Safe Food_ Bacteria, Biotechnology, and Bioterrorism - Marion Nestle [100]
In this statement, Mr. Conway also expressed a common theme: Golden Rice holds so much promise that no questioning of its value is justified.
As it turns out, if Greenpeace activists had known a bit more about basic and applied nutrition, they could have provided even further cause for skepticism about the promise of Golden Rice. To begin with, the “bioavailability” of beta-carotene, the amount that is absorbed and converted to vitamin A, is quite low—10% or less by some estimates—which explains why conversion ratios to vitamin A may be as high as 12 to 1. Also, an enzyme (from the intestine or liver) splits beta-carotene into two molecules of vitamin A (see figure 13). Like all enzymes, this one is a protein that must be synthesized in the body. Beta-carotene, like vitamin A, is fat-soluble, meaning that it requires some fat in the diet to aid its absorption and transport. People whose diets are adequate in fat and protein are able to use beta-carotene more efficiently than those who are malnourished. Furthermore, vitamin A deficiency is often the most visible manifestation of generalized protein-energy malnutrition, in part caused by intestinal or parasitic infections that interfere with the absorption of beta-carotene and its conversion to vitamin A.30 We do not yet know the extent to which malnourished children—those most at risk of vitamin A deficiency—can absorb and use the beta-carotene in Golden Rice. In addition to such doubts, Golden Rice may prove costly. The companies may be donating the technology to create the rice, but farmers will still have to sell it, and people will still have to pay for it. Moreover, in many countries where vitamin A deficiency is common, food sources of beta-carotene are plentiful, but people believe the foods inappropriate for young children, do not cook them enough to make them digestible, or do not consume enough fat to permit much in the way of absorption. It remains to be seen whether the beta-carotene in Golden Rice will fare better under such circumstances. Overall, vitamin A deficiency is a complicated health problem affected by cultural and societal factors as well as dietary factors. In this situation, the genetic engineering of a single nutrient or two into a food, while attractive in theory, raises many questions about its benefits in practice.
In 2001, I sent a brief letter outlining these nutritional points to the Journal of the American Dietetic Association.31 An electronic copy appeared on the Internet and drew responses from colleagues around the world. A British scientist (who identified himself as a Fellow of the Royal Society) wrote, “It would seem to me that the simplest way to find out if vitamin A rice [sic] works as a vitamin supplement is to try it out. If it doesn’t then what has been lost except a lot of hot air and propaganda; on the other hand if it does work and your letter has delayed its introduction, could you face the children who remain blind for life as a consequence?”
The writer seems to suggest that even if beta-carotene contributes just a little to alleviating vitamin A deficiency, no questioning of the theoretical premise of Golden Rice—and, by implication, food biotechnology—is acceptable. Anyone who raises questions about the potential value of Golden Rice bears moral responsibility for 500,000 cases of childhood blindness and millions of deaths from vitamin A deficiency each year. What I find most striking about such views is their implication that complex societal problems—in this case, malnutrition—are more easily solved by private-sector, commercially driven science than by societal decisions and political actions.
We already know that questions about the ability of Golden Rice to help people overcome deficiencies of vitamin A will not be answerable for several years. While waiting