Papaya tree is commonly found in tropical areas around the world. The fruits are consumed as food and medicine. Dried and powdered stems and leaves are prepared as medicinal teas to protect against infections and improve digestion. Papaya leaves and their extracts are also marketed as dietary supplements to enhance the immune system and improve platelet function.

In vitro, papaya leaves exhibit immunomodulatory ⁽¹⁾, antioxidant ⁽⁹⁾, and anticancer ^(11) (12) effects. The leaf extracts contain antibacterial compounds that inhibit bacterial growth ⁽⁴⁾. In mice, a powdered suspension of papaya leaves increased thrombocyte count ⁽²⁾ and a water extract reduced alcohol-induced stomach damage ⁽⁵⁾. Hypoglycemic effects were reported with its use in a diabetic rat model ⁽¹⁰⁾, and the extract also appears to have low toxicity ⁽⁶⁾.

Use of papaya leaf extract to treat dengue fever and increase platelet counts has been described ⁽³⁾. A randomized trial also found significant increases in platelet count in patients with dengue fever ⁽¹³⁾, but a meta-analysis determined that current evidence is insufficient ⁽¹⁴⁾. Therefore, papaya leaf extracts should not be used to improve platelet counts until more is known about its efficacy and adverse effects in humans.