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How vitamin C boosts quercetin's antiviral action
The antiviral effects of zinc, vitamin C and quercetin reinforce each other, say supplement experts. The more we delve into the matter, the more convinced we become that they are right.
What we already knew about zinc
What we already knew about quercetin
And this we already knew about vitamin C
A few days ago we wrote about an older study in which supplementation with a quercetin preparation protected against colds. This preparation also contained a significant amount of vitamin C. According to the makers of the conscious supplements, the antiviral effects of vitamin C enhance those of quercetin.
The figure below is taken from that article. You look at the concentration of quercetin in the blood of the test subjects.
If you have any idea how quickly quercetin disappears from the body, you will consider the measured concentrations to be remarkably high. Apparently vitamin C increases the bioavailability of quercetin.
A 1988 study
The researchers released a virus into a petri dish with human cells. If the viruses were able to penetrate and damage the cells, the cells formed a plaque. The larger the plaque, the greater the damage caused by the virus.
In a series of tests, the Belgians looked at whether quercetin and the related flavonoid luteolin could reduce the viral havoc - and whether the addition of vitamin C still had an effect.
The figures below show that luteolin was a better virus inhibitor than quercetin. Vitamin C had no influence on the antiviral effect of luteolin, but did increase the antiviral effect of quercetin.
The researchers suspect that the hydroxyl group in the third position of the molecule makes quercetin vulnerable to conversion into inactive substances. That would explain why luteolin, lacking this hydroxyl group, is a more effective antiviral than quercetin.
Vitamin C, in itself a strong antioxidant, protects the 3-hydroxyl group of quercetin and reduces the risk of inactivation, the Belgians write.