The Association of Pre-Pregnancy Obesity and Breast Milk Fatty Acids Composition and the Relationship of Postpartum Maternal Diet,Breast Milk Fatty Acids and Infant Growth

Abstract

Objectives:

This study aimed to evaluate the effect of prepregnancy obesity on fatty acid profile in breast milk, to determine the relationship between maternal diet and fatty acids in breast milk, and to investigate the relationship between fatty acids in breast milk and infant growth.

Materials and Methods:

Twenty normal-weight mothers, 20 obese mothers, and their infants were recruited. Breast milk samples were collected at 50–70 days postpartum. Breast milk fatty acid was analyzed with gas chromatography. Infant body weight, height, and head circumference were taken from medical records at birth and during study visits at 2 months. Dietary intake was assessed by trained dietitians using a 24-hour dietary recall method.

Results:

Alpha-linolenic acid (ALA, p = 0.040), docosahexaenoic acid (DHA, p = 0.019), and total n-3 fatty acid (p = 0.045) in total milk were found to be higher in normal-weight mothers compared with obese mothers. A positive association was found between C20:4 n-6 in foremilk and weight for age percentile (r = 0.381, p = 0.031; β = 29.966, p = 0.047).

Conclusions:

Prevention of prepregnancy obesity is important for future generations, as prepregnancy obesity has many adverse effects on the mother and infant and may affect the composition of breast milk.

Introduction

Obesity is an increasing societal problem affecting women of reproductive age.¹ Prepregnancy obesity increases not only the risk of maternal complications such as gestational diabetes mellitus and preeclampsia, but it also increases neonatal complications such as miscarriage, stillbirth, fetal chromosomal anomalies, preterm birth, and fetal macrosomia.^2,3 Moreover, prepregnancy obesity increases the risk of long-term health outcomes such as obesity, cognitive development deficits, cardiovascular disease, type 2 diabetes mellitus, greater all-cause mortality, and cancer in infants.⁴ Breastfeeding is among the mechanisms through which maternal obesity affects the nutritional status of infants.⁵ It also may affect breast milk fatty acid, which is critical for infants' neurodevelopment.⁶

Human breast milk, which is unique for infants, provides nutrients that support optimal growth and development during infancy.^7,8 The World Health Organization (WHO) recommends that infants should be exclusively breastfed for the first 6 months of life and they should be breastfed with complementary foods for up to 2 years and beyond.⁹ Lipids, which contribute 40–55% of the total energy of breast milk, are the largest source of energy in breast milk.¹⁰ Breast milk lipids play an important role as a source of energy and are responsible for structural and regulatory functions.¹¹ Linoleic acid (LA, C18:2 n-6) and alpha-linolenic acid (ALA, C18:3 n-3) from polyunsaturated fatty acids (PUFAs) cannot be synthesized neither by the mother nor by neonatal, so they should be taken from the diet.¹¹

Long-chain fatty acids such as arachidonic acid (ARA, C20:4 n-6), eicosapentaenoic acid (EPA, C20:5 n-3), and docosahexaenoic acid (DHA, C22:6 n-3) can be synthesized from LA and ALA by de nova synthesis in the liver, however, that synthesis is not enough to meet the requirements.^12,13 So breast milk is a source of ARA, EPA, and DHA for infants who are exclusively breastfed.¹⁴ The fatty acid profile of breast milk, especially long-chain PUFA, varies depending on the maternal diet.¹⁵ Arachidonic acid (AA), EPA, and DHA, which are PUFAs, are significant for regulating growth, immune function, inflammatory responses, motor systems, and cognitive development in infants.¹⁶

Considering the adverse effects of prepregnancy obesity on mothers and infants, it is needed to investigate how prepregnancy obesity affects the composition of breast milk and infant growth. In this context, although there are studies examining the effect of maternal body mass index (BMI) on fatty acid composition in breast milk,^5,6,11,14 there is no study that investigated the effect of maternal BMI in both foremilk and hindmilk. Thus, this study aimed to evaluate the effect of prepregnancy obesity on fatty acid profile in foremilk and hindmilk, to determine the relationship between maternal diet and fatty acids in breast milk, and to investigate the relationship between fatty acids in breast milk and infant growth.

Materials and Methods

Subjects and study design

Twenty normal-weight mothers (prepregnancy BMI: 18.50–24.99 kg/m²) and 20 obese mothers (prepregnancy BMI: ≥30 kg/m²) and their infants were recruited. Mothers were included in this study during their visit to Child Health and Diseases, Hematology, Oncology Training and Research Hospital (Ankara, Turkey) for their babies' second-month follow-up. To be eligible, mothers needed to have a healthy infant, give vaginal delivery, labor between 37th and 42nd weeks of pregnancy, labor over a 2,500-g baby, and have babies exclusively breastfed. Mothers were excluded if they had any maternal health problem, which might affect breastfeeding or study results, smoked or consumed alcohol, had a pregnancy with multiples, labored under a 2,500-g baby, had preeclampsia, or gestational diabetes history during pregnancy. A brief study questionnaire was applied to mothers through face-to-face interviews.

This study was carried out in accordance with the ethical standards recognized by the Declaration of Helsinki and all procedures were approved by the Hacettepe University Noninterventional Clinical Research Ethics Board (GO 17/843-13). Written informed consent was obtained from all participants at the beginning of the study.

Anthropometric measurements and assessment of anthropometric infant outcomes

Prepregnancy body weight and weight gain during pregnancy were recorded from patient history forms. Maternal height was measured during the interview. Infant body weight, height, and head circumference at birth were taken from medical records, and second-month assessments were measured during follow-up using infant scale, infantometer, and tape measure, respectively.

Infants' anthropometric measurements were converted to weight-for-age percentile values according to the WHO child growth standards.^17,18

Dietary record analysis

Dietary intake was assessed using a 24-hour dietary recall method at second month postpartum. Energy, fiber, percentage of carbohydrate, protein, total fat, saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), and PUFAs in total energy were calculated using the BeBIS: Nutrition Data Base Software (Istanbul, Turkey).

Breast milk collection

Breast milk samples were collected by using Medela Swing Maxi electric breast pump in plastic bottles. All bottles were cleaned in warm soapy water and sterilized after each usage. Breast milk samples were collected between 9:00 am and 11:00 am from a breast that mothers did not breastfeed lastly. Five milliliters of foremilk was collected and mothers asked to keep breastfeeding their infants for about 10 minutes, and 5 mL of hindmilk was collected afterward.¹⁹ All breast milk samples were kept in sterile plastic bags and stored at −80°C until analysis.

Fatty acid analysis of breast milk

Fatty acid analysis was performed according to the “Association of Official Agricultural Chemist official method 996.06.”²⁰ The method consisted of extraction, methylation, gas chromatography (GC) analysis, and calculation steps. Briefly, 5 mL of breast milk was thawed and placed in Mojonnier flask. To extract fat, pyrogallic acid, internal standard (triundecanoin), ethanol, and NH₄OH were added into the flask and heated in a shaking water bath for 40 minutes. After cooling to room temperature, diethyl ether and petroleum ether were added and shaken in a wrist shaker for 20 minutes. Then the mixture was left at room temperature for 1 hour for layer separation. The top layer that contained fat was collected and evaporated under fume hood with N₂ steam. Extracted fat was methylated by BF₃ and toluene in an oven at 100°C for 45 minutes.

After cooling to room temperature, hexane, double-distilled H₂O, and Na₂SO₄ were added and fatty acid methyl ester containing layer was collected into GC vials for analysis.

A Thermo Finnigan GC trace equipped with a flame ionization detector, an autosampler, and a Supelco 2560 fused-silica capillary column (100 m × 0.25 mm internal diameter, 0.2 μm film thickness) was used for analysis. Individual fatty acid peaks were identified and quantified by comparing their retention times with the Supelco 37 component FAME mix standard mixture. The analytical average of foremilk and hindmilk was given as “total” fatty acids. Results were shown as a percentage in total fatty acid (% w/w).⁵

Statistical analysis

All analyses were completed using Statistical Package for the Social Sciences (SPSS) version 23.0 software. Descriptive statistical variables are presented as mean ( $\bar{X}$ ), standard deviation, minimum and maximum values. Mann–Whitney U test was used to examine the differences between normal-weight and obese mothers. Correlation analyses were performed with the Spearmen correlation test. To examine the association between fatty acids in breast milk and percentile of infants, the data were adjusted for maternal age, education, prepregnancy BMI, gestational weight gain, and parity. The results were considered statistically significant when p < 0.05 in 95% confidence interval.

Results

The characteristics of mothers and infants are presented in Table 1. Obese mothers had significantly higher parity than normal-weight mothers (p = 0.009). Although prepregnancy BMI was significantly higher in obese mothers (p = 0.000), gestational weight gain did not differ between groups (p > 0.05). There was no significant difference between the characteristics of infants according to maternal prepregnancy BMI (p > 0.05).

Table 1.

Characteristics of Mothers and Infants

	Normal weight (n = 20)	Obese (n = 20)
	$\bar{x}$ ± SD (minimum to maximum)	$\bar{x}$ ± SD (minimum to maximum)	p
Mothers
Age (years)	27.1 ± 4.5 (19.0 to 34.0)	29.5 ± 5.3 (20.0 to 35.0)	0.125
Parity	1.7 ± 0.8 (1.0 to 3.0)	2.4 ± 0.7 (1.0 to 3.0)	0.009^a
Prepregnancy BMI (kg/m²)	22.7 ± 2.0 (18.7 to 24.9)	31.8 ± 2.7 (30.1 to 40.2)	0.000^a
Gestational weight gain (kg)	7.1 ± 5.3 (1.0 to 23.0)	3.7 ± 5.8 (−12.0 to 11.0)	0.146
Infants
Gestational age (weeks)	39.0 (37.0 to 42.0)	38.0 (37.0 to 40.0)	0.073
Gender (male/female)	11/9	7/13	0.257
Birth
Weight (g)	3,310.8 ± 354.3 (2,640.0 to 4,140.0)	3,323.0 ± 337.4 (2,800.0 to 3,860.0)	0.850
Length (cm)	49.9 ± 1.5 (46.0 to 52.0)	50.7 ± 1.6 (48.0 to 54.0)	0.215
Head circumference (cm)	34.9 ± 1.4 (32.0 to 37.0)	34.8 ± 1.6 (32.0 to 37.5)	0.764
Second month
Weight (g)	5,449.0 ± 787.4 (4,000.0 to 6,900.0)	5,754.5 ± 671.0 (4,670.0 to 7,000.0)	0.285
Length (cm)	57.8 ± 3.3 (51.0 to 62.5)	58.2 ± 2.3 (54.0 to 62.0)	0.838
Head circumference (cm)	39.9 ± 0.9 (38.0 to 41.5)	39.4 ± 1.7 (36.5 to 42.0)	0.327

Bold values indicates statistical significance (p < 0.05).

p < 0.05.

$\bar{x}$ , mean; BMI, body mass index; SD, standard deviation.

Mothers' energy and macronutrient intake at the second month of lactation are presented in Table 2. While no group differences in energy, carbohydrates, proteins, total fat, SFA, MUFA, and PUFA intake were observed, fiber intake was significantly higher in obese mothers than in normal-weight mothers (p = 0.027).

Table 2.

Mothers' Energy and Macronutrient Intake, as Determined from the 24-Hour Dietary Recall at the Second Month of Lactation

Energy and macronutrient intake	Normal weight (n = 20), $\bar{x}$ ± SD (minimum to maximum)	Obese (n = 20), $\bar{x}$ ± SD (minimum to maximum)	p
Energy (kcal)	2,084.9 ± 512.3 (1,032.0 to 3,069.5)	2,363.9 ± 485.8 (1,834.9 to 3,246.6)	0.234
Carbohydrates (%E)	49.1 ± 9.8 (23.0 to 63.0)	50.4 ± 9.0 (32.0 to 65.0)	0.725
Proteins (%E)	13.3 ± 3.1 (7.0 to 19.0)	14.1 ± 3.3 (9.0 to 20.0)	0.605
Total fat (%E)	35.0 ± 8.1 (18.0 to 48.0)	35.6 ± 6.7 (23.0 to 49.0)	0.957
SFA (%E)	11.8 ± 4.4 (5.0 to 24.5)	11.2 ± 3.5 (6.3 to 19.1)	0.665
MUFA (%E)	12.9 ± 3.3 (8.3 to 17.8)	12.9 ± 3.5 (7.3 to 21.0)	0.892
PUFA (%E)	8.4 ± 2.9 (4.4 to 14.3)	8.6 ± 2.1 (5.6 to 13.2)	0.607
Fiber (g)	20.3 ± 7.0 (11.0 to 34.2)	25.3 ± 7.1 (12.3 to 41.3)	0.027^a

Bold values indicates statistical significance (p < 0.05).

p < 0.05.

$\bar{x}$ , mean; MUFA, monounsaturated fatty acid; PUFA, polyunsaturated fatty acid; SD, standard deviation; SFA, saturated fatty acid.

Breast milk fatty acid profile according to maternal prepregnancy BMI is presented in Table 3. When total milk was compared, C20:3 n-6 (p = 0.030), C20:4 n-6 (p = 0.042), total n-3 (p = 0.045), C18:3 n-3 (p = 0.040), and C22:6 n-3 (p = 0.019) were found significantly higher in normal-weight mothers than in obese mothers. The foremilk of normal-weight mothers had significantly higher C20:3 n-6 (p = 0.015), total n-3 (p = 0.045), and C22:6 n-3 (p = 0.044) than those of foremilk of obese mothers. Total MUFAs in foremilk of obese mothers were higher than that of normal-weight mothers (p = 0.020). In addition, foremilk (p = 0.032), hindmilk (p = 0.015), and total milk (p = 0.004) of obese mothers had higher C16:1 n-7 than that of normal-weight mothers.

Table 3.

Breast Milk Fatty Acid Profile According to Maternal Prepregnancy Body Mass Index

	Normal weight (n = 20)			Obese (n = 20)
	Foremilk	Hindmilk	Total	Foremilk	Hindmilk	Total
Fatty acids	$\bar{x}$ ± SD (minimum to maximum)	$\bar{x}$ ± SD (minimum to maximum)	$\bar{x}$ ± SD (minimum to maximum)	$\bar{x}$ ± SD (minimum to maximum)	$\bar{x}$ ± SD (minimum to maximum)	$\bar{x}$ ± SD (minimum to maximum)
Total SFA	35.99 ± 6.27 (26.81 to 47.02)	39.39 ± 4.94 (28.88 to 47.22)	37.69 ± 5.10 (30.13 to 44.58)	35.41 ± 6.04^a (16.71 to 43.86)	38.46 ± 5.01^a (20.53 to 44.42)	36.94 ± 5.19 (18.62 to 43.65)
C14:0	5.68 ± 2.08 (3.16 to 10.62)	6.35 ± 2.14 (3.46 to 11.30)	6.02 ± 1.99 (3.31 to 10.62)	4.90 ± 1.72^a (1.55 to 8.40)	5.78 ± 1.38^a (3.98 to 9.09)	5.34 ± 1.49 (3.31 to 8.68)
C16:0	14.38 ± 3.67^b (9.98 to 23.05)	17.85 ± 3.48^b (13.22 to 28.33)	16.12 ± 3.34 (12.15 to 25.48)	15.16 ± 4.7 (0.00 to 22.17)	16.57 ± 5.13 (0.00 to 23.61)	15.87 ± 4.74 (0.00 to 22.89)
C18:0	4.22 ± 0.75^b (2.96 to 5.91)	5.25 ± 0.88^b (4.21 to 7.95)	4.73 ± 0.69 (3.58 to 6.41)	4.34 ± 1.33 (0.00 to 6.17)	4.68 ± 1.54 (0.00 to 7.89)	4.51 ± 1.37 (0.00 to 6.23)
Total MUFA	29.42 ± 4.52^c (22.62 to 39.22)	31.46 ± 3.42 (23.74 to 36.37)	30.44 ± 3.72 (23.18 to 36.14)	33.63 ± 6.16^c (23.37 to 49.19)	32.53 ± 5.53 (26.52 to 53.65)	33.08 ± 5.29 (27.14 to 51.42)
C16:1 (n-7)	0.50 ± 0.40^b,c (0.00 to 1.38)	1.19 ± 0.61^b,d (0.31 to 2.48)	0.84 ± 0.40^e (0.16 to 1.81)	1.75 ± 3.14^c (0.00 to 14.56)	2.06 ± 2.07^d (0.32 to 10.51)	1.91 ± 2.57^e (0.54 to 12.54)
C18:1 (n-9)	27.65 ± 3.81 (21.57 to 35.05)	28.79 ± 3.39 (22.08 to 34.77)	28.22 ± 3.42 (21.83 to 33.42)	29.33 ± 3.31 (23.37 to 35.17)	28.01 ± 3.14 (18.48 to 34.34)	28.67 ± 2.80 (22.86 to 34.01)
Total PUFA	31.13 ± 7.00^b (18.94 to 44.53)	26.18 ± 5.50^b (16.80 to 35.97)	28.65 ± 5.52 (18.74 to 40.00)	27.98 ± 5.74 (17.09 to 41.35)	25.09 ± 4.34 (18.80 to 31.17)	26.53 ± 4.66 (17.94 to 34.35)
Total n-6	25.36 ± 4.80 (17.16 to 33.50)	25.83 ± 5.65 (16.56 to 35.97)	25.59 ± 5.17 (16.86 to 34.57)	24.70 ± 4.32 (16.81 to 31.32)	24.83 ± 4.34 (18.41 to 31.06)	24.77 ± 4.09 (17.61 to 31.19)
C18:2 (n-6)	23.85 ± 4.62 (15.71 to 32.03)	24.16 ± 5.47 (15.52 to 34.44)	24.01 ± 5.00 (15.61 to 33.05)	23.54 ± 4.23 (16.09 to 30.53)	23.25 ± 4.10 (16.34 to 30.06)	23.39 ± 3.97 (16.22 to 30.30)
C18:3 (n-6)	0.22 ± 0.17 (0.00 to 0.50)	0.27 ± 0.19 (0.09 to 0.92)	0.25 ± 0.12 (0.08 to 0.54)	0.18 ± 0.18 (0.00 to 0.77)	0.17 ± 0.12 (0.00 to 0.39)	0.18 ± 0.13 (0.00 to 0.58)
C20:2 (n-6)	0.23 ± 0.19^b (0.00 to 0.47)	0.38 ± 0.10^b (0.18 to 0.54)	0.31 ± 0.12 (0.09 to 0.47)	0.26 ± 0.21 (0.00 to 0.56)	0.33 ± 0.15 (0.00 to 0.67)	0.30 ± 0.14 (0.00 to 0.58)
C20:3 (n-6)	0.54 ± 0.21^c (0.00 to 0.83)	0.53 ± 0.15 (0.33 to 0.87)	0.53 ± 0.15^e (0.18 to 0.76)	0.28 ± 0.31^a,c (0.00 to 0.77)	0.51 ± 0.19^a (0.00 to 0.78)	0.40 ± 0.21^e (0.00 to 0.77)
C20:4 (n-6)	0.50 ± 0.21 (0.00 to 0.87)	0.46 ± 0.13 (0.25 to 0.71)	0.48 ± 0.15^e (0.18 to 0.79)	0.29 ± 0.31 (0.00 to 0.74)	0.43 ± 0.20 (0.00 to 0.67)	0.36 ± 0.19^e (0.00 to 0.69)
Total n-3	5.77 ± 6.24^b,c (0.39 to 20.89)	0.35 ± 0.26^b (0.00 to 1.08)	3.06 ± 3.15^e (0.24 to 10.63)	3.28 ± 4.88^a,c (0.00 to 20.49)	0.25 ± 0.16^a (0.00 to 0.51)	1.77 ± 2.45^e (0.00 to 10.37)
C18:3 (n-3)	0.52 ± 0.29^b (0.00 to 1.13)	0.23 ± 0.25^b (0.00 to 1.03)	0.38 ± 0.19^e (0.05 to 0.75)	0.34 ± 0.32 (0.00 to 1.13)	0.16 ± 0.10 (0.00 to 0.32)	0.25 ± 0.17^e (0.00 to 0.67)
C20:5 (n-3)	1.30 ± 3.35 (0.00 to 13.36)	0.04 ± 0.04 (0.00 to 0.12)	0.67 ± 1.68 (0.00 to 6.71)	2.39 ± 4.85^a (0.00 to 20.49)	0.03 ± 0.04^a (0.00 to 0.13)	1.21 ± 2.43 (0.00 to 10.28)
C22:6 (n-3)	3.95 ± 6.32^c (0.00 to 20.89)	0.08 ± 0.06 (0.00 to 0.16)	2.01 ± 3.16^e (0.00 to 10.50)	0.55 ± 1.64^c (0.00 to 6.46)	0.06 ± 0.09 (0.00 to 0.36)	0.31 ± 0.83^e (0.00 to 3.28)
n-6/n-3 ratio	16.96 ± 20.25^b (0.99 to 83.96)	84.82 ± 77.17^b (17.67 to 366.67)	50.94 ± 46.86 (9.82 to 225.31)	24.17 ± 23.78^a (1.02 to 62.45)	83.69 ± 24.96^a (39.16 to 116.38)	49.82 ± 13.53 (27.64 to 75.27)

Bold values indicates statistical significance (p < 0.05).

p < 0.05 Differences between foremilk and hindmilk in obese mothers are expressed.

p < 0.05 Differences between foremilk and hindmilk in normal-weight mothers are expressed.

p < 0.05 Differences between normal-weight and obese mothers in foremilk are expressed.

p < 0.05 Differences between normal-weight and obese mothers in hindmilk are expressed.

p < 0.05 Differences between normal-weight and obese mothers in total milk are expressed.

$\bar{x}$ , mean; MUFA, monounsaturated fatty acid; PUFA, polyunsaturated fatty acid; SD, standard deviation; SFA, saturated fatty acid.

While total PUFAs (p = 0.037), total n-3 (p = 0.000), and C18:3 n-3 (p = 0.001) were significantly higher in foremilk compared with hindmilk in normal-weight mothers, C16:0 (p = 0.001), C18:0 (p = 0.000), C16:1 (p = 0.000), C20:2 n-6 (p = 0.017), and n-6/n-3 ratio (p = 0.000) were significantly lower. Whereas total n-3 (p = 0.002) and C20:5 n-3 (p = 0.029) were significantly higher in foremilk compared with hindmilk in obese mothers, total SFA (p = 0.042), C14:0 (p = 0.033), C20:3 n-6 (p = 0.029), and n-6/n-3 ratio (p = 0.000) were significantly lower. Regardless of maternal prepregnancy BMI, total n-3 was found to be higher in foremilk (p = 0.000 and p = 0.002, respectively) and the n-6/n-3 ratio (p = 0.000 and p = 0.000, respectively) was found to be higher in hindmilk of both normal-weight and obese mothers.

Correlation between dietary intake parameters (energy, carbohydrates, proteins, total fat, SFA, MUFA, and PUFA) and lipid profile in breast milk at the second month of lactation is shown in Table 4. While MUFA in hindmilk decreased as dietary carbohydrate intake increased (r = −0.339, p = 0.032), MUFA in hindmilk increased as dietary protein intake increased (r = 0.352, p = 0.026).

Table 4.

Correlation Between Dietary Intake Parameters and Lipid Profile in Breast Milk at the Second Month of Lactation

Breast milk fatty acid	Dietary intake
	Energy (kcal)		CHO (%E)		PRO (%E)		Fat (%E)		SFA (%E)		MUFA (%E)		PUFA (%E)
	r	p	r	p	r	p	r	p	r	p	r	p	r	p
Foremilk
C18:3 (n-3)	−0.068	0.677	−0.212	0.189	0.179	0.268	0.302	0.058	0.279	0.081	0.233	0.148	0.012	0.941
C18:2 (n-6)	−0.083	0.609	0.251	0.118	−0.172	0.288	−0.030	0.852	−0.339	0.032^a	−0.120	0.459	0.333	0.036^a
C20:4 (n-6)	−0.157	0.334	0.260	0.105	0.003	0.983	−0.180	0.267	−0.140	0.389	−0.229	0.156	−0.136	0.401
C20:5 (n-3)	0.094	0.563	−0.278	0.083	0.194	0.230	0.311	0.051	0.347	0.028^a	0.204	0.208	0.054	0.742
C22:6 (n-3)	−0.035	0.830	0.125	0.442	−0.144	0.377	−0.222	0.168	−0.091	0.577	−0.103	0.528	−0.121	0.457
n-6	−0.123	0.449	0.291	0.069	−0.190	0.239	−0.073	0.654	−0.356	0.024^a	−0.150	0.356	0.269	0.093
n-3	0.036	0.824	−0.289	0.071	−0.023	0.887	0.248	0.123	0.344	0.030^a	0.229	0.156	0.039	0.811
n-6/n-3	−0.029	0.867	0.193	0.260	0.053	0.757	−0.100	0.561	−0.288	0.088	−0.106	0.540	0.039	0.822
SFA	−0.065	0.688	0.207	0.199	−0.117	0.472	−0.285	0.075	−0.067	0.683	−0.294	0.066	−0.295	0.065
MUFA	−0.070	0.669	−0.254	0.113	0.242	0.132	0.160	0.323	0.103	0.528	0.302	0.058	0.036	0.825
PUFA	0.070	0.668	0.010	0.953	−0.144	0.374	0.172	0.287	−0.016	0.924	0.038	0.817	0.246	0.125
Hindmilk
C18:3 (n-3)	0.197	0.223	−0.223	0.166	0.67	0.682	0.252	0.117	0.386	0.014^a	0.158	0.331	−0.012	0.940
C18:2 (n-6)	−0.096	0.554	0.224	0.164	−0.214	0.185	0.027	0.870	−0.256	0.110	−0.095	0.558	0.302	0.058
C20:4 (n-6)	−0.029	0.859	0.203	0.210	0.078	0.631	−0.106	0.513	−0.124	0.446	−0.337	0.033^a	0.197	0.222
C20:5 (n-3)	0.085	0.604	−0.064	0.695	0.156	0.335	0.033	0.841	0.226	0.161	−0.012	0.940	−0.114	0.485
C22:6 (n-3)	−0.118	0.469	0.198	0.222	0.286	0.074	−0.281	0.080	−0.153	0.347	−0.362	0.022^a	−0.253	0.115
n-6	−0.081	0.619	0.228	0.158	−0.209	0.195	0.024	0.885	−0.246	0.125	−0.114	0.483	0.307	0.054
n-3	0.122	0.453	−0.037	0.819	0.169	0.297	0.081	0.620	0.231	0.151	−0.064	0.696	−0.165	0.309
n-6/n-3	−0.255	0.153	0.125	0.489	−0.053	0.768	−0.105	0.562	−0.255	0.153	−0.108	0.550	0.256	0.151
SFA	−0.018	0.913	0.087	0.593	−0.054	0.743	−0.271	0.091	0.102	0.529	−0.195	0.227	−0.394	0.012^a
MUFA	−0.135	0.405	−0.339	0.032^a	0.352	0.026^a	0.144	0.375	0.180	0.268	0.305	0.056	−0.067	0.680
PUFA	−0.081	0.617	0.222	0.169	−0.208	0.197	0.031	0.848	−0.239	0.138	−0.113	0.486	0.314	0.049^a

Bold values indicates statistical significance (p < 0.05).

Spearmen correlation analysis.

p < 0.05.

CHO, carbohydrate; MUFA, monounsaturated fatty acid; PRO, protein; PUFA, polyunsaturated fatty acid; SFA, saturated fatty acid.

Whereas there was a negative correlation between dietary SFA intake and C18: 2 n-6 and total n-6 in foremilk (r = −0.339, p = 0.032 and r = −0.356, p = 0.024, respectively), there was a positive correlation between dietary SFA intake and C20:5 n-3 and total n-3 in foremilk (r = 0.347, p = 0.028 and r = 0.344, p = 0.030, respectively). Moreover, a positive correlation was found between dietary SFA intake and C18:3 n-3 in foremilk (r = 0.386, p = 0.014). There was a negative correlation between dietary MUFA intake and C20:4 n-6 and C22:6 n-3 in hindmilk (r = −0.337, p = 0.033 and r = −0.362, p = 0.022, respectively).

While there was a negative correlation between dietary PUFA intake and SFA in hindmilk (r = −0.394, p = 0.012), a positive correlation was found between dietary PUFA intake and PUFA in hindmilk and C18:2 n-6 in foremilk (r = 0.314, p = 0.049 and r = 0.333, p = 0.036, respectively).

All associations were observed after adjusting for potential confounders, which included maternal age, education, prepregnancy BMI, gestational weight gain, and parity in Table 5. A positive association was found between C20:4 n-6 in foremilk and weight-for-age percentile values (r = 0.381, p = 0.031; β = 29.966, p = 0.047).

Table 5.

Associations Between Breast Milk Fatty Acids and Infants' Percentile Scores at the Second Month

Fatty acid	Weight for age
	Foremilk				Hindmilk
	β	p	r	p	β	p	r	p
C18:3 (n-3)	2.680	0.848	0.018	0.924	14.976	0.543	0.132	0.495
C18:2 (n-6)	−0.403	0.685	−0.057	0.758	−0.456	0.607	−0.048	0.805
C20:4 (n-6)	29.966	0.047^a	0.381	0.031^a	−11.720	0.651	−0.155	0.423
C20:5 (n-3)	−0.493	0.623	−0.128	0.487	−9.812	0.932	0.019	0.921
C22:6 (n-3)	−0.682	0.465	−0.080	0.665	18.224	0.757	0.055	0.776
n-6/n-3	0.022	0.915	0.020	0.915	−0.014	0.867	−0.032	0.867
SFA	0.807	0.239	0.043	0.817	1.075	0.245	−0.020	0.916
MUFA	0.065	0.934	0.207	0.255	−0.648	0.508	0.100	0.606
PUFA	−0.625	0.339	−0.152	0.406	−0.404	0.635	−0.048	0.803

Bold values indicates statistical significance (p < 0.05).

Spearmen correlation and linear regression analysis. β, r, and p are corrected values after adjustment for potential confounders: maternal age, education, prepregnancy BMI, gestational weight gain, and parity.

p < 0.05.

BMI, body mass index; MUFA, monounsaturated fatty acid; PUFA, polyunsaturated fatty acid; SFA, saturated fatty acid.

Discussion

This study found significant differences in fatty acid profile in foremilk and hindmilk of obese and normal-weight mothers. ALA, DHA, and total n-3 fatty acids in total milk were found to be higher in normal-weight mothers compared with obese mothers. Moreover, total n-3 fatty acids in foremilk and n-6/n-3 ratio in hindmilk were found to be higher in both obese and normal-weight mothers. In addition, dietary carbohydrate intake was negatively correlated with MUFA in hindmilk, while dietary protein intake was positively correlated with MUFA in hindmilk. While there was a positive correlation between dietary SFA intake and total n-3 in foremilk, a negative correlation was found between dietary SFA intake and total n-6 in foremilk. As PUFA intake in the diet increases, PUFA in hindmilk increases, while SFA in hindmilk decreases. Furthermore, ARA in foremilk was positively associated with weight-for-age percentile values.

The study of Mäkelä et al.¹⁴ compared breast milk collected at the third month of lactation; while total n-3 and DHA in breast milk were found to be lower in overweight mothers (prepregnancy BMI ≥25 kg/m²) than in normal-weight mothers (prepregnancy BMI <25 kg/m²), no significant difference was observed in ALA. In another study, while DHA and EPA were found to be lower in overweight mothers than in normal-weight mothers, there was no significant difference in total n-3 fatty acid between groups.²¹ In a study examining breast milk of 21 obese (prepregnancy BMI ≥30 kg/m²) and 21 normal-weight mothers (prepregnancy BMI 18–25 kg/m²) in the second month of lactation, total SFA, total MUFA, and total n-6 fatty acids did not differ between groups. Nevertheless, total n-3, ALA, EPA, and DHA were found to be lower in obese mothers than in normal-weight mothers.⁶

In this study, similar to previous studies, total n-3, DHA, and ALA were found to be higher in normal-weight mothers than in obese mothers. Fatty acid profile in breast milk changed and it was thought that related changes occurred due to differences in the mobilization of endogenous fatty acid stores and differences in synthesis in the maternal liver and breast tissue with maternal obesity or maternal dietary differences.³

Even though it is known that the fat content in hindmilk is approximately two to three times that of foremilk,^22,23 there are no studies comparing the percentage of fatty acids in foremilk and hindmilk in obese and normal-weight mothers. In a study in South African lactating women, after maternal age, BMI, number of children, infant age, and gender were added as covariates, while total n-3 PUFA was found to be higher in hindmilk than in foremilk, and the n-6/n-3 PUFA ratio was found to be lower.²⁴ In this study, while total n-3 was found to be higher in foremilk than in hindmilk in both normal-weight and obese mothers, the n-6/n-3 ratio was found to be lower in both groups.

Fatty acids in breast milk are endogenously synthesized by the mammary gland or taken from maternal plasma, and both of these fatty acid sources may change due to maternal diet.^10,15 Maternal diet has been reported to affect fatty acid profile in breast milk, but the effect is not clear.²⁵ In a previous study, a negative correlation was found between carbohydrate intake in maternal diet and MUFA in breast milk.¹¹ In our study, a negative correlation was shown between carbohydrate intake and MUFA in hindmilk. In addition, SFA intake was negatively correlated with n-6 in foremilk and positively correlated with n-3 in foremilk.

Although the reason could not be exactly explained, it was thought that the fatty acid composition of breast milk was affected not only by maternal diet but also by maternal stores. In addition, it was thought that a 24-hour dietary recall may not fully reflect the diet pattern of mothers.

In another study, it has been shown that SFA and MUFA in maternal diet are associated with SFA and MUFA in transitional milk, and maternal dietary PUFA is associated with PUFA in mature milk.¹² In a study investigating fatty acids in breast milk at fifth week postpartum and fatty acid pattern of maternal diet, it was shown that the n-3/n-6 ratio in maternal diet during lactation may affect PUFA composition in breast milk.²⁶ A study conducted on Greek women stated that maternal PUFA intake was positively correlated with total PUFA, total n-3, DHA, and LA in breast milk at the first month postpartum.²⁷ In our findings, a positive correlation was found between maternal dietary PUFA and PUFA in breast milk.

The fatty acid profile of breast milk, especially PUFA content, has great importance for the growth and development of infants who are exclusively breastfed.^28,29 In our study, weight-for-age percentile values were used to accurately evaluate the growth of the infant and the relationship between fatty acids in breast milk (50–70 days), and percentile values were examined. Our findings showed a positive association between ARA in foremilk and weight-for-age percentile values. In a study examining the relationship between fatty acids in breast milk and infant growth, while infant BMI for age at 6 months was inversely associated with colostrum (2–4 days) AA and DHA and positively associated with n-6/n-3 ratio, no significant association was found between fatty acids in mature milk (28–32 days) and infant growth.⁵

In another study, it was shown that DHA, EPA, and n-3 PUFA at 6-week postpartum early breast milk were positively related to the sum of four skinfold thickness measurements at the 12th month. Moreover, breast milk ARA at 6 weeks postpartum was negatively associated with weight, BMI, and lean body mass up to 4 months postpartum. Based on these results, they stated that n-3 PUFA in breast milk was shown to stimulate fat mass growth over the first year of life, while ARA seems to be involved in the regulation of overall growth, especially in the early postpartum period.³⁰ While breast milk SFA in the postpartum third month was positively correlated weight gain and BMI increase of a 13-month-old child, no significant correlation was found with n-6 fatty acids and anthropometric measurements of the child.¹⁴

Total n-6 PUFA in breast milk at 4–8 weeks postpartum showed a negative correlation with both infant weight and percentage of fat mass.³¹ In another study, no significant association was found between n-6 PUFA and infant growth.³² There is no general consensus on the results of the studies conducted and it is thought that the reasons for this are a collection of breast milk at different times (such as colostrum and mature milk), different ways (such as percentile values, weight, and skinfold thickness), and at different times (such as age of 3, 6, and 13 months) of infant growth.

There are some limitations to our study. Because of ethical reasons, the fatty acid composition in the erythrocytes of infants could not be examined. Also, our dietary history was limited to 24-hour dietary recall.

Conclusions

Prepregnancy obesity changed fatty acid profile in foremilk, hindmilk, and total milk. ALA, DHA, and total n-3 were found to be higher in normal-weight mothers compared with obese mothers. Regardless of maternal BMI, total n-3 was higher in foremilk, while the n-6/n-3 ratio was higher in hindmilk in both groups. Maternal diet affected the fatty acid profile of breast milk. Moreover, ARA in foremilk was positively associated with infant growth. Within the scope of all these results, prevention of prepregnancy obesity is important for future generations, as prepregnancy obesity has many adverse effects on the mother and infant and may affect the composition of breast milk.

Footnotes

Acknowledgments

The authors would like to thank all the volunteers for the participation in this study.

Authors' Contributions

T.T-G. and M.F. reviewed the literature, designed the study, collected the data, carried out laboratory and data analyses, interpreted the data, and wrote the draft and final version of the article. N.K. and A.K-U. contributed to the data collection and drafted the article. All the authors critically reviewed and approved the final version of the article.

Disclosure Statement

No competing financial interests exist.

Funding Information

This study was supported by the Scientific and Technological Research Council of Turkey (TUBITAK; grant No. 317S038).

References

Poston

, Caleyachetty

, Cnattingius

, et al. Preconceptional and maternal obesity: Epidemiology and health consequences. Lancet Diabetes Endocrinol, 2016; 4(12):1025–1036.

, Han

, Zhu

, et al. Pre-pregnancy body mass index in relation to infant birth weight and offspring overweight/obesity: A systematic review and meta-analysis. PLoS One, 2013; 8(4):e61627.

Álvarez

, Muñoz

, Ortiz

, et al. Impact of maternal obesity on the metabolism and bioavailability of polyunsaturated fatty acids during pregnancy and breastfeeding. Nutrients, 2020; 13(1):19.

Wilson

, Messaoudi

. The impact of maternal obesity during pregnancy on offspring immunity. Mol Cell Endocrinol, 2015; 418(Pt 2):134–142.

de la Garza Puentes

, Martí Alemany

, Chisaguano

, et al. The effect of maternal obesity on breast milk fatty acids and its association with infant growth and cognition—The PREOBE follow-up. Nutrients, 2019; 11(9):2154.

Panagos

, Vishwanathan

, Penfield-Cyr

, et al. Breastmilk from obese mothers has pro-inflammatory properties and decreased neuroprotective factors. J Perinatol, 2016; 36(4):284–290.

Lyons

, Ryan

, Dempsey

, et al. Breast milk, a source of beneficial microbes and associated benefits for infant health. Nutrients, 2020; 12(4):1039.

Cacho

, Lawrence

. Innate immunity and breast milk. Front Immunol, 2017; 8:584.

World Health Organization. Breastfeeding. Available from: https://www.who.int/health-topics/breastfeeding#tab=tab_2 [Last accessed: May 15, 2021].

10.

Andreas

, Kampmann

, Mehring Le-Doare

. Human breast milk: A review on its composition and bioactivity. Early Hum Dev, 2015; 91(11):629–635.

11.

Kim

, Kang

, Jung

, et al. Breast milk fatty acid composition and fatty acid intake of lactating mothers in South Korea. Br J Nutr, 2017; 117(4):556–561.

12.

Scopesi

, Ciangherotti

, Lantieri

, et al. Maternal dietary PUFAs intake and human milk content relationships during the first month of lactation. Clin Nutr, 2001; 20(5):393–397.

13.

Uauy

, Mena

, Rojas

. Essential fatty acids in early life: Structural and functional role. Proc Nutr Soc, 2000; 59(1):3–15.

14.

Mäkelä

, Linderborg

, Niinikoski

, et al. Breast milk fatty acid composition differs between overweight and normal weight women: The STEPS Study. Eur J Nutr, 2013; 52(2):727–735.

15.

Ballard

, Morrow

. Human milk composition: Nutrients and bioactive factors. Pediatr Clin North Am, 2013; 60(1):49–74.

16.

Martin

, Ling

, Blackburn

. Review of infant feeding: Key features of breast milk and infant formula. Nutrients, 2016; 8(5):279.

17.

Borghi

, de Onis

, Garza

, et al. Construction of the World Health Organization child growth standards: Selection of methods for attained growth curves. Stat Med 30, 2006; 25(2):247–265.

18.

Duggan

. Anthropometry as a tool for measuring malnutrition: Impact of the new WHO growth standards and reference. Ann Trop Paediatr, 2010; 30(1):1–17.

19.

Schueler

, Alexander

, Hart

, et al. Presence and dynamics of leptin, GLP-1, and PYY in human breast milk at early postpartum. Obesity (Silver Spring), 2013; 21(7):1451–1458.

20.

Mossoba

, Kramer

, Delmonte

, et al. AOAC Official Method 996.06, Fat (Total, Saturated, and Unsaturated in Foods), Hydrolytic Extraction Gas Chromatographic Method, First Action 1996, Revised 2001. AOCS Press: Urbana, IL; 2003.

21.

García-Ravelo

, Díaz-Gómez

, Martín

, et al. Fatty acid composition and eicosanoid levels (LTE(4) and PGE(2)) of human milk from normal weight and overweight mothers. Breastfeed Med, 2018; 13(10):702–710.

22.

Saarela

, Kokkonen

, Koivisto

. Macronutrient and energy contents of human milk fractions during the first six months of lactation. Acta Paediatr, 2005; 94(9):1176–1181.

23.

Marangoni

, Agostoni

, Lammardo

, et al. Polyunsaturated fatty acid concentrations in human hindmilk are stable throughout 12-months of lactation and provide a sustained intake to the infant during exclusive breastfeeding: An Italian study. Br J Nutr, 2000; 84(1):103–109.

24.

Siziba

, Chimhashu

, Siro

, et al. Breast milk and erythrocyte fatty acid composition of lactating women residing in a peri-urban South African township. Prostaglandins Leukot Essent Fatty Acids, 2020; 156:102027.

25.

Bravi

, Wiens

, Decarli

, et al. Impact of maternal nutrition on breast-milk composition: A systematic review. Am J Clin Nutr, 2016; 104(3):646–662.

26.

Nishimura

, Barbieiri

, Castro

, et al. Dietary polyunsaturated fatty acid intake during late pregnancy affects fatty acid composition of mature breast milk. Nutrition, 2014; 30(6):685–689.

27.

Antonakou

, Skenderi

, Chiou

, et al. Breast milk fat concentration and fatty acid pattern during the first six months in exclusively breastfeeding Greek women. Eur J Nutr, 2013; 52(3):963–973.

28.

Lauritzen

, Carlson

. Maternal fatty acid status during pregnancy and lactation and relation to newborn and infant status. Matern Child Nutr, 2011; 7(Suppl 2):41–58.

29.

Innis

. Impact of maternal diet on human milk composition and neurological development of infants. Am J Clin Nutr, 2014; 99(3):734s–741s.

30.

Much

, Brunner

, Vollhardt

, et al. Breast milk fatty acid profile in relation to infant growth and body composition: Results from the INFAT study. Pediatr Res, 2013; 74(2):230–237.

31.

Nuss

, Altazan

, Zabaleta

, et al. Maternal pre-pregnancy weight status modifies the influence of PUFAs and inflammatory biomarkers in breastmilk on infant growth. PLoS One, 2019; 14(5):e0217085.

32.

Criswell

, Iszatt

, Demmelmair

, et al. Predictors of human milk fatty acids and associations with infant growth in a Norwegian birth cohort. Nutrients, 2022; 14(18):3858.