Page 1 of 4

Infant formula Cristina Pentelescu and Belén Ortega MorenoAnalytical Chemistry 2010- 2011

Aluminum content of Spanish Infant formula

Introduction Infant formulas are milk-based feeds for infants which have been developed as alternatives to breast milk. Though cow’s milk is the main ingredient of many infant formulas they are sophisticated products which have been designed to meet the specific nutritional needs of children from babies born pre-term through to infants of several years of age. There are also noncow’s milk-based formulas, often made from soya, for infants with intolerances or allergies to cow’s milk. [1]There has been a long and significant history documenting the contamination of infant formulas by aluminium and consequent health effects in children. Exposure of adults to aluminium occurs through drinking water, food additives and antacids or buffered

analgesics. However, aluminium and its compounds appear to be poorly absorbed and are eliminated effectively in the urine. It has been reported that neonates are more susceptible to exposure because of their greater intestinal absorption because of an immature gastrointestinal tract [2]. In infants, aluminium toxicity has been relatively well documented in the case of neonates with impaired renal function, and ill, premature or low birth weight neonates [3]. High aluminium levels in infant formulae have been implicated in aluminium intoxication in two infants with neonatal uraemia [4].Given the evident toxicological impact of aluminium on neonates, it is desirable that infant formulae should be proportionally similar or lower in aluminium concentrations to human milk.

Aim of the studyThe aims in the present study were to analyze the concentration of aluminium in the majority of infant formulas sold commercially in Spain, to estimate the theoretical toxic aluminium intake in comparison with the provisional tolerable weekly intake (PTWI) established by the joint FAO/WHO Expert Committee on Food Additives (WHO 1989).

Sample collection Most infant formulae were purchased directly from manufacturers. The remainders were obtained from a distribution company in Pamplona, Spain. A total of 82 different infant formulae from nine different manufacturers were studied. Formulae included both powder (n=61) and ready-to-use preparations (14), such as those based on cow’s milk (68) or soy based formulae (7). Cow’s milk-based formulae included: preterm formula (n=7), starter formula (adapted, n=16-formula for infants from the first day to 4–5 months of age following the European Society of Pediatric Gastroenterology and Nutrition recommendations-and non-adapted, n=4-formula prepared for infants from birth to 12 months of age under American Academy of Pediatrics regulations), follow-up formula (19) and

specialized formula- hypoallergenic (12), designed for lactose intolerant (7), or inborn errors of metabolism (10) formulae. Infant formulae were stored in accordance with the directions on the label. Containers were kept in the dark at room temperature in a humidity controlled room.

Sample handling In order to minimize risk of contamination, all plastic material or implements that came in contact with the samples were cleaned previously with 5% nitric acid solution for 6 days and later rinsed three times with ultrapure water before use.

Page 2 of 4

Sample treatment Infant formula samples (0.3000 g powder, 1.500 ml liquid) were placed in high pressure Teflon digestion bombs and digested with 4ml sub-boiling nitric acid in

a closed acid-decomposition microwave. The solutions obtained were then diluted up to 10 ml with ultrapure deionized water and kept in frozen storage at –20 °C until analysis. Samples were digested in triplicate.

Instrumental analysisAluminium concentration was determined by graphite furnace atomic absorption spectrometry (GFAAS). The operating parameters and optimizing temperature programme of the instrument are given in table 1. Digested samples were diluted in matrix modifier solution (1.4 g magnesium nitrate Mg(NO3)2∙ 6H2O and 2ml Triton X-100 were diluted in 1 l with ultrapure water). Injections (20 ml) were made in triplicate on L’vov platforms positioned inside pyrolytically coated tubes. Samples were quantified by reference to a calibration curve obtained for aqueous standards. Working standard solutions (0-80 µg/l) were made up each day by dilution from stock 1000 µg/l standard solution in enough sub-boiling nitric acid to a final acid concentration similar to prepared samples. All solutions were kept in the covered carousel throughout the analysis to prevent any contamination.

Table 1. Instrumental parameters and optimizing furnace programme for aluminium determination.

Results and discussion

Aluminium contents in infant formula

Table 2 shows the aluminium concentrations for each of the different types of infant formulae. The wide variability in aluminium content found in some of the formulations included in this study is of special relevance. The variability of aluminium content is a result of the way it can be incorporated in the infant formulae. The total aluminium content can originate from:

(1) The raw material—cow’s milk or isolated soy protein

(2) Contamination during processing from surfaces of metallic equipment or utensils;

(3) Additives or mineral supplements(4) Migration from the containers during storage

Each factor could explain the high variability in the aluminium concentrations found in the different infant formulae. Lower aluminium values in standard formulae (starter and follow-up formulae) in comparison with specialized, preterm and soya formulae are readily apparent.

Table 2. Aluminium content in different types of studied infant formulae (µg/l).

Lower levels found in raw cow’s milk show that this by itself is not necessarily the greatest source of aluminium. However, the large ranges of aluminium content observed in standard formulae are indicative of the potential for contamination during manufacture.

Page 3 of 4

It is well known that aluminium is associated with proteins. Table 3 summarizes the aluminium levels found in different infant formulae, focusing on the main protein.

The highest aluminium content is provided by those formulae based on whole milk followed by skim-milk-based formulae and lastly, formulae that include whey proteins or casein in its composition (table 3). This is a clear evidence of the involvement of intrinsic aluminium from a protein source on the final level found in standard formulae. The present tendency to reduce the protein content and replace different proteins with whey protein to mimic the protein profile found in human milk may advantageously influence the aluminium content of newer types of infant formula.

The complex manufacturing process of specialized formulae seems to play an important role in the degree of aluminium contamination. The highest aluminium value was found in formulae designed for inborn errors of metabolism (443± 112 µg/l), an intermediate level was found for formulae without lactose (399± 451 µg/l) and, finally, the lowest content was found in hypoallergenic formulae (294± 945 µg/l). The probable source of aluminium contamination might be the added formula ingredients (calcium and phosphate salts, vitamins, and other minerals) and the complex processing operations in which infant formulae come into contact with aluminium containing surfaces and equipment for the long periods that their preparation requires.

In order to know the influence of the aggregation state on the amount of aluminium found in infant formula, we evaluated statistically the aluminium contents in both powder and ready-to-use liquid formulae.

For 14 pairs of infant formulae (powder and liquid forms), the aluminium content did not differ significantly between powder and liquid data groups, although the aluminium content in ready-to-use formulae had a tendency to be lower than in powder formulae. (See table 4.)

Table 4. Aluminium levels (µg/l) from different types of infant formulae studied attending to aggregation state (powder or liquid formulae).

Figure 1 compares the weekly aluminium intake (percentage of PTWI) estimated for each type of infant formulae studied. Starter and follow-up formulae contributed the lowest aluminium intake (about 4% PTWI), specialized formulae, such as hypoallergenic formulae gave an intermediate intake (11–12% PTWI) and soya formulae contributed the highest intake (15% PTWI). Figure 2 contains the estimated weekly aluminium intake by infants fed on preterm formulae.

Page 4 of 4

Figure 1. PTWI (%) for aluminium estimated from infant

formulae Figure 2. Weekly dietary aluminium intake for infants

fed on premature infant formulae and human milk (mg week-1).

Conclusion

When the different infant formulae were considered as whole, median aluminium content was 340 µg/l. However, seen separately, median aluminium values of different brands ranged from 142 to 436 µg/l. Considering both points, recommending an upper limit to be set in infant formulae around 300–400 µg/l is a reasonable target that manufacturers could take on without excessive economic cost. This concentration of aluminium compared with a human milk reference value from published levels (3-79 µg/l)1 is very high. In view of these results it seems suitable to call for an effort to control as far as possible the critical points of aluminium contamination and to modify the industrial handling process in order to obtain formulations with less than 300 µg/l of Al.

It has been shown that of the infant formulae studied, the aluminium level was higher than that found in human milk, especially for complex formulae such as premature, specialized and soya. Most infants who consumed infant formulae containing more than this limit had a raised plasma aluminium concentration and so could be at risk of aluminium toxicity [5].

References

[1]- http://www.biomedcentral.com/1471-2431/10/63/prepub[2]- Sedman et al. 1985[3]- Sedman et al. 1984a,b, Moreno et al. 1994, Puntis et al. 1986, Bishop et al. 1997[4]- (Freundlich et al. 1985, 1990).[5]- Hawkins et al. 1994.

1 Ballabriga et al. (1994) and Fernandez-Lorenzo et al. (1999) found an aluminium content in Spanish human milk of 6.5 ± 5.3 µg/l (n=16, range 0.9–19.8 µg/l) and 23.9 ± 9.6 µg/l (n=45, 7–42 µg/l), respectively.

Present work is based on the article “Aluminium content of Spanish infant formula”Authors: I. Navarro-Blascoa; J. I. Alvarez-GalindoaUniversity of Navarra Faculty of Sciences Department of Chemistry Pamplona (Navarra) E-31080 Spain,Online publication date: 10 November 2010