Evening primrose oil (EPO)

What is evening primrose oil?

Evening primrose oil (EPO) is a dietary supplement prepared from the seeds of the evening primrose plant, which is native to North and South America. 

Evening primrose oil contains high levels of the omega-6 essential fatty acids gamma-linolenic acid and linoleic acid.  Essential fatty acids, also known as polyunsaturated fats, are needed for good health but are not made by the body and need to be included in your diet (found in nuts, seeds and oils from nuts and seeds) or through supplements.

Historically, evening primrose oil was used as a topical remedy for bruises, wounds and inflammation of the skin. Today EPO supplements are promoted for use in several conditions including some types of eczema, premenstrual syndrome (PMS) and rheumatoid arthritis. However, there isn't enough evidence to support its use in these conditions.

Evening primrose oil and MS

In the late 1970s there were a small number of trials of essential fatty acids in multiple sclerosis, some of which included EPO capsules. One study found the length and severity of relapses was slightly improved in people using a spread containing linoleic acid but not in a parallel group taking capsules which contained evening primrose oil. However, the dose of linoleic acid in the capsules was lower than that found in the spread. Another arm of the study in people with progressive MS found the capsules containing evening primrose oil had no effect.

Although the benefits of evening primrose oil haven't been proven, in 1984, three double-blind trials of linoleic acid in people with MS were reanalysed. The trials were carried out in the 1970s and all used sunflower seed oil as the source of linoleic acid. The pooled data suggested that those with no, or low levels of, disability at the start of treatment had slower rates of progression. The severity and duration, but not the number, of relapses were also decreased regardless of the initial level of disability. However, some of the statistical methods that were used during the reanalysis have since been questioned, so these results are not considered definitive.

With the exception of a small study in 2018, which looked at the effects of evening primrose oil on fatigue and quality of life, there has been no further research published on EPO and MS. In this most recent trial, participants still took their standard treatment (beta interferon or glatiramer acetate) alongside the evening primrose oil. Although the group who received evening primrose oil reported a significant increase in some aspects of quality of life such as cognition, vitality and life satisfaction along with a reduction in pain and fatigue, there was no impact on quality of life in general and evening primrose oil did not prevent progression.

Evidence suggests that evening primrose oil is generally safe, and well tolerated, in most adults. The most common side effects include abdominal pain and nausea, but these are usually temporary.

Evening primrose oil should only be used as part of a balanced diet. For more advice, you could ask your GP to refer you to a dietitian.

Find out more

Majdinasab N, et al.
The effect of evening primrose oil on fatigue and quality of life in patients with multiple sclerosis.
Neuropsychiatric Disease and Treatment 2018;14:1505-1512.
Full article (link is external)
Dworkin RH, et al.
Linoleic acid and multiple sclerosis: a reanalysis of three double-blind trials.
Neurology 1984;34:1141-1145.
Summary (link is external)
Bates D, et al.
Polyunsaturated fatty acids in treatment of acute remitting multiple sclerosis.
BMJ 1978;2(6149):1390-1391.
Full article (link is external)
Bates D, et al.
Trial of polyunsaturated fatty acids in non-relapsing multiple sclerosis.
BMJ 1977;2(6092):932-933.
Full article (PDF, 500kb) (link is external)
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