Guava or Psidium guajava L. is a tropical tree that belongs to myrtle family (Myrtaceae).
The small fruit tree is native to Southern Mexico and Northern South America. The tree grows abundantly in tropical and subtropical regions of the world. 
Guava tree produces oval light green or yellow guava fruits. The fruits contain edible seeds inside. Some of the largest guava producing countries are India, China, Kenya, Mexico, Venezuela, Colombia, and Brazil. 
Guava fruits have exquisite taste. They are eaten fresh or made into juice, jam, pickles, syrup, ice cream or other food items.
Guava fruit and leaves are known for their nutritional values, and medicinal uses in folk treatments. Traditionally guava leaves extracts and tea are home remedies for diarrhea, rheumatism, diabetes, mouth ulcers, skin infections, wound, and cough.  
Recent medical experiments have investigated the nutritional and therapeutic benefits of guava fruits for human health. 
The article reviews some evidence based benefits of guava, its nutritional facts, and potential side effects.
Guava Nutrition Facts
Guava is a superfood and nutritional powerhouse. The humble fruit contains a great amount of vitamin C (2-5 times more than citrus fruits), iron, calcium, phosphorus, potassium, and magnesium. Guava is a good source of calcium, carotenoids, polyphenols, dietary fiber and sugar. 
Vitamin C, natural antioxidants, and lycopene in the fruit are good for your skin health. 
Magnesium and other minerals in guava are beneficial for nutrient absorption and promoting fertility.
The potassium content in the fruit can keep blood pressure level in check. Guava has 80% water content that can keep your body and skin hydrated.
Health Benefits of Guava Based on Science
1. Guava can Reduce Blood Pressure and Blood Cholesterol Level
Scientific research suggest that consuming guava in increased amount can lower blood pressure and cholesterol level among hypertensive patients.
The soluble dietary fiber and potassium content in guava has beneficial effects for the lowering cholesterol, triglycerides and increasing good or High-density lipoprotein (HDL) cholesterol.
A 1993 research study published in the Journal of Human Hypertension, investigated the beneficial effects of high potassium and soluble fiber-rich guava diet in reducing blood lipids and blood pressure. 
The study was conducted among 145 hypertensives patients divided into two groups. One of the groups with 72 patients consumed 0.5-1.0 kg of guava daily and experienced a substantial reduction in bad cholesterol and BP than the controlled group.
2. Guava May Lower Blood Sugar Levels
Guava fruit and the leaves may control the blood sugar level among diabetic patients.
In Chinese folk medicine and Ayurveda, guava fruit and its extracts are used as a remedy for diabetes mellitus. A recent study published in the American Journal of Chinese Medicine, investigated the hypoglycemic action of guava juice in diabetic mice and human volunteers. In the study consumption of 1 kg. Of guava juice significantly lowered blood glucose. 
The efficacy of guava and guava leaves for diabetes control is documented in many ethnobotanical and clinical research. Consumption of Guava and buttermilk preparation once daily for 15 days is a diabetes home remedy in Andhra Pradesh, India. Elsewhere in India and Togo, guava leaves tea and fresh guava is considered a remedy for high blood sugar.
A number of laboratory tests on animal and humans established the antidiabetic effects of guava.
A 2005 study reported in the journal Methods and Findings in the Experimental and Clinical Pharmacology, states that oral administration of 50–800 mg/kg guava leaf extract could lower blood glucose level in the rats. The researchers found out that important phytoconstituents in the leaf extracts such as polyphenolic compounds, quercetin, flavonoids, guiajaverin, tannins,
and pentacyclic triterpenoids are responsible for these antidiabetes effects. 
In another clinical trial, 40 diabetic patients orally consumed 500 mg. Of guava fruit in capsule form for 5 weeks. There was a marked reduction in blood sugar level beginning in the 3rd, 4th, and 5th week (12.3%, 24.79%, and 7.9%). 
3. Guava Has Anticancer Effects
According to researchers, guava can prevent cancer in a number of ways.
The Asian Pacific Journal of Cancer Prevention (2016) discusses the anticancer activities of guava namely — cell proliferation, scavenging free radicals, apoptosis, regulation of gene expression, modulation of DNA damage repair, etc. 
An ethnopharmacological survey in the West Bank Palestine studied the efficacy of guava leaves decoction in treating cancer. The findings are promising, as daily consumption of 100g of guava decoction showed significant improvement in lung and stomach cancers. 
Numerous clinical trial experimented anticancer effects of guava leaves on animal and humans. In one of these studies reported in Nutrition and Cancer (2007) guava leaf extracts inhibited prostate cancer growth. [11, 12].
4. Guava May Treat Gastrointestinal Infections
In many cultures, guava fruit, guava leaves, and bark powder are the most popular home remedies for various stomach disorders including dysentery, diarrhea, indigestion, bloating, stomach aches, etc.
Researchers have experimented the anti-diarrheal effects of guava in numerous clinical studies.
According to a research report published in BMC Complementary and Alternative Medicine, flavonoid Quercetin is the most active anti-diarrheal component in guava decoction. Dried guava leaves and its decoction can effectively fight off common diarrhoeal pathogens. 
5. Guava May Reduce Menstrual Pain
In Tahiti guava is a folk remedy for the period or menstrual cramps, premature labor, miscarriage, uterine bleeding, etc.
In recent time medical scientists have clinically investigated the efficacy of guava and its extracts in relieving many women health issues.
The results are promising.
A medical review of South-Asian medicinal plants documented the therapeutic benefits and uses of guava for women health care. Guava is one of the 2000 plant species that is used as medicine in this part of the world. Guava has potential benefits for treating menstrual disorders, profuse uterine bleeding, postpartum hemorrhage, etc. 
A 2007 clinical study reported in the Journal of Ethnopharmacology investigates the efficacy of guava leaf extracts in reducing menstrual pain. 197 young women (average age 19) participated the trial and took a dose of guava extracts 6 mg/day for 4 months. The participants experienced a significant reduction in the menstrual pain and other disorders. 
6. Guava May Treat Respiratory Disorders
Raw guava leaves and its tender shoots are chewed as home remedy for sore throats, cough, and cold in Mexico, Malaysia, South Africa, and in some parts of India. In Tanzania and Nigeria guava leaves and bark were reported to be effective remedy for tuberculosis. [16,17] 
The researchers have investigated the anti-cough activities of guava leaves in the laboratory as well. A 1999 clinical study on rats and guinea pigs confirm the antibacterial and anti-cough effects of guava leaves. 
In another study (Journal of Ethnopharmacology, 2012) guava leaves extracts proved to be effective in inhibiting respiratory pathogens including S. aureus, K. pneumonia, Cryptococcus neoformans, and Moraxella catarrhalis. 
7. Guava May Treat Dental Infections
Guava leaves and twigs are folk remedy for mouth ulcers, toothache, and dental infections in different cultures.
In 2014 Indian researchers have investigated the positive therapeutic effects of guava leaves in treating periodontal diseases. 
Other clinical research gives evidence on the efficacy of guava leaf extracts in preventing dental plaques, and its antibacterial effects against dental infections — Streptococcus mutans (tooth decay and cavity), Streptococcus mitis, Streptococcus oralis, and Lactobacillus casei. 
8. Guava is Good for Skin Health
Guava leaves extracts and its shoots have potent antibacterial effects against various skin diseases. A 2009 study published in the Scientific Research Essays states the efficacy of guava extracts in inhibiting bacterial pathogens such as Streptococcus pyogenes, E. coli, Proteus mirabilis, and S. aureus. Guava leaves may fight off these bacterial strains in patients with wound, tissue or skin injury, burns, etc. 
Side Effects of Guava
Guava is a safe food. If you are using guava and its leaves for medicinal purpose do not continue the home treatment for more than 12 weeks. It is recommended that you consume guava in moderation if you are pregnant and breastfeeding.
Guava is a delicious tropical fruit with immense nutritional value.
The simple fruit is rich in vitamins, minerals, and dietary fibers. Folk medicinal traditions in many parts of the world use guava fruit and guava leaf extracts for therapeutic purposes.
Recent scientific investigations verify many of these anecdotal claims. Guava is a potent remedy for cardiovascular diseases, preventing cancer, controlling diabetes, stomach infections, skin disorders, etc. the fruit and its leaf supplements can boost your immune system as well.