Written by Marcia Egles, MD. The researchers conducted an analysis of caffeine consumption, and concluded that the lower diabetic risk correlated with higher caffeine intakes.
The worldwide rates of type-2 diabetes have increased, particularly in Asian countries where the prevalence was previously low. (1) In Japan, the prevalence increased from about 5% of the population in 1970 to 15% by 1990. (2) Type-2 diabetes mellitus (also known as non-insulin dependent diabetes, or adult-onset diabetes) is a disease characterized by high blood sugar levels due to an impaired response of the body to insulin. The many complications of diabetes can include heart and circulatory disease, kidney failure, blindness and nerve damage. (3)
Prior research in Europe and the United States (4,5) had found that caffeine from coffee consumption is associated with a decreased risk for the development of type-2 diabetes. The researchers in this Japanese study sought to determine a similar relationship between green tea consumption and the risk of type-2 diabetes. (6)
The study involved new analysis of existing data collected since 1988 on over 110,000 people in the Japan Collaborative Study for Cancer Risk. This new analysis made use of detailed questionnaires answered by 17,000 healthy middle aged men and women (6727 men and 10,686 women) 40-65 years of age who also returned a follow-up questionnaire five years later. The self-reported questionnaires encompassed diet, exercise habits, smoking, alcohol consumption, medical problems and family medical history, as well as height and weight. (6)
Using the five-year follow-up data, the rates of the development of diabetes were compared across various groupings of people. The participants who consumed 6 or more cups of green tea (about 180 mg caffeine) or 3 cups of coffee (about 450 mg caffeine) had their risk of diabetes lowered by 33% and 42% respectively when compared to those who did not consume these beverages. The researchers conducted an analysis of caffeine consumption, and concluded that the lower diabetic risk correlated with higher caffeine intakes. These relationships were strongest in women and in overweight men. (6)
Source: Iso, Hiroyasu, Chigusa Date, Kenji Wakai, Mitsuru Fukui, and Akiko Tamakoshi. “The Relationship between Green Tea and Total Caffeine Intake and Risk for Self-Reported Type 2 Diabetes among Japanese AdultsGreen Tea Reduces Diabetes Risk.” Annals of Internal Medicine 144, no. 8 (2006): 554-562.
Posted July 22, 2008.
Abstractor’s Note: This study suggests the need of a clinical trial to confirm these early findings.
References:
- King H,et al. Global burden of diabetes, 1995-2025: prevalence, numerical estimates, and projections. Diabetes Care. 1998: 21: 1414-31.
- Ohmura T, et al. Prevalence of type-2 (non-insulin-dependent) diabetes mellitus and impaired glucose tolerance in the Japanese general population: the Hisayama Study. Diabetologia. 1993: 36: 1198-2003
- www.diabetes.org
- Van Dam RM, Feskens EJ. Coffee consumption and risk of type 2 diabetes mellitus. Lancet. 2002; 360: 1477-8.
- Salazar-Martinez E, et al. Coffee consumption and risk for type-2 diabetes mellitus. Ann. Intern. Med. 2004: 140: 1-8.
- Hiroyasu Iso, et al. The relationship between green tea and total caffeine intake and risk for self-reported type-2 diabetes among Japanese adults. Annals of Internal Medicine. 18 April 2006: 144:8: 554-562.
