Volunteers receiving the polyphenol-rich drink experienced improvements in their symptoms of the common cold indicating a strengthening of the body’s immune defences, according to findings published in the British Journal of Nutrition.
“The study population can be characterised as having impaired immune defence, similar to subjects eating an unbalanced diet or exposed to physical stress, and thus, being sensitive for nutritional benefits,” wrote researchers from Rudolf Wild GmbH and Berlin-based CRO analyze & realize.
“Therefore, the study population can be further considered as an appropriate target to demonstrate the clinical benefits of an immune stimulation and there is no reason to assume that the observed improvement cannot be extrapolated to the general population.”
Polyphenols are receiving extensive research due to their potent antioxidant activity, their ability to mop-up harmful free radicals, and the associated health benefits. Many have also been implicated in possible protection against diseases such as cancer and cardiovascular disease, while some have been reported to potentially offer protection from Alzheimer's.
The new study, funded by Rudolf Wild GmbH, indicates a potential role as an immune booster.
The German scientists recruited 98 people reporting symptoms of the common cold that started in the previous 24 hours. The participants were randomly assigned to received the polyphenol-rich beverage of a control beverage twice a day for 10 days.
At the end of the study, results showed a significant decrease in the severity of symptoms, including ‘general feeling of sickness’, ‘stuffy nose/sniffle’, ‘sore throat and/or difficulty swallowing’, ‘headache and/or joint aches’, and ‘hoarseness and/or cough’. This showed a “clear improvement”, said the researchers, compared with the placebo group that showed less of a decrease. The difference between the groups was “highly significant”, said the researchers.
Commenting on the potential mechanism, the researchers note that previous studies have shown that green tea catechins and L-theanin may improve the function of T-cells, thereby boosting immune function.
The presence of the compound cyanidin 3-O-glucoside in grapes may also explain the results. An earlier study has reported that the compound may inhibit COX-1 and COX-2 enzymes in a similar way to “non-steroidal anti-inflammatory and analgesic drugs such as aspirin and ibuprofen, explaining the pronounced effect on headache and joint pains seen in the [polyphenol-rich juice] group”.
The vitamin C content of the juice (61.4 milligrams per 500 ml) may also be enhancing immune function, added the researchers.
“The results of the present study suggest that consumption of the investigated polyphenol-rich beverage strengthens the body’s defence and improves immune function in the general population, which may translate into clinically measurable effects in individuals having impaired immune defence due to physical stress or already existing infections,” they concluded.
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Source: British Journal of Nutrition
Published online ahead of print, doi:10.1017/S0007114510002047
“Immune-modulating efficacy of a polyphenol-rich beverage on symptoms associated with the common cold: a double-blind, randomised, placebo-controlled, multi-centric clinical study”
Authors: K. Schutz, M. Sass, A. de With, H-J. Graubaum, J. Grunwald