Preliminary Review Suggests Green Tea May Benefit Blood Sugar Health

by | Jul 18, 2013 | 2013, Antioxidants, Blood Sugar, Diabetes, Pancreatic Health

Written by Greg Arnold, DC, CSCS. Research included showed a 5.3 and 10.4% decrease in blood sugar compared to control groups.

Diabetes is now the leading cause of both blindness and kidney failure in the United States. The cost of diabetes in the United States is $174 billion and affects 25.8 million Americans (1). The number of people with diabetes has more than doubled globally over the past 30 years and is expected to rise to 439 million by 2030, representing 7.7% of the total adult population of the world aged 20–79 years of age (2). Type 2 diabetes accounts for nearly 90% of diabetes cases (3) and can be attributed to 5 major lifestyle factors: diet, physical activity, smoking, obesity, and alcohol consumption (4, 5).

Since individuals with impaired fasting glucose or impaired glucose tolerance are in high risk for developing type 2 diabetes (3), finding affordable, effective ways to help maintain proper blood sugar health is crucial. Now a new review of the literature (6) suggests that green tea may help.

In the study, researchers analyzed data from 16 studies. Each study was comprised of 34 to 240 subjects supplementing with green tea catechins ranging from 208 to 1207 milligrams per day and lasting from 2 weeks to 6 months. Using the Jadad scale to assess study quality (7), 7 of the 17 studies were classified as high quality (Jadad score > 4), and the remaining 9 trials were low quality (Jadad score < 4).

Overall, the 16 studies showed a statistically significant benefit of green tea catechins on blood sugar. Looking at individual studies, the high-quality study with the greatest decrease in fasting blood sugar was a 2012 study. In this study, 34 postmenopausal women supplemented 800 milligrams of green tea catechins per day for 2 months, decreasing their fasting blood sugar by 2.6% (103 to 101 milligrams/deciliter) compared to a 2.7% increase in 32 women in the placebo group (97 to 99 mg/dL) (p = 0.008). Of the low-quality studies, the greatest results were seen in a 2009 study. In this study, 23 patients with type 2 diabetes supplemented 582.8 milligrams of green tea catechins per day for 12 weeks, decreasing their fasting blood sugar 5.9% (134.1 to 126.2 mg/dL) compared to a 4.5% increase in 20 patients with type 2 diabetes in the placebo group (130.2 to 135.1 mg/dL) (p < 0.05).

While the results are encouraging, the researchers admit that “Green tea consumption significantly decreased fasting glucose concentrations only in studies that included subjects with risk of the metabolic syndrome,” many of which had small numbers of participants and were for short periods of time. Therefore, “additional long-term and high-quality randomized clinical trials specifically designed to evaluate the effects of green tea on glucose control and insulin sensitivity are needed to further evaluate and confirm these findings.”Another factor to consider is the psycho-stimulating and addictive effects of caffeine that are present in brewed teas which range from 14 to 61 mg per serving of (6 to 8 oz), and therefore consumption of green tea can be habit forming (10).

Source: Liu, Kai, et al. “Effect of green tea on glucose control and insulin sensitivity: a meta-analysis of 17 randomized controlled trials.” The American journal of clinical nutrition 98.2 (2013): 340-348 .

© 2013 American Society for Nutrition

Posted July 18, 2013.

Greg Arnold is a Chiropractic Physician practicing in Hauppauge, NY.  You can contact Dr. Arnold directly by emailing him at PitchingDoc@msn.com or visiting his web site at www.PitchingDoc.com

References:

  1. “2011 National Diabetes Fact Sheet” posted on the CDC Website.
  2. Danaei G, Finucane MM, Lu Y, Singh GM, Cowan MJ, Paciorek CJ, Lin JK, Farzadfar F, Khang YH, Stevens GA, et al. National, regional, and global trends in fasting plasma glucose and diabetes prevalence since 1980: systematic analysis of health examination surveys and epidemiological studies with 370 country-years and 2.7 million participants. Lancet 2011;378:31–
  3. Gerstein HC, Santaguida P, Raina P, Morrison KM, Balion C, Hunt D, Yazdi H, Booker L. Annual incidence and relative risk of diabetes in people with various categories of dysglycemia: a systematic overview and meta-analysis of prospective studies. Diabetes Res Clin Pract 2007; 78:305–12.
  4. Hu FB, Manson JE, Stampfer MJ, Colditz G, Liu S, Solomon CG, Willett WC. Diet, lifestyle, and the risk of type 2 diabetes mellitus in women. N Engl J Med 2001;345:790–7.
  5. Mozaffarian D, Kamineni A, Carnethon M, Djousse L, Mukamal KJ, Siscovick D. Lifestyle risk factors and new-onset diabetes mellitus in older adults: the Cardiovascular Health Study. Arch Intern Med 2009; 169:798–807.
  6. Liu K.  Effect of green tea on glucose control and insulin sensitivity: a meta-analysis of 17 randomized controlled trials.  Am J Clin Nutr 2013 Jun 26. [Epub ahead of print]
  7. Moher D, Pham B, Jones A, Cook DJ, Jadad AR, Moher M, Tugwell P, Klassen TP. Does quality of reports of randomized trials affect estimates of intervention efficacy reported in meta-analyses. Lancet 1998;352:609–13.
  8. Wu AH, Spicer D, Stanczyk FZ, Tseng CC, Yang CS, Pike MC. Effect of 2-month controlled green tea intervention on lipoprotein cholesterol, glucose, and hormone levels in healthy postmenopausal women. Cancer Prev Res (Phila) 2012;5:393–402.
  9. Nagao T, Meguro S, Hase T, Otsuka K, Komikado M, Tokimitsu I, Yamamoto T, Yamamoto K. A catechin-rich beverage improves obesity and blood glucose control in patients with type 2 diabetes. Obesity (Silver Spring) 2009;17:310–7.
  10. Chin, Jenna M., et al. “Caffeine content of brewed teas.” Journal of analytical toxicology 32.8 (2008): 702-704.