(스크랩) MedScape- 비타민C의 섭취가 2형당뇨의 위험을 낮춘다.

Vitamin C Intake Linked to Lower Risk for Type 2 Diabetes CME

News Author: Laurie Barclay, MD
CME Author: Désirée Lie, MD, MSEd
Disclosures

Release Date: July 29, 2008;Valid for credit through July 29, 2009

Authors and Disclosures

Laurie Barclay, MD
Disclosure: Laurie Barclay, MD, has disclosed no relevant financial relationships.

Désirée Lie, MD, MSEd
Disclosure: Désirée Lie, MD, MSEd, has disclosed no relevant financial relationships.

Brande Nicole Martin
Disclosure: Brande Nicole Martin has disclosed no relevant financial information.

July 29, 2008 — Higher plasma vitamin C level and, to a lesser degree, fruit and vegetable intake, are associated with a decreased risk for type 2 diabetes, according to the results of a population-based, prospective cohort study reported in the July 28 issue of the Archives of Internal Medicine.

"Epidemiologic studies suggest that greater consumption of fruit and vegetables may decrease the risk of diabetes mellitus, but the evidence is limited and inconclusive," write Anne-Helen Harding, PhD, from the University of Cambridge, United Kingdom, and colleagues from the European Prospective Investigation of Cancer–Norfolk study. "Plasma vitamin C level is a good biomarker of fruit and vegetable intake, but, to our knowledge, no prospective studies have examined its association with diabetes risk. This study aims to examine whether fruit and vegetable intake and plasma vitamin C level are associated with the risk of incident type 2 diabetes."

From 1993 to 1997, a total of 21,831 healthy participants aged 40 to 75 years underwent baseline measurement of plasma vitamin C level and evaluation of habitual intake of fruit and vegetables with use of a semiquantitative food frequency questionnaire. Between February 1993 and the end of December 2005, there were 735 clinically incident cases of diabetes diagnosed during 12 years of follow-up.

Plasma vitamin C level was strongly inversely associated with diabetes risk. After adjustment for demographic, lifestyle, and anthropometric variables, the odds ratio (OR) of diabetes in the top quintile of plasma vitamin C was 0.38 (95% confidence interval [CI], 0.28 - 0.52). Adjusted OR of diabetes in the top quintile of fruit and vegetable intake was 0.78 (95% CI, 0.60 - 1.00).

"Higher plasma vitamin C level and, to a lesser degree, fruit and vegetable intake were associated with a substantially decreased risk of diabetes," the study authors write. "Our findings highlight a potentially important public health message on the benefits of a diet rich in fruit and vegetables for the prevention of diabetes."

Limitations of this study include possible measurement error in the determination of dietary intake, lack of data on actual vitamin C content of individual components of fruit and vegetable intake, reliance on self-report for diagnosis of diabetes, and potential confounders.

"Our findings of a striking inverse association between the risk of diabetes and plasma vitamin C or fruit and vegetable intake should be confirmed in other prospective studies in different settings and in specifically designed clinical trials," the study authors write. "However, the strong independent association observed in this prospective study, together with biological plausibility, provides persuasive evidence of a beneficial effect of vitamin C and fruit and vegetable intake on diabetes risk. Because fruit and vegetables are the main sources of vitamin C, the findings suggest that eating even a small quantity of fruit and vegetables may be beneficial and that the protection against diabetes increases progressively with the quantity of fruit and vegetables consumed."

The European Prospective Investigation of Cancer–Norfolk study is supported by grants from the Cancer Research Campaign; the Medical Research Council; the Stroke Association; the British Heart Foundation; the Department of Health; the Commission of the European Union's Europe Against Cancer Programme; Research Into Ageing; and the Department for Environment, Food and Rural Affairs. Three of the study authors have obtained funding. The other study authors have disclosed no relevant financial relationships.

Arch Intern Med. 2008;168:1493-1499.

Clinical Context

One key dietary recommendation to prevent chronic disease is to eat at least 5 servings of fruits and vegetables daily, but evidence for this protective effect against type 2 diabetes has been inconclusive. Plasma vitamin C level is a good biomarker of fruit and vegetable intake that can be used to assess the risk for diabetes because in Western populations, approximately 90% of vitamin C is obtained from this source.

This is a prospective, population-based cohort study to examine the risk for type 2 diabetes and intake of fruits and vegetables and plasma vitamin C levels.

Study Highlights

• Included were 21,831 men and women aged 40 to 75 years at baseline who were recruited from 35 general practices in the European Prospective Investigation of Cancer–Norfolk cohort.
• Excluded were those with diabetes at baseline.
• Participants completed a detailed lifestyle and questionnaire at baseline, and physical activity was classified as sedentary, moderately active, active, and very active.
• Plasma vitamin C concentrations were measured, and participants completed a 130-item semiquantitative food frequency questionnaire relating to food consumption within the past year.
• The foods reflected important sources of nutrients in the British diet and included 11 questions related to fruit intake and 26 related to vegetable intake.
• Cases of diabetes were ascertained by multiple methods, including self-report of clinician diagnosis; medication use; and record linkage to diabetes databases, registers, hospital admission records, and national statistics mortality data.
• Of the cohort, 19,246 participants had vitamin C levels available.
• Mean age was 58 years, and mean body mass index (BMI) was 26 kg/m² for men and women.
• Plasma vitamin C levels were higher in women than in men.
• Plasma vitamin C level was inversely associated with age, BMI, waist circumference, total energy intake, and fat intake and was positively associated with fruit, vegetable, and fiber intake.
• Those in the top quintile of vitamin C level were more likely to consume alcohol, be educated, have nonmanual jobs, be physically active, be nonsmokers, and take vitamin supplements.
• During 12 years of follow-up, there were 735 cases of incident diabetes (rate, 3.2%).
• Season, total energy intake, and fat and fiber intakes were not associated with the incidence of diabetes.
• The mean plasma vitamin C level was lower in men and women with diabetes vs those without diabetes (0.76 mg/dL vs 0.95 mg/dL).
• Plasma vitamin C level was inversely associated with the incidence of diabetes.
• The OR for diabetes of those in the highest quintile of plasma vitamin C was 0.23 in the unadjusted model; in a model adjusted for BMI and waist circumference, the OR for diabetes was 0.38, which was statistically significant (P < .001).
• There was also a significant trend for protection against diabetes across quintiles of vitamin C level.
• In the subsample of participants who had hemoglobin A1c level measured at baseline, with hemoglobin A1c level of less than 7% (ie, less likely to have diabetes), the OR for those in the top vs the bottom quintile was 0.46.
• The OR for incident diabetes for those in the top quintile of fruit and vegetable intake was 0.87 in the unadjusted model and 0.78 in the adjusted model.
• The association with diabetes risk was stronger for fruit vs vegetable intake.
• The OR for diabetes in the top vs the bottom quintile of fruit intake was 0.70; for vegetable intake, the OR for diabetes was 0.80.
• The authors concluded that there was a strong inverse association between vitamin C and diabetes risk and a weaker association between fruit and vegetable intake and diabetes risk.
• They also noted that low levels of vitamin C were present before the onset of diabetes and suggested that increasing intake is likely to offer protection against diabetes.

Pearls for Practice

• Plasma vitamin C levels are inversely associated with the risk for type 2 diabetes.
• There is an inverse association between fruit and vegetable intake and the risk for type 2 diabetes, with a greater effect for fruit intake.