Feature

The Good Oil?

Debate continues as to the medical efficacy of evening primrose oil, but this hasn't deterred the DSIR from examining ways of cheaply producing the material.

By Max J. Kennedy

Evening primrose oil has gained high popularity as an alternative medicine for a variety of complaints. Each year, New Zealanders consume three million EPO capsules, or 1.5 tonnes, at a cost of $1.2 million, representing a major market. EPO oil is available from pharmacies and health food shops for about $20 for fifty 500 mg capsules.

The reason New Zealanders are consuming EPO is because of its apparent health benefits, using it to treat premenstrual tension, breast pain, alcohol withdrawal, rheumatoid arthritis, and atopic eczema, amongst other problems.

Worldwide, about 3,000 patients have been involved in trials of EPO in hospital-based research studies. The main side effects are mild gastrointestinal events such as stool softening and nausea, a consequence of any oil usage.

Rejected As Medicine

The high cost of the substance, and its apparent health benefits, has led manufacturers to apply for its reclassification as a medicine. This would give EPO suppliers the ability to advertise the material's therapeutic or medicinal properties, and would also reduce the price to consumers.

The New Zealand Medicines Assessment Advisory Committee (NZMAAC) recently declined such an application, citing inadequate proof of efficacy. NZMAAC considers it unlikely that such an application will be granted in the near future. In 1984, the Health Department was so concerned that EPO was being advertised as a medicine that they issued a warning on radio advising the public not to buy EPO. This is in contrast to the UK, where three EPO products are now available on prescription, and Japan, where EPO is added to infant milk.

The substance's unofficial status in New Zealand has meant the local consumer has no means of discerning the purity of the oil purchased. In the past, some EPO products have been spiked with cheaper oils. In addition, dosage information is haphazard and informal.

Ironically, New Zealand is one of the world's main producers of the evening primrose seeds from which EPO is produced. Evening primrose is grown in Canterbury and the either seeds are exported to the UK for processing, or EPO is extracted from them in New Zealand.

Active Component

The active component within EPO that is attracting interest is gamma linolenic acid (GLA). GLA is a precursor of the prostaglandins, a group of important short-lived regulating molecules. The metabolic pathway progresses from linoleic acid, to GLA, to dihomo-gammalinolenic acid, to prostaglandin E1. Prostaglandins have a similar function to hormones, and are involved in smooth-muscle contractions, particularly in areas where tissues are disturbed.

The enzyme that converts linoleic acid to GLA is called delta-6- desaturase. If this enzyme fails to function correctly, prostaglandin deficiency can lead to a large number of illnesses. Hence, EPO's use for a variety of conditions. Agents that block the action of delta-6- desaturase include foods rich in saturated fats and cholesterol, alcohol in moderate to large amounts, some viral infections and cancers, zinc deficiency, and catecholamines released during stress and fasting. The intake of GLA helps to overcome incorrectly functioning delta-6-desaturase.

The main sources of GLA are EPO (7-10% GLA), blackcurrant seed oil (16-17% GLA) and borage seed oil (24-25% GLA). Controversy currently exists over which oil is therapeutically the best source of GLA. It has been claimed that the GLA in borage and blackcurrant oils is not as effective as the GLA in EPO. The difference is attributed to different fatty acid patterns or triglyceride structures in each of the oils. Further research will have to be conducted to definitively answer the question of which is the best source of GLA and why.

DSIR Research

In New Zealand, two research efforts have been undertaken looking at ways of producing GLA. The DSIR has evaluated Spirulina platensis and Spirulina maxima as sources of GLA. Both these species are imported as dried cells and are sold in health food shops as "spirulina". It was feared that overseas distributors might have been bulking up such preparations with a cheaper product from Chlorella. The study concluded that it was unlikely that spirulina would provide serious competition for other sources of GLA.

The DSIR has developed a promising production approach, using microorganisms. Fungal production of GLA has been noted, and at least three companies worldwide are considering production of GLA from microbial sources.

After screening many microorganisms, DSIR scientists identified a fungus (Mucor hiemalis), which accumulates an oil with up to 31% GLA. The Industrial Development unit has considerable expertise in microbial oil production, and has been able to produce one litre of GLA-rich microbial oil from the fungus in pilot plant trials.

Given the considerable interest, both within New Zealand and internationally, in the substance, there is good potential in the DSIR's investigation of methods of concentrating the GLA present in microbial and plant oils to produce highly pure GLA.

Max Kennedy is with DSIR Industrial Development .