RCT: Garlic and onion extract reduces risk of respiratory disease in elderly

This study, from University of Granada, Spain, is the first controlled, randomised, and double-blind study conducted with a mixture of garlic and onion extract concentrate, demonstrating its protective effect on respiratory diseases in elderly healthy volunteers in residential care facilities.

Residents living in residential care facilities are at higher risk of pneumonia, influenza, and recently, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

Although vaccination against these pathogens in this population is widespread, outbreaks persist, resulting in morbidity and mortality. Moreover, once infected, residents are more likely to develop complications, such as lower respiratory tract illness, one of the most common reasons​ for transfer to the hospital.

Therefore, there is clearly an urgent need to develop preventive therapeutic strategies that reduce the incidence and/or the severity of respiratory infections, according to the authors of the new study, adding that different plant-based natural herbal formulations and related compounds, could be a high-value therapeutic approach for these conditions.

Previous in-vitro studies​ have reported that the supplementation of a formula that includes concentrated garlic and onion shows broad-spectrum antimicrobial activity against multidrug-resistant bacteria isolated from human samples, and is also effective against porcine reproductive and respiratory syndrome virus (PRRS), as reported in experimental and human studies​.

However, few studies report the benefits of Allium extracts in the prevention of infectious processes. Moreover, most of them focus on the benefits of garlic or onion separately, not studying the effects of their combination

Therefore, the aim of this study was to evaluate the impact of daily consumption of a combination of garlic and onion extract concentrate rich in organosulfur compounds, severity, and duration of respiratory tract infections in healthy elderly volunteers who live in a nursing home.

The study

The study enrolled 65 healthy older volunteers of both sexes who lived in the nursing home Residencia de Mayores Claret in Granada (Spain), aged more than 65 years.

A controlled, randomized, double-blind, 2 parallel-group study was carried out for 36 weeks during the months with the highest incidence of respiratory diseases (October 2020–June 2021). Eligible volunteers were equally assigned to the product or the placebo group (33 subjects in the active group and 33 in the placebo group).

Participants were randomized to receive either the active or a placebo product. The active product (Aliocare, DOMCA SAU., Granada, Spain) contained concentrated onion extract (86 mg) standardized in organosulfur compounds derived from propiin (10 mg per capsule), garlic powder (14 mg), and microcrystalline cellulose (9892-Capsucel, Laboratorios Guinama, La Pobla de Vallbona, Valencia, Spain) up to 450 mg, whereas the placebo product only contained 450 mg of microcrystalline cellulose. 

The demographic and clinical characteristics of the subjects at the beginning of the study were similar in both study groups

The study’s primary outcome was the incidence of respiratory diseases of infectious origin (RDIO), mainly influenza-like illness (ILI), the common cold, and COVID-19. 

Every 28 days during the study, 14 clinical parameters related to these illnesses were monitored: cough, fever, nasal congestion, throat pain, headache, bone pain, fatigue, chest pain, difficulty breathing, loss of smell/taste, nausea, diarrhea, lack of appetite, and sleeping problems. Moreover, medication intake and total illnesses were followed during the intervention. 

The severity of the events was analysed by counting the number of symptoms experienced by each volunteer and for how many days the symptoms lasted. In all cases, the treatment group had a lower number of symptom events than the control group, being statistically significant for cough, bone pain, fatigue, shortness of breath, and lack of appetite. In addition, it can be stated that the severity of RDIO episodes was significantly lower since the number of symptoms of the volunteers in the treatment group was 3.2 times lower and their duration 3.5 times lower.

Regarding limitations in this study. the authors note the main limitation is related to the fact that this was not a multicentric study since the possibility of including additional participants from other nursing homes was limited due to the pandemic during the study period. 

Mechanism of action

The authors note that different compounds from garlic or onion can act synergically to exert beneficial effects after their administration.Allicin from garlic is extremely unstable and is rapidly transformed in other compounds such as dithiins or diallyl disulfide but other organosulfur compounds found in garlic, like alliin, can contribute to its beneficial effects due to the reported anti-inflammatory properties​.In onion, the most common sulfur compound is propiin (S-propyl-L-cysteine sulfoxide) that, due to the action of alliinase, leads to propiin derivatives, such as thiosulfinates and thiosulfonates compounds such as PTS and PTSO, which are more stable and exhibit interesting biological properties as antimicrobial, anti-inflammatory, or antitumor activities​.Although there is no evidence in the literature on its ability to prevent infectious processes in humans, there are many preclinical studies that support our results.Accordingly, different studies with these propiin derivatives have been carried out in farm animals, which have demonstrated protective effects against infections in animals. Furthermore, these compounds have demonstrated the ability to modulate the gut microbiome in aquatic and terrestrial animals​, promoting the development of lactic acid bacteria to the detriment of enteropathogenic bacteria, improving host immunity, maintaining intestinal homeostasis, and inhibiting inflammation​.While most of the studies based on the intake of garlic linked their effects to the action of allicin, in the case of onion, the studies related their benefits to quercetin​. The antiviral activity​ of this compound against influenza viruses, rhinovirus, and SARS-CoV-2 virus has also been studied. In contrast, only a few studies have been carried out on the benefits of the organosulfur compounds from onion.

Source: Nutrients

https://doi.org/10.3390/nu15102308​

"Beneficial Effects of Daily Consumption of Garlic and Onion Extract Concentrate on Infectious Respiratory Diseases in Elderly Resident Volunteers"

García-García, J.; Gracián, C.; Baños, A.; Guillamón, E.; Gálvez, J.; Rodriguez-Nogales, A.; Fonollá, J.