High-sensitivity HPLC with coulometric array detection enabled us to quantify the intestinal absorption of carotenoids ingested from a single vegetable salad. Essentially no absorption of carotenoids was observed when salads with fat-free salad dressing were consumed. A substantially greater absorption of carotenoids was observed when salads were consumed with full-fat than with reduced-fat salad dressing.

Single equimolar doses (0.5 mumol/kg body wt) of lutein and/or beta-carotene in true solution in oil were given to eight adult subjects and 13 blood samples were taken during the subsequent 840 h. Whereas the mean serum concentration of lutein showed a single maximum at 16 h, that of beta-carotene peaked at 6 h and then again at 32 h. Subsequently, lutein and beta-carotene were cleared at approximately the same rate from the serum. The mean (+/- SEM) areas under the curve (AUCs) for lutein and beta-carotene during the first 440 h differed significantly: 59.6 +/- 9.0 and 26.3 +/- 6.4 mumol.h/L, respectively (P < 0.005). AUC values did not correlate with initial serum concentrations of the given carotenoid or with the order of dosing. When combined in the same dose, beta-carotene significantly reduced the serum AUC values for lutein to 54-61% of control values (P < 0.025), whereas lutein reduced the AUC value for beta-carotene in five subjects but enhanced it in three subjects. Effects of lutein on the AUC for beta-carotene were inversely related to the AUC for beta-carotene alone. Thus, carotenoids clearly interact with each other during intestinal absorption, metabolism, and serum clearance, although individual responses can differ markedly.

Vitamin A deficiency (VAD) affects over 250 million people worldwide and is one of the most prevalent nutritional deficiencies in developing countries, resulting in significant socio-economic losses. Provitamin A carotenoids such as β-carotene, are derived from plant foods and are a major source of vitamin A for the majority of the world's population. Several years of intense research has resulted in the production of ‘Golden Rice 2’ which contains sufficiently high levels of provitamin A carotenoids to combat VAD. In this report, the focus is on the generation of transgenic maize with enhanced provitamin A content in their kernels. Overexpression of the bacterial genes crtB (for phytoene synthase) and crtI (for the four desaturation steps of the carotenoid pathway catalysed by phytoene desaturase and ζ-carotene desaturase in plants), under the control of a ‘super γ-zein promoter’ for endosperm-specific expression, resulted in an increase of total carotenoids of up to 34-fold with a preferential accumulation of β-carotene in the maize endosperm. The levels attained approach those estimated to have a significant impact on the nutritional status of target populations in developing countries. The high β-carotene trait was found to be reproducible over at least four generations. Gene expression analyses suggest that increased accumulation of β-carotene is due to an up-regulation of the endogenous lycopene β-cylase. These experiments set the stage for the design of transgenic approaches to generate provitamin A-rich maize that will help alleviate VAD.