This summary is based on ‘Determining the osmolality of over-concentrated and supplemented infant formulas’ by Steele et al. 2012
It may not be something that we often think of, but the concentration of an infant formula can have major health effects. Osmolality is a measure of how concentrated a liquid is, and high osmolality in infant formulas is known to have negative effects. Formulas with high osmolality disrupt the water concentration in the infant gut, leading to water being drawn out of the infant's system and into the gut. This can lead to gastrointestinal issues such as diarrhoea and dehydration and can put stress on the kidneys. It also is thought to be involved in the development of necrotising enterocolitis, a devastating disease that can affect premature infants where there is inflammation and bacterial invasion of the gut which can be fatal1. Consequently, there are recommendations for osmolality levels in infant formulas, with lower levels recommended for premature infants2. Appropriate osmolality ensures the formula is easily digestible and does not impose excessive osmotic pressure on an infant's immature gastrointestinal system.
When infants are failing to grow, it can be necessary to over-concentrate and supplement formula or expressed breast milk, as they require more nutrients. There has been little research into how this affects the osmolality of the formula, which as mentioned can have important health effects. The study summarised here examines how over-concentrating and supplementing infant formulas affects their osmolality, to help understand the potential risks and establish safety guidelines.
This study tested 11 commercially available infant formula brands. Each brand was tested with standard preparation according to the manufacturer’s instructions, over-concentrating the formula by using a greater amount of the powder than recommended in the same amount of water, and supplementing the formula by adding thickeners and/or high energy supplements to increase their energy content. The osmolality of each preparation was then determined and compared against established guidelines which consider a value of 400 mOsm/kg to be the safe upper limit.
The standard preparation of most of the infant formulas gave osmolality levels within the safe range. When over-concentrated, there was an increase in osmolality, but only one formula was found to exceed the safe threshold. The effect of over-concentrating was found to be linear, which means osmolality at different concentrations can be predicted accurately. This formula is not recommended for over-concentration; therefore, this was expected. Supplementation increased the osmolality in most cases, with carbohydrate supplements causing the greatest increase and fat supplements causing a minimal increase. Some supplementation did cause an osmolality which exceeded the safe threshold.
In conclusion, over-concentrating and supplementing infant formulas was found to be safe in most cases in this study. Adhering to preparation guidelines is sufficient to ensure a safe level of osmolality, even in the case of over-concentration. Supplementation is more complicated, therefore further guidelines in this area may be useful. This is especially relevant for premature infants at risk of necrotising enterocolitis, however evidence on the effect of minor changes in osmolality on disease risk is lacking. Better understanding of the risks associated with formula concentration will benefit the health and development of infants relying on these critical nutritional sources.
References
- WILLIS DM, CHABOT J, RADDE IC, CHANCE GW. Unsuspected hyperosmolality of oral solutions contributing to necrotizing enterocolitis in very-low-birth-weight infants. Paediatrics. 1977 Oct 1;60(4):535-8.
- Shaw V, Lawson M. Nutritional assessment, dietary requirements, feed supplementation. Clinical paediatric dietetics. 2007 Jan 1:3-20.
