With these new methods it becomes possible to discover what these compounds are doing in plants, how much is present in foods, how they are absorbed and how they function in the body. The methods developed in Glasgow for flavonol measurements in plants, as well as in plasma, urine and body tissues, are now internationally recognised. Early results so far include demonstration of the absorption of flavonols. Plasma concentration of quercetin can increase 12 fold with a supplement of tea or onions. The metabolic fates of flavonols and how that affects bioactivity is the subject of current research with Dr Christine Edwards in the Department of Human Nutrition.
Enormous differences exist in the flavonol content of seemingly similar common foods.
This observation has huge implications for nutrition research, since in order to establish how much flavonols people are consuming from diet records, it is essential to have details about plant food varieties. Alternatively we can measure a biomarker. Early studies are promising, showing that plasma concentration or urinary excretion both closely reflect dietary intake. The contribution of flavonols to total antioxidant capacity is the topic of new projects from MAFF and Scottish Soft Fruit Growers in collaboration with the Rowett Research Institute and Guys Hospital, London. Major food sources are onions, tomato products, tea, and for some people, red wine.