Search

Fruit and vegetable consumption produces changes in several biomarkers in blood. The present study aimed to examine the dose-response curve between fruit and vegetable consumption and carotenoid (α-carotene, β-carotene, β-cryptoxanthin, lycopene, lutein and zeaxanthin), folate and vitamin C concentrations. Furthermore, a prediction model of fruit and vegetable intake based on these biomarkers and subject characteristics (i.e. age, sex, BMI and smoking status) was established. Data from twelve diet-controlled intervention studies were obtained to develop a prediction model for fruit and vegetable intake (including and excluding fruit and vegetable juices). The study population in the present individual participant data meta-analysis consisted of 526 men and women. Carotenoid, folate and vitamin C concentrations showed a positive relationship with fruit and vegetable intake. Measures of performance for the prediction model were calculated using cross-validation. For the prediction model of fruit, vegetable and juice intake, the root mean squared error (RMSE) was 258.0 g, the correlation between observed and predicted intake was 0.78 and the mean difference between observed and predicted intake was - 1.7 g (limits of agreement: - 466.3, 462.8 g). For the prediction of fruit and vegetable intake (excluding juices), the RMSE was 201.1 g, the correlation was 0.65 and the mean bias was 2.4 g (limits of agreement: -368.2, 373.0 g). The prediction models which include the biomarkers and subject characteristics may be used to estimate average intake at the group level and to investigate the ranking of individuals with regard to their intake of fruit and vegetables when validating questionnaires that measure intake.

The objective was to quantify the vitamin A equivalency of beta-carotene in two diets using a dual-isotope dilution technique and the apparent beta-carotene absorption as measured by the oral-faecal balance technique. Seventeen healthy adults with an ileostomy completed the 4-week diet-controlled, cross-over intervention study. Each subject followed both diets for 2 weeks: a diet containing vegetables low in beta-carotene content with supplemental beta-carotene in salad dressing oil ('oil diet'; mean beta-carotene intake 3.1 mg/d) and a diet containing vegetables and fruits high in beta-carotene content ('mixed diet'; mean beta-carotene intake 7.6 mg/d). Daily each subject consumed a mean of 190 microg [13C10]beta-carotene and 195 microg [13C10]retinyl palmitate in oil capsules. The vitamin A equivalency of beta-carotene was calculated as the dose-corrected ratio of [13C5]retinol to [13C10]retinol in serum. Apparent absorption of beta-carotene was determined with oral-faecal balance. Isotopic data quantified a vitamin A equivalency of [13C10]beta-carotene in oil of 3.6:1 (95 % CI 2.8, 4.6) regardless of dietary matrices differences. The apparent absorption of (labelled and dietary) beta-carotene from the 'oil diet' (30 %) was 1.9-fold higher than from the 'mixed diet' (16 %). This extrinsic labelling technique can measure precisely the vitamin A equivalency of beta-carotene in oil capsules, but it does not represent the effect of different dietary matrices.

Data on the vitamin A equivalency of beta-carotene in food are inconsistent. We quantified the vitamin A equivalency (microg) of beta-carotene in two diets using the dual-isotope dilution technique and the oral-faecal balance technique. A diet-controlled, cross-over intervention study was conducted in twenty-four healthy adults. Each subject followed two diets for 3 weeks each: a diet containing vegetables low in beta-carotene with supplemental beta-carotene in salad dressing oil ('oil diet') and a diet containing vegetables and fruits high in beta-carotene ('mixed diet'). During all 6 weeks, each subject daily consumed a mean of 55 (sd 0.5) microg [13C10]beta-carotene and 55 (sd 0.5) microg [13C10]retinyl palmitate in oil capsules. The vitamin A equivalency of beta-carotene was calculated as the dose-corrected ratio of [13C5]retinol to [13C10]retinol in serum and from apparent absorption by oral-faecal balance. Isotopic data quantified a vitamin A equivalency of [13C10]beta-carotene in oil of 3.4 microg (95 % CI 2.8, 3.9), thus the bio-efficacy of the beta-carotene in oil was 28 % in the presence of both diets. However, data from oral-faecal balance estimated vitamin A equivalency as 6:1 microg (95 % CI 4, 7) for beta-carotene in the 'oil diet'. beta-Carotene in the 'oil diet' had 2.9-fold higher vitamin A equivalency than beta-carotene in the 'mixed diet'. In conclusion, this extrinsic labelling technique cannot measure effects of mixed vegetables and fruits matrices, but can measure precisely the vitamin A equivalency of the beta-carotene in oil capsules.