Producing the omega-3 fatty acids DHA and EPA in oilseed crops

Is the world supply of omega-3 fatty acids adequate for optimal human nutrition?

PURPOSE OF REVIEW

To delineate the available sources of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) for human consumption and to determine if the available supply is capable of supplying the nutrient levels recommended by expert bodies.

RECENT FINDINGS

There are converging opinions among experts, professional organizations and health professionals that a recommendation for a daily individual consumption of 500 mg of EPA/DHA would provide health benefits, and this translates to an annual human consumption of 1.3 million metric tons. Current human consumption of EPA/DHA is estimated to be only a small fraction of this amount and many people may suffer from suboptimal health as a result of low intake. EPA and DHA originate in the phytoplankton and are made available in the human food chain mainly through fish and other seafood.

SUMMARY

The fish catch is not elastic and in fact has long since reached a plateau. Aquaculture has grown rapidly, but most of the fish oil produced is currently being used to support aquaculture feed and so this would appear to limit aquaculture growth - or at least the growth in availability of fish sources of EPA/DHA. Vegetable oil-derived alpha-linolenic acid, though relatively plentiful, is converted only at a trace level in humans to DHA and not very efficiently to EPA, and so cannot fill this gap. Microbial EPA/DHA production can in the future be increased, although this oil is likely to remain more expensive than fish oil. Plant sources of EPA and DHA have now been produced in the laboratory via transgenic means and will eventually clear regulatory hurdles for commercialization, but societal acceptance remains in question. The purpose of this review is to discuss the various sources of omega-3 fatty acids within the context of the potential world demand for these nutrients. In summary, it is concluded that fish and vegetable oil sources will not be adequate to meet future needs, but that algal oil and terrestrial plants modified genetically to produce EPA and DHA could provide for the increased world demand.

Understanding and manipulating plant lipid composition: Metabolic engineering leads the way

The manipulation of plant seed oil composition so as to deliver enhanced fatty acid compositions suitable for feed or fuel has long been a goal of metabolic engineers. Recent advances in our understanding of the flux of acyl-changes through different key metabolic pools such as phosphatidylcholine and diacylglycerol have allowed for more targeted interventions. When combined in iterative fashion with further lipidomic analyses, significant breakthroughs in our capacity to generate plants with novel oils have been achieved. Collectively these studies, working at the interface between metabolic engineering and synthetic biology, demonstrate the positive fundamental and applied outcomes derived from such research.