Faculty of Medicine, University of Ruhuna Dr. Thushari Bandara Senior Lecturer Faculty of Medicine, University of Ruhuna Sri Lanka

Study on the fatty acid composition in breast milk during the period of exclusive breast feeding Bandara T1,Hettiarachchi M1, Liyanage C1, Amarasena S1, Bannikoppa PS2, Tomas T2 1Faculty of Medicine, University of Ruhuna, Sri Lanka 2St. Johns Research Institute, Bangalore, India  

Background Breast milk from healthy & well-nourished mothers is recommended as the most preferred form of feeding for infants during their first half of infancy. Milk fat provides energy, essential fatty acids & fat-soluble vitamins for breastfed infants. The body stores of fatty acids in the infants are limited. However, their rapidly growing tissues require higher amounts of fatty acid deposition.

Background contd.. Studies have conducted to determine the fatty acids content in breast milk of the lactating mothers in various geographical regions. However, the information on the composition of breast milk from Sri Lankan lactating mothers remain scarce.

Objective This study was conducted, to report on the composition of fatty acids in breast milk during the first 6 months of lactation and to assess whether the fat mass of the lactating mother influences the fatty acid composition of breast milk.

Methodology Ethical Consideration Ethical approval for the study protocol was granted by the Ethical Review Committee of the Faculty of Medicine, University of Ruhuna, Sri Lanka.

Study design, inclusion/exclusion criteria & subject recruitment Study was cross-sectional. Forty eight healthy exclusively breast feeding mothers were recruited to represent three phases of exclusive breast feeding; - from birth up to 2 months, - 2-4 months and - 4-6 months, at the well baby clinics in Galle, using purposive random sampling technique. Age of mothers was 18 - 40 years Parity was less than 4. All infants were full term and healthy.

Exclusion Criteria Mothers with twin or more babies, mothers with fluid retention diseases i.e., kidney, heart and hypothyroidism, mothers who have had complicated pregnancies and mothers whose infants were with any congenital anomalies, chronic diseases or any illness that could affect breastfeeding or growth were excluded.

Collection of breast milk A single mid-milk sample (25 mL) was collected from each mother between 9.00 -11.00 hours. Samples were collected into sterile polypropylene bottles. Mothers were requested to collect breast milk samples by hand expression from one breast. Mothers were instructed to clean the breast & hands thoroughly before the sample collection & sit on a chair or on the floor comfortably.

Collection of breast milk contd.. To collect mid-stream milk, the mothers were requested to put the baby to breast & after few minutes (5 min) collect milk & then continue feeding. Sample bottles were sealed tightly with parafilm & transported to the laboratory immediately in ice boxes, frozen quickly & kept at -70◦C until transported to India in dry ice. Analysis was done at the St. John’s Research Institute, Bangalore, India.

Measurement of fatty acid composition of breast milk Fatty acids from breast milk total lipids (from 500 μl of breast milk) were analyzed by Gas chromatography using a flame ionization detector (Varian 3800; Varian, Palo Alto, CA, USA).

Measurement of fatty acid composition of breast milk contd.. Brief procedure involved, the extraction of total lipids followed by the trans-methylation of all fatty acids using BF3-methanol. The fatty acid methyl esters were then separated based on the chain length & degree of saturation by injection onto a 50 m, 0.2 mm capillary column (FAME, Varian) with nitrogen carrier gas. Individual fatty acids were identified against reference fatty acids.

Brief procedure contd.. The odd-chain FA – heptadecanoic acid, C17:0 was used as an internal standard in each sample. Based on the internal standard, total fatty acid contents of the samples were calculated & each identified fatty acid was expressed as a percentage of the total content of the identified fatty acids.

Demographic data & the anthropometric data of the mothers and infants were collected. Mother’s body composition was determined by using deuterium-dose-to-mother technique

Principle & methodology Determination of body composition by deuterium dose-to-mother technique Principle & methodology 1. Mother drinks 10g (99.8%) deuterium 2. Deuterium mixes with the mother’s body water 3. The baby consumes deuterium in his mother’s milk 4. Saliva/urine is sampled from the mother and from the baby for two weeks (basal, 5h, day 3, day 4, day 13 & day 14)

Sample Collection Plan Date Mother (Saliva) Baby (Urine) 1 (Pre dose) √ 1 (Post dose) 3 4 13 14

The enrichment of deuterium in the mother’s body water gradually decreases. The enrichment of deuterium in the baby’s body water gradually increases and then decreases. Deuterium enrichment in saliva/urine samples was determined by IRMS. Enrichment data was plotted on a logarithmic scale. Curve fitting and calculation of the mother’s body composition were performed using solver function in an Excel spreadsheet.

Statistical Analysis Statistical analysis was done using SPSS (version 20, Chicago). Differences of the fatty acid composition between groups were analyzed using independent sample test (Kruskal-Wallis Test). Association between fatty acid composition in breast milk & the maternal characteristics, mother’s body composition & demographic data were assessed by Spearman’s rho correlation. p-value <0.05 was considered as statistically significant.

Results Mean age ± SD of the mothers was 27.8 ± 6.2 years. Mean parity was 2 ± 1. Mean % FM of the mothers was 23.5 ± 7.9.

Table 1. Demographic characteristics, anthropometry and body composition of lactating mothers (n=48) Information Mean ± SD Age (years) 27.8 (6.2) Parity 2 ± 1 Body weight (kg) 51.3 ± 11.0 Height (m) 1.52 ± 0.05 BMI (kg/m2) 22.0 ± 4.1 Fat mass (kg) 12.6 ± 6.2 Fat Free Mass (kg) 38.7 ± (6.1) % FM 23.5 ± 7.9

Table 2. Fatty acid composition (as % to the total fatty acid content) of human milk1 Infant’s age groups All infants < 2months 2-4 months 4-6months Octanoic acid (C8) 0.26 ± 0.19 0.26 ± 0.21 0.12 ± 0.13 0.21 ± 0.19 Decanoic acid (C10) 3.09 ± 0.88 2.44 ± 0.70 2.66 ± 0.56 2.73 ± 0.76 Lauric acid (C12) 22.64 ± 5.81 20.94 ± 6.20 23.23 ± 3.31 22.27 ± 5.24 Myristic acid (C14) 15.49 ± 3.11 15.13 ± 2.82 16.39 ± 2.23 15.66 ± 2.74 Myristoleic acid (C14:1) 0.69 ± 0.34a 0.86 ± 0.19a 0.69 ± 0.22a 0.75 ± 0.26 Palmitic acid (C16) 19.11 ± 2.65 20.13 ± 3.07 18.26 ± 1.59 19.17 ± 2.58 Palmitoleic acid (C16:1) 4.56 ± 1.88 4.95 ± 1.41 4.31 ± 1.52 4.6 ± 1.61 Octadecanoic acid (C18) 3.12 ± 0.46c 3.46 ± 0.43c 3.08 ± 0.53c 3.22 ± 0.50 Eladic acid (C18:1t) 0.05 ± 0.14 0.18 ± 0.38 0.09 ± 0.30 0.10 ± 0.29 Oleic acid (C18:1c) 21.73 ± 4.76 22.63 ± 5.06 21.28 ± 3.26 21.88 ± 4.38 Linoleic acid (C18:2n6) 7.24 ± 1.61 6.9 ± 1.31 7.92 ± 1.66 7.36 ± 1.56 γ - Linolenic acid (C18:3n3) 0.26 ± 0.15 0.46 ± 0.70 0.34 ± 0.16 0.35 ± 0.42 Arachidic acid (C20) 0.04 ± 0.11 0.04 ± 0.08 0.02 ± 0.05 0.03 ± 0.08 Dihomo-γ- linolenic acid (C20:3n6) 0.84 ± 1.38b 0.79 ± 1.09b 0.33 ± 0.15b 0.65 ± 1.03 Arachidonic acid (C20:4n6) 0.56 ± 0.14 1.11 ± 1.34 0.56 ± 0.15 0.75 ± 0.81 Docosapentaenoic acid (C22:5n3) 0.06 ± 0.09 0.03 ± 0.06 0.05 ± 0.08 Docosahexaenoic acid (C22:6n3) 0.60 ± 0.37 1.12 ± 1.22 0.63 ± 0.28 0.78 ± 0.78 1 There were 16 breast milk samples in each age group; results are presented as mean±SD a, b, c superscripts given in a raw indicated significant difference (p<0.05)

1. Octanoic acid 2. Decanoic acid 3. Lauric acid 4. Myristic acid 5. Myristoleic acid 6. Palmitic acid 7. Palmitoleic acid 8. Octadecanoic acid 9. Eladic acid 10. Oleic acid 11. Linoleic acid 12. γ - Linolenic acid 13.Arachidic acid 14.Dihomo-γ- linolenic acid 15.Arachidonic acid 16.Docosapentaenoic acid 17. Docosahexaenoic acid

Association of the each % fatty acid with maternal characteristics such as age, body weight, BMI, parity and % FM was assessed using Spearman’s rho correlation

Table 3. Spearman’s correlation (r) of the % FA with maternal characteristics1. Fatty acid Mother’s age Mother’s body weight Parity Mother’s BMI %FM of the mother C8 0.086 (0.561) 0.264 (0.070) 0.082 (0.580) 0.293 (0.044) * 0.177 (0.240) C10 -0.193 (0.188) -0.207 (0.158) 0.012 (0.933) -0.093 (0.529) -0.054 (0.722) C12 -0.135 (0.362) -0.362 (0.011) * -0.029 (0.843) -0.284 (0.051) -0.183 (0.223) C14 -0.202 (0.169) -0.470 (0.001) ** -0.122 (0.407) -0.368 (0.010) * -0.272 (0.067) C14:1 0.228 (0.119) 0.320 (0.026) * 0.147 (0.319) 0.315 (0.029) * 0.404 (0.005) ** C16 0.088 (0.553) 0.376 (0.009) ** 0.034 (0.817) 0.354 (0.014) * 0.178 (0.237) C16:1 0.039 (0.795) -0.013 (0.930) 0.270 (0.063) 0.336 (0.022) * C18 0.150 (0.310) 0.289 (0.046) * 0.100 (0.499) 0.089 (0.555) C18:1t 0.223 (0.128) 0.046 (0.756) -0.002 (0.988) 0.178 (0.225) 0.011 (0.940) C18:1c 0.129 (0.381) 0.311 (0.031) * 0.003 (0.982) 0.174 (0.238) 0.137 (0.364) C18:2n6 0.073 (0.624) 0.097 (0.513) 0.035 (0.814) 0.067 (0.652) 0.051 (0.736) C18:3n3 0.181 (0.219) 0.001 (0.996) 0.073 (0.620) -0.061 (0.680) C20 0.035 (0.811) -0.099 (0.502) -0.008 (0.959) -0.084 (0.568) 0.169 (0.262) C20:3n6 -0.009 (0.950) 0.116 (0.432) 0.007 (0.960) 0.024 (0.874) -0.088 (0.559) C20:4n6 0.206 (0.160) 0.366 (0.011)** 0.149 (0.312) 0.287 (0.048) * 0.093 (0.540) C22:5n3 0.290 (0.045)* 0.326 (0.024)* 0.175 (0.234) 0.294 (0.042) * 0.140 (0.354) C22:6n3 0.258 (0.076) 0.448 (0.001) ** 0.082 (0.578) 0.405 (0.004) ** 0.171 (0.257) 1Results are presented as correlation coefficient (p value) *Correlation is significant at the 0.05 level

Correlation of the % FA with maternal characteristics Parity did not show any significant association with any of the fatty acid. % Fat mass of the mother showed significant positive correlations with Myristoleic (r=0.404, p=0.005) & Palmitoleic (r=0.336, p=0.022) acids. However, present study did not show any significant associations between the % of any of the fatty acid in breast milk & the birth weight, weight gain or BMI of the infants.

Conclusions 1. Lauric acid (C12) is the most abundant fatty acid (22.3% ± 5.2) found in human milk of Sri Lankan mothers. 2. Percentages of oleic (C18:1c), palmitic (C16) and myristic acid (C14) are also higher in breast milk.

Conclusions contd… 3. Fatty acid composition of human milk of Sri Lankan mothers varies considerably with respect to, Octanoic acid (C8), Octadecanoic acid(C18:1t), γ - Linolenic acid (C18:3n3), Arachidic acid (C20), Dihomo-γ- linolenic acid (C20:3n6), Arachidonic acid (C20:4n6), Docosapentaenoic acid (C22:5n3) and Docosahexaenoic acid (C22:6n3). This may be attributed to the diet and genetic variations of the mothers.

Conclusions contd.. 4. The percentages of octadecanoic acid (C18) myristoleic acid (C14:1) and dihomo-γ- linolenic acid (C20:3n6) are significantly different between 3 phases of lactation (birth to 2 months, 2-4 months and 4-6 months). 5. Human milk of Sri Lankan mothers contains fairly high amounts of arachidonic acid & DHA. 6. However, the linoleic and γ-linolenic acid percentages are low compared to the values reported.

Limitation Present study did not evaluate the diet of the lactating mothers which has been reported to be the main determinant of the fatty acids in breast milk.

Acknowledgements International Atomic Energy Authority (IAEA) for funding through IAEA/SRI/16826. Medical Officers of Health, Nursing Sisters, Public Health Midwives. All participants of the study. St. John’s Research Institute, India.

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