 It is well known that deficiencies in certain vitamins and minerals can lead to significant impairment of immune function and an increased susceptibility to infection, which can be reversed by supplementation in deficient individuals. However, it is unclear to what extent supplementation may aid in maintaining an optimal balance within the immune system in adequately nourished individuals. So researchers in New Zealand tried supplementing with kiwi fruit. In a petri dish, gold kiwi fruit puree appeared to boost natural killer cell activity in human blood and boost the response to a tetanus vaccine. But does what happens in a petri dish happen in people? There was a study in which two immune-related sets of genes were found to be upregulated by eating three kiwi fruit a day. But does this translate into actually helping us fight off infection? We didn't know until this study. Researchers in New Zealand found that the consumption of gold kiwi fruit reduces the severity and duration of certain upper respiratory tract infections. Symptoms. Why study gold kiwi fruits? Because the study was funded by the company that owns the patent to gold kiwi fruit. A few dozen elderly individuals randomized to one or two groups, eating two bananas a day or eating four kiwi fruit a day for a month, and then they switched. The next month, the banana group ate kiwis and the kiwi fruit group ate bananas. The rationale for providing bananas as kind of like the placebo was to provide an alternative fruit that had relatively similar calories but lower nutritional value. The purpose of the study was to determine whether regular consumption of gold kiwi fruit reduces the incidence, duration, and severity of symptoms of upper respiratory tract infections like the common cold comparison to bananas. They found no reduction in overall incidence, but those that did get sick during the kiwi fruit phase had significantly reduced severity and duration of head congestion and the duration of sore throat. And not just by little. I mean, the sick banana eaters suffered for five days with the sore throat and congestion, compared to the kiwi fruit eaters who felt better after just a day or two. That's significant. The reason they studied older individuals is that they tended to be more susceptible to respiratory infections. Small children are another at-risk group, averaging twice as many upper respiratory tract infections as adults, four to six a year. So 66 preschoolers were randomized into the same two groups, kiwi fruit versus bananas. And not only were there, again, significant improvements in the symptoms of those who got sick while on kiwi fruit, fewer got sick in the first place. 45% lower odds of a cold or flu-like illness, which means that the children needing kiwis had almost a 50% reduction in the chance of having a cold or flu. This suggests a kiwi fruit consumption may be a daily prescription for health, though about 1 in 150 children report being allergic to kiwi fruit, which ranks them at number three after milk and eggs and above peanuts in a survey of 3,500 kids as the most common food allergies, and so are not for everyone.