[Biological markers for the intake of fruit and vegetables]

No available dietary assessment method is without error in measuring dietary intake. This has led to an increased interest in biological markers of dietary intake. This article is a review of the literature investigating whether the concentration of carotenoids in blood can serve as biological markers for the intake of fruit and vegetables. The literature indicates an association between intake of fruit and vegetables and the concentration of total carotenoids, alfa-carotene, beta-carotene, lutein and beta-cryptoxanthin in plasma. The same association was not observed for plasma lycopene. Results from several studies also indicate that plasma alfa-carotene and plasma total carotenoids are more suitable as biological markers of the intake of fruit and vegetables than the other carotenoids. As there are large individual variations in the plasma carotenoid response after intake, carotenoids in blood will be a better marker of intake at group level than individual level. Furthermore, the average value from several measurements of carotenoids in blood will be a better marker of long-term intake than a single measurement. Several factors in addition to fruit and vegetables influence the concentration of carotenoids in blood. It is important to assess these factors when carotenoids in blood are used as biological markers of the intake of fruit and vegetables.