Further research on antioxidants for disease prevention

Plant-based diets may have a protective role against diseases such as cardiovascular disease and some cancers due to the antioxidant content of many plants, report scientists, confirming previous theories about the health potential of antioxidants.

The scientists, working in a European-funded project, studied both foods and human clinical trials and confirmed many earlier findings.

They noted that previous research shows antioxidants naturally present in tea, grape skin, rosemary and spinach can improve the nutritional value of some processed foods. Certain processed food products are vulnerable to oxidative changes, which can adversely affect flavour and colour of foods, and so make them less appealing to eat. Antioxidants improve the product quality and storage potential.

In a human clinical trial, researchers investigated the bioavailability of carotenoids and folate in spinach processed in different ways, in a group of 28 men and 42 women.

Consumption of spinach significantly increased mean plasma folate concentration and the extent of processing of spinach also seemed to play a role in determining bioavailability, with beta-carotene being more bioavailable after processing the spinach. Intake of the vegetable resulted in changes in some of the antioxidant enzymes in red blood cells.

Another human intervention study evaluated the bioavailability of quercetin in apple and blackcurrant juices. Across a range of doses, about 0.5 per cent of the quercetin intake was excreted in urine. Urinary excretion of quercetin could therefore be used as a marker of availability, the team reports.

The scientists also used model systems to evaluate the antioxidant capacities and functions of a range of food extracts. They examined the different compounds in plant foods such as berries, herbs, fruits and vegetables that possess antioxidant activity.

Among fruit wines, blackcurrant and bilberry wines contained the highest antioxidant concentrations. Red wine was also high, but white wine was low. Also they showed that flavonols (antioxidants found in tea and chocolate) can also act as pro-oxidants.

Catechins, the components in tea, and in particular epigallocatechin gallate, had the greatest antioxidant effect, according to the team.

Further information on the project can be obtained from Prof Brittmarie Sandstrom at ofn@xiy.qx​.