Middle-aged volunteers who ate a combination of bilberries, lingonberries, black currants, and chokeberries for eight weeks showed a significant increase in blood levels of polyphenols, with compounds like quercetin increasing by up to 80 per cent, according to findings published in the Journal of Agricultural and Food Chemistry.
The subject of bioavailability is a hot topic in nutrition circles, particularly for antioxidants. Many tests of antioxidant activity do not provide any data on the subsequent bioavailability, a point highlighted by Professor Jeffrey Blumberg from Tufts University in a recent interview with NutraIngredients.
“We shouldn’t throw out [the antioxidant assays like] ORAC, FRAP, and similar tests,” said Prof Blumberg, “but these simple assays equate isocyanides, carotenoids, tocopherols, and stilbenes, for example, as somehow equivalent. It doesn’t tell us anything about bioavailability, antagonism, and synergies.”
In background information in the new JAFC paper, the health benefits of polyphenols are predominantly determined by their bioavailability, but this “is still poorly known”, said Raika Koli and her co-workers from the Finnish National Institute for Health and Welfare.
For their new study, 72 middle-aged subjects were recruited to participate in the eight week randomized, placebo-controlled dietary intervention trial. Participants were randomly assigned to receive 160 grams of berries a day as a puree or juice, or placebo as sugar-water, sweet semolina or rice porridge, or jelly sweets, for eight weeks.
The daily berry intervention provided about 837 mg of various types of polyphenols, said the researchers, thereby doubling the average intake of these compounds in Finnish adults, previoulsy reported to be about 860 mg per day.
At the end of the study, increases in blood levels of various polyphenols, including quercetin (up to 84 per cent), p-coumaric acid (40 per cent), caffeic acid (100 per cent), vanillic acid (31 per cent), and 3-(3-hydroxyphenyl)propionic acid (up to 31 per cent), were observed in the berry-fed group, compared to the control group.
This was accompanied by significant increases in the excretion of various polyphenols in the urine.
“In conclusion, polyphenols are bioavailable from berries in humans,” wrote the researchers. “However, due to metabolism and differences in the degree of uptake of different polyphenols, the polyphenol profile in plasma and urine differ greatly from the polyphenol profile in berries.
“The potential health effects of these compounds, particularly the metabolites, should be explored further,” they added.
Antioxidants are big business. The number of products with ‘antioxidants inside’ style labels is mushrooming, according to Mintel’s Global New Products Database (GNPD). In 2009, there were 409 launches globally with ‘antioxidants’ flagged on the labels, compared with 154 in 2005 and 299 in 2007 – and that is just in marquee supplement formats such as vitamin A, C E, selenium, CoQ10, and zinc.
The overall market for antioxidants was valued at a whopping $12bn (€8.8bn) in 2009, according to Euromonitor International.
The science, testing and regulation surrounding antioxidants will be discussed at the upcoming NutraIngredients Antioxidants 2010 Conference. For more information and to register, please click here.
Source: Journal of Agricultural and Food Chemistry
Published online ahead of print, doi: 10.1021/jf9024823
“Bioavailability of Various Polyphenols from a Diet Containing Moderate Amounts of Berries”
Authors: R. Koli, I. Erlund, A. Jula, J. Marniemi, P. Mattila, G. Alfthan