Scientific evidence gathered in recent years supports the nutritional quality of breast milk to feed newborns and infants, due to the specificity and bioavailability of its nutrients and the contribution of live cells, digestive enzymes, immunomodulators and growth factors.1 However, a high percentage of 6-month (54.1%) and one-year-old infants (78.3%) are fed with infant formulas.2 These milks attempt to reproduce the properties, composition and bioavailability of breast milk.3

Spain's Royal Decree 867/2008, of May 23, amending community directive (2006/141/EC), approves the Technical-Sanitary Regulation (TSR) that specifically deals with initiation and continuation infant formulas, establishing minimum and maximum values of nutritional content.4 Its purpose is to provide values to establish the nutritionally adequate contributions of infant formulas. These values are independently established from scientific tests performed in human infants, taking breast milk composition as a reference.5 There is no specific directive regarding the composition of growing-up milks, so manufacturers follow existing recommendations for continuation milks.6 Notwithstanding, although the manufacture of artificial milks is assumed to comply with Royal Decree 867/2008 on the TSR4, it would be interesting to find out whether they adhere to the maximum or minimum values allowed and their relationship with health.

It would also be interesting to analyse the degree to which the nutritional contribution of artificial milks complies with the recommended content, to verify that the artificial milks being prescribed to infants adequately meet their energy and nutritional needs.

In view of this situation, we intend to assess the degree to which infant formulas comply with the TSR and analyse whether the nutritional composition of these milks satisfies the daily recommended intake in infants.

Samples of initiation, continuation, growing-up and special artificial milks commercially available in Spain and related to the pharmaceutical environment have been selected. The nutritional composition figures were taken from the information provided by the manufacturer on the bottles and cartons available for sale and from the Parapharmacy Catalogue 2010.7 Values are expressed in units/100ml of milk reconstituted from dry extract.

The mean values of energy and nutrients contained in each milk group (initiation, continuation, growth and special) have been calculated.

A total of 31 infant formulas were assessed, of which 18 were initiation formulas, 10 were continuation formulas, and 3 were growth formulas. Tables 1a and 1b show their nutritional composition. The main differences between initiation and continuation formulas are a higher energy and nutrient content of the latter. Growing up have a higher energy content of energy (76kcal/100ml), proteins, phosphorus, calcium, retinol, vitamin D, riboflavin and folates compared to the continuation ones.

Table 1c shows the nutritional content of infant milks with their serum protein, polyunsaturated fatty acid, prebiotic and nucleotide content. Most infant formulas contain serum protein, nucleotides, arachidonic, docosahexaenoic, linoleic and α-linolenic acids, docosahexaenoic acid is also present in growing up milks. The most common prebiotics are galacto-oligosaccharides.

Table 2 indicates the mean energy and nutrient content. The percentage of compliance has been calculated for initiation and continuation artificial milks.

Initiation infant formulas comply with the regulation in regard to their macronutrient content. However, levels of micronutrients such as phosphorus, calcium, retinol, vitamins D, E, C, thiamine, riboflavin, vitamins B6, B12 and folates are lower than mean reference values. They contain more iron and niacin.

As for continuation formulas, they comply with regulations in terms of macronutrient content, but not in terms of micronutrients, since their levels of vitamins D, E, C, retinol, thiamine, riboflavin, niacin, vitamins B6, B12 and folates fall below mean reference values, while their mineral (phosphorus, calcium and iron) content exceeds regulation limits. These discrepancies between regulation and real levels are minor, and all micronutrients are within the limits permitted by the regulation and never at their extreme values.

The mean concentrations of energy and nutrients in breast milk and initiation artificial milks in Table 1a are presented in Table 3, as well as the comparison between initiation milk and breast milk and between growing up milks and cow's milk.

When comparing breast milk with initiation milk, we observed that the mean concentration of proteins in the latter is higher. This is also true of micronutrients such as phosphorus, calcium and iron, and vitamins such as retinol, D, E, thiamine, riboflavin, niacin, B6, B12 and folates. Growing up milks, when compared with cow's milk, present a higher energetic content (76kcal/100ml), and higher levels of carbohydrates, iron, vitamins D, E, C, retinol, niacin and folates.

Table 4 shows that the intake of 910ml of initiation milk provides, and in several cases exceeds, the daily recommended amount. The contribution of phosphorus, retinol, vitamin E, C, thiamine, riboflavin, niacin, B6, B12 and folates is higher than recommended.

Intake of 500 ml of continuation milk has been shown to meet 36% of energy requirements, about 50% of macronutrients, vitamin B6 and niacin requirements, between 60% and 70% of the requirements of calcium, iron, retinol and vitamin D, and over 80% of the requirements of phosphorus, vitamin E, vitamin C, thiamine, riboflavin, vitamin B12 and folates.

The daily intake of 500 ml of growing up milk provides 30% of the energy recommended, about 50% of proteins and vitamin C, between 60% and 70% of the requirements of calcium, iron, niacin and folates and more than 80% of the requirements of phosphorus, retinol, vitamin D, riboflavin and vitamin B12. As for the content of glucides, vitamin E, B6 and thiamine, growing up milk does not fufil 50% of the recommendations.

The study performed on nutritional compliance of the leading brands of Spanish infant milks and their ability meet the infant's nutritional needs shows the need to review this regulation in the light of new scientific advances achieved in recent years in some nutrients. The analysis performed has shown that the energy and macronutrient content of the main infant milks is located in the centre of the range indicated in the TSR4 and matches the amounts recommended.9,10 Infant milks provide more iron and micronutrients than breast milk due to their lower bioavailability.13 The main micronutrients in initiation milks are vitamins E, C, B-group vitamins and folates, and vitamin B12 in continuation milks. The amounts of vitamins and minerals contained in initiation milks, as well as in continuation milks, fall within the average range of the TSR European directive.4 When comparing the nutritional content of cow's milk with that of growing up milks, much higher levels of glucides, iron, retinol, vitamin D, vitamin E, vitamin C, niacin and folates is observed, as well as a higher retinol and vitamin B content.12

This study also presents the nutritional composition of a wide range of infant milks commercially available in Spain, which has been used to perform the analysis of their nutritional composition.

Our results show that the content of energy and macronutrients in initiation and continuation milks complies with the TSR European directive.4

Likewise, these milks have an energy and macronutrient content that is close to the values established in the RDI in the period from 0 to 6 months; and for children aged 6–12 months these values meet 36% of energy requirements and between 40% and 50% of macronutrient requirements. Initiation and continuation milks contain vitamins and minerals within the average range of the TSR,4 but the nutritional content is much higher than the values established by the RDI for retinol (133.5%) vitamin E (166%), vitamin C (174%), thiamine (179%), riboflavin (230%), niacin (151%), vitamin B6 (142%), vitamin B12 (500%) and folates (214%) in initiation milks, and for vitamin B12 (283%) in continuation milks. This may imply an excessive, and even harmful, nutritional content, since the RDIs are based on the appropriate intake to maintain the health of practically every healthy individual in the group,14 and they are calculated by organisations and corporations expert in nutrition that edit their own reference values.15,16 The concentration of micronutrients in initiation milks exceeds E, C, B-group vitamin and folate content by 140%. The toxicity of vitamin C, since it is a hydrosoluble vitamin, is very low, as excess intake increases renal excretion.17 Different studies have associated the high levels of vitamins in infant formulas with an increase in fat mass, obesity and diabetes,18 but these studies should be interpreted with caution, since there are other genetic and environmental factors that may affect the development of these pathologies. In accordance with Gale et al.,19 feeding with infant formulas leads to a higher accumulation of fat, which may later represent a higher risk of obesity. This study shows a difference in body composition between breast-fed children and formula-fed children. Breast-fed children have higher fat mass until they are 8 months old and this tendency is reversed at 12 months. There is no further follow-up, and it is therefore unclear how these children develop later. The PROBIT study20 does not show any difference in weight, size or adiposity at 6.5 years when comparing breast-fed children and artificial milk-fed children, although there was a difference at 1 year of age. Several studies show that an above-normal weight increase in children during the first 2 years of their life is associated with a greater risk of obesity in the future.21,22

Continuation milks contain levels of vitamin B12 (283%) that exceed the daily RDI values. It is interesting to note that, at 6 months of age, the child does not only receive this type of milk but also complementary feeding, so the intake of micronutrients would be more elevated. This does not breach regulations, since it complies with the TSR,4 but it should be reviewed because it could be harmful.

Another reason why the TSR4 should be reviewed in initiation milks is that if we compare them with breast milk, which is the gold standard of childhood feeding and whose nutritional composition is taken as reference, we find elevated concentrations of proteins and much higher levels of micronutrients such as calcium (152%), iron (947%), vitamin D (1400%), vitamin E (342%), thiamine (393%), riboflavin (289%), niacin (392%), vitamin B6 (360%), vitamin B12 (329%) and folates (181%), although they all fall within the permitted range. According to the study by Weber et al.,23 the excess of proteins in infant formulas affects the body mass index (BMI) and increases the risk of suffering from obesity during school years. However, the protein content of the milks included in this study is higher than that of our study, since the amount of proteins contained in initiation formulas in Spain, which are included in the study tables, ranges from 1.2 to 1.6g/dl, in comparison with 1.25–2.05g/dl in the study by Weber et al. As for continuation milks, the case is, if applicable, more remarkable, since Spanish formulas range from 1.3 to 2g/dl, in comparison with 1.6–3.2g/dl in the study by Weber et al.

As for iron intake, an elevated daily intake may have negative consequences with regard to the absorption of other minerals,24 pro-oxidant effects25 and harmful symptoms in diseases in which iron absorption is increased.26 Since the bioavailability of iron is lower in artificial milks than in breast milk, the amounts that should be provided in artificial milks are higher.13 As for vitamins, several studies have demonstrated that babies fed with infant milks have higher plasma vitamin levels than breast-fed infants.27–29 Moreover, it is widely known that feeding with infant formula30,31 and breast milk enriched with micronutrients32,33 may lead to a rapid weight increase, which is a risk factor for the development of obesity.34–36 As for growth milks, they are supplemented with micronutrients such as iron (2583.3%), retinol (232.33%), vitamin D (2889%), vitamin E (1518.5%), vitamin C (193.33%), niacin (1251.85%) and folates (358.33%). However, we believe supplementary vitamins and minerals would not offer any benefit to the average infant population, as observed in adults,37–39 although it would be necessary to perform specific studies in children on the extra contribution of vitamins and minerals.

Taking into account the recommendations in force for artificial milks with respect to energy and nutrient intake, all these fall within reference values, so they comply with the TSR.4 Although initiation milks comply with the reference values, their consumption guarantees, and in most cases exceeds, the RDI, so there is an excess of nutrient supplementation. After reviewing the different aspects of the composition and supplementation of infant formulas, we are concerned that the reference values for artificial milks and the RDI for 0- to 6-month infants appear to be significantly elevated when compared with breast milk.

The standard analysis of artificial milks in Spain shows that they comply with the nutritional needs with regard to energy, macronutrients, calcium and iron, most requirements.

In conclusion, although the nutritional composition of infant milks falls within the TSR reference values4 with regard to energy and macronutrients, it would be necessary to review and improve the contribution of micronutrients based on the infant's nutritional requirements and taking into account the possible adverse effects.

At present, there is insufficient scientific basis to conclude that infant formulas rich in vitamins may be “to a large extent” the cause of the current obesity epidemics.

The authors declare that there are no conflicts of interest.