A single dose of sodium nitrate does not improve oral glucose tolerance in patients with type 2 diabetes mellitus

Dietary nitrate (NO₃^-) supplementation has been proposed as an emerging treatment strategy for type 2 diabetes. We hypothesized that ingestion of a single bolus of dietary NO₃^- ingestion improves oral glucose tolerance in patients with type 2 diabetes. Seventeen men with type 2 diabetes (glycated hemoglobin, 7.3% ± 0.2%) participated in a randomized crossover experiment. The subjects ingested a glucose beverage 2.5 hours after consumption of either sodium NO₃^- (0.15 mmol NaNO₃^- · kg^-1) or a placebo solution. Venous blood samples were collected before ingestion of the glucose beverage and every 30 minutes thereafter during a 2-hour period to assess postprandial plasma glucose and insulin concentrations. The results show that plasma NO₃^- and nitrite levels were increased after NaNO₃^- as opposed to placebo ingestion (treatment-effect, P = .001). Despite the elevated plasma NO₃^- and nitrite levels, ingestion of NaNO₃^- did not attenuate the postprandial rise in plasma glucose and insulin concentrations (time × treatment interaction, P = .41 for glucose, P = .93 for insulin). Despite the lack of effect on oral glucose tolerance, basal plasma glucose concentrations measured 2.5 hours after NaNO₃^- ingestion were lower when compared with the placebo treatment (7.5 ± 0.4 vs 8.3 ± 0.4 mmol/L, respectively; P = .04). We conclude that ingestion of a single dose of dietary NO₃^- does not improve subsequent oral glucose tolerance in patients with type 2 diabetes.