Among the benefits of the EFAs (essential fatty acids) are their haemorheological (red blood cell) properties and some pharmaceuticals also have beneficial effects on blood rheology (cell size and shape). Evening primrose oil is used to increase the blood levels of prostaglandin E1. There is experimental evidence that PGE1 improves red cell deformability by increasing the fluidity of the lipid bilayer of the red cell membrane.

A major problem in this field is the number of spurious agents sold as evening primrose oil and this is not a recent phenomenon. In 1980 the NZ Institute of Chemistry published a report on the analyses of the 11 brands sold as evening primrose oil: 9 of the 11 were spurious. For this reason I recommend only the 3 brands for which I have seen independent analysis of oil content. These brands are EFAMOL (an English product); EPO a New Zealand product and an Australian product – Naudicelle.

The need to take such a supplement usually relates to the dysfunction or inaction of the enzyme delta-6-desaturase which catalyses the first elongation of both omega-6 and omega-3 fatty acids. D-6-D becomes dysfunctional in a number of situations which include – after infections by viruses, in diabetes, in cancer, after radio therapy, and with increasing age. There is substantial evidence that blood rheology becomes abnormal in such states.

The significance of the omega-3 fatty acids, particularly EPA/DHA is that they have a similar effect on red cell deformability to PGE1. A Japanese study used spin-labeling to show that the lipid bilayer of diabetic red cells was much more viscous that that of healthy subjects. After a short period on sardine oil (I think 3 weeks) it was not possible to identify the diabetic red cells by this technique. Flaxseed oil contains alphalinolenic acid – the smallest of the omega-3 fatty acids and it needs a functional D-6-D to elongate and desaturate to EPA, so it is not recommended for conditions where D-6-D may be dysfunctional. On the basis of a book written by 2 physicians who described their experience with flaxseed oil, I have recommended it on 2 occasions but it proved ineffective.

Borage seed oil and black currant seed oil have about 18.6% of gammalinolenic acid vs about 9.2% for evening primrose oil. This was used in an advertising campaign in English women’s’ magazines with the claim “Because there is twice as much GLA in our oil you only need to take half the number of capsules.” While the statement is correct in fact – from a clinical viewpoint there is a major difference. Given that the aim of ingesting GLA is to increase the blood levels of PGE1, an experiment aimed at determining the effects of the different GLA-containing oils produced the following results. Borage seed oil – 2pg/ml; black currant seed oil – 7pg/ml; evening primrose oil – 82pg/ml. That study showed that it was not the AMOUNT of GLA which was important but its AVAILABILITY for conversion.

It has been published also that 2000mg daily of evening primrose oil had no effect of blood levels of PGE1, but 4000 and 6000 mg daily produced significant increases in PGE1. For that reason I recommend that 4000mg daily is the basic dose irrespective of age or bodyweight. NOTE that it is not possible to predict which patient will respond to any haemorheological agent – and any treatment should be assessed at 6 weeks. If no benefit is discernible then change.

On the basis of a trial of fish oil in elderly people I recommend 2000mg of fish oil with food 3 times daily. Cod liver oil is NOT part of this regimen – look for salmon oil or I noted that the earliest oil studied (MaxEPA) was cheaper in the USA. While there are a number of pharmaceuticals which appear to have haemorheological benefits the most studied is TRENTAL and should be considered if the oils do not have benefits. Trental was devised to lower blood viscosity and has been shown to improve red cell deformability. The bioflavonoids in gingko extract have been shown to improve cerebral blood flow. GINKOBA is the most studied of these and is used at 3 x 40mg tabs daily.