High plasma total homocysteine (tHcy) concentration is reported to be a risk factor for vascular diseases. We investigated the extent to which serum folate and plasma tHcy respond to a high intake of natural folate from food. Thirty-seven healthy females volunteered to participate in a crossover dietary intervention. The study included a baseline period and two 5-week diet periods (low- and high-folate diets) with a 3-week washout in between. The low-folate diet contained one serving of both vegetables and frui/, while during the high-folate diet the subjects ate at least seven servings of vegetables, berries, and citrus frui/. Serum and erythrocyte (RBC) folate, serum vitamin B12, and plasma tHcy concentrations were measured at the baseline and at the end of each diet period. The mean concentrations of serum and RBC folate were 11·0 (sd 3·0) nmo/ and 412 (sd 120) nmo/ at the end of the low-folate diet and 78 (95 % CI 62, 94) % and 14 (95 % CI 8, 20) % higher in response to the high-folate diet (P<0·001). The serum concentration of vitamin B12 remained unchanged during the intervention. The mean plasma tHcy concentration was 8·0 μmo/ at the end of the low-folate diet and decreased by 13 (95 % CI 9, 18) % in response to the high-folate diet (P<0·001). In conclusion, a diet high in fresh berries, citrus fruit, and vegetables effectively increases serum and RBC folate and decreases plasma homocysteine.