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.
BACKGROUND: There is a need for objective and universally applicable biomarkers for the intake of foods believed to affect human health. OBJECTIVE: The purpose of this feeding study was to test whether plasma concentrations of carotenoids could be used to distinguish recommended consumption of mixed fruits and vegetables (five a day) from the current national intake of fruits and vegetables (two a day). DESIGN: A strict crossover design was chosen to correct for observed interindividual variations in carotenoid response. A total of 40 healthy subjects were included in the study. After 1 week run-in period with no fruits and vegetables in the diet, one group was given two portions (300 g) of fruits and vegetables daily, while another group was given five portions (750 g) for 14 days. Following a 2 week wash-out period and 1 week run-in, the regimens were switched between the groups. Fruits and vegetables were combined to match a typical Norwegian diet. RESULTS: Enhanced intake from two to five portions of mixed fruits and vegetables increased plasma concentrations of alpha-carotene (P=0.033) and lutein (P=0.051) in a crossover analysis. Analysis of data in the parallel part of the study revealed differences between the high and low intake for plasma concentrations of alpha-carotene (P=0.013) and beta-carotene (P=0.016). A trend was also evident for plasma concentrations of lycopene (P=0.057) and lutein (P=0.076) in the parallel analysis. No effect of high vs low intake of fruits and vegetables was observed for plasma concentrations of beta-cryptoxanthin, zeaxanthin, cholesterol and triacylglycerols. CONCLUSION: The study indicates that plasma concentration of alpha-carotene, beta-carotene and lutein may be used to assess changes of fruit and vegetable intake corresponding to an increase from the present national intake in Norway to the recommended amount of five portions of fruits and vegetables daily. SPONSORSHIP: Norwegian Research Council, National Nutrition Council, Throne Holst Foundation for Nutrition Research and Freia Chokoladefabriks Medisinske Fond.
OBJECTIVE: Reproducible and valid methods for measuring fruit and vegetable consumption among young school children are urgently needed. The aim of this study was to test the reproducibility and the validity of a newly developed questionnaire on the intake of fruit and vegetable among Norwegian 6th graders. The questionnaire consisted of a 24-h recall part and a food frequency part. DESIGN: A total of 114 pupils completed the questionnaire two times 14 days apart, and another 85 pupils completed the questionnaire and 7-day food diaries. SUBJECTS: Pupils of 6th grade with a mean age of 11.9 y. RESULTS: Spearman correlation coefficients between the frequency part of the questionnaire administered two times varied from 0.62 for fruit to 0.83 for potato, and no difference was seen between the average intakes from the two 24-h recalls. The 24-h recall part of the questionnaire gave higher estimates for the average intake of fruit and juice compared to the 7-day record, while no difference was observed for vegetable intake. Spearman correlation coefficients between the frequency part and the records varied from 0.21 for fruit and potato to 0.32 for the total intake of fruit and vegetable. CONCLUSION: Both the 24-h recall and the frequency part gave a consistent response on separate occasions over the test-retest study period. The 6th graders were capable of recording yesterday's intake of vegetable, but overestimated the intake of fruit and juice. The ability to rank subjects based on the frequency part was rather low.
BACKGROUND: Enhanced cyclooxygenase-2 (COX-2) expression is associated with carcinogenesis, ischemia, angiogenesis, inflammation, and neurodegeneration. The preventing effect of aspirin and nonsteroidal anti-inflammatory drugs is partly due to inhibition of the COX-2 enzyme. Fruit and vegetables (FVs) contain numerous compounds that may decrease disease risk by several different mechanisms, for example through the inhibition of COX-2 activity. OBJECTIVE: We tested the hypothesis that an increased intake of FVs would modulate the COX-2 expression in peripheral blood cells. DESIGN: A strictly controlled dietary crossover study (n = 39). After 1 week run-in period with no FVs in the diet, one group was given two portions of FVs (2 FV), while another group was given five portions (5 FV) daily for 14 days. Following a 2 weeks washout period and 1 week run-in, the regimens were switched between the groups. Gene expression analysis of COX-2 mRNA in blood samples was performed by quantitative real-time-PCR. RESULTS: No significant treatment effect of diet intervention was found in the crossover analyses (P = 0.74). However, the individual variation in response may seem large. CONCLUSIONS: These data does not contradict the recommendations for an increased intake of FVs. Further studies on expression directly and indirectly, through analysis of factors regulating and being regulated by COX-2, should be carried out. A first step would be to evaluate the correspondence between COX-2 mRNA expression and products of the COX pathway, like prostaglandins. Naturally occurring polymorphisms of COX-2 promoters and coding regions might contribute to functional variations and response to different diets. SPONSORSHIP: Norwegian Research Council, National Nutrition Council, Throne Holst Foundation for Nutrition Research, Freia Chokoladefabriks Medisinske Fond and the Norwegian Cancer Society.