Some of us may have heard that horseradish and garlic supplements help ease cold and flu. (Maybe your mum or dad used to give you a raw clove to suck on when you complained of a sore throat.) But is it actually effective at easing colds? Let's take a look at the science.
Blooms High Strength Horseradish and Garlic Complex claims it has:
a soothing antimicrobial action that helps fight off the bugs that can cause colds and flu and provides symptomatic relief from upper respiratory tract infections.
Others, such as those promoted by Swisse and Blackmores, claim to be “traditionally used in Western Herbal Medicine to provide symptomatic relief of sinusitis, hay fever and upper respiratory tract infections”. And the Swisse and Blackmores products (and many others) add additional ingredients, commonly vitamin C, which is claimed to be beneficial for “immune health”.
There are two categories of “evidence” allowed by the Therapeutic Goods Administration (TGA) to validate indications or claims made for complementary medicines: scientific or traditional.
Scientific evidence is based on the scientific literature, such as trials in humans. Traditional evidence is based on theories outside modern conventional medicine, such as Western herbal medicine, traditional Chinese medicine and homeopathy.
So, what does the research say?
A search of the medical journal database PubMed failed to find any clinical trials on the combination of horseradish (Armoracia rusticana) and garlic (Allium sativum), with or without vitamin C. Nor were any clinical trials found on horseradish alone.
The authors of a 2014 Cochrane review concluded there was insufficient clinical trial evidence supporting garlic in preventing or treating the common cold. A single 2001 trial (from the Garlic Centre in the UK) suggested garlic may prevent the common cold, but more studies were needed to validate this finding. Claims of effectiveness appear to rely largely on poor-quality evidence.
A 2013 Cochrane systematic review explored whether taking vitamin C (0.2g a day or more) reduced the incidence, duration or severity of the common cold. The 29 trial comparisons involving 11,306 participants found taking vitamin C regularly failed to reduce the incidence of colds in the general population.