Giving rats a special vitamin-like supplement called nicotinamide riboside for three months seems to boost certain 'good' gut bacteria, especially when they're eating a high-fat diet.

What we've found so far is that nicotinamide riboside supplementation may increase levels of certain gut bacteria in rats fed a high-fat diet. Our analysis of the available research suggests a consistent direction in the evidence, though we are still building our understanding. We reviewed one key assertion from the data, which indicates that giving nicotinamide riboside to rats over a three-month period appears to boost specific gut bacteria, particularly Erysipelotrichaceae and Ruminococcaceae, when the animals are consuming a high-fat diet [1]. This finding is supported by 45.0 individual study references or data points, with no studies indicating a contrary effect [1]. While the number of supporting data points is high, we are only drawing from a single synthesized assertion at this stage, meaning our view is still limited in scope. We do not yet know how this effect might vary with dosage, duration, or rat strain, nor whether similar results would occur in humans. The evidence we've reviewed leans toward a positive association between nicotinamide riboside and these bacterial families in the context of high-fat diets in rats. However, we emphasize that this is based on what we've analyzed so far—not a final conclusion. Since gut bacteria can influence metabolic health, this line of research may help us better understand how supplements interact with the microbiome under specific dietary conditions. Still, we cannot determine the broader implications or mechanisms from the current evidence alone. Practical takeaway: In lab rats on a high-fat diet, nicotinamide riboside seems linked to increases in certain gut microbes, but we don’t know what this means for health or whether it applies to people.