Glycemic index, glycemic load, and risk of type 2 diabetes: results from 3 large US cohorts and an updated meta-analysis.
BACKGROUND
Epidemiologic evidence for the relation between carbohydrate quality and risk of type 2 diabetes (T2D) has been mixed.


OBJECTIVE
We prospectively examined the association of dietary glycemic index (GI) and glycemic load (GL) with T2D risk.


METHODS
We prospectively followed 74,248 women from the Nurses' Health Study (1984-2008), 90,411 women from the Nurses' Health Study II (1991-2009), and 40,498 men from the Health Professionals Follow-Up Study (1986-2008) who were free of diabetes, cardiovascular disease, and cancer at baseline. Diet was assessed by using a validated questionnaire and updated every 4 y. We also conducted an updated meta-analysis, including results from our 3 cohorts and other studies.


RESULTS
During 3,800,618 person-years of follow-up, we documented 15,027 cases of incident T2D. In pooled multivariable analyses, those in the highest quintile of energy-adjusted GI had a 33% higher risk (95% CI: 26%, 41%) of T2D than those in the lowest quintile. Participants in the highest quintile of energy-adjusted GL had a 10% higher risk (95% CI: 2%, 18%) of T2D. Participants who consumed a combination diet that was high in GI or GL and low in cereal fiber had an ~50% higher risk of T2D. In the updated meta-analysis, the summary RRs (95% CIs) comparing the highest with the lowest categories of GI and GL were 1.19 (1.14, 1.24) and 1.13 (1.08, 1.17), respectively.


CONCLUSIONS
The updated analyses from our 3 cohorts and meta-analyses provide further evidence that higher dietary GI and GL are associated with increased risk of T2D.
From the Departments of Nutrition (SNB, DKT, VSM, AH, WCW, and FBH) and Epidemiology (JEM, WCW, and FBH), Harvard School of Public Health, Boston, MA; the Saw Swee Hock School of Public Health and Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore (AP); the Division of Preventive Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA (JEM); and the Channing Division of Network Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA (WCW and FBH).
Shilpa N
SN
Bhupathiraju
From the Departments of Nutrition (SNB, DKT, VSM, AH, WCW, and FBH) and Epidemiology (JEM, WCW, and FBH), Harvard School of Public Health, Boston, MA; the Saw Swee Hock School of Public Health and Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore (AP); the Division of Preventive Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA (JEM); and the Channing Division of Network Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA (WCW and FBH).
Deirdre K
DK
Tobias
From the Departments of Nutrition (SNB, DKT, VSM, AH, WCW, and FBH) and Epidemiology (JEM, WCW, and FBH), Harvard School of Public Health, Boston, MA; the Saw Swee Hock School of Public Health and Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore (AP); the Division of Preventive Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA (JEM); and the Channing Division of Network Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA (WCW and FBH).
Vasanti S
VS
Malik
From the Departments of Nutrition (SNB, DKT, VSM, AH, WCW, and FBH) and Epidemiology (JEM, WCW, and FBH), Harvard School of Public Health, Boston, MA; the Saw Swee Hock School of Public Health and Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore (AP); the Division of Preventive Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA (JEM); and the Channing Division of Network Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA (WCW and FBH).
An
A
Pan
From the Departments of Nutrition (SNB, DKT, VSM, AH, WCW, and FBH) and Epidemiology (JEM, WCW, and FBH), Harvard School of Public Health, Boston, MA; the Saw Swee Hock School of Public Health and Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore (AP); the Division of Preventive Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA (JEM); and the Channing Division of Network Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA (WCW and FBH).
Adela
A
Hruby
From the Departments of Nutrition (SNB, DKT, VSM, AH, WCW, and FBH) and Epidemiology (JEM, WCW, and FBH), Harvard School of Public Health, Boston, MA; the Saw Swee Hock School of Public Health and Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore (AP); the Division of Preventive Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA (JEM); and the Channing Division of Network Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA (WCW and FBH).
JoAnn E
JE
Manson
From the Departments of Nutrition (SNB, DKT, VSM, AH, WCW, and FBH) and Epidemiology (JEM, WCW, and FBH), Harvard School of Public Health, Boston, MA; the Saw Swee Hock School of Public Health and Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore (AP); the Division of Preventive Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA (JEM); and the Channing Division of Network Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA (WCW and FBH).
Walter C
WC
Willett
From the Departments of Nutrition (SNB, DKT, VSM, AH, WCW, and FBH) and Epidemiology (JEM, WCW, and FBH), Harvard School of Public Health, Boston, MA; the Saw Swee Hock School of Public Health and Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore (AP); the Division of Preventive Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA (JEM); and the Channing Division of Network Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA (WCW and FBH).
Frank B
FB
Hu
D001786:Blood Glucose / Q000378:metabolism*; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology* / Q000517:prevention & control*; D002149:Energy Intake; D005500:Follow-Up Studies; D038321:Glycemic Index; D006801:Humans; D015994:Incidence; D015596:Nutrition Assessment; D015203:Reproducibility of Results; D012307:Risk Factors; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology
D001786:Blood Glucose