Myth busters: Do age-old cold and flu remedies work?

As well as Jennifer Bowden’s columns in the NZ Listener and online here at listener.co.nz, subscribers can now look forward to a new fortnightly online only column where Jennifer explores myths around food and nutrition.

Generations of families have age-old cold and flu remedies, like steaming bowls of homemade chicken soup or soothing warm lemon and honey drinks. But do these work? And if so, what’s the science behind them?

In a study published in 1978 in the journal Chest, scientists compared the impact on nasal mucus of hot chicken soup, hot water and cold water. Notably, hot water and hot chicken soup helped slightly to decongest mucus in the nasal passages of healthy adults, more so than drinking cold water.

Researchers credited part of that effect to nasal inhalation of water vapour. They also noted that the chicken soup “appears to possess an additional substance” that led to it more effectively clearing nasal mucus than hot water. Shortly after, in 1980, another study reported that chicken broth helped thin mucus in the lungs, even more so when the broth was spiced.

So, what about chicken soup seemingly helps to clear mucus? In 2000, again in the journal Chest, researcher Stephen Rennard and his colleagues reported that chicken soup had modest anti-inflammatory effects in their lab-based cellular tests. They theorised that these anti-inflammatory effects might be responsible for alleviating some of the symptoms of upper respiratory tract infections, such as the common cold and flu.

However, with the Covid-19 pandemic raging in 2020, Rennard implored people not to extend the significance of his earlier findings beyond their limited scope. Yes, the chicken soup had an effect, but it was a modest effect and was only demonstrated in a lab-based cellular study, not a clinical trial.

Moreover, Rennard noted that the anti-inflammatory effect of chicken soup could increase infection risk, as inflammation is a valuable part of our body’s immune response to fighting viruses and other invaders, even if it causes annoying symptoms.

Perhaps a lemon and honey drink to soothe throats and coughs is a better option?

Human use of honey for health dates back thousands of years, and it now has well-established scientific evidence of antibacterial, anti-inflammatory, wound healing and antioxidant activities. In New Zealand, mānuka honey is prized for its medicinal properties and is known to be especially potent in this regard. Meanwhile, lemon juice is a known vitamin C source, enabling our immune system to function optimally.