










































































Black tea decreases postprandial blood glucose levels in healthy humans and contains high-molecular-weight polyphenols that inhibit α-glucosidase and α-amylase in vitro: a randomized, double blind, placebo-controlled, crossover trial
							| Functional Foods in Health and Disease - Online ISSN: 2160-3855; Print ISSN: 2378-7007



	

				
						
 
	Skip to main content
	Skip to main navigation menu
		Skip to site footer


			

				
					
						Open Menu
					
										
																Functional Foods in Health and Disease - Online ISSN: 2160-3855; Print ISSN: 2378-7007
										

				


				
				
					
					
						
																					
				
					Home
				
										
									
										Food Science Publisher
									
								
	
									
										Functional Food Center
									
								


							
	
				
					Current
				
							
	
				
					Archives
				
							
	
				
					About
				
										
									
										About the Journal
									
								
	
									
										Aims and Scope
									
								
	
									
										Contact
									
								
	
									
										Editing Services
									
								
	
									
										Editorial Team
									
								
	
									
										Express Peer Review
									
								
	
									
										Graphical Abstract
									
								
	
									
										Journal Insights
									
								
	
									
										Privacy Statement
									
								
	
									
										Submissions
									
								


							
	
				
					Announcements
				
							
	
				
					Search
				
							



				

																						
									
										
										Search
									
								

													

					

					
								
				
					Register
				
							
	
				
					Login
				
							



					

				
			

		

						
			
				


			
		
			
				Home
			
			/
		
	
			
				Archives
			
			/
		
	
				
					Vol. 11 No. 5 (2021): May 2021
				
				/
			
	
			
									Research Articles
							
		



	
		  	 

		
	
		Black tea decreases postprandial blood glucose levels in healthy humans and contains high-molecular-weight polyphenols that inhibit α-glucosidase and α-amylase in vitro: a randomized, double blind, placebo-controlled, crossover trial
	


	
	
		

							
					Authors

						
							
								Yoshikazu Isono
							
															
									Biwako Research Institute, Otsuka Foods Co., Ltd.
																	
																																				
																		
										https://orcid.org/0000-0003-1031-2887
									
								
													
	
							
								Hisako Watanabe
							
															
									Biwako Research Institute, Otsuka Foods Co., Ltd.
																	
																																		
	
							
								Masafumi Kumada
							
															
									Biwako Research Institute, Otsuka Foods Co., Ltd.
																	
																																		
	
							
								Tsuyoshi Takara
							
															
									Medical Corporation Seishinkai, Takara Clinic
																	
																																		
	
							
								Shin-ichiro Iio
							
															
									ORTHOMEDICO Inc
																	
																																		


				
			
																	
					
												DOI:
					

					
						
							https://doi.org/10.31989/ffhd.v11i5.791
						
					
				
			

						
										
					Abstract

					Background: To prevent diabetes, it is important to control postprandial glycemic levels. Studies have suggested that consuming black tea decreases the risk of type 2 diabetes; however, only a few studies have examined the effects of black tea on postprandial glycemic control after consuming starch-rich foods. In addition, the mechanism underlying the suppression of postprandial glucose levels remains unclear.
Objective: To investigate the effects of black tea on postprandial blood glucose levels in healthy humans and to identify the components of black tea that inhibit digestive enzymes.
Methods: The inhibitory activity of black tea on digestive enzymes was measured, and the inhibitory components were fractionated. Healthy Japanese adults ingested 200 ml of black tea, and its effect on postprandial blood glucose and insulin levels were investigated. 
Results: Black tea dose-dependently inhibited α-glucosidase, sucrase, and α-amylase activity. The major components responsible for this inhibition were high–molecular-weight polyphenols. The galloyl moieties present in these compounds play an important role in their inhibitory activities. Two randomized, double-blind, placebo-controlled, crossover studies of healthy human subjects (total n = 46) were conducted to investigate the effect of black tea on blood glucose and insulin levels. Combined data from the two studies showed that black tea ingestion (200 mL) after cooked rice intake (200 g) significantly reduced the incremental area under the curve of glucose (P =.024) and insulin (P =.014) compared to placebo drink.
Conclusions: The high–molecular-weight polyphenols in black tea inhibited α-glucosidase, sucrase, and α-amylase activity in a dose-dependent manner. Furthermore, black tea ingestion after eating cooked rice significantly reduced the incremental area under the curve of glucose and insulin. These effects of black tea could be attributed to the inhibition of digestive enzymes by high–molecular-weight polyphenols containing galloyl groups.
Keywords: black tea, blood glucose, α-glucosidase, α-amylase, polyphenol

				
			
			

						
																																																																																																
					
													Author Biographies
											

						
								
																																							Yoshikazu Isono,  Biwako Research Institute, Otsuka Foods Co., Ltd. 
																	

								
									Senior Researcher

								

							
	
								
																																							Hisako Watanabe,  Biwako Research Institute, Otsuka Foods Co., Ltd. 
																	

								
									Researcher
								

							
	
								
																																							Masafumi Kumada,  Biwako Research Institute, Otsuka Foods Co., Ltd. 
																	

								
									chief of the chemical lab.
								

							
	
								
																																							Tsuyoshi Takara,  Medical Corporation Seishinkai, Takara Clinic 
																	

								
									physician
								

							
	
								
																																							Shin-ichiro Iio,  ORTHOMEDICO Inc 
																	

								
									section chief
								

							


				
			
						
		


		

						
										
					
						Downloads
					

						
								
	
													


		
	[Abstract]

	
							
	
								
	
													


		
	[Full Article]

	
							


				

						
						
				
					
						Published
					

					
																			2021-05-12
																	

				
							

			
						
										

											
							
								Issue
							

							
								
									Vol. 11 No. 5 (2021): May 2021
								
							

						
					
											
							
								Section
							

							
								Research Articles
							

						
					
									

			
						
										
					
						License
					

										Authors retain the copyright of their articles and grant the Functional Food Center (FFC) and its journals the right of first publication under the terms of the Creative Commons Attribution 4.0 International License.

This license permits unrestricted use, distribution, and reproduction in any medium, including commercial use, provided the original author(s) and source are properly credited. Authors may post and share their published work freely, provided that the original publication in this journal is acknowledged.

By submitting to this journal, authors confirm that their manuscripts are original, not under consideration elsewhere, and that they hold the necessary rights to grant this license. The Functional Food Center encourages open scientific exchange and allows derivative and extended works, provided attribution to the original publication is maintained.

				

			
			

		

	




	




	


							



	

	

					
				About the Journal      Editing Services      Graphical Abstract      Journal Insights        Submissions        Editorial Team       Privacy Statement        Contact        Current        Archives

 

			

		
		Open Journal Systems Hosting and Support by: OpenJournalSystems.com


	










