Animal study | Quercetin helps prevent virus infection after strenuous exercise
There are indications that supplementation with a large dose of quercetin protects athletes against viral infections, we wrote in the first months of the corona age. We found a somewhat older animal study by scientists at the University of South Carolina that further substantiates the virus-inhibiting effect of quercetin - and reveals how you can increase the virus-inhibiting effect of quercetin.
The researchers experimented with 4 groups of mice. One group did nothing, received no supplements, but was infected with an H1N1 influenza virus on day 1 of the experiment in a dose that should theoretically kill half of the mice. [Con-Plac]
The second group had had to run on a treadmill in the three days preceding the infection until they literally could no longer. Shortly after the last session, the researchers infected the animals with the virus. [Ex-Plac]
A third group of mice did not run, but had been given a daily dose of quercetin for the 7-day period prior to infection. If the mice had been adult humans, they would have been given 80-100 milligrams of quercetin daily. [Con-Q] The researchers administered the flavonoid in combination with unknown amounts of vitamin B3 and vitamin C. These vitamins should improve the bioavailability of quercetin.
And you guessed it: a fourth group of mice had to run on a treadmill and were given quercetin. [Ex-Q]
In the days after the infection, the researchers checked whether the mice became ill. The figure below shows how they rated and scored the disease in the mice.
The running sessions reduced the mice's resistance, and increased the chance that they would become ill - and die - from the virus. However, quercetin supplementation completely reversed the negative effect of the treadmill sessions.
It was striking that quercetin also protected the inactive mice against disease and death.
"Quercetin feeding was an effective preventive strategy to offset the increase in susceptibility to infection that was associated with stressful exercise",
summarize the researchers. "If our data can be clinically translated, they may lead to an important nutritional strategy to decrease the risk of infection, which can be a problem in athletes and military personnel, who are often exposed to combinations of severe physical, psychological, and environmental stress."
Well yes, but...
"One of the findings of the present study suggests that short-term quercetin feedings before infection (i.e., primary prevention) can delay the onset of sickness following intranasal inoculation of the virus", write the Americans.
"Although it is easy to conclude, therefore, that quercetin protected the animals from infection, it is also possible that this was due to reduced inflammation, which would be expected to blunt the symptoms. Indeed, quercetin is known to have potent anti-inflammatory properties."
"Both of these outcomes would be considered positive responses to quercetin feeding, especially in this case, since overall morbidity and mortality were benefited by quercetin. However, in certain cases, a more rapid appearance and resolution of symptoms may be a more favorable outcome. It is important to note that a quercetin-induced reduction in inflammatory processes may not always result in a reduction in susceptibility to infection; it has been shown that inflammation is necessary for the efficient elimination of influenza virus infection."
"This is clearly an aspect that should be considered in future studies in which the dose and timing of quercetin administration in relation to virus challenge are investigated."
The research was not funded by the supplement industry, but by the US military.
Am J Physiol Regul Integr Comp Physiol. 2008 Aug;295(2):R505-9.
Supplementation with quercetin and vitamin C reduces the risk of coronavirus infection by a factor of 12 11.12.2020
Quercetin protects athletes from colds and flu 08.04.2020
Quercetin sabotages influenza virus 07.04.2020