Researchers at the Wageningen University in the Netherlands took a different approach to understand the effect of NAD+ pre-cursers and their influence on health. They presented a poster publication during the “10th World Congress on Polyphenols Applications” about an experiment to test the effects of marginal dietary supplementation with Nicotinamide Riboside (NR) on metabolic flexibility and anti-oxidant response in mice exposed to a high fat diet. This is in particular interesting because most studies with NR have been done at higher therapeutic levels as opposed to levels more typical for daily supplementation with an aim to maintain health.
The researchers fed two groups of adult male mice with a high fat diet containing dosing of 5 or 30 mg NR/kg. They measured body weight, lean mass, fat mass and feed intake weekly. After 14 weeks the metabolic flexibility was assessed with a fasting and re-feeding challenge using indirect calorimetry. With indirect calorimetry a measurement of respiratory exchanges takes place. Oxidation of the energetic substrates by the body is associated with oxygen consumption, carbon dioxide production, and heat release specific to the nature of the energetic substrates being oxidized. In the following week (so at 15 weeks) the researchers determined the anti-oxidant response in epididymal white adipose tissue.
The results showed that in the fasting and re-feeding challenge, the delta respiratory exchange ratio (ΔRER) was higher when comparing 30 to 5 mg/kg NR dosing thus indicating an increase in metabolic flexibility. In addition the expression levels of anti-oxidant genes were enhanced in the 30 mg/kg group compared to the 5 mg/kg group. The body physiological parameters were not affected by the dietary NR.
From these results it is still not possible to conclude what is the minimum level at which NR supplementation impacts the body as there are no intermediate dose test results between 5mg and 30mg / kg but it seems reasonable to conclude that NR supplementation does impact at a dosing level of 30mg / kg in mice.
Using FDA specified guidelines we can calculate the Human Equivalent Dose (HED) for the NR diet given to the mice. Using this guideline 30mg/kg dosing in mice translates into a HED of approx. 2.4mg/kg. Or into approximately 170mg daily nicotinamide riboside dosing for a person weighing 70kg. This is below the limit wrt to side effects and safety and less than the typical serving sizes of 250mg of supplements on the market. The result supports the view that NR supplementation may help maintain health as we age.
Here the updated overview of Nicotinamide Riboside dosing in various studies.
You can find the poster presentation summary here.