Mice treated with diallyl sulphide, a compound found in garlic, experienced an increased number of white blood cells and number of cells producing antibodies compared to mice not treated with diallyl sulphide. 

The effect of diallyl sulphide from garlic on the immune systems of mice 

In a study by Lui et al., it was found that low concentrations of garlic oil-led  the majority of T-helper cells to respond toward the Th1 type. At high concentrations of garlic oil, T-helper cells were more oriented toward the Th2 type. 
However, a study from Zamani et. Al demonstrated that in rats, garlic oil oriented T-helper cells more toward the Th2 type by increasing IL-4 production in the spleen blood cells.

How garlic oil affects T-helper cells 

Aged garlic extract increased IL-10 In peripheral blood monocytes by inhibiting TNF-a and IL-6, which are inflammatory cytokines that play a key role in the pathogenesis of SARS-CoV-2. 

Aged garlic extract effects on  IL-10 and the pathogenesis of SARS-CoV-2  

Aged garlic extract decreased IL-12 production in peripheral blood monocytes, which in turn could decrease pro-inflammatory cytokines such as IFN-y and IL-2.

The effects of aged garlic extract on IL-12 and the pathogenesis of SARS-CoV-2 

Garlic contains bioactive sulphur-containing compounds, such as sulphoxide and polyphenols, which can strengthen the immune system. 

Santa Clara University

- Licorice 
- Garlic 
- Tea
- Ethanolic leaves extracts of the common fig 
- Hexane leaves extract of mango

Yang F. et al. state that pomegranate, black pepper, papaya, soybeans, long pepper, black caraway, barberry, European plum, Chinese box thorn and white mulberry also have immunomodulatory properties that may help prevent COVID-19. Considering their cheap price compared to other measures, consumption of these functional food plants may be a cost-effective strategy to prevent cases of COVID-19. 

Examples of functional food plants with immunomodulatory and antiviral effects that may help fight against COVID-19 

Yang, F., Zhang, Y., Tariq, A., Jiang, X., Ahmed, Z., Zhihao, Z., Idrees, M., Azizullah, A., Adnan, M., & Bussmann, R. W. (2020). Food as medicine: A possible preventive measure against coronavirus disease (COVID-19). Phytotherapy research : PTR, 10.1002/ptr.6770. Advance online publication. https://doi.org/10.1002/ptr.6770

Food as medicine: A possible preventive measure against coronavirus disease (COVID-19)

Licorice contains a saponin callled glycyrrhizin, which has antiviral and immunomodulatory responsibilities. 

The impact of licorice on the immune system

The impact of garlic on the immune system 

The leaves of green tea and black tea contain gallic acid, epigallocatechin gallate and quercetin, which are responsible for immunomodulatory activities. 

The impact of tea on the immune system 

Ethanolic leaves extracts of the common fig have been used in the past to fight various gastrointestinal, cardiovascular, respiratory and inflammatory problems. It was found that oral administration of the extract improved the humoral and cell-mediated immune responses. 

How ethanolic leaves extracts of the common fig benefit the immune system

In vivo oral administration of hexane leaves extract of mango resulted in immunomodulatory activity in white blood cells and bone marrow hematopoietic cells, which was seen through an increased WBC count and increased size of the thymus and spleen. 

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