Abstract: The present invention provides methods to improve oral absorption of nicotinamide or nicotinamide riboside or both nicotinamide and nicotinamide riboside via gastric (stomach) uptake or via intestinal uptake into the portal circulation blood. Mixtures of nicotinamide or nicotinamide riboside or both nicotinamide and nicotinamide riboside with botanical sources of flavonoids such as Hibiscus Sabdariffa dried calyces or cocoa powder or aronia berries are prepared. The above mixtures, with a pH modifier if needed, are to make the pyridinium cation form of nicotinamide or nicotinamide riboside or both nicotinamide and nicotinamide riboside and such pyridinium cation forms will form associations of pyridinium cations of nicotinamide or nicotinamide ribose or both vitamins with positively-charged aggregating molecular forms to facilitate transport of the vitamins across gastric wall and intestinal wall mucosal environments to portal blood.