PhD ThesisDiets 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.Agriculture and Horticulture Development Board
(AHDB