Nutritional intervention and impact of polyphenol on glycohemoglobin (HbA1c) in non-diabetic and type 2 diabetic subjects: Systematic review and nmeta-analysis

Critical Reviews in Food Science and Nutrition

Volumn 57, Issue 5, 2017, Pages 975-986

  Palma Duran, Susana A ^a   Vlassopoulos, Antonis ^a   Lean, Mike ^a   Govan, Lindsay ^a   Combet, Emilie ^a  

^a UNIVERSITY OF GLASGOW   (United Kingdom)

Author keywords

antioxidant; Glycation; meta analysis; nutrition; polyphenols; supplementation

Indexed keywords

ANTIOXIDANTS; MEDICAL APPLICATIONS;

ANTI-INFLAMMATORIES; GLYCATION; META ANALYSIS; POLYPHENOLS; STRESS MODULATION; SUPPLEMENTATION; SYSTEMATIC REVIEW; TYPE 2 DIABETES MELLITUS;

NUTRITION;

ANTIINFLAMMATORY AGENT; ANTIOXIDANT; GLUCOSE BLOOD LEVEL; GLYCOSYLATED HEMOGLOBIN; POLYPHENOL;

BLOOD; DIABETES COMPLICATIONS; DIABETES MELLITUS, TYPE 2; DIETARY SUPPLEMENT; GLUCOSE BLOOD LEVEL; HUMAN; META ANALYSIS; METABOLISM; RANDOMIZED CONTROLLED TRIAL (TOPIC);

ANTI-INFLAMMATORY AGENTS; ANTIOXIDANTS; BLOOD GLUCOSE; DIABETES COMPLICATIONS; DIABETES MELLITUS, TYPE 2; DIETARY SUPPLEMENTS; HEMOGLOBIN A, GLYCOSYLATED; HUMANS; POLYPHENOLS; RANDOMIZED CONTROLLED TRIALS AS TOPIC;

EID: 85007320386     PISSN: 10408398     EISSN: 15497852     Source Type: Journal    
DOI: 10.1080/10408398.2014.973932     Document Type: Article

References (77)

1. American Diabetes Association. (2012). Diagnosis and classification of diabetes mellitus. Diabetes Care. 33:S64–S71.
2. Balzer, J., Rassaf, T., Heiss, C., Kleinbongard, P., Lauer, T., Merx, M., Heussen, N., Gross, H. B., Keen, C. L., Schroeter, H., and Kelm, M., (2008). Sustained benefits in vascular function through flavanol-containing cocoa in medicated diabetic patients a double-masked, randomized, controlled trial. J. Am. Coll. Cardiol. 51(22):2141–2149. doi:10.1016/j.jacc.2008.01.059
3. Banini, A. E., Boyd, L. C., Allen, J. C., Allen, H. G., and Sauls, D. L., (2006). Muscadine grape products intake, diet and blood constituents of non-diabetic and type 2 diabetic subjects. Nutrition. 22(11–12):1137–1145. doi:10.1016/j.nut.2006.08.012
4. Barr, E. L., Boyko, E. J., Zimmet, P. Z., Wolfe, R., Tonkin, A. M., and Shaw, J. E., (2009). Continuous relationships between non-diabetic hyperglycaemia and both cardiovascular disease and all-cause mortality:The Australian Diabetes, Obesity, and Lifestyle (AusDiab) study. Diabetologia. 52(3):415–424. doi:10.1007/s00125-008-1246-y
5. Basu, A., Newman, E. D., Bryant, A. L., Lyons, T. J., and Betts, N. M., (2013). Pomegranate polyphenols lower lipid peroxidation in adults with type 2 diabetes but have no effects in healthy volunteers:A pilot study. J. Nutr. Metab.2013:1–7.
6. Bhatt, J. K., Thomas, S., and Nanjan, M. J., (2012). Resveratrol supplementation improves glycemic control in type 2 diabetes mellitus. Nutr. Res. 32(7):537–541. doi:10.1016/j.nutres.2012.06.003
7. Biesalski, H. K. (2007). Polyphenols and inflammation:Basic interactions. Curr. Opin. Clin. Nutr. Metab. Care. 10(6):724–728.
8. Blevins, S. M., Leyva, M. J., Brown, J., Wright, J., Scofield, R. H., and Aston, C. E., (2007). Effect of cinnamon on glucose and lipid levels in Non–insulin-dependent type 2 diabetes. Diabetes Care. 30(9):2236–2237.
9. Brown, A. L., Lane, J., Coverly, J., Stocks, J., Jackson, S., Stephen, A., Bluck, L., Coward, A., and Hendrickx, H., (2009). Effects of dietary supplementation with the green tea polyphenol epigallocatechin-3-gallate on insulin resistance and associated metabolic risk factors:Randomized controlled trial. Br. J. Nutr. 101(06):886–894.
10. Browner, W. S., Pressman, A. R., Lui, L.-Y., and Cummings, S. R., (1999). Association between serum fructosamine and mortality in elderly women the study of osteoporotic fractures. Am. J. Epidemiol. 149(5):471–475.
11. Campbell-Tofte, J. I., Molgaard, P., Josefsen, K., Abdallah, Z., Hansen, S. H., Cornett, C., Mu, H., Richter, E. A., Petersen, H. W., Norregaard, J. C., and Winther, K., (2011). Randomized and double-blinded pilot clinical study of the safety and anti-diabetic efficacy of the Rauvolfia-Citrus tea, as used in Nigerian traditional medicine. J. Ethnopharmacol. 133(2):402–411. doi:10.1016/j.jep.2010.10.013
12. Cho, Y.-Y., Baek, N.-I., Chung, H.-G., Jeong, T.-S., Lee, K. T., Jeon, S.-M., Kim, H.-J., McGregor, R. A., and Choi, M.-S., (2012). Randomized controlled trial of Sajabalssuk (Artemisia princeps Pampanini) to treat pre-diabetes. Eur. J. Integr. Med. 4(3):e299–e308.
13. Chuang, C. C., and McIntosh, M. K. (2011). Potential mechanisms by which polyphenol-rich grapes prevent obesity-mediated inflammation and metabolic diseases. Ann. Rev. Nutr. 31:155–176. doi:10.1146/annurev-nutr-072610-145149
14. Crozier, A., Jaganath, I. B., and Clifford, M. N., (2009). Dietary phenolics:Chemistry, bioavailability and effects on health. Nat. Prod. Rep. 26(8):1001–1043.
15. Curtis, P. J., Sampson, M., Potter, J., Dhatariya, K., Kroon, P. A., and Cassidy, A., (2012). Chronic ingestion of flavan-3-ols and isoflavones improves insulin sensitivity and lipoprotein status and attenuates estimated 10-year CVD risk in medicated postmenopausal women with type 2 diabetes:a 1-year, double-blind, randomized, controlled trial. Diabetes Care. 35(2):226–232. doi:10.2337/dc11-1443
16. Dallas, C., Gerbi, Al., Elbez, Y., Caillard, P., Zamaria, N., and Cloarec, M., (2013). Clinical study to assess the efficacy and safety of a citrus polyphenolic extract of red orange, grapefruit, and orange (sinetrol-xpur) on weight management and metabolic parameters in healthy overweight individuals. Phytother. Res 28(2):212–218.
17. Davis, P. A., and Yokoyama, W., (2011). Cinnamon intake lowers fasting blood glucose:Meta-analysis. J. Med. Food. 14(9):884–889.
18. Dilis, V., and Trichopoulou, A., (2010). Antioxidant intakes and food sources in Greek adults. J. Nutr. 140(7):1274–1279.
19. Evans, M., Sharma, P., and Guthrie, N., (2012). Bioavailability of citrus polymethoxylated flavones and their biological role in metabolic syndrome and hyperlipidemia. In:Readings in Advanced Pharmacokinetics–Theory, Methods and Applications, pp. 267–285. Noreddin, A., Ed., InTech, Rijeka, Croatia
20. Fenercioglu, A. K., Saler, T., Genc, E., Sabuncu, H., and Altuntas, Y., (2010). The effects of polyphenol-containing antioxidants on oxidative stress and lipid peroxidation in Type 2 diabetes mellitus without complications. J. Endocrinol. Invest. 33(2):118–124. doi:10.3275/6564
21. Follmann, D., Elliott, P., Suh, I., and Cutler, J., (1992). Variance imputation for overviews of clinical trials with continuous response. J. Clin. Epidemiol. 45(7):769–773.
22. Fukino, Y., Ikeda, A., Maruyama, K., Aoki, N., Okubo, T., and Iso, H., (2008). Randomized controlled trial for an effect of green tea-extract powder supplementation on glucose abnormalities. Eur. J. Clin. Nutr. 62(8):953–960. doi:10.1038/sj.ejcn.1602806
23. Fukino, Y., Shimbo, M., Aoki, N., Okubo, T., and Iso, H., (2005). Randomized controlled trial for an effect of green tea consumption on insulin resistance and inflammation markers. J. Nutr. Sci. Vitamin. 51(5):335–342.
24. Hanhineva, K., Törrönen, R., Bondia-Pons, I., Pekkinen, J., Kolehmainen, M., Mykkänen, H., and Poutanen, K., (2010). Impact of dietary polyphenols on carbohydrate metabolism. Int. J. Mol. Sci. 11(4):1365–1402.
25. He, Z. D., Qiao, C. F., Han, Q. B., Cheng, C. L., Xu, H. X., Jiang, R. W., But, P. P., and Shaw, P. C., (2005). Authentication and quantitative analysis on the chemical profile of cassia bark (cortex cinnamomi) by high-pressure liquid chromatography. J. Agr. Food Chem. 53(7):2424–2428.
26. Higgins, J. P. T., and Altman, D. G., (2008). Assessing risk of bias. In: Cochrane Handbook for Systematic Reviews of Interventions, Version 5.0.1, Chapter 8, pp. 8.1–8.53. Higgins, J. P. T., and Green, S., Eds., John Wiley & Sons.
27. Howes, J. B., Tran, D., Brillante, D., and Howes, L. G., (2003). Effects of dietary supplementation with isoflavones from red clover on ambulatory blood pressure and endothelial function in postmenopausal type 2 diabetes. Diabetes Obes. Metab. 5(5):325–332.
28. Hsu, C. H., Liao, Y. L., Lin, S. C., Tsai, T. H., Huang, C. J., and Chou, P., (2011). Does supplementation with green tea extract improve insulin resistance in obese type 2 diabetics? A randomized, double-blind, and placebo-controlled clinical trial. Altern. Med. Rev. 16(2):157–163.
29. Hussain, S. A., (2007). Silymarin as an adjunct to glibenclamide therapy improves long-term and postprandial glycemic control and body mass index in type 2 diabetes. J. Med. Food. 10(3):543–547. doi:10.1089/jmf.2006.089
30. Jakuš, V., and Rietbrock, N., (2004). Advanced glycation end-products and the progress of diabetic vascular complications. Physiol. Res. 53(2):131–142.
31. Jayawardena, M. H., de Alwis, N. M., Hettigoda, V., and Fernando, D. J., (2005). A double blind randomised placebo controlled cross over study of a herbal preparation containing Salacia reticulata in the treatment of type 2 diabetes. J. Ethnopharmacol. 97(2):215–218. doi:10.1016/j.jep.2004.10.026
32. Kerr, D., Partridge, H., Knott, J., and Thomas, P. W., (2011). HbA1c 3 months after diagnosis predicts premature mortality in patients with new onset type 2 diabetes. Diabetic Med. 28(12):1520–1524.
33. Khaw, K. T., Wareham, N., Bingham, S., Luben, R., Welch, A., and Day, N., (2004). Association of hemoglobin A1c with cardiovascular disease and mortality in adults:the European prospective investigation into cancer in Norfolk. Ann. Intern. Med. 141(6):413–420.
34. Klein, G. A., Stefanuto, A., Boaventura, B. C., de Morais, E. C., Cavalcante Lda, S., de Andrade, F., Wazlawik, E., Di Pietro, P. F., Maraschin, M., and da Silva, E. L., (2011a). Mate tea (Ilex paraguariensis) improves glycemic and lipid profiles of type 2 diabetes and pre-diabetes individuals:A pilot study. J. Am. Coll. Nutr. 30(5):320–332.
35. Klein, G. A., Stefanuto, A., Boaventura, B. C. B., de Morais, E. C., Cavalcante, L. S., de Andrade, F., Wazlawik, E., Di Pietro, P. F., Maraschin, M., and da Silva, E. L., (2011b). Mate tea (Ilex paraguariensis) improves glycemic and lipid profiles of type 2 diabetes and pre-diabetes individuals:A pilot study. J. Am. Coll. Nutr. 30(5):320–332.
36. Kudolo, G. B., Delaney, D., and Blodgett, J., (2005). Short-term oral ingestion of Ginkgo biloba extract (EGb 761) reduces malondialdehyde levels in washed platelets of type 2 diabetic subjects. Diabetes Res. Clin. Pract. 68(1):29–38. doi:10.1016/j.diabres.2004.08.007
37. Lamikanra, O., Grimm, C. C., Rodin, J. B., and Inyang, I. D., (1996). Hydroxylated stilbenes in selected American wines. J. Agri. Food Chem. 44(4):1111–1115.
38. Lu, T., Sheng, H., Wu, J., Cheng, Y., Zhu, J., and Chen, Y., (2012). Cinnamon extract improves fasting blood glucose and glycosylated hemoglobin level in Chinese patients with type 2 diabetes. Nutr. Res. 32(6):408–412.
39. Mackenzie, T., Leary, L., and Brooks, W. B., (2007). The effect of an extract of green and black tea on glucose control in adults with type 2 diabetes mellitus:Double-blind randomized study. Metabolism. 56(10):1340–1344. doi:10.1016/j.metabol.2007.05.018
40. Mandeville, J. S., Froehlich, E., and Tajmir-Riahi, H. A., (2009). Study of curcumin and genistein interactions with human serum albumin. J. Pharm. Biomed. Anal. 49(2):468–474.
41. Mang, B., Wolters, M., Schmitt, B., Kelb, K., Lichtinghagen, R., Stichtenoth, D. O., and Hahn, A., (2006). Effects of a cinnamon extract on plasma glucose, HbA1c, and serum lipids in diabetes mellitus type 2. Eur. J. Clin. Invest. 36(5):340–344.
42. Mellor, D. D., Sathyapalan, T., Kilpatrick, E. S., Beckett, S., and Atkin, S. L., (2010). High-cocoa polyphenol-rich chocolate improves HDL cholesterol in type 2 diabetes patients. Diabetic Med. 27(11):1318–1321.
43. Mirzaei, K., Hossein-Nezhad, A., Karimi, M., Hosseinzadeh-Attar, M. J., Jafari, N., Najmafshar, A., and Larijani, B., (2010). Effect of green tea extract on bone turnover markers in type 2 diabetic patients:A double-blind, placebo-controlled clinical trial study. DARU J. Pharm. Sci. 17(Suppl 1):38–44.
44. Mittman, N., Desiraju, B., Fazil, I., Kapupara, H., Chattopadhyay, J., Jani, C. M., and Avram, M. M., (2010). Serum fructosamine versus glycosylated hemoglobin as an index of glycemic control, hospitalization, and infection in diabetic hemodialysis patients. Kidney Int. 78:S41–S45.
45. Moher, D., Liberati, A., Tetzlaff, J., and Altman, D. G., (2009). Preferred reporting items for systematic reviews and meta-analyses:the PRISMA statement. PLoS Med. 6(7):1–6. doi:10.1371/journal.pmed.1000097
46. Movahed, A., Nabipour, I., Lieben Louis, X., Thandapilly, S. J., Yu, L., Kalantarhormozi, M., Rekabpour, S. J., and Netticadan, T., (2013). Antihyperglycemic effects of short term resveratrol supplementation in type 2 diabetic patients. Evid Based Compl. Alt. Med. 2013:851267. doi:10.1155/2013/851267. Epub 2013 Sep 1.
47. Mulnier, H. E., Seaman, H. E., Raleigh, V. S., Soedamah-Muthu, S. S., Colhoun, H. M., and Lawrenson, R. A., (2006). Mortality in people with type 2 diabetes in the UK. Diabetic Med. 23(5):516–521.
48. Nagao, T., Meguro, S., Hase, T., Otsuka, K., Komikado, M., Tokimitsu, I., Yamamoto, T., and Yamamoto, K., (2009). A catechin-rich beverage improves obesity and blood glucose control in patients with type 2 diabetes. Obesity (Silver Spring). 17(2):310–317. doi:10.1038/oby.2008.505
49. Ogawa, S., Matsumae, T., Kataoka, T., Yazaki, Y., and Yamaguchi, H., (2013). Effect of acacia polyphenol on glucose homeostasis in subjects with impaired glucose tolerance:A randomized multicenter feeding trial. Exp. Ther. Med. 5(6):1566–1572.
50. Overman, A., Chuang, C. C., and McIntosh, M., (2011). Quercetin attenuates inflammation in human macrophages and adipocytes exposed to macrophage-conditioned media. Int. J. Obesity. 35(9):1165–1172.
51. Pan, A., Sun, J., Chen, Y., Ye, X., Li, H., Yu, Z., Wang, Y., Gu, W., Zhang, X., and Chen, X., (2007). Effects of a flaxseed-derived lignan supplement in type 2 diabetic patients:A randomized, double-blind, cross-over trial. Plos One. 2(11):e1148.
52. Rau De Almeida Callou, K., Sadigov, S., Lajolo, F. M., and Genovese, M. I., (2010). Isoflavones and antioxidant capacity of commercial soy-based beverages:Effect of storage. J. Agr. Food Chem. 58(7):4284–4291.
53. Rosenow, A., Noben, J. P., Jocken, J., Kallendrusch, S., Fischer-Posovszky, P., Mariman, E. C., and Renes, J., (2012). Resveratrol-induced changes of the human adipocyte secretion profile. J. Proteome Res. 11(9):4733–4743. doi:10.1021/pr300539b
54. Ryan, E. A., Imes, S., Wallace, C., and Jones, S., (2000). Herbal tea in the treatment of diabetes mellitus. Clin. Invest. Med. Med. Clinique et Experimentale 23(5):311–317.
55. Sadowska-Bartosz, I., Galiniak, S., and Bartosz, G., (2014). Kinetics of glycoxidation of bovine serum albumin by methylglyoxal and glyoxal and its prevention by various compounds. Molecules. 19(4):4880–4896.
56. Selvin, E., Steffes, M. W., Zhu, H., Matsushita, K., Wagenknecht, L., Pankow, J., Coresh, J., and Brancati, F. L., (2010a). Glycated hemoglobin, diabetes, and cardiovascular risk in nondiabetic adults. N. Engl. J. Med. 362(9):800–811. doi:10.1056/NEJMoa0908359
57. Selvin, E., Marinopoulos, S., Berkenblit, G., Rami, T., Brancati, F. L., Powe, N. R., and Golden, S. H., (2004). Meta-analysis:Glycosylated hemoglobin and cardiovascular disease in diabetes mellitus. Ann. Int. Med. 141(6):421–431.
58. Selvin, E., Steffes, M. W., Zhu, H., Matsushita, K., Wagenknecht, L., Pankow, J., Coresh, J., and Brancati, F. L., (2010b). Glycated hemoglobin, diabetes, and cardiovascular risk in nondiabetic adults. N. Eng. J. Med. 362(9):800–811.
59. Shan, B., Cai, Y. Z., Sun, M., and Corke, H., (2005). Antioxidant capacity of 26 spice extracts and characterization of their phenolic constituents. J. Agr. Food Chem. 53(20):7749–7759.
60. Singh, R., Barden, A., Mori, T., and Beilin, L., (2001). Advanced glycation end-products:A review. Diabetologia. 44(2):129–146.
61. Song, T., Barua, K., Buseman, G., and Murphy, P. A., (1998). Soy isoflavone analysis:Quality control and a new internal standard. Am. J. Clin. Nutr. 68(6 Suppl):1474S–1479S.
62. Sowers, M. F. R., Crawford, S., McConnell, D. S., Randolph, J. F., Gold, E. B., Wilkin, M. K., and Lasley, B., (2006). Selected diet and lifestyle factors are associated with estrogen metabolites in a multiracial/ethnic population of women. J. Nutr. 136(6):1588–1595.
63. Tome-Carneiro, J., Larrosa, M., Yanez-Gascon, M. J., Davalos, A., Gil-Zamorano, J., Gonzalvez, M., Garcia-Almagro, F. J., Ruiz Ros, J. A., Tomas-Barberan, F. A., Espin, J. C., and Garcia-Conesa, M. T., (2013). One-year supplementation with a grape extract containing resveratrol modulates inflammatory-related microRNAs and cytokines expression in peripheral blood mononuclear cells of type 2 diabetes and hypertensive patients with coronary artery disease. Pharmacol. Res. 72:69–82. doi:10.1016/j.phrs.2013.03.011
64. Toolsee, N. A., Aruoma, O. I., Gunness, T. K., Kowlessur, S., Dambala, V., Murad, F., Googoolye, K., Daus, D., Indelicato, J., Rondeau, P., Bourdon, E., and Bahorun, T., (2013). Effectiveness of green tea in a randomized human cohort:Relevance to diabetes and its complications. Biomed. Res. Int. 2013:412379. doi:10.1155/2013/412379
65. Touvier, M., Druesne-Pecollo, N., Kesse-Guyot, E., Andreeva, V. A., Fezeu, L., Galan, P., Hercberg, S., and Latino-Martel, P., (2013). Dual association between polyphenol intake and breast cancer risk according to alcohol consumption level:A prospective cohort study. Breast Cancer Res. Treat. 137(1):225–236. doi:10.1007/s10549-012-2323-y
66. Tresserra-Rimbau, A., Medina-Remón, A., Pérez-Jiménez, J., Martínez-González, M. A., Covas, M. I., Corella, D., Salas-Salvadó, J., Gómez-Gracia, E., Lapetra, J., and Arós, F., (2013). Dietary intake and major food sources of polyphenols in a Spanish population at high cardiovascular risk:The PREDIMED study. Nutr. Metab. Cardiovasc. Dis. 23(10):953–959.
67. Vafa, M., Mohammadi, F., Shidfar, F., Sormaghi, M. S., Heidari, I., Golestan, B., and Amiri, F., (2012). Effects of cinnamon consumption on glycemic status, lipid profile and body composition in type 2 diabetic patients. Int. J Prev. Med. 3(8):531.
68. Vanschoonbeek, K., Thomassen, B. J. W., Senden, J. M., Wodzig, W. K. W. H., and van Loon, L. J. C., (2006). Cinnamon supplementation does not improve glycemic control in postmenopausal type 2 diabetes patients. J. Nutr. 136(4):977–980.
69. Vinson, J. A., Burnham, B. R., and Nagendran, M. V., (2012). Randomized, double-blind, placebo-controlled, linear dose, crossover study to evaluate the efficacy and safety of a green coffee bean extract in overweight subjects. Diab. Metab. Synd. Obesity Targets Ther. 5:21.
70. Vlassopoulos, A., Lean, M. E., and Combet, E., (2013). Influence of smoking and diet on glycated haemoglobin and “pre-diabetes” categorisation:A cross-sectional analysis. BMC Public Health 13:1013. doi:10.1186/1471-2458-13-1013
71. WHO Consultation. 1999. Definition, Diagnosis and Classification of Diabetes Mellitus and Its Complications. Vol. 1:Part 1. Provisional report of WHO consultation, Geneva, Switzerland.
72. WHO. (2011). Use of Glycated Haemoglobin (HbA1c) in Diagnosis of Diabetes Mellitus. Abbreviated report of a WHO Consultation, Geneva, Switzerland.
73. Xie, Y., and Chen, X., (2013). Structures required of polyphenols for inhibiting advanced glycation end products formation. Curr. Drug Metab. 14(4):414–431.
74. Zamora-Ros, R., Knaze, V., Lujan-Barroso, L., Romieu, I., Scalbert, A., Slimani, N., Hjartaker, A., Engeset, D., Skeie, G., Overvad, K., Bredsdorff, L., Tjonneland, A., Halkjaer, J., Key, T. J., Khaw, K. T., Mulligan, A. A., Winkvist, A., Johansson, I., Bueno-de-Mesquita, H. B., Peeters, P. H., Wallstrom, P., Ericson, U., Pala, V., de Magistris, M. S., Polidoro, S., Tumino, R., Trichopoulou, A., Dilis, V., Katsoulis, M., Huerta, J. M., Martinez, V., Sanchez, M. J., Ardanaz, E., Amiano, P., Teucher, B., Grote, V., Bendinelli, B., Boeing, H., Forster, J., Touillaud, M., Perquier, F., Fagherazzi, G., Gallo, V., Riboli, E., and Gonzalez, C. A., (2013). Differences in dietary intakes, food sources and determinants of total flavonoids between Mediterranean and non-Mediterranean countries participating in the European Prospective Investigation into Cancer and Nutrition (EPIC) study. Br. J. Nutr. 109(8):1498–1507. doi:10.1017/s0007114512003273
75. Zheng, X. X., Xu, Y. L., Li, S. H., Hui, R., Wu, Y. J., and Huang, X. H., (2013). Effects of green tea catechins with or without caffeine on glycemic control in adults:A meta-analysis of randomized controlled trials. Am. J. Clin. Nutr. 97(4):750–762. doi:10.3945/ajcn.111.032573
76. Zibadi, S., Rohdewald, P. J., Park, D., and Watson, R. R., (2008). Reduction of cardiovascular risk factors in subjects with type 2 diabetes by pycnogenol supplementation. Nutr. Res. 28(5):315–320. doi:10.1016/j.nutres.2008.03.003
77. Zoungas, S., Chalmers, J., Ninomiya, T., Li, Q., Cooper, M. E., Colagiuri, S., Fulcher, G., De Galan, B. E., Harrap, S., and Hamet, P., (2012). Association of HbA1c levels with vascular complications and death in patients with type 2 diabetes:Evidence of glycaemic thresholds. Diabetologia. 55(3):636–643.