vegetarians (Brants et al., 1990; Hunt et al., 1988; Lowik et al., 1990). Among vegetarians, zinc concentrations in serum, plasma, hair, urine, and saliva are either the same as or lower than those of nonvegetarians (Anderson et al., 1981; Freeland-Graves et al., 1980a, 1980b; Hunt et al., 1998; Kadrabova et al., 1995; King et al., 1981; Krajcovicova-Kudlackova et al., 1995; Levin et al., 1986; Srikumar et al., 1992). The variations in these status indicators are most likely due to the amount of phytate, fiber, calcium, or other inhibitors of zinc absorption in the vegetarian diets. Individuals consuming vegetarian diets were found to be in positive zinc balance (Ganapathy et al., 1981; Hunt et al., 1998).
The requirement for dietary zinc may be as much as 50 percent greater for vegetarians and particularly for strict vegetarians whose major food staples are grains and legumes and whose dietary phytate:zinc molar ratio exceeds 15:1. At this time there are not sufficient data to set algorithms for establishing dietary requirements for zinc on the basis of the presence and concentration of other nutrients and food components.
Long-term alcohol consumption is associated with impaired zinc absorption and increased urinary zinc excretion. Low zinc status is observed in approximately 30 to 50 percent of alcoholics. Thus, with long-term alcohol consumption, the daily requirement for zinc will be greater than that estimated via the factorial approach.
The dietary sources of zinc vary widely. Zinc is abundant in red meats, certain seafood, and whole grains. Because zinc is mainly located in the germ and bran portions of grains, as much as 80 percent of the total zinc is lost during milling. Many breakfast cereals are fortified with zinc. Studies measuring zinc content in human milk are summarized in Table 12-1.