Uncertainty Assessment. An uncertainty factor (UF) of 2 was selected based on the limitations of the data involving pyridoxine doses of less than 500 mg/day.

Derivation of a UL. The NOAEL of 200 mg/day was divided by the UF of 2 to obtain a UL of 100 mg/day for adults:

Some concern for pregnant and lactating women could arise from the data available in the literature on congenital defects, B₆ dependency, and antilactogenic effects (Donaldson and Bury, 1982; Foukas, 1973; Gardner et al., 1985; Hunt et al., 1954; Marcus, 1975; Philpot et al., 1995; Scaglione and Vecchione, 1982). Scientifically based, controlled studies designed to assess the potential adverse effects of pyridoxine intake by pregnant and lactating women are lacking. As noted above, the weight of the evidence from controlled studies in animals during pregnancy reveals no adverse effects related to teratogenicity, and the evidence from humans reveals no adverse effects from intakes up to 200 mg/day. Therefore, a UL of 100 mg/day was set for pregnant and lactating women as well. The ULs for children and adolescents were calculated from the UL for adults by using the method described in Chapter 3; this method adjusts for body size.