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.