The numbers of days suffering from a sore throat were cut from 5.4 to 2 days as a result of eating kiwifruit, compared to bananas, while the numbers of days of suffering from head congestion fell from 4.7 to 0.9 days, researchers report in the British Journal of Nutrition.
Consuming the kiwifruit led to increases in blood levels of vitamin C, but researchers from the New Zealand Institute for Plant and Food Research and Massey University.
“This study shows that the micronutrients provided by regular eating of gold kiwifruit appear to be important in reducing symptoms of colds and other upper respiratory infections,” said lead author Dr Denise Hunter.
“While we do not know what compounds produce these results, these findings suggest that eating gold kiwifruit on a regular basis throughout the winter period may reduce the severity of some cold symptoms.”
The study was funded by Zespri International Limited, and the company also provided the fresh and free-dried gold kiwifruit used in the study.
Cold stats
The common cold is one of the most widespread illnesses in the world. It is estimated that adults suffer from between two and four episodes annually, whilst children in school may have as many as 12 episodes per year.
A recent Cochrane review estimated that the total economic impact of cold-related work loss exceeds $20 billion per year. As a result, Americans spend around $2.9 billion on over-the-counter drugs (and another $400 million on prescription medicines) for symptomatic relief of cold.
Study details
If further data supports the findings of the new study, it could see kiwifruit added to a list of potential cold remedies. The researchers recruited 37 healthy over-65 year olds and asked them to eat four kiwifruit daily for four weeks then switch to two bananas per day (or vice versa) with a four week kiwifruit/banana-free period prior to each treatment period.
Results indicated a reduction in self-reported cold symptoms with gold kiwifruit compared to banana, with sore throat symptoms reducing from 5.4 to 2 days and head congestion from 4.7 to 0.9 days.
The researchers also reported an easing in the severity of symptoms of head congestion during the gold kiwifruit period.
Markers of immune health were not significantly affected by consumption of the kiwifruit or banana, they added.
Take home
“Regular consumption of gold kiwifruit by community-dwelling older people has a positive and significant influence on a number of plasma antioxidants, including vitamins C and E (a-tocopherol), and lutein/zeaxanthin, and significantly reduces cellular damage from oxidative stress, namely lipid peroxidation,” said the researchers.
“Furthermore, when participants consuming gold kiwifruit experienced symptoms of upper respiratory tract infections, many symptoms tended to be shorter in duration and less severe; this was significant for duration and severity of head congestion, and duration of sore throat.
“Although the mechanisms behind the influence of enhanced plasma antioxidants and dietary analytes on improved symptoms of upper respiratory tract infectionsafter consumption of gold kiwifruit remain speculative, the reduction in duration and severity of selected upper respiratory tract infections symptoms indicates that gold kiwifruit may provide an important and clinically relevant contribution to lessening the burden of respiratory infection in older individuals.”
Source: British Journal of Nutrition
Published online ahead of print, FirstView Articles, doi: 10.1017/S0007114511006659
Authors: D.C. Hunter, M.A. Skinner, F.M. Wolber, C.L. Booth, J.M.S. Loh, M. Wohlers, L.M. Stevenson, M.C. Kruger