Nicotinamide riboside supplementation safe but ineffective in obese, insulin-resistant men
Dietary nicotinamide riboside (NR) supplementation in 2,000-mg doses daily over a 12-week period is safe, a recent study has shown. However, it does not improve insulin sensitivity and whole-body glucose metabolism in obese, insulin-resistant men.
NR supplementation failed to improve insulin sensitivity, endogenous glucose production, and glucose disposal and oxidation. NR supplementation also had no effect on resting energy expenditure, lipolysis, oxidation of lipids or body composition.
On the other hand, there were no serious adverse events caused by NR supplementation. Safety blood tests were also normal.
In this investigator-initiated randomized, placebo-controlled, double-blinded and parallel-group designed clinical trial, a total of 40 healthy, sedentary men (age range, 40–70 years) with a body mass index of >30 kg/m2 were randomly assigned to 12 weeks of NR (1,000 mg twice daily) or placebo.
The effects of NR supplementation on insulin sensitivity were determined by a hyperinsulinaemic euglycaemic clamp and substrate metabolism by indirect calorimetry and labeled substrates of tritiated glucose and palmitate.
Whole-body dual-energy X-ray absorptiometry and MRI scans were used to determine body composition and fat mass distribution. Finally, MR spectroscopy was used to obtain measurement of intrahepatic lipid content.
“Animal studies suggest a positive role for NR on insulin sensitivity and hepatic steatosis in models of obesity and type 2 diabetes,” the authors said. “NR, an NAD+ precursor, is a member of the vitamin B-3 family now available as an over-the-counter supplement.”