The young leaves of the guava plant are used in traditional medicine in tropical countries. These leaves contain a number of beneficial substances, including antioxidants like vitamin C and flavonoids such as quercetin. Drinking a tea made by soaking guava leaves in hot water may be beneficial in treating diarrhea, lowering cholesterol and preventing diabetes.
Guava leaf tea may help to inhibit a variety of diarrhea-causing bacteria. People with diarrhea who drink this type of tea may experience fewer stools, less abdominal pain, less watery stools and a quicker recovery, according to Drugs.com. A study published in the "Revista do Instituto de Medicina Tropical de São Paulo" in 2008 found that guava-leaf extracts inhibited the growth of Staphylococcus aureus bacteria, which is a common cause of diarrhea.
Drinking guava leaf tea may cause beneficial changes in your cholesterol and triglyceride levels. Study participants who drank guava leaf tea had lower total cholesterol, low-density lipoprotein levels and triglycerides after eight weeks whether or not they were receiving medical treatment to lower their cholesterol levels, according to an article published in "Nutrition & Metabolism" in February 2010. Their levels of beneficial high-density lipoprotein were not affected. Other trials have shown similar benefits, with study lengths ranging from four weeks to 12 weeks and doses ranging from 0.4 to 1 kilogram per day, according to Drugs.com.
Japan has approved guava leaf tea as one of the Foods for Specified Health Uses to help with the prevention and treatment of diabetes. Compounds in the tea inhibit the absorption of two types of sugars, maltose and sucrose, helping to control blood sugar levels after meals. The article published in "Nutrition & Metabolism" described two studies showing this effect. The first study showed the short-term benefits, as participants who drank guava leaf tea after consuming white rice had decreases in blood sugar that were greater after 30 minutes, 90 minutes and 120 minutes than when the same study participants ate the same amount of white rice followed by drinking hot water. In the second, longer-term study participants with either prediabetes or mild Type 2 diabetes who drank guava leaf tea with every meal for 12 weeks had lower fasting blood-sugar levels than before they started drinking the tea.
Studies showing the benefits of guava leaf tea are still preliminary, and more evidence is needed to verify the beneficial effects found by the few existing studies. However, there are no well-documented adverse effects or drug interactions with guava leaf tea. Pregnant women may want to avoid drinking this type of tea, as there isn't sufficient evidence about its safety at this time.
Bruso, Jessica. "The Health Benefits of Guava Leaf Tea." Healthy Eating | SF Gate, http://healthyeating.sfgate.com/health-benefits-guava-leaf-tea-3347.html. 09 December 2018.