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Evening Primrose Oil - Effective or Not?

Evening primrose oil is commonly recommended for women with PMS. Almost every list of traditional remedies for premenstrual syndrome mentions this oil because it is rich in gamma linolenic acid, an anti-inflammatory omega-6 fatty acid. Its use for PMS is further helped by the positive results of early studies investigating its benefit for women with this condition. However, recent studies have failed to repeat the successes of earlier studies. Is evening primrose oil effective for PMS? Is borage oil a recommended substitute? Read on to find out.
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The Health Benefits of Evening Primrose Oil

Evening primrose oil is the oil extracted from the seeds of the plant, Oenothera biennis, a North American wildflower and not a true primrose plant.

This oil is rich in gamma linolenic acid or GLA. The matured seeds of evening primrose contain about 10% of this essential fatty acid and also 65% of linolenic acid, its precursor. Most of the medicinal benefits of evening primrose oil is attributed to its GLA content.

In traditional medicine, evening primrose is commonly used to treat skin diseases as well as promote wound healing. The oil is also popularly used to reduce the pains and aches associated with premenstrual syndrome.

Other medicinal properties of evening primrose oil include its anti-inflammatory, antioxidant, vasodilatory and blood thinning effects.

It should be noted that gamma linolenic acid is not the only medicinal constituent of evening primrose oil.

The oil is also rich in vitamin E and the amino acid, phenylalanine. In fact, some experts believe that these other constituents are more important than gamma linolenic acid.

Evening primrose oil supplements are generally considered as safe. The side effects reported in clinical trials are mild and easily resolved. Such side effects include gastrointestinal complaints, nausea and headache.

Because evening primrose oil has anti-platelet properties, it can be classified as an anticoagulant agent. Therefore, it should not be combined with anticoagulant drugs such as warfarin. Such combinations will only increase the risk of serious bleeding.

In addition, evening primrose oil is not recommended for people placed on phenothiazines, a family of tranquilizers. It should also be avoided by pregnant women.

Long-term use of evening primrose oil may, however, be potentially harmful. One study found that long-term use of this oil was linked with increased risks of inflammation, suppression of the immune system and clot formation in blood vessels.

What is GLA?

Gamma linolenic acid is an omega-6 fatty acid. It was first isolated from evening primrose oil but can also be found in safflower oil, borage oil, blackcurrant seed oil and hemp seed oil.

To formulate supplements rich in gamma linolenic acid, evening primrose oil is often combined with borage oil. This is because borage oil contains double the amount of the essential fatty acid as evening primrose oil.

Besides plant oils, gamma linolenic acid can also be found in oats, barley and spirulina.

Gamma linolenic acid is naturally synthesized in the body from linolenic acid. The conversion is catalyzed by the enzyme known as delta-6 desaturase or D6D.

When the level or efficiency of D6D falls, the synthesis of gamma linolenic acid suffers and all the biochemical processes depending on it are affected. D6D performance can be affected by old age, dietary deficiencies and certain diseases.

Unlike most of the other omega-6 fatty acids that are pro-inflammatory, gamma linolenic acid has an anti-inflammatory effect.

It is used to synthesize prostaglandins which are essential to the functioning of the immune system.

Because gamma linolenic acid was first extracted from evening primrose, a plant once called king’s cure-all, it was believed to be effective in the treatment of a lot of diseases.

However, recent evidences suggest that evening primrose is not effective for most of the conditions for which it was previously recommended. Researchers have already demonstrated that this omega-6 fatty acid does not improve atopic dermatitis (eczema) and that it has no anti-cancer properties.

How Evening Primrose Oil May Help PMS

Evening primrose oil is used in the management of PMS (premenstrual syndrome) because it is believed to help restore a normal fatty acid profile in women.

Studies show that women experiencing PMS have an imbalance of essential fatty acids.

Specifically, researchers found that although these women have high levels of omega-6 fatty acids such as linolenic acid, they have low levels of the metabolites synthesized from linolenic acid.

Therefore, women with PMS have low levels of gamma linolenic acid, arachidonic acid and the other compounds downstream of linolenic acid in the synthetic pathway leading to the production of prostaglandins.

In one study, the researchers found that the level of gamma linolenic acid was barely detectable in women with PMS.

Therefore, they believed that PMS may be the result of poor conversion of linolenic acid to gamma linolenic acid.

It is, therefore, reasonable to expect that supplementing with gamma linolenic acid can help sidestep this metabolic bottleneck and raise the levels of the metabolites of linolenic acids required to restore a normal fatty acid profile in women with PMS.

GLA, Inflammation and PGE1

Evening primrose oil is recommended for women experiencing PMS because of possible benefits from its constituents. For example, the gamma linolenic acid in the oil may lower inflammation and this can, in turn, improve some of the symptoms of PMS.

Some experts have even suggested that PMS may be the result of a deficiency of gamma linolenic acid.

Such deficiency may result from poor dietary intake of the omega-6 fatty acid or from an impairment in the functioning of D6D, the enzyme responsible for synthesizing gamma linolenic acid from linolenic acid in the body.

The anti-inflammatory property of evening primrose oil is due to gamma linolenic acid. Gamma linolenic acid is used to synthesize the anti-inflammatory prostaglandin known as PGE1.

The increased production of PGE1 is the reason why evening primrose oil relieves the joint pain associated with arthritis. It may also serve a similar purpose in women experiencing PMS. However, PGE1 also serves another important role in the body.

PGE1 lowers the levels of prolactin, a pituitary hormone released to promote breast development and lactation.

Excessively high levels of prolactin have been reported in some women while they experienced PMS. In addition, this hormone has been linked to some of the symptoms of PMS especially breast tenderness. Therefore, evening primrose oil may help with PMS by raising the production of PGE1.

Evening Primrose Oil, Hormones and Neurotransmitters

The antioxidant and anti-inflammatory properties of evening primrose oil can help reduce oxidative stress and inflammation in the body. These actions can enhance immune functions, reduce inflammation and restore hormonal balance.

In addition, these medicinal effects can promote neurotransmitter balance in the central nervous system.

This is important because most of the core symptoms of PMS involve mood and emotions. In addition, researchers currently believe that PMS is the result of negative interactions between sex hormones and neurotransmitters in the brain.

The antioxidant property of vitamin E, the anti-inflammatory property of gamma linolenic acid and the role of phenylalanine in the syntheses of certain brain chemicals are all important to modulating the interaction between sex hormones and neurotransmitters.

Preliminary studies indicate that evening primrose can protect the body against nerve damage and also boost signal transmission between the neurons of the nervous system.

These protective and stimulatory roles in the nervous system can improve nerve transmission and help reduce the depression felt by women when experiencing PMS.

Evening Primrose Oil and Other Symptoms of PMS

Besides the emotional symptoms, evening primrose oil may also reduce some of the physical symptoms of PMS. The oil is often used to treat migraine headache and joint pain. Therefore, it can reduce aches, pain and fatigue associated with PMS.

Lastly, evening primrose oil has been used to treat acne and rosacea. It does reduce sebum production as well as inflammation in the skin. Since acne often breaks out during PMS in some women, evening primrose oil may help prevent chronic acne.

Even though evening primrose oil should provide these benefits, does it really help with PMS?

Studies on Evening Primrose Oil and PMS

Most of the early studies investigating the benefits of evening primrose oil for women with PMS found that the oil could help.

However, newer studies chalked up those results to placebo effects and found no evidence that evening primrose oil helped reduce PMS symptoms.

Positive Studies

In an open label study published in the journal, Clinical Uses of Essential Fatty Acids, in 1982, a group of researchers determined that evening primrose oil helped with some of the symptoms of PMS.

In this study, the researchers recruited 68 women and gave each of them 1 – 2 grams of essential primrose oil per day beginning 3 days before the usual start of their PMS symptoms until the onset of their menses.

The participants were then asked to report any improvements in their PMS symptoms for the next 3 months. The results of the study showed that 61% of them experienced complete relief from their PMS symptoms while 23% had partial relief.

The most commonly reported PMS symptom relieved was breast pain.

While this study produced excellent results to support the use of evening primrose oil in the treatment of PMS, its design was flawed.

First, it was an open label study and had a small study size. In addition, it had no placebo, no control group and the study was not double-blinded. Therefore, the study was opened to bias from both the participants and researchers.

Lastly, there was no objective assessment of the efficacy of evening primrose oil on PMS symptoms. Rather, the subjective reports of the participants were taken as the final data upon which the results of the study were based.

Other early studies reached the same conclusion. Some of these include a 1989 study published in the journal, Current Therapeutic Research and a 1986 study published in Progress in Lipid Research.

Negative Studies

The positive results recorded in the early studies were not replicated in later studies. One of the earliest studies to find evening primrose oil ineffective in the treatment of PMS was published in the journal, Human Psychopharmacology: Clinical and Experimental, in 1989.

In this study, the researchers recruited 12 women who had a defined pattern of depression and anxiety during their premenstrual periods. Then, over a period of 2 months, these women were randomly assigned to either placebo or a combination of Efamol and Efavit.

Efamol and Efavit are both dietary supplements. Efamol contains evening primrose oil and tuna oil. Efavit is an omega-3 supplement enriched with vitamins A, C, D and E.

Out of the 10 women who completed the study, the results showed that depression and anxiety improved regardless of whether placebo or evening primrose oil supplement was given.

Therefore, the researchers concluded that the observed efficacy of evening primrose oil was only due to placebo effect.

A similar study was also published in The Medical Journal of Australia in 1990. In this study, Efamol (4 grams daily) was also the evening primrose oil supplement given to the participants.

The researchers recruited 38 women and monitored 10 symptoms associated with PMS. The study was randomized, placebo-controlled, double-blind and crossed over after 3 menstrual cycles.

After 6 cycles, the researchers reported that there were improvements in PMS symptoms in all the women involved in the study. However, there was no difference between the placebo group and the group given evening primrose oil.

The researchers also concluded that the improvements experienced by women taking evening primrose oil during PMS were solely due to placebo effect.

A meta-analysis of past studies investigating the use of evening primrose oil in the management of PMS was published in the journal, Controlled Clinical Trials, in 1996.

Out of the 7 studies selected for the analysis, only 2 were well-designed enough to factor heavily in the review. And those studies failed to find any benefits for using evening primrose oil in the treatment of PMS.

The reviewers, therefore, concluded that current evidence showed that the oil has little value for women with PMS.

In Conclusion

Evening primrose oil cannot be recommended for the management of PMS because there is no scientific evidence to support its use for this purpose.

Since the only studies to find it useful for women with PMS are old and poorly designed, it is only proper to only consider newer studies that eliminated bias by using techniques such as double blind, treatment randomization, placebos and controls.

The case for evening primrose oil is further weakened by placebo-controlled studies that showed that placebos also relieve PMS symptoms and to the same degree as evening primrose oil supplements.

Currently, it is not clear whether it is evening primrose oil or gamma linolenic acid that is to blame.

Therefore, while some experts recommend other oils (borage oil, for example) richer in gamma linolenic acid for women with PMS, the failure of evening primrose oil does not indicate that more gamma linolenic acid is what is required for PMS relief.





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