FIGURE 1.

Folate intake and plasma folate levels over 1980–2010. Mean folate intake over 1980–2010 (A). All folate intakes were energy adjusted. Total folate intake was calculated from foods (both unfortified and folic acid fortified) and supplements, synthetic folic acid intake from fortified foods and supplements, dietary folate intake from unfortified and fortified foods, and natural folate intake from the folate naturally present in both unfortified and fortified foods. Mean plasma folate levels before (1990) and after (2000) folic acid fortification (B). Within the Nurses’ Health Study, plasma folate was measured for 3880 participants in 1989–1990, and 696 participants in 2000–2001.