societies today became common beginning between 5,000–10,000 years ago (He and MacGregor, 2007; MacGregor and de Wardener, 1998; Man, 2007). Most commentators believe that the reason for early salt use was food preservation (MacGregor and de Wardener, 1998; Multhauf, 1978) and that this early use was the origin of the current high consumption. Nevertheless, with the advent of extensive salt mining and improved transportation beginning in China more than 4,000 years ago (Adshead, 1992), the characteristic taste of salted food became widely expected and accepted (Multhauf, 1978). Indeed, it has been argued that many distinguishing characteristics of human society and culture owe their origins to the desire for salt and the salt trade (Beauchamp, 1987; Bloch, 1963; Fregley, 1980).
It is difficult to know how much salt was consumed by humans prior to recent times, since the only good way to estimate intake is to determine 24-hour urinary excretion (for the most part, excess salt is not stored in the body; therefore salt balance under most normal conditions is reflected by equal input and output). Nevertheless, estimates based on historical records have been made. In an estimate of early usage, the average daily sodium intake in certain parts of China in 300 B.C. was reported to be nearly 3,000 mg/d for women and 5,000 mg/d for men (Adshead, 1992). Multhauf (1978) estimated that, in France and Britain in 1850, the human culinary intake of sodium was 4,000–5,000 mg/d. These numbers, if reliable, are within the range of the amounts consumed in many societies today (INTERSALT Cooperative Research Group, 1988). Thus, high salt intake by humans does not have its origins in twentieth-century food processing, but instead likely reflects food processing needs, especially preservation of food, that originated thousands of years ago. It should also be acknowledged that similarities in intake over time and across many different ethnic groups have led to speculation that there may be some as-yet-unknown physiological or nutritional factor that predisposes humans to desire a high salt intake (Fessler, 2003; Kaunitz, 1956; McCarron et al., 2009; Michell, 1978), but there is little experimental support for this hypothesis (Luft, 2009), and some limited data are inconsistent with it (Beauchamp et al., 1987). Further experimental evaluation about whether human sodium intake at levels far above any known physiological need is under metabolic regulation will be of interest.
Taste and flavor are terms that are often confused. The word “taste” has two meanings, one technical and the other as commonly used in the English language, which encompasses the larger concept of flavor. In this chapter, the word taste is used in its technical sense, but in other chapters of this document, it is often used in its more generic sense.