Garlic and onion for preventing upper respiratory tract infection Original paper

In this randomized controlled trial, a supplement containing garlic powder and onion extract decreased the risk of upper respiratory tract infection in older adults.

The effect of a supplement containing garlic powder and onion extract on the risk of upper respiratory tract infection in older adults.

The researchers also assessed 14 symptoms of an upper respiratory tract infection (e.g., cough, fever, nausea, and fatigue) and medication intake.

66 older adults (average age of 84; 80% women, 20% men) living in a residential care facility in Spain.

In this 36-week randomized controlled trial, the participants ingested a supplement containing garlic powder (14 mg) and onion extract (86 mg) or a placebo daily. The outcomes were assessed at baseline and every 4 weeks during the study.

The incidence of upper respiratory tract infection (i.e., the common cold and flu-like illness) was reduced in the supplement group. Additionally, the supplement group experienced a lower number of symptoms and a shorter duration of symptoms, compared with the placebo group. More specifically, the supplement group experienced a lower number of symptom events for cough, bone pain, fatigue, and difficulty breathing.

Because the participants were residents at a facility and this study took place during the months of October 2020 to July 2021, they had to follow certain COVID-19 protocols, which included mandatory use of masks and isolation. The participants were also vaccinated against flu and pneumonia and received two doses of the Pfizer vaccine for COVID-19.