La vitamine C et le diabète

Le stress oxydatif est une situation dans laquelle la quantité de radicaux libres dépasse les niveaux de substances neutralisantes mentionnées en tant qu'antioxydants.
Les radicaux libres se forment de façon disproportionnée dans le diabète. Leurs niveaux anormalement élevés et la baisse simultanée des mécanismes antioxydants de défense peuvent endommager les organites cellulaires et les enzymes, augmenter la peroxydation lipidique (les dommages aux membranes cellulaires) et favoriser le développement de la résistance à l'insuline.
L'acide ascorbique (la vitamine C) réduit la pression et la rigidité artérielle dans le diabète de type 2.

DIABÈTE DE TYPE II:PLUS DE DÉTAILS

RÉFÉRENCE
​Veuillez lire l'article complet  (en anglais seulement) : 
​Abstract
Experimental evidence suggests that acute parenteral administration of high-dose ascorbic acid has beneficial vascular effects in type 2 diabetes. We studied the hemodynamic effects of chronic oral supplementation in this condition.
Thirty patients, 45 to 70 years of age, with type 2 diabetes, were randomly assigned in a double-blind manner to receive 500 mg ascorbic acid daily by mouth or placebo. Patients were studied at baseline and after 4 weeks of assigned treatment.
The central aortic augmentation index (AgIx) and the time to wave reflection (Tr) were derived from radial artery pulse wave analysis data. AgIx and Tr were used as measures of systemic arterial stiffness and aortic stiffness, respectively. Ascorbic acid decreased brachial systolic blood pressure from 142.1+/-12.6 (SD) to 132.3+/-12.1 mm Hg (difference [95% CI] 9.9 [4.7, 15.0]; P<0.01), brachial diastolic pressure from 83.9+/-4.8 to 79.5+/-6.0 mm Hg (4.4 [1.8, 7.0]; P<0.01), and AgIx from 26.8+/-5.5% to 22.5+/-6.8% (4.3 [1.5, 7.1]; P<0.01). Tr increased from 137.1+/-12.6 to 143.4+/-9.2 ms (-6.3 [-10.1, -2.5]; P<0.01). Placebo had no hemodynamic effects, and this difference between treatments was significant (P<0.01 for blood pressure and Tr, P=0.03 for AgIx).
We have therefore shown that after 1 month, oral ascorbic acid lowered arterial blood pressure and improved arterial stiffness in patients with type 2 diabetes. 
As strict control of blood pressure reduces cardiovascular risk in diabetes, ascorbic acid supplementation may potentially be a useful and inexpensive adjunctive therapy. 
Larger and longer studies now need to be performed.

Hypertension. 2002 Dec;40(6):804-9.
Ascorbic acid reduces blood pressure and arterial stiffness in type 2 diabetes.
Mullan BA1, Young IS, Fee H, McCance DR.​