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Evening primrose oil trials for rheumatoid arthritis

Trial 1

In this trial, 49 people with rheumatoid arthritis who were on non-steroidal anti-inflammatory drugs (NSAIDs) were randomised to take one of the following once a day for 12 months:

  • 6 g (540 mg GLA) EPO
  • EPO with fish oil
  • placebo tablets.

Participants were asked to take their normal dose of NSAIDs during the first three months of the trial but were advised to reduce or stop it depending on their symptoms afterwards.

  • 94% of participants who got EPO alone and 93% who received EPO combined with fish oil reported a significant improvement of disease-related symptoms, including pain and morning stiffness, compared to only 30% of the placebo group – this was a significant difference.
  • EPO was also significantly effective in reducing the use of NSAIDs during the trial period.
  • Most participants’ symptoms came back during the three months that followed treatment, so EPO didn’t seem to alter the long-term disease activity.
  • Two participants on EPO withdrew from the trial because of nausea and diarrhoea.

Trial 2

Researchers evaluated the outcome of 40 people with rheumatoid arthritis who received daily doses of either 6 g EPO (540 mg GLA) or olive oil for six months.

  • Participants given EPO had a significant improvement in morning stiffness compared to participants given olive oil, but there were no significant differences between both treatment groups with respect to pain reduction and overall disease severity.
  • Most participants in this trial didn’t stop taking NSAIDs.
  • Four out of 19 participants taking EPO had to withdraw because of nausea, flu-like symptoms or their condition getting worse.


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