Materials

Seven brands of IFM powders for the age bracket 0-6 months were purposively sampled from stores in Nairobi, Kenya and coded T, U, V, W, X, Y and Z.

Chemicals and reagents

All chemicals and reagents were of analytical grade. Concentrated nitric acid, hydrogen peroxide and aluminum sulphate, were sourced from Thomas Backers Chemicals Ltd Mumbai India. Standards for nickel, cadmium and lead were purchased from Fluka Chemie GmbH Aldrich chemical company, INC, USA.

Laboratory procedures

Digestion of the powders followed the procedure by Picciano (2001). Briefly, 2.5 g of powder was accurately weighed into a Kjeldahl flask, 15 ml of concentrated nitric acid and 5 ml of 10% hydrogen peroxide were added and the resulting solution heated until there were no more brown fumes. The resulting mixture was filtered through Whatman paper No.1 into 50 ml volumetric flask and its volume topped up with deionized water to the mark. The measurements for Al, Cd, Pb and Ni were done in triplicates using computerized Varian Atomic absorption Spectrometer (Model: AA-10, Varian, USA). The instrumental parameters are presented in Table 1.

Method validation procedures

Freshly prepared standard stock solutions were serially diluted andused to obtain calibration curves with linearity values as presented in Table 2. The correlation coefficient values were a good indicator of the linearity for AAS instrument for precision and accuracy of results (Duan et al., 2003). Further, using recovery tests where samples were repeatedly spiked with known amounts of standards prior to measurements were performed to confirm the accuracy of the instruments (Duan et al., 2003). The percentage recoveries obtained were good, falling between 98.1-99.9%.

Statistical analysis

Data were analyzed with SPSS 17.0 for windows. The mean and standard deviation of means were calculated. The Estimated Weekly Intake (EWI) per body weight of the infant for the metal ions in each brand of formula milk were then calculated based on the feeding table provided in each brand of formula milk (0-6 months). The data were analyzed by one-way analysis of variance (ANOVA) and Duncan’s multiple range tests was used to separate means (P < 0.05).

RESULTS AND DISCUSSION

The levels of Al, Cd, Pb and Ni in seven brands of IFM for infants aged 0-6 months sold in Nairobi County, Kenya are presented in Table 3 and the EWI are presented in Table 4.

Except for Cd, all brands of IFM (0-6 months) contained Al, Pb and Ni. These ranged as follows: Al (1.054±0.085 µg/g  in  brand  T to  2.156±0.423  µg/g  in  brand  X);  Pb(0.018±0.001 µg/g in brand V to 0.059±0.002 µg/g in brand W), Ni (0.022±0.001 µg/g in brand X to 0.032±0.001 µg/g in brand T). Except for brands T and V, all other brands had levels of Pb above the KEBS maximum limit of 0.02 ppm. Infants are at a critical point of their brain development and exposure to elements pose severe health risks since the effect is compounded by the fact that even at low levels of exposure, metals bio-accumulate in vital organs and persists in adulthood (Nevin, 2000; Needleman et al., 2002; Lanphear et al., 2008).  The findings  therefore  raise  a health concern  toinfants who consume the brands. A further concern is the labelling of the packages. In this study, Pb was identified in the samples, but not reported on the labels of the containers. These study findings indicate an increased health risk with the consumption of IFM resulting in not only the exposure, but the bioaccumulation of the elements Al, Pb and Ni.

There were statistically significant differences of the elements between brands (p<0.001). This would be expected and these differences can be attributed to the different manufacturing practices, quality of raw materials, and packaging containers used (Khalifa and Ahmad, 2010). Comparing the metal ion levels and the maximum possible weekly intake (Table 4), the EWI of Al and Pb were below the Provisional Tolerable Weekly Intake (PTWI) set by the Joint Committee on Food Additives of the FAO and the EU Scientific Committee for infant feeding, an indication that the IFM are safe for consumption. These findings may generate a debate on whether the campaigns on consumption of IFM should be encouraged although it is understandable that under some unavoidable circumstances exclusive breast feeding is an impossible undertaking. The labels on the IFM packages should include even the minimal safe amounts of all elements as this not only informs the consumers, but have implications on their choice in promoting their consumption. 

In this study, we affirm the presence of trace elements (Al, Cd, Pb and Ni) in IFM brands in the Kenyan market. Although below the WHO set limits, the findings are an indication of caution regarding consumption of IFM unless under unavoidable circumstances as the risks of their bioaccumulation are inevitable.

The authors did not declare any conflict of interest.