Table 1.
Summary of the different study findings showing health-enhancing potential of tea amino acid L-theanine.
| Agent | Species | Dosage | Study outcomes | Suggested/Observed effect | References |
|---|---|---|---|---|---|
| L-theanine | Mice | 50, 100, 200 mg/kg | The tea amino acid theanine reduced the levels of liver enzymes (AST and ALT) and MDA, however, increased the activities of CAT, SOD, and GR | Antioxidant, hepatoprotective | Li et al., 2012 |
| L-theanine | Mice | 10 mg/kg | It reduced the levels of AST, ALT, and the expression of Bax and cleaved caspase-3. | Hepatoprotective | Nagai et al., 2015 |
| L-theanine | Mice | 50, 100, and 200 mg/kg | Tea amino acid theanine reduced the levels of bilirubin, AST, ALT, TNF-α, and IL-1β and also increased the activities of antioxidant enzymes and GSH contents. | Hepatoprotective, antioxidant | Jiang et al., 2012 |
| L-theanine | Mice | 10 and 100 mg/kg | L-theanine increased the contents of hepatic and heart glutamate without affecting in tumors, and also GSH. | Antioxidant, anticancer | Sugiyama and Sadzuka, 2004 |
| L-theanine | Rats | 8 mg/kg | Unique tea amino acid theanine reduced the different levels of aminotransferase, IL-1β, γ-GT, TGF-β, IL-6, and CTGF and the degree of lipid peroxidation. | Anti-inflammatory, hepatoprotective | Pérez-Vargas et al., 2016 |
| L-theanine | Broiler | 100, 200, and 300 mg/kg | It decreased the relative concentrations of cytokines IFN-γ and IL-2 in serum, and mRNA expression of IL-6 and TNF-α in thymus as well as IL-2 and IFN-γ in spleen. L-theanine also improved the antioxidative status by improving the serum GSH-Px, SOD, and relative CAT levels. In addition, it improved performance in broilers. | Immunomodulatory, antioxidant | Saeed et al., 2018 |
| L-theanine | Broiler | 100, 200, and 300 mg/kg | It has positive effects on immunity and gut microbe by increasing the community of commensal bacteria in poultry. | Antibacterial and immune modulator | Saeed et al., 2019 |
| L-theanine | Broiler | 400 | It is a safe feed supplement up to 400 mg/kg and could boost the immune function of broilers. | Immunomodulatory | Wen et al., 2012 |
| L-theanine | rats | 4 g/kg (review) | It is found as promising liver protective agent via improving/restoring the antioxidant enzyme activities like SOD, CAT, and GSH, and inhibiting the production of MDA. | Antioxidant, hepatoprotective | Liang et al., 2015 |
| L-theanine | Piglets | 80 mg/kg | Tea amino acid (theanine) improved body weight gain, and anti-inflammatory cytokine production including TNF-α, IFN-γ, and IL-10. | Anti-inflammatory, growth promoter | Hwang et al., 2008 |
| L-theanine | Poultry | Review | L-theanine amino acid as a powerful natural antistressor can also enhance productivity and health status in poultry industry. | Growth promoter, antistressor | Saeed et al., 2017 |
| L-theanine | Human | 10 or 100 mg/kg | L-theanine impeded the adriamycin (ADR) efflux from Ehrlich ascites carcinoma cells and sustained the concentration of ADR in cancer cells, however in normal tissue like liver and heart ADR increase was not noted. | Antitumor | Sadzuka et al., 1996 |
| L-theanine | Mice | 2 and 4 mg/kg | L-theanine significantly inactivated the NF-κB and ERK/p38, and prevent the oxidative damage of neuronal cells. | Memory enhancing | Kim et al., 2009 |
Abbreviations: ALT, alanine aminotransferase; AST, aspartate aminotransferase; CAT, catalase; CTGF, connective tissue growth factor; ERK, extracellular signal-regulated kinase; GR, glutathione reductase; GSH, glutathione; IL, interleukin; IFN, interferon; MDA, malondialdehyde; NF, nuclear factor; SOD, superoxide dismutase; TGF, transforming growth factor; TNF, tumor necrosis factor. TGF, transforming growth factor; ERK, extracellular signal-regulated kinase; CTGF,connective tissue growth factor; NF, nuclear factor;