The study, published in the Journal of Functional Foods, reports that consumption of lingonberry juice for eight weeks improved the functioning of blood vessels in rats with high blood pressure. The authors found that treatment with cranberry or blackcurrant juices was not able to improve functioning in the same way.
The researchers, led by Anne Kivimaki from the Institute of Biomedicine at the University of Helsinki, Finland, said that the substantially higher level of phenolic compounds found in lingonberries compared to the other berries tested may explain the research results.
“The present study, to the best of our knowledge, is the ﬁrst to compare the effects of long-term treatment with lingonberry, cranberry and blackcurrant juices on vascular function in a spontaneously hypertensive rat (SHR) model,” said Kivimaki and her colleagues.
The most common group of polyphenols is the ﬂavonoids, which consist of over 6000 chemically different compounds that give colour and flavour to berries.
Dietary ﬂavonoids have been suggested to decrease the risk of ischemic stroke and cardiovascular mortality, however the polyphenol content of berries is affected by post-harvesting processes including pressing, pasteurization and drying.
Kivimaki and her co-workers said that ﬂavanols, a sub-group of flavonoids, have been shown to inhibit the development of atherosclerosis in animal models, to improve endothelial function and platelet reactivity, and to reduce blood pressure in humans.
They added that the cardioprotective effects of polyphenol-rich foods are thought, at least in part to be due to their ability to improve the control of vascular tone by endothelium (blood vessel walls). For example by improving endothelium-dependent nitric oxide (NO) mediated relaxation, they said.
The new study compared the effects of long-term dietary treatments with juices made from Finnish berries, cranberry (Vaccinium oxycoccos), lingonberry (Vaccinium vitis-idaea) and blackcurrant (Ribes nigrum) on blood pressure and vascular function in rats with high blood pressure.
Kivimaki and her colleagues reported that lingonberry intake “normalized the impaired endothelium-dependent relaxation seen in the cranberry, blackcurrant and control rats.”
Further investigations revealed the phenolic content of the berry juices differed among cranberry, lingonberry and blackcurrant.
The researchers concluded that the lingonberry juice improves the functioning of blood vessel endothelium in spontaneously hypertensive rats, but added that this effect could not be shown to lower blood pressure in the rat model.
Kivimaki and her team found that the total amount of phenolic compounds was almost two times higher in lingonberry juice compared to the cranberry juice.
“Lingonberry juice contained ﬂavonols, ﬂavan-3-ols and procyanidins, which is one group of ﬂavanols, notably more than other juices ... Unfortunately, we were able to identify only these main phenolic groups, not individual components. Therefore it remains open whether the observed antihypertensive effect of lingonberry juice is related to one or a few compounds in the three groups shown to be enriched in lingonberry juice or is it a sum effect of these groups,” said the researchers.
Source: Journal of Functional Foods
Published online ahead of print, doi: 10.1016/j.jff.2011.05.001
“Lingonberry juice improves endothelium-dependent vasodilatation of mesenteric arteries in spontaneously hypertensive rats in a long-term intervention”
Authors: A.S. Kivimaki, P.I. Ehlers, A.M. Turpeinen, H. Vapaatalo, R. Korpela