This open, randomized, cross-over, placebo-controlled study aims to investigate the effects of vinegar on glucose metabolism, endothelial function and circulating lipid levels in subjects with impaired glucose tolerance or type 2 diabetes, using the arteriovenous difference technique.

Subjects with IGT or type 2 diabetes will be randomised to consume 20ml vinegar (6% acetic acid) or placebo before a mixed meal. Plasma samples will be taken for 300min from the radial artery and from a forearm vein for measurements of glucose, insulin, triglycerides, non-esterified fatty acids (NEFA) and glycerol. Muscle blood flow will be measured with strain-gauge plethysmography. Glucose flux will be calculated as the arteriovenous difference of glucose multiplied by the blood flow rates.

Inclusion Criteria:

1. Subjects with impaired glucose tolerance or newly diagnosed type 2 diabetes before the initiation of medication therapy
2. Recreationally active
3. With stable body weight and diet during the last two months.

Exclusion Criteria:

1. Any systemic disease (besides glucose abnormalities)
2. Any medication therapy
3. Diabetic complications