The effect of calcium salts, ascorbic acid and peptic pH on calcium, zinc and iron bioavailabilities from fortified human milk using an in vitro digestion/Caco-2 cell model

The calcium, zinc, and iron bioavailabilities of human milk with commercial and noncommercial human milk fortifiers (HMFs) were evaluated under a variety of conditions: peptic digestion at pH 2 and pH 4, supplementation of ascorbic acid, and addition of three calcium salts. The noncommercial HMFs consisted of casein phosphopeptides (CPPs), alpha-lactalbumin, colostrum, and hydrolyzed whey protein concentrate (WPC). They were mixed with human milk (HM) and calcium, zinc, and iron were added. Ascorbic acid (AA) was added in certain studies. The commercial HMFs were Nestle FM-85, Similac HMF (SHMF), and Enfamil HMF (EHMF). All HMFs were compared to S-26/SMA HMF. Results showed that the peptic pH (2 vs. 4) had no effect on mineral bioavailability. Addition of different calcium salts had no effect on calcium cell uptake and cell ferritin levels (An indicator of iron uptake), however, the addition of calcium glycerophosphate/gluconate increased zinc uptake by Caco-2 cells. Addition of AA significantly increased ferritin levels, with no effect on calcium or zinc uptake. Among the commercial HMFs, FM-85 was significantly lower in zinc uptake than S-26/SMA, and HM+EHMF was significantly higher than HM+S-26/SMA. Cell ferritin levels were significantly higher for HM+S-26/SMA than for all other commercial fortifiers. None of the commercial HMFs were different from HM+S-26/SMA in calcium uptake.