Enhancing Plant Seed Oils for Human Nutrition

The age of true designer plant oils has arrived. Using the tools of biotechnology, it is now possible to modify the fatty acid content of oilseed plants to change the relative abundance of individual fatty acids in seed oil for health purposes or to produce nutritional fatty acids not normally found in crop plants. Fats and oils are an essential part of the human diet, and as a species we consume a lot of them, on average 25 kg per person per year, mostly (80%) from plant sources (Subar et al., 1998; USDA, 2008). Since at least the 1930s, it has been realized that not all fats are created equal in terms of human nutrition. Studies in rats determined that certain polyunsaturated fatty acids (PUFAs) derived from plants, namely, linoleic and linolenic acids, were necessary to sustain life in animals (Burr et al., 1932). Other unsaturated fatty acids, such as oleic and eleostearic acids, could not substitute for these omega-6 and omega-3 PUFAs. It is now known that while animals, including humans, can make monounsaturated fatty acids from sugar, they do not have the necessary desaturases to convert oleic into linoleic and linolenic acids and must derive them from their diet (Wallis et al., 2002). These PUFAs, it turns out, are further converted in humans to arachidonic acid (ARA) and eicosapentaenoic acid (EPA), which are in turn precursors to important molecules that regulate the immune response and to docosahexaenoic acid (DHA), an important component of membranes, especially in the brain (Tocher et al., 1998).