Background

Concerns

Specific Guidelines

General Rules of Thumb

Powdered Formulas

Breast Milk

After hospital discharge, some very low birth weight infants may need to consume a formula with higher energy density than that of standard formulas to maintain adequate intake. These include infants with feeding problems (see section on assessment of feeding) and/or very high energy needs (see section on energy needs). Concentration of the energy density of formula or the addition of modular nutritional products are valuable tools in the nutritional care of VLBW infants. Care should be taken when considering decreasing the density of an infant's feedings. Please see the decision tree about changing formula concentration.

There are some concerns about concentrating infant formulas. As valuable as it may be for some infants, this procedure should only be used when clearly indicated and closely monitored. Concerns include:

- Adequacy of fluid intake: Prior to increasing energy density of formula or milk feedings, an assessment of adequacy of fluid intake should be done. Please see section on nutrition intake assessment.
- Renal solute load: Increasing energy density by concentrating the formula increases renal solute load. In order to handle the increased renal solute load, the infant must be able to take in adequate fluid. In general, the infant should be able to consume greater than 120 cc/kg/d to maintain adequate hydration. Although there are reports of increasing concentrations above 24 kcal/oz, few data are reported to support the safety of this practice. The increased renal solute load in an infant with immature kidneys and tenuous fluid balance poses some risk to the infant.
- Dilution of protein and nutrient content: Energy density is sometimes increased with the addition of carbohydrate or fat sources. When this is done, the percentage of energy from carbohydrate, fat, and protein should be calculated. Fat shouldn't exceed 60%, and protein should be greater than 7%. In general, these supplements shouldn't be added to 20 kcal/oz milk or straight breastmilk because the protein content of the feeds will be reduced to less than 7%. Assessment of tolerance to each component should be monitored.

Specific Guidelines for Concentration of Formula have been prepared by Lori Brizee, MS, RD and Susan Casey, RD for the Washington State Office of Children with Special Health Care Needs publication, *Nutrition Interventions for Children with Special Health Care Needs. *These guidelines follow:

In general, it is safe to concentrate formulas to 24 kcal/oz (0.8 kcal/mL) and to add modular carbohydrate and/or fat products to increase concentration up to 30 kcal/oz (1 kcal/mL). In situations when fluid, protein, vitamin and mineral intake is limited (e.g., and infant with feeding difficulties and/or fluid restriction leading to intakes <130 ml/kg/d) concentrations greater than 24 kcal/oz decrease free water intake and increase potential renal solute load (PRSL). Fomon provides a discussion of renal solute load (RSL), PRSL, and assessment of water balance based on fluid intake and PRSL. Infants with limited fluid intake, and on concentrated formulas need to be monitored frequently to insure tolerance of formula and adequacy of hydration.

Accuracy in measuring powdered formulas is a major concern, especially when altering energy density. Traditionally, powdered infant formulas have been assumed to contain 40 kcal/TBSP and many people have assumed that a scoop equaled 1 TBSP. **These assumptions are not necessarily true**.

Prior to writing these guidelines, two clinical dietitians at Children's Hospital and Regional Medical Center (Susan Casey RD,CD and Lori Brizee RD,CD) did an informal study to evaluate traditional methods of preparing powdered formulas.

**Study methods:** Tablespoons were measured and weighed for 8 different formulas. In addition, cups and scoops were measured and weighed for six of these formulas. Ross Labs or Mead Johnson produced all formulas. Measurements were done using "Good Cook" brand plastic measuring tablespoons and cups, and the scoops included in the formula cans. Weights were done on a CHRMC's pharmacy scale, which is accurate to 0.0001 gm. Weights were recorded to the nearest 0.1 gram. The formulas measured were: Similac with Iron, Similac Neocare, Isomil, and Similac PM 60/40 (by Ross Labs), and Enfamil with Iron, Prosobee, Pregestimil, and Nutramigen (by Mead Johnson). Five measurements were done for each formula using a tablespoon or a scoop, and 3 measurements were done for each formula using a cup, unless a difference of greater than 5% was found. The average tablespoon, cup and scoop weights of each formula were used to calculate kcal/TBSP and kcal/scoop. {The calories per gram of formula were calculated by multiplying the number of ounces of formula a can makes by calories per ounce to get the total calories per can, and then dividing calories per can by grams formula powder per can, which gives calories per gram of formula powder.}

**Results:** The weight of a tablespoon of formula varied by 5-10% for each formula and the weight of a scoop varied by 3-10% for each formula. The weights of a cup of formula varied by <5% for each formula. The amount of energy in 1 TBSP of formula, __measured with a measuring tablespoon__, varied between formulas from 33 to 43.8 kcal with an average of 36.7kcal/TBSP for all the formulas measured. The caloric value of 1 TBSP formula, __measured with a measuring cup__, varied from 30.3 to 40.2kcal/TBSP between formulas with an average of 32.6 kcal for all the formulas measured. The caloric value of one scoop of formula varied from 40.5 to 50.9 kcal between formulas, with an average of 44 kcal for all the formulas measured.

**Conclusions:** Our assumptions that a TBSP of infant formula is equal to a scoop and that each contains 40 kcal are not true. Depending on how we prepare "20 kcal/oz" formula, we can get anywhere from 15.2 to 22.8 kcal/oz (Possible methods of preparation: 1 *scoop *added to 2 oz of water to make 2.2 oz, __or__ 1 *tablespoon* plus water to make 2 oz, __or__ 1 *cup* plus water to make 32 oz. This is not an issue for healthy, normally growing infants; but, it could be an issue for infants who have abnormal growth and/or who need altered formulas.

**Recommendations:** When accuracy in measurement is imperative, liquid concentrate formulas are our first choice. If powders must be used, they should be weighed on a gram scale, accurate to the nearest 0.5 gram. Caloric value of 1 gram of formula should be calculated by taking the total caloric value for 1 can of formula (total ounces formula made per can x kcal/oz = total caloric value for 1 can of formula) and divide by the grams formula powder in the can. [For example: A 400 gm can Similac with Iron Powder by Ross Labs makes 105 oz of 20 kcal/oz formula. 105 oz X 20 kcal/oz = 2100 kcal/can; 2100kcal/400gm = 5.25 kcal/gm formula powder.] If powders must be used, and a scale is not available, use the instructions given by the formula producer to make increased caloric density formula. Both Ross Labs and Mead Johnson have written instructions for making altered caloric concentrations of their formulas. Contact your formula company representatives for this information.

Although "best practices" have not been established, fortification of breast milk for supplemental bottle feedings is sometimes offered as an intervention for breastfed infants who have difficulties with adequate intakes.

Breast milk may be concentrated up to 24 kcal per ounce by the addition of appropriately measured powered formula. Alternatively, concentrated formulas may be offered as supplementary feedings between feedings at the breast.

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Page reviewed: March 24, 2015