Past animal studies had suggested that flavonoids, which are found in red wine, along with green tea, apples, blueberries, cocoa and onions, may assist immune function, leading the researchers to wonder if they could find the same type of outcomes in human studies.
To do so, the team pooled all the available human data to see if there was a nutrition intervention that could be investigated. The results showed that adults are one-third more protected from upper respiratory tract infections—alias the common cold—if they eat foods rich in flavonoids or take flavonoid supplements, compared with those who don’t.
Potential for one cold less a year
Researcher Andrea Braakhuis from the University of Auckland, with her colleagues collected data from a large number of randomised controlled trials, analysing patterns of upper respiratory track infections, the number of days people experienced cold symptoms, changes in key immune biomarkers and total flavonoid intake.
“The findings show that if you’re generally healthy, eating flavonoids found in lots of fruits and vegetables can help stave off the bugs over winter,” said Dr Braakhuis.
She said most adults will have up to three colds a year, and children can have up to five, with symptoms including a sore throat, cough, runny nose and headache.
Based on the research’s findings, anyone who has an average of three colds a year will have this number reduced to two.
“We’d all love to make it through winter without one of these nasty colds. They’re a leading cause of visits to a doctor, yet antibiotics don’t help, so it’s worth giving flavonoids a go as part of a healthy diet,” she added.
Just an extra glass of the red should do it
Nutrition scientists are learning more about components in foods thought to have anti-viral, anti-inflammatory and antioxidant properties, so can help reduce the incidence of coughs and colds and boost immune function.
At this stage, Dr Braakhuis said it’s too soon to recommend whether foods or supplements are a better source of flavonoids, and what the ideal dose is. It currently looks like the flavonoid intake that might be required to stave off colds is not very high, with it suspected that just a glass of red, or its equivalent in fruits and vegetables, would provide enough extra flavonoids a day to make a difference.
“Eating five serves of veggies and two serves of fruit each day in a variety of colours will put you well on the path to getting enough flavonoids. Make sure your dinner plate is at least half full of vegetables, sip green tea over winter, and enjoy the occasional red wine,” Dr Braakhuis advised.