Tea consumption and risk of type 2 diabetes mellitus: a systematic review and meta-analysis update

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Abstract

Objective

Tea has been suggested to decrease blood glucose levels and protect pancreatic β cells in diabetic mice. However, human epidemiological studies showed inconsistent results for the association between tea consumption and type 2 diabetes mellitus (T2DM) risk. The aim of this study was to conduct a meta-analysis to further explore the association between tea consumption and incidence of T2DM.

Design

Systematic review and meta-analysis.

Methods

We performed a systematic literature search up to 30 August 2013 in PubMed, EMBASE, Chinese Wanfang Database and CNKI database. Pooling relative risks (RRs) were estimated by random-effect models. Two kinds of subgroup analyses (according to sex and regions) were performed. Sensitive analyses were performed according to types of tea.

Results

Overall, no statistically significant relationship between tea consumption and risk of T2DM was found based on 12 eligible studies (pooling RR 0.99, 95% CI 0.95 to 1.03). Compared with the lowest/non-tea group, daily tea consumption (≥3 cups/day) was associated with a lower T2DM risk (RR 0.84, 95% CI 0.73 to 0.97). Subgroup analyses showed a difference between men and women. Overall, the RRs (95% CI) were 0.92 (0.84 to 1.00) for men, and 1.00 (0.96 to 1.05) for women, respectively. Tea consumption of ≥3 cups/day was associated with decreased T2DM risk in women (RR 0.84, 95% CI 0.71 to 1.00). Overall, the RRs (95% CIs) were 0.84 (0.71 to 1.00) for Asians, and 1.00 (0.97 to 1.04) for Americans and Europeans, respectively. No obvious change was found in sensitivity analyses.

Conclusions

The results suggest that daily tea consumption (≥3 cups/day) is associated with a lower T2DM risk. However, further studies are needed to enrich related evidence, especially with regard to types of tea or sex.

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Most cited references 39

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Economic costs of diabetes in the U.S. In 2007.

(2008)

The prevalence of diabetes continues to grow, with the number of people in the U.S. with diagnosed diabetes now reaching 17.5 million. The objectives of this study are to quantify the economic burden of diabetes caused by increased health resource use and lost productivity, and to provide a detailed breakdown of the costs attributed to diabetes. This study uses a prevalence-based approach that combines the demographics of the population in 2007 with diabetes prevalence rates and other epidemiological data, health care costs, and economic data into a Cost of Diabetes Model. Health resource use and associated medical costs are analyzed by age, sex, type of medical condition, and health resource category. Data sources include national surveys and claims databases, as well as a proprietary database that contains annual medical claims for 16.3 million people in 2006. The total estimated cost of diabetes in 2007 is $174 billion, including $116 billion in excess medical expenditures and $58 billion in reduced national productivity. Medical costs attributed to diabetes include $27 billion for care to directly treat diabetes, $58 billion to treat the portion of diabetes-related chronic complications that are attributed to diabetes, and $31 billon in excess general medical costs. The largest components of medical expenditures attributed to diabetes are hospital inpatient care (50% of total cost), diabetes medication and supplies (12%), retail prescriptions to treat complications of diabetes (11%), and physician office visits (9%). People with diagnosed diabetes incur average expenditures of $11,744 per year, of which $6,649 is attributed to diabetes. People with diagnosed diabetes, on average, have medical expenditures that are approximately 2.3 times higher than what expenditures would be in the absence of diabetes. For the cost categories analyzed, approximately $1 in $5 health care dollars in the U.S. is spent caring for someone with diagnosed diabetes, while approximately $1 in $10 health care dollars is attributed to diabetes. Indirect costs include increased absenteeism ($2.6 billion) and reduced productivity while at work ($20.0 billion) for the employed population, reduced productivity for those not in the labor force ($0.8 billion), unemployment from disease-related disability ($7.9 billion), and lost productive capacity due to early mortality ($26.9 billion). The actual national burden of diabetes is likely to exceed the $174 billion estimate because it omits the social cost of intangibles such as pain and suffering, care provided by nonpaid caregivers, excess medical costs associated with undiagnosed diabetes, and diabetes-attributed costs for health care expenditures categories omitted from this study. Omitted from this analysis are expenditure categories such as health care system administrative costs, over-the-counter medications, clinician training programs, and research and infrastructure development. The burden of diabetes is imposed on all sectors of society-higher insurance premiums paid by employees and employers, reduced earnings through productivity loss, and reduced overall quality of life for people with diabetes and their families and friends.

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Whole-grain and fiber intake and the incidence of type 2 diabetes.

Arpo Aromaa, Jukka Montonen, Paul Knekt … (2003)

Epidemiologic evidence of a preventive effect of whole grain against type 2 diabetes is mainly based on data from women. Information specific to men and women is needed. The objective was to study the relation between the intake of whole grain and fiber and the subsequent incidence of type 2 diabetes. The design was a cohort study of 2286 men and 2030 women aged 40-69 y and initially free of diabetes. Food consumption data were collected from 1966 through 1972 with the use of a dietary history interview covering the habitual diet during the previous year. During a 10-y follow-up, incident type 2 diabetes cases were identified in 54 men and 102 women from a nationwide register. Whole-grain consumption was associated with a reduced risk of type 2 diabetes. The relative risk (adjusted for age, sex, geographic area, smoking status, body mass index, energy intake, and intakes of vegetables, fruit, and berries) between the highest and lowest quartiles of whole-grain consumption was 0.65 (95% CI: 0.36, 1.18; P for trend = 0.02). Cereal fiber intake was also associated with a reduced risk of type 2 diabetes. The relative risk between the extreme quartiles of cereal fiber intake was 0.39 (95% CI: 0.20, 0.77; P = 0.01). An inverse association between whole-grain intake and the risk of type 2 diabetes was found. The similar result for cereal fiber intake suggests that the whole-grain association is due to cereal fiber or another factor related to cereal fiber intake.

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Glycemic effects of postmenopausal hormone therapy: the Heart and Estrogen/progestin Replacement Study. A randomized, double-blind, placebo-controlled trial.

Alka M. Kanaya, David M. Herrington, Eric Vittinghoff … (2003)

Randomized trials of postmenopausal hormone therapy have found differing effects on fasting glucose levels. No trial has evaluated the effect of hormone therapy on diabetes incidence. To evaluate the effect of hormone therapy on fasting glucose level and incident diabetes. Randomized, double-blind, placebo-controlled trial. 20 U.S. clinical centers. 2763 postmenopausal women with coronary heart disease who were followed for 4.1 years. At baseline, 734 women had diabetes, 218 women had impaired fasting glucose, and 1811 women were normoglycemic; the 2029 women without diabetes were followed for incident diabetes. 0.625 mg of conjugated estrogen plus 2.5 mg of medroxyprogesterone acetate daily, or placebo. Fasting glucose level was measured at baseline, at year 1, and at the end of the trial. Incident diabetes was defined by self-report of diabetes or disease complication, fasting glucose level of 6.9 mmol/L or greater (> or =126 mg/dL), or initiation of therapy with diabetes medication. Fasting glucose levels increased significantly among women assigned to placebo but did not change among women receiving hormone therapy. The incidence of diabetes was 6.2% in the hormone therapy group and 9.5% in the placebo group (relative hazard, 0.65 [95% CI, 0.48 to 0.89]; P = 0.006). The number needed to treat for benefit to prevent one case of diabetes was 30 (CI, 18 to 103). Changes in weight and waist circumference did not mediate this effect. In women with coronary disease, hormone therapy reduced the incidence of diabetes by 35%. This observation provides important insights into the metabolic effects of postmenopausal hormones but is insufficient to recommend the use of hormones for secondary prevention of heart disease.

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Author and article information

Journal

Journal ID (nlm-ta): BMJ Open

Journal ID (iso-abbrev): BMJ Open

Journal ID (hwp): bmjopen

Journal ID (publisher-id): bmjopen

Title: BMJ Open

Publisher: BMJ Publishing Group (BMA House, Tavistock Square, London, WC1H 9JR )

ISSN (Electronic): 2044-6055

Publication date Collection: 2014

Publication date (Electronic): 22 July 2014

Volume: 4

Issue: 7

Electronic Location Identifier: e005632

Affiliations

[1 ]Department of Nutrition, Daping Hospital, The Third Military Medical University , Chongqing, People's Republic of China

[2 ]Department of Cardiology, Daping Hospital, The Third Military Medical University , Chongqing, People's Republic of China

[3 ]Social Medical Science Research Centre, National Research Institute for Family Planning , Beijing, People's Republic of China

[4 ]National Research Institute for Family Planning , Beijing, People's Republic of China

Author notes

JY and Q-XM contributed equally.

[Correspondence to ] Chunyu Zeng; chunyuzeng01@ 123456163.com and Xu Ma; genetic@ 123456263.net.cn

Article

Publisher ID: bmjopen-2014-005632

DOI: 10.1136/bmjopen-2014-005632

PMC ID: 4120344

PubMed ID: 25052177

SO-VID: 91570f70-4cfe-4775-855e-825e3ba5d71f

License:

This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/

History

Date received : 6 May 2014

Date revision received : 30 June 2014

Date accepted : 4 July 2014

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Tea consumption and risk of type 2 diabetes mellitus: a systematic review and meta-analysis update

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Abstract

Objective

Design

Methods

Results

Conclusions

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AIP Publishing: Coronavirus

Most cited references 39

Economic costs of diabetes in the U.S. In 2007.

Whole-grain and fiber intake and the incidence of type 2 diabetes.

Glycemic effects of postmenopausal hormone therapy: the Heart and Estrogen/progestin Replacement Study. A randomized, double-blind, placebo-controlled trial.

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Cited by 27

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