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Ashwagandha is a traditional remedy for stress; it is under investigation for its potential to boost immune function.
Lung Function
In a clinical trial on 40 elite cyclers, 8-week supplementation with ashwagandha improved respiratory endurance [1].
In a study of 133 people with tuberculosis, ashwagandha and other herbals in combination with antibiotics relieved coughing and fever better than antibiotics alone. In another study of 99 people with tuberculosis, ashwagandha improved symptoms, inflammation, and body weight [2, 3].
Polysaccharides extracted from ashwagandha suppressed coughing in guinea pigs as effectively as codeine [4, 5].
In baby rats, withaferin A also protected the lungs against inflammation and oxidative stress caused by toxic bacterial lipopolysaccharides (LPS) [6].
Viral Infections
An herbal remedy containing ashwagandha sped up recovery from viral hepatitis in 29 patients [7].
In T cells (CD8+) isolated from 38 people with HIV infection, ashwagandha extract reduced the production of a disease progression marker (CD38 production) [8].
In chicken infected with infectious bursal disease virus, dietary supplementation with ashwagandha reduced viral load and increased T cell activity [9].
Ashwagandha has also shown antiviral activity against HIV, herpes, and infectious bursal disease in cell-based studies [10, 11, 12, 13].
A computational simulation study found that withaferin A has the potential to block an enzyme required by the virus that caused the 2009 swine flu pandemic (H1N1) to spread (neuraminidase) [14].
Interestingly, a recent simulation study suggested that withanone may help prevent the SARS-Cov-2 virus from binding to the ACE2 receptor, and thus entering cells [15].
Asthma
In asthmatic mice, pretreatment with withaferin A reduced airway inflammation, injury, and scarring. This compound also had anti-inflammatory effects in human cells isolated from the airway lining [16, 17].
Immunity
In a small trial of 5 people, ashwagandha extract improved the immune response by activating white blood cells. In two other trials on 142 people, an herbal mix containing ashwagandha increased the activity of natural killer cells [18, 19].
In mice, ashwagandha extract enhanced immunity by activating bone marrow cells, macrophages, and lymphocytes [20, 21].
It also increased the levels of Th1 cytokines and prevented the depletion of white blood cells in stressed mice [22].
Finally, in a combined mouse and cell study, withaferin A inhibited the activity of myeloid-derived suppressor cells (MDSCs). These dysfunctional immune cells can stimulate tumor growth and prevent the immune system from attacking cancer cells [23, 24].
