Target Fortification of Breast Milk: Predicting the Final Osmolality of the Feeds

Abstract

For preterm infants, it is common practice to add human milk fortifiers to native breast milk to enhance protein and calorie supply because the growth rates and nutritional requirements of preterm infants are considerably higher than those of term infants. However, macronutrient intake may still be inadequate because the composition of native breast milk has individual inter- and intra-sample variation. Target fortification (TFO) of breast milk is a new nutritional regime aiming to reduce such variations by individually measuring and adding deficient macronutrients. Added TFO components contribute to the final osmolality of milk feeds. It is important to predict the final osmolality of TFO breast milk to ensure current osmolality recommendations are followed to minimize feeding intolerance and necrotizing enterocolitis. This study aims to develop and validate equations to predict the osmolality of TFO milk batches. To establish prediction models, the osmolalities of either native or supplemented breast milk with known amounts of fat, protein, and carbohydrates were analyzed. To validate prediction models, the osmolalities of each macronutrient and combinations of macronutrients were measured in an independent sample set. Additionally, osmolality was measured in TFO milk samples obtained from a previous clinical study and compared with predicted osmolality using the prediction equations. Following the addition of 1 g of carbohydrates (glucose polymer), 1 g of hydrolyzed protein, or 1 g of whey protein per 100 mL breast milk, the average increase in osmolality was 20, 38, and 4 mOsm/kg respectively. Adding fat decreased osmolality only marginally due to dilution effect. Measured and predicted osmolality of combinations of macronutrients as well as single macronutrient (R2 = 0.93) were highly correlated. Using clinical data (n = 696), the average difference between the measured and predicted osmolality was 3 ± 11 mOsm/kg and was not statistically significant. In conclusion, the prediction model can be utilized to estimate osmolality values after fortification.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1. Prediction: linear correlation between increase in osmolality and added amount of each macronutrient in 100 mL of breast milk.

Graphs on carbohydrates (glucose polymer), protein 1(whey protein), protein 2 (hydrolyzed protein), and fat from top to bottom.

Fig 2. Validation 1: correlation between measured osmolality increase (i.e. measurements using a freezing point device) and predicted osmolality increase (i.e. calculations from the prediction equations) on single macronutrient.

Graphs on carbohydrates (glucose polymer), protein 1 (whey protein), protein 2 (hydrolyzed protein), and fat from top to bottom.

Fig 3. Validation 2: correlation between measured (i.e. measurements using a freezing point device) and predicted (i.e. calculations from the prediction equations) osmolality of breast milk with added combinations of macronutrients (Fat: F, Whey Protein: P, Glucose Polymer Carbohydrates: C).

The average quantity to fortify in 100 mL breast milk was 1.3 mL (0.0, 3.2) (min, max), 1.2 g (0.6, 1.5), 1.8 g (1.1, 2.7) for F, P, C, respectively.

Fig 4. Deviation between the measured and predicted osmolality, using clinical samples from the pilot target fortification (TFO) study (n = 696).

Fig 5. Osmolality change on fortified breast milk with carbohydrates after 24 hours of storage at 4°C.

Diamond symbol represents baseline osmolality that measured immediate when breast milk was fortified and round symbol represents osmolality that measured after 24 hours storage at 4°C.