On the other hand, 3-hydroxybutyric acid, together with nicotinic acid, has shown to confer anti-inflammatory effects in TNF-α by decreasing the level of pro-inflammatory proteins (iNOS, COX-2) or secreted cytokines (IL-6 and IL-1β)24, which might explain the continuously increased levels of 3-hydroxybutyric acid observed in the different COVID-19 positive groups. Here, TNF is linked to COVID-19.