose oil 1300 consists of 100% pure, cold pressed oil of Evening Primrose (Oenothera lamarchiana), a potent source of Gamma Linolenic Acid (GLA), an omega 6 fatty acid produced in human metabolism.

Evening Primrose Oil Supplement Facts:
Amount Per Softgel
Calories - 13
Evening Primrose Oil - 1300 mg *
GLA (Gamma Linolenic Acid) - 117 mg

See here to purchase Evening-Primrose-Oil supplement

Evening Primrose Oil benefits
Evening primrose oil has antioxidant and anti-inflammatory properties.
Evening primrose oil has shown inconsistent results in the treatment of atopic dermatitis and other medical conditions.
Neither fish oils or EPO have been found to be helpful in reducing mastalgia (breast pain).

Evening primrose oil benefit
The whole topic of which oils and in which amounts are ideal for maintaining health and fighting disease is very complicated, but overall, in my opinion, We prefer to use Fish Oils or flax seed, rather than evening primrose oil supplements. However, we may alter our opinion if new research finds evening primrose oil has definite clinical benefits.

Mastalgia
Evening primrose oil and fish oil for severe chronic mastalgia: a randomized, double-blind, controlled trial.
Blommers J,. rije Universiteit University Medical Center, Amsterdam, The Netherlands.
Am J Obstet Gynecol. 2002 Nov;187(5):1389-94.
The purpose of this study was to evaluate the effect of evening primrose oil and fish oil on breast pain in premenopausal women with severe chronic mastalgia, in a randomized double-blind factorial clinical trial. One hundred twenty women were placed randomly into four groups: (1) fish oil and control oil, (2) evening primrose oil and control oil, (3) fish and evening primrose oils, or (4) both control oils during 6 months. Corn oil and corn oil with wheat germ oil were used as control oils. The change in the percentage of days with breast pain after 6 months of treatment was analyzed on an intention-to-treat basis. The decrease in days with pain was 12 % for evening primrose oil and 13% for its control oil; the decrease in days with pain was 15% for fish oil and 10% for its control oil. All groups showed a decrease in pain. Neither evening primrose oil nor fish oil offered clear benefit over control oils in the treatment of mastalgia.

Fibroadenoma
Effect of evening primrose oil on clinically diagnosed fibroadenomas.
Kollias J. Nottingham City Hospital, Nottingham, UK.
Breast. 2000 Feb;9(1):35-6.
The effects of oil of evening primrose oil on fibroadenomas was assessed over a 6-month period. Eleven out of 21 (52%) of fibroadenomas receiving evening primrose oil and 8 out of 19 (42%) controls reduced in size. This study demonstrates that evening primrose oil does not significantly effect the natural history of breast fibroadenomas.

Review
The whole topic of which oils and in which amounts are ideal for maintaining health and fighting disease is very complicated, but overall, in our opinion, we prefer to use fish oils or flax seed, rather than oil of evening primrose supplements. However, we may alter my opinion if new research finds evening primrose oil has definite clinical benefits.

Oil of evening primrose studies
Quantitative analysis of anti-inflammatory and radical scavenging triterpenoid esters in evening primrose oil.
Knorr R. Friedrich-Schiller-University Jena, Semmelweisstrasse 10, D-07743 Jena, Germany.
J Agric Food Chem. 2004 Jun 2;52(11):3319-24.
Cold pressed, nonraffinated evening primrose oil was recently found to contain lipophilic triterpenoidal esters with radical scavenging and anti-inflammatory properties. A simple and robust method for the quantitative analysis of these 3-O-trans-caffeoyl derivatives of betulinic, morolic, and oleanolic acid was developed and validated. Separation was achieved by normal phase chromatography on a Diol column and with hexane/ethyl acetate (50:50) as eluent. The analytes could be determined directly in the oil matrix, without need of a previous removal of the triglycerides. Normal phase LC ESI-MS with a makeup flow of polar modifier was used for checking the identity and purity of analyte peaks. Samples from 22 commercially available EPOs were analyzed. The average caffeoyl ester contents were 58 mg/100 g in cold pressed oils and 4.7 mg/100 g in partially raffinated oils. In fully raffinated evening primrose oil samples, the concentration was below the limit of detection. The influence of extraction temperature on the content of caffeoyl esters in nonraffinated evening primrose oil was investigated with seeds of Oenothera biennis and Oenothera lamarckiana, respectively. With O. lamarckiana, the concentration of caffeoyl esters in the oil increased with rising pressure and temperature, whereas no such dependency was found with O. biennis. Microscopic analysis revealed some differences in the histology of the seed testa, which may explain in part the differing behaviors in the extraction experiments. There was a difference between O. biennis and O. lamarckiana oils with respect to the relative amounts of the three esters. The temperature of the extraction process had no effect on the ratio of the compounds.

Evening primrose oil benefit questions
Q. I have heard about using evening primrose oil for nights sweats associated with menopause. Can you substantiate this claim? Also, does it interact negatively with the aphrodisiac herb tongkat ali?
   A. We have not seen good studies that show evening primrose oil use has a major influence on night sweats associated with menopause. The herb should not interfere with it.

Q. Does evening primrose oil have any adverse effect on the liver? My mom takes two GNC evening primrose oil capsules (1,300mg) each day. She recently had a CAT scan and now her doctor wants to do a PET scan on her liver as they see some “things” on the liver that they want to take a closer look at. My mom is wondering if the evening primrose oil is perhaps effecting her liver. Also, what is the difference between a 500mg and 1,300mg capsule of evening primrose oil?
   A. We have not come across any human studies indicating the use of evening primrose oil has a detrimental effect on the liver.

Q. Do oil of evening primrose studies show any benefit in terms of heart disease reduction?
   A. We have not seen studies with oil of evening primrose as a benefit for cardiovascular conditions but will update this site as new research is published.

Q. I notice that when I take 1300 mg of evening primrose oil it has a lubricating effect. I think this is why so many women are passionate about it. You don't get the same effect from fish oil. However, I recently read a study that advises against over consuming omega 6 oils in ratio to omega 3 oils. Is evening primrose oil bad for the heart?
   A. We have not seen any evidence that small or reasonable amounts of evening primrose oil supplements are harmful to the cardiovascular system as long as people are ingesting a good amount of fish or omega-3 fatty acids.

Q. I am 51 years old and I have been taking evening primrose oil for years. Sometime last year I started getting hot flashes and this was the period when I decided to give the primrose oil a brake. I went back on and it within two weeks the hot flashes were gone. I am now taking 2 x 1300 mg per day -- primrose oil, along with 2 x 1000mg flaxseed oil. My questions: Should I take the evening primrose oil along with the flaxseed oil? Can I take Omega-3 also and what dosage?
   A. In order to give the proper advice, a health provider with a good knowledge of these supplements and their health benefits and who knows your medical condition really well would be the appropriate person to consult with.