From: The Tale of the Three Little Pigments
The gold vexation
Too much of a good thing: among the fossil hominids described by Richard Leakey and colleagues is a partial skeleton of Homo erectus from Kenya showing pathological changes consistent with chronic vitamin A poisoning. It was suggested that hypervitaminosis symptoms were the result of a change in the dietary habits of H. erectus to include a high intake of animal liver. There is a long history of vitamin A poisoning among arctic travellers and fishermen who consumed the livers of polar bears, seals, husky dogs or flatfish.
Generally speaking, however, hypervitaminosis A is a rare condition. On the other hand, UNICEF estimates that more than 140 million pre-school children and more than seven million pregnant women, are seriously vitamin A deficient, precipitating over a million child deaths each year. Of the 118 countries affected, most are in Asia, sub-Saharan Africa and South and Central America. Vitamin A deficiency is a leading cause of child blindness in developing countries. It also limits growth, weakens the body’s immune system and increases mortality. The condition and its treatment have been understood at least as far back as the time of the classical Greeks, and possibly even the ancient Egyptians. Consume liver (or fish liver oil) is the answer. But what if, as throughout the developing world, these remedies are of limited availability, too expensive, or precluded culturally by adherence to a vegetarian diet?
The Golden Rice project was born as a response to this predicament. Rice grains, the main food source in many of the regions with endemic vitamin D deficiency, are low in β-carotene, a precursor of vitamin A synthesis. But rice leaves, like all green plant tissues, make plenty of β-carotene. There’s evidently a gap somewhere in the terpenoid synthesis pathway of rice grains, the consequence of genes being disabled during seed development. It turned out this blockage could be overcome by introducing genes encoding two enzymes of carotenoid biosynthesis: the synthetase that converts endogenous GGPP into phytoene; and a bacterial enzyme that introduces four double bonds into phytoene, completing the metabolic sequence leading to carotenes. It took years to get the system working with high efficiency but now there are varieties of rice, biofortified with golden carotenoids, to levels in excess of 30 μg g-1 fresh weight, that amply meet the recommended dietary daily allowance for adequate conversion to vitamin A. By ‘introducing genes’ I mean, of course, using transgenics, which pitches Golden Rice straight into the ongoing stand-off between biotechnology and the Green Movement. This issue is complex, fast-moving and won’t be analysed here. Suffice to say that the scientists who conceived and realised the Golden Rice project really should be household names, respected for their brilliant work: Ingo Potrykus, Peter Beyer, Adrian Dubock, Peter Bramley. They were motivated to apply their deep knowledge and expertise to solve a humanitarian problem. What have their extremist opponents contributed? Tearing down fences and tearing up plants. And the politics of this is getting uglier. It’s now being suggested that online information warfare, conducted by state-sponsored hackers, is driving even further the wedge between the scientists and environmentalists who ought to be on the same side.
Meanwhile, the vitamin deficient wait, suffer and die.