Cranberries help immune system fight colds and flu
If you drink half a litre of cranberry juice daily, you're more likely to emerge unscathed from the flu season. Nutritionists at the University of Florida come to this conclusion in an article published in Nutrition Journal. The study was funded by Ocean Spray, a cranberry juice manufacturer.
There is evidence that cranberries have a mild anti-bacterial effect in the body. Although cranberries are not an antibiotic, consuming them changes the environment in the bladder into one where the bacteria that cause bladder infections do not flourish as easily.
Little is known about the effects of cranberries on the immune system. The researchers suspect that they may well have an effect. In 2011 they published the results of a human study in which consumption of red grape juice activated the immune system. [J Med Food. 2011 Jan-Feb; 14(1-2): 69-78.] So might cranberry juice have the same effect?
During the flu season at the start of the year the researchers gave 22 subjects 450 ml cranberry juice and 23 others a placebo. The composition of the juice was the same as cranberry juice you can buy. The researchers then kept track of how often the subjects were ill in the ensuing 10 weeks.
The figure below shows that cranberry juice didn't prevent the subjects from getting flu or a cold, but it did reduce the gravity of the symptoms of viral infections. The sections with asterisks are the ones where the differences between the cranberry and the placebo group are statistically significant.
When they examined blood samples, the researchers discovered that the gamma-delta-T cells developed faster in the cranberry group than in the placebo group. Gamma-delta-T cells are immune cells that are most active in the bowels. They have characteristics of the learned immune system and of the innate immune system, and become more active if you consume fruit and teas that are rich in phenols.
It looks as though cranberries boost the activity of natural killer [NK] cells.
What's more, the immune cells in the cranberry group produced more interferon-gamma after 10 weeks. Interferon-gamma is a protein that immune cells use to fight infections.
Nutr J. 2013 Dec 13;12:161.
How drinking two glasses of cranberry juice per day improves your health 19.09.2019
Animal study: cranberries are an anti-aging drug 19.03.2014
Two-week cranberry course gives six months protection against bladder infections 25.01.2014