- Food is an exceedingly complex mixture of nutrient and nonnutrient substances.
- A substance listed as Generally Recognized as Safe (GRAS) achieves this determination on the adequacy of safety, as shown through scientific procedures or through experience based on common use.
- An estimated daily intake (EDI) is based on two factors: the daily intake of the food in which the substance will be used and the concentration of the substance in that food.
- Food hypersensitivity (allergy) refers to a reaction involving an immune-mediated response, including cutaneous reactions, systemic effects, and even anaphylaxis.
- The vast majority of food-borne illnesses in developed countries are attributable to microbiologic contamination of food.
The nature of food is responsible for the uniqueness of food toxicology. Food cannot be commercially produced in a definable environment under strict quality controls and thus cannot meet the rigorous standards of chemical identity, purity, and good manufacturing practice met by most consumer products. The fact that food is harvested from the soil, the sea, or inland waters or is derived from land animals subject to the unpredictable forces of nature makes the constancy of raw food unreliable. Food is more complex and variable in composition than all other substances to which humans are exposed, and humans are exposed more to food than to any other chemicals!
Nature and Complexity of Food
Food is an exceedingly complex mixture whether it is consumed in the “natural” (unprocessed) form or as a highly processed “Meal Ready to Eat” (MRE). Nonnutrient substances (substances other than carbohydrates, proteins, fats, or vitamins/minerals) may be contributed by food processing, but nature provides the vast majority of nonnutrient constituents. Table 30–1 indicates that natural, or minimally processed, foods contain far more nonnutrient than nutrient constituents.
Table 30–1 Nonnutrient substances in food. |Favorite Table|Download (.pdf)
Table 30–1 Nonnutrient substances in food.
Number of Identified Nonnutrient Chemicals
Importance of the Gastrointestinal Tract
The constituents of food and other ingesta (e.g., drugs, contaminants, and inhaled pollutants dissolved in saliva and swallowed) are physicochemically heterogeneous, and the primary mechanisms for intestinal absorption are passive or simple diffusion, active transport, facilitated diffusion, and pinocytosis. Each mechanism characteristically transfers a defined group of constituents from the lumen into the body (Table 30–2).
Table 30–2 Systems transporting enteric constituents. |Favorite Table|Download (.pdf)
Table 30–2 Systems transporting enteric constituents.
Sugars (e.g., fructose, mannose, and xylose, which may also be transported by facilitated diffusion), lipid-soluble compounds, water
D-Xylose, 6-deoxy-1,5-anhydro-d-glucitol, glutamic ...