Some carotenoids such as α-carotene and β-carotene have provitamin A activity following cleavage in humans, but many of the carotenoids such as lutein and lycopene act mainly as antioxidants. The carotenoid content of plants vary, with β-carotene and cryptoxanthine being two important structural forms found in yellow and orange fruits. Carotenoids are increasingly being linked to the prevention of certain types of cancer, possibly because of the antioxidant activity that they possess. The carotenoid content of many of the common Western fruits, as well as their bioavailability, have been reported in the literature, However, much less information is available on some of the less commonly eaten tropical fruits. Both papaya and mango have a high concentration of carotenoids, that explains the orange and red colours of their fruits, and are important sources of nutrients such as vitamin for their local populations where the fruits are grown.
The plasma levels of carotenoids in 14 subjects have been investigated by researchers1 following feeding of papaya and mango in the form of juice, fresh fruit or dried slices. The subjects were split into two groups (mango and papaya) and fed three types of meals on distinct experimental days consisting of the three types of fruit preparations along with yogurt and bread. Blood samples were taken at fasting and then at 4 and 8 hours postprandially. The main carotenoids found in plasma following ingestion of both fruits were α-carotene and β-carotene, with small amounts of zeathanthin. In addition, subjects consuming papaya had large quantities of lycopene and cryptoxanthin in their plasma. Consuming all types of sample preparation caused large rises in the serum retinol levels of subjects, suggesting that these fruits can contribute towards vitamin A status. However, there was no difference between the fruit preparations in this regard.
Comparing the three forms of preparation showed that both papaya and mango consumed in juice form or fresh fruit showed an increased bioavailability of carotenoids compared to the dry fruit, as measured by the rise in plasma levels. The principle factor influencing the absorption of carotenoids is the freeing of the compounds from the chromoplast within the cell in which they are contained, and subsequent dissolution in fat droplets. This may explain the improved absorption of carotenoids from juice and fresh fruit compared to dry fruit. Juice is a homogenised mixture that has little cell structure remaining with the carotenoids free in solution. Fresh fruit is high in water and therefore tends to be easy to homogenise in the mouth. Dry fruit in contrast, may be more difficult to mechanically break down, and hence the lower biolavailabilities seen in this study.
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