Research from the 1930s to the 1950s established that a deficit of n-6 EFAs leads to an inflammatory skin condition in both animals and humans. More recently, it has been established that there is no deficit of LA in atopic eczema. Instead, concentrations of LA tend to be elevated in blood, milk and adipose tissue of patients with atopic eczema, whereas concentrations of LA metabolites are substantially reduced. This suggests reduced conversion of LA to GLA (i.e. delta-6-desaturase) is responsible In most studies, but not all, administration of GLA has been found to improve the clinically assessed skin condition, the objectively assessed skin roughness, and the elevated blood catecholamine concentrations of patients with atopic eczema. Atopic eczema may be a minor inherited abnormality of EFA metabolism in some cases (Horrobin 2000).
Clinical studies While early results appear promising, including a meta-analysis published in 1998 that found that oral EPO provided significant improvement for patients with atopic eczema (Morse et al 1989), more recent studies appear to have reached an almost unanimous negative conclusion.
Evening primrose oil, as well as its combination with fish oils, taken for 16 weeks failed to improve symptoms of atopic dermatitis compared with placebo in another double-blind study of 102 adults (Berth-Jones & Graham-Brown 1993). Another study (Oliwiecki & Burton 1994) found that a combination of EPO and fish oil was ineffective in the treatment of psoriasis, and another found it also to be ineffective in atopic eczema, apart from a certain subgroup who failed to show increased erythrocyte DGLA levels and for whom adherence to inclusion criteria and the study protocol were questionable (Henz et al 1999).
In 2000 a substantial review was conducted by the NHS Health Technology Assessment Programmes, looking at more than 1 5 studies involving either EPO or borage oil in the treatment of atopic dermatitis, and it was concluded that the largest and best reported studies showed no convincing effect (Hoare et al 2000). Most recently a randomised, double blind, placebo-controlled parallel group trial of 1 51 patients treated with high-dose borage oil (920 mg GLA) found in favour of the placebo (Takwale et al 2003).
The effects of EPO supplementation in children with atopic eczema has also been investigated, producing both positive and negative results once again (Bamford et al 1985, Biagi et al 1988, Hederos & Berg 1996, Wright & Burton 1982).
Clinical note — Company interest bias in the evidence?
The research into the efficacy of EPO has attracted much criticism from different members of the scientific community. In particular, attention has been paid to the > 2007 Elsevier Australia
contrast between early 'strikingly' positive findings and the negative conclusions currently being drawn as a result of more in-depth analysis regarding the efficacy of EPO in the treatment of some conditions. While some may justifiably argue that as with all research it is due to the improvement in techniques, design etc. one editorial published in 2003 in the British Medical Journal implies that research funding from the manufacturers, selective inclusion of positive only studies in previous reviews and meta-analyses as well as partial suppression of negative findings has had a part to play (Williams 2003).
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