Abstract

Dietary vegetables and fruit may play a significant role in atherosclerosis. We investigated the effects of a high intake of vegetables, berries, and citrus fruit along with a diet low in total and saturated fat on plasma concentrations of lipids, lipoprotein(a), antioxidants, oxidised LDL (OxLDL), folate, homocysteine, and on serum paraoxonase-1 activity. We also determined whether gene polymorphisms affect diet response of plasma homocysteine and serum paraoxonase-1 activity. Thirty-seven healthy females consumed two diets (low and high vegetable diets) in a controlled crossover intervention. The plasma measurements were determined at the baseline and at the end of diet periods.

The average plasma concentrations of total, LDL, and HDL cholesterol were 5.0 mmol/l, 2.8 mmol/l, and 1.7 mmol/l, respectively, on the low vegetable diet, and decreased by 8%, 8%,and 5%, respectively, in response to the high vegetable diet. The high vegetable diet increased the plasma concentrations of alpha-carotene, beta-carotene, lutein-zeaxanthin, beta-cryptoxanthin, and vitamin C by 133%, 134%, 107%, 65%, and 25%, respectively, compared with the low vegetable diet. There were no differences in the plasma concentrations of OxLDL between the low and high vegetable diets. The mean serum paraoxonase-1 activity was lower at the end of the high vegetable diet (226 U/l) than at the end of the low vegetable diet (240 U/l). Subjects having a genotype with high baseline paraoxonase-1 activity showed the most extensive reduction in their serum enzyme activities.

The high vegetable diet enhanced the serum and erythrocyte folate concentrations by 78% and 14%, respectively, and reduced the plasma homocysteine by 13% compared with the low vegetable diet. The dietary treatment was effective even among subjects homozygous for C₆₇₇T mutation in methylenetetrahydrofolate reductase gene, who are susceptible to high homocysteine levels.

In conclusion, a high intake of vegetables, berries, and citrus fruit resulted in reduced plasma total and LDL cholesterol concentrations and enhanced plasma antioxidant levels. The high vegetable diet also effectively increased blood folate concentrations and reduced plasma homocysteine concentration.