Biological effects of fruit and vegetables.

摘要

A strong and persistent effect of plant foods on the prevention of lifestyle diseases has emerged from observational studies. Several groups of phytochemicals have been identified as potentially health promoting in animal studies, including cholesterol-lowering factors, antioxidants, enzyme inducers, apoptosis inducers etc. In human intervention studies, the dose levels achieved tend to be lower than the levels found to be effective in animal models and sampling from target organs is often not possible. In this study, a controlled parallel dietary human intervention was performed with 43 volunteers, providing 600 g fruits and vegetables daily or in the controls a carbohydrate-rich drink to balance energy intake for 24 days. Surrogate markers of oxidative damage to DNA, protein and lipids, enzymic defence and lipid metabolism were determined in blood and urine. It was found that a high intake of fruits and vegetables tends to increase the stability of lipids towards oxidative damage. Markers of oxidative enzymes indicated a steady increase in glutathione peroxidase (GPX1) activity in erythrocytes during intervention with fruits and vegetables but there was no effect on GPX1 transcription levels in leucocytes. No change occured in glutathione-conjugating or -reducing enzyme activities in erythrocytes or plasma, and there were no effects on the transcription of genes involved in phase 2 enzyme induction or DNA repair in leucocytes. Fruit and vegetable intake decreased the level of total cholesterol and low density lipoprotein (LDL)-cholesterol, but did not affect sex hormones. In conclusion, it has been shown that total cholesterol and LDL-cholesterol, markers of peripheral lipid oxidation and erythrocyte GPX1 activity are affected by high intakes of fruit and vegetables. This finding provides support for a protective role of dietary fruit and vegetables against CVD. [This paper was presented at the Summer Meeting of the Nutrition Society held in Norwich, UK, from 28 June to 1 July, 2005.]