• Eleven healthy adults who took 250 mg of NMN for 12 weeks displayed a fivefold increase in blood serum insulin levels after two months.
  • The supplementation regimen substantially raised blood plasma NAD+ levels after the first month, which tapered off with continued NMN usage.
  • The study showed for the first time that taking NMN increases blood plasma NMN levels, a phenomenon not observed in whole blood, for distribution to cells and tissues throughout the body.

Supplementing rodents with NMN has been shown to improve metabolic, cardiovascular, and neurological health. Furthermore, taking NMN dramatically raises middle-aged adult blood NAD+ levels and enhances physical performance and improves prediabetic women’s muscle insulin sensitivity. Whether supplementing with NMN improves other health parameters in adults, like markers of metabolic health, needs further investigation.

Along those lines, published in Clinical Nutrition ESPEN, Uchiyama and colleagues from Osaka University in Japan showed that taking 250 mg of oral NMN daily for about three months conferred a fivefold elevation in blood serum insulin levels. The researchers went on to show that this supplementation regimen dramatically raised blood plasma NAD+ levels after one month, which tapered off in the subsequent two months of consuming NMN. Taking NMN also increased NMN levels in blood plasma — the liquid component of blood devoid of cells — for circulatory distribution to cells and tissues throughout the body. The study’s findings confirm that NMN supplementation increases NAD+ levels and show that NMN elevates a marker of metabolic health, insulin levels, which helps the body use the sugar glucose for energy.

NMN Increases Insulin and NAD+ Levels

Uchiyama and colleagues sought better insight into NMN’s effects on human metabolism, so they measured insulin levels in blood serum — blood plasma with clotting factors removed. The initial average blood insulin concentration was 6.95 µIU/mL, which significantly increased fivefold to 39.2 µIU/mL after two months of NMN. At the third month of NMN supplementation, insulin levels tapered off and were lowered to 28.1 µIU/mL. Insulin levels were measured after lunch, and blood glucose levels that rise after eating stimulate higher blood insulin levels. Along those lines, the results show that NMN supplementation for two months increases insulin levels after meals to help the body’s usage of glucose for energy.

Effect of NMN on Blood Serum Insulin Levels: Significant Fivefold Increase at Two Months, Continued Elevation at Three Months
(Yamane et al., 2023 | Clinical Nutrition ESPEN) NMN increases blood serum insulin levels fivefold. At two months of taking NMN, insulin levels increased a significant jump of about fivefold. At three months, insulin levels were still higher, albeit non-significant.

As with most studies examining NMN’s effects on humans, the Japan-based research group sought to find how NMN affects NAD+ levels. They measured blood plasma NAD+ levels at one, two, and three months of taking NMN and a month after stopping NMN supplementation. They found, on average, that NMN increased NAD+ levels over fivefold after one month, which tapered off at two and three months. The NAD+ concentrations at one, two, and three months of taking NMN were all significant. A month after NMN cessation, NAD+ levels dropped to near their initial concentrations. These findings confirm NMN increases blood NAD+ and suggests that higher NAD+ levels taper off for months during supplementation.

Effect of NMN on Blood Plasma NAD+ Concentrations: Substantial Increase at One and Two Months, Tapering at Three Months, Return to Baseline at Four Months
(Yamane et al., 2023 | Clinical Nutrition ESPEN) NMN substantially increases blood plasma NAD+ concentrations. After one month, blood plasma NAD+ levels substantially increased, which persisted to two months. After three months, NAD+ levels tapered to a non-significant elevation. At four months (one month after NMN cessation), NAD+ levels returned to about baseline.

Since previous studies have shown that in whole blood, containing plasma, blood cells, and clotting factors, NMN concentrations don’t increase by taking NMN, Ochiyama and colleagues measured NMN concentrations in blood plasma, devoid of blood cells. Interestingly, they found that NMN levels more than doubled throughout the NMN supplementation regimen and that they fell back to baseline levels a month after stopping supplementation. Importantly, there was an extensive distribution of NMN concentration values for the eleven study participants, suggesting large differences in abilities to absorb NMN across individuals. Blood cells have significant effects when measuring NMN concentrations, and previous studies have shown taking NMN doesn’t increase NMN concentrations in whole blood. Higher NMN concentrations in plasma without blood cells than in whole blood potentially means that blood cells quickly metabolize the majority of blood NMN.

“We successfully measured the plasma NMN concentration for the first time to our knowledge,” said Ouchiyama and colleagues.

Effect of NMN on Blood Plasma NMN Levels: Significant Increase at One, Two, and Three Months, Return to Baseline at Four Months after Cessation
(Yamane et al., 2023 | Clinical Nutrition ESPEN) NMN significantly increases blood plasma NMN levels. NMN supplementation substantially increased blood plasma NMN levels at one, two, and three months of supplementing. One month after NMN cessation (month four), plasma NMN levels returned to about baseline.

Preventing Diabetes with NMN

The study confirmed that supplementing with a modest dose of NMN (250 mg/day) substantially increases blood NAD+ levels, which taper off with months of continued supplementation. Interestingly, NMN also increased postprandial (after a meal) insulin levels. Since a previous study has shown that NMN also increases muscle insulin sensitivity in prediabetic women, producing more insulin with NMN could be a way to prevent diabetes, a metabolic condition marked by low insulin and insulin insensitivity.