Carrots and cancer : the bioavailability of polyacetylene from carrots and their assocation with biomarkers of cancer risk

Abstract

Diets high in fruit and vegetables are correlated with better health outcomes and lower risk of chronic diseases such as cardiovascular disease and cancer. Bioactive phytochemicals, including polyphenols, carotenoids and isothiocyanates, in these foods are thought to be at least partly responsible for these protective effects. Specific foods also correlate well with these outcomes, such as carrots. As carrots are high in β-carotene, this compound is commonly thought to be the bioactive substance eliciting the anti-cancer effect, and there are many observational data to suggest higher intakes, and higher plasma levels, confer a reduced risk of cancer. However, supplement studies have little effect and can even increase the risk of cancer in certain populations. The polyacetylene group of compounds, also present in carrots, are gaining interest due to their anti-cancer and anti-inflammatory actions in vitro and in rodent studies. However, little is known about their effect in humans. This work provides novel analysis of the polyacetylene content of carrots, related vegetables, and mixed dishes containing them to create a database of polyacetylene values for commonly eaten foods. The resulting database was used to investigate the intake in a population of adults from the UK. The effect of cooking was also investigated to ensure the retention of compounds during processing. Little is known about the bioavailability of these compounds and so a human trial was conducted to investigate whether polyacetylenes could be seen in blood plasma after consumption of either 100g or 250g of boiled carrots. Finally, a dietary intervention trial was conducted, investigating the effect of consumption of 100g of boiled white carrot (containing polyacetylenes but not β-carotene), served with butter, on biomarkers of cancer risk compared to a fibre-matched control (oatcakes). Cooked carrots were the most important source of polyacetylenes in the diet of the UK population investigated. Therefore, carrots were chosen to be a viable method of polyacetylene intake for a dietary intervention study. Boiled carrot retained phytochemicals better than fried carrot, and cooking the carrot whole rather than in disks or quarters could offer protection from losses during cooking. Falcarinol and falcarindiol-3-acetate were detected in the blood plasma after consumption of carrot. This is the first study to show the presence of polyacetylenes in blood plasma after consumption of whole boiled carrot. The results of a dietary intervention showed a trend for a reduction in prostaglandin E2 metabolite in the carrot group (p=0.07) but not the oatcake control group. There was no effect on any other biomarker measured (IL-6 or lymphocyte DNA damage). Regular consumption of a moderate amount of carrot can reduce a marker of inflammation in healthy adults.