Abstract
Carotenoids are bioactive compounds with widely accepted health benefits. Their quantification in human faeces can be a useful non-invasive approach to assess their bioavailability. Identification and quantification of major dietary carotenoids in human faeces was the aim of the present study. Faeces and dietary intake were obtained from 101 healthy adults (45–65 years). Carotenoid concentrations were determined by HPLC in faeces and by 3-day food records in dietary intake. Carotenoids quantified in faeces (μg/g dry weight, median) were: β-carotene (39.5), lycopene (20), lutein (17.5), phytoene (11.4), zeaxanthin (6.3), β-cryptoxanthin (4.5), phytofluene (2.9). α-carotene (5.3) and violaxanthin were found 75.5% and 7.1% of the faeces. The carotenoids found in the highest concentrations corresponded to the ones consumed in the greatest amounts (μg/d): lycopene (13,146), phytoene (2697), β-carotene (1812), lutein+zeaxanthin (1148). Carotenoid concentration in faeces and in dietary intake showed correlation for the total non-provitamin A carotenoids (r = 0.302; p = 0.003), phytoene (r = 0.339; p = 0.001), phytofluene (r = 0.279; p = 0.005), lycopene (0.223; p = 0.027), lutein+zeaxanthin (r = 0.291; p = 0.04) and β-cryptoxanthin (r = 0.323; p = 0.001). A high proportion of dietary carotenoids, especially those with provitamin A activity and some of their isomers, reach the large intestine, suggesting a low bioavailability of their intact forms.
Highlights
Carotenoids have been widely studied owing to their beneficial properties on health
While it is known that a fraction of carotenoids taken up by the enterocytes can be cleaved by beta-carotene oxygenases (BCO1/2) into apo-carotenoids, there is scant information about further metabolism, biodistribution or excretion [6]
Samples were obtained from an analytical observational study assessing lutein and zeaxanthin dietary intake and short- and long-term status markers to assess their predictive value for macular pigment optical density and visual function in apparently healthy subjects [10]
Summary
Carotenoids have been widely studied owing to their beneficial properties on health. In addition to the provitamin A activity that some exhibit, there are others related to their anti-oxidant, anti-inflammatory, photo-protective and immunological capacity [1,2]. Some studies have found that approximately 70% of carotenoids may remain in the final digesta [3,4,5]. This means that significant concentrations could reach the colon. It is not known whether carotenoids can be further taken up or whether a significant proportion is fermented to unknown metabolites. This is important as studies indicate that polar metabolites and/or derivatives appear to be bioactive and interact with transcription factors such as NF-κB and Nrf and nuclear receptors such as RXR/RAR [2].
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