Contaminants that are introduced early in the production process are a major problem. Introduction of contaminants can occur via contaminated animal feeds, impure water, and inadequately composted manure, or by “contamination during production and harvest, initial processing and packing, distribution, and final processing” (Tauxe, 1997). Others are introduced or enhanced in the process of food storage and preparation. Reports of incidences of bacterial food-borne illnesses in the United States between 1996 and 2001 have declined: Yersinia (49 percent), Listeria (35 percent), Campylobacter (27 percent), and Salmonella (15 percent) (Pinner et al., 2003). These declines may be due to new food safety measures that were put in place in the 1990s.
Infections with E. coli, however, have not shown a similar decline. The number of E. coli contamination events in the United States declined only between 2000 and 2001, suggesting a year-to-year variation rather than a consistent trend (Bender et al., 2004). Overall, reports of trends in meat contamination indicate that the prevalence of E. coli in ground beef may not have changed (FSIS, 2003).
Importantly, concerns regarding nutrient deficiencies and toxicities have been raised because of the acknowledged capability of genetic engineering to markedly change the composition of plant foods. Thus, modifications of food composition must consider the potential impact on nutrient deficiencies, toxicities, interactions, and/or other imbalances. The deletion of essential nutrients from foods or, more likely, their enhancement, has the potential of influencing the risk of nutrient deficiencies or toxicities, respectively, in the general or subsets of the population, depending on exposure patterns. In this context it should be noted that to date most nutrient toxicities are due to the addition of nutrient levels in excess of normal physiologic needs, achieved through fortification or due to the excessive consumption of nutrient supplements.
The concepts of nutrient deficiencies were developed several decades ago (Youmans, 1941), and have been undergoing significant change since then (Bendich, 2001). One recent conceptualization of deficient intakes is expressed by an Institute of Medicine report, that is, the “level of intake of a nutrient below which almost all healthy people can be expected, over time, to experience deficiency symptoms of a clinical, physical, or functional nature” (IOM, 1994).
This concept recognizes that single and multiple nutrient deficiencies may have multiple manifestations that are expressed at diverse levels of intake, determined by gender, age, physiological state (e.g., puberty, postmenopause, preg-