Ask an answerable question (PICO)：
Patients in diabetes control is mostly based on the three persistent approach among diet control, regular exercise and medication control. Of which medication control is the main method currently. However, long-term use of diabetes medication, not only the side effects from medication on physiological functions, but also be prone to tolerability. It is also being doubt to result in the safety of patients with heart or lung dysfunction or impaired liver and kidney functions. In order to achieve the control of blood sugar regulation and delay the occurrence of complications, many patients try to inquire traditional diet therapy to assist diabetes control. The author is asked by patients many often that bitter melon extracts could lower blood sugar. Therefore, the authors were motivated to discuss the effect of bitter melon extracts on blood sugar in type 2 diabetes.
The Method and Analysis of Literature Review：
The search of literatures was using EBM PICO method. "Can bitter gourd lower blood sugar in adults with type 2 diabetes Mellitus?" was asked as an answerable question. The key words were included Patients as “Type 2 Diabetes Mellitus, Type 2 DM, Noninsulin-dependent diabetes mellitus”, Interventions as “Bitter gourd, Momordica charantia, Bitter melon, Bitter squash, Balsam pear”, and Outcomes as “Blood sugar, Blood glucose, Glycaemia, Glycemia, Fasting plasma glucose, HbA1C”. The data banks of literatures were conducted from Cochrane Library, PubMed, Medline, ProQuest Health, Google Scholar, and Airiti Library. The search strategies by using the Boolean logic “AND, OR, and NOT” were implemented. “Humans” subjects, the research design of "Randomized Controlled Trial and Systematic Review", language as "English", searching years from 2014 to the present were limited. And the exclusion criteria were (1) non-type 2 diabetes, (2) non-18 years Adults, (3) non-bitter gourd or other dietary therapies. After exclusion of irrelevant or repeated papers, 2 systematic review with meta-analyses and 1 RCT were finally included.
The Systematic Review Appraisal Sheet (2019) and the Cochrane Risk of Bias Tool were accorded to appraise the quality of study in systematic review and randomized controlled trial respectively. The OCEBM Levels of Evidence table (2011) was used to rank the level of evidence body of study. The results of the first study of systematic review showed that bitter gourd compared to placebo had significant differences in reducing fasting blood glucose (MD= -0.72; I2=14%), reducing postprandial blood glucose (MD= -1.43; I2=0%), and reducing HbA1c (MD= -0.31; I2=0%). The results of the second study of systematic review showed that the bitter gourd compared to placebo also had significant differences in reducing fasting blood glucose (MD= -25.03; I2=98%) and reducing HbA1c (WMD= -0.2%). The results of the included randomized controlled trial showed that patients with type 2 diabetes who add on treatment with 1.5 gm/day of bitter gourd tablets daily had effective in controlling blood sugar, lowering total cholesterol and improving HDLc (p < .05).
Conclusions and Recommendations：
Bitter melon extracts could reduce fasting blood glucose, postprandial blood sugar and HbA1c, however, the oral hypoglycemic agents (OHAs) were more effective than bitter melon extracts in lowering elevated fasting plasma glucose level, postprandial glucose and HbA1C. Moreover, each study does not standardize the formulation, location, dosage form and amounts of bitter melon extracts. It results in high variability, imprecision and downgrade the quality of evidence. Although bitter melon extracts have been used as nutritious supplement or herbs for type 2 diabetes, some research results are still contradictory. Therefore, the safety and effectiveness of bitter melon extracts for the treatment of patients with type 2 diabetes are still controversy.