Breastfeeding is the optimal source of nutrition for infants, supporting their healthy development. Maternal diet during breastfeeding is associated with human milk (HM) composition and may provide an opportunity to reduce infants’ risk of conditions such as eczema and food allergies. Thus, it is critical to understand changes in maternal diet during the postpartum period.
Aims
To explore maternal diet variation during lactation.
Methods
In a nested substudy within the PRIMA birth cohort, maternal diet was assessed using food frequency questionnaires (FFQs) at two and four months postpartum. Changes in food groups and nutrients over time were examined using a linear mixed model, considering breastfeeding and feeding practices and work status.
Results
FFQs were obtained from 226 healthy lactating mothers, of whom 170 filled out the complete FFQs at both time points. Mothers adhered to the Dutch dietary guidelines, with a mean ± standard deviation decrease in energy intake at four months compared with two months postpartum (2106 ± 616 vs. 2220 ± 621 kcal/day; p < 0.05). We found no differences in intake for most food groups, adjusted for energy intake, over time. Intake of alcoholic beverages increased from two to four months postpartum (p < 0.001). Consumption of food groups containing major food allergens was stable for eggs, nuts, and seeds, whereas intake of milk and milk products decreased over time (p < 0.01). Milk and milk product intake was dependent on breastfeeding and feeding practices, with exclusively breastfeeding mothers consuming less than mothers who combined breastfeeding with formula feeding (p < 0.001), independent of timing.
Conclusion
Postpartum diets of mostly highly educated women are relatively stable, except for changes in the intake of specific food groups, and correlate with breastfeeding and feeding practices. These shifts should be considered when studying maternal diet’s association with HM composition, specifically with regard to maternal allergen intake and its potential effect on infants’ risk of allergies.
Human milk (HM) provides optimal nutrition for infants, supporting their healthy development. During the lactation period, the nutritional needs of mothers with regard to additional energy and most nutrients are considerable and essential for the health of both mother and infant [1]. For example, the energy required for the production of 1 L milk is estimated to be around 700 kcal, and the total milk production over four months of lactation reflects the energy equivalent needed during pregnancy [2, 3]. In addition, the maternal diet is associated with the composition of HM [4, 5]. Both maternal polyunsaturated fatty acids (PUFAs) and docosahexaenoic acid—obtained through, for example, fish consumption—are linked to their corresponding levels in milk. In addition, the intake of eggs may be associated with levels of egg allergen ovalbumin in HM [6]. Both allergen exposure and PUFA levels in milk seem to be associated with allergic diseases [7‐9]. The adaptability of the maternal diet influences the presence of food allergens in HM, thereby affecting the infant’s exposure to these allergens, even before the introduction of solid foods. This may in turn provide a window of opportunity to reduce the risk of food allergies in infants.
Dietary guidelines for breastfeeding women in the Netherlands are currently limited to dietary reference values (DRVs) for a selection of nutrients. These values are based on nutrient needs of nonlactating women plus the average amount secreted in HM during the first six months postpartum. However, DRVs do not serve as a guidance for individuals but are intended to be used by health professionals [10]. Partly based on these DRVs specifically for lactating women, the Netherlands Nutrition Center advices them to follow the Wheel of Five and increase the intake of specific product groups [11]. Still, both the established DRVs and guidance by the Netherlands Nutrition Center do not account for changes in HM composition during the first six months postpartum, nor for changing maternal dietary habits.
The lactation period is subject to numerous changes that may affect maternal dietary habits. Despite their importance, data on fluctuations in the maternal diet during lactation are scarce. For the general population, diets are relatively stable over time, [12, 13] which cannot necessarily be assumed for postpartum and lactating women, as their dietary needs change according to their breastfeeding and feeding practices. The World Health Organization recommends exclusive breastfeeding (EBF) for the first six months after birth [14]. In 2023, the proportion of mothers exclusively breastfeeding at delivery was 53% in the Netherlands [15]. However, at two months postpartum, the EBF rate dropped to 42%, and at four months, the EBF rate had further decreased to 39%. By then, many infants were either exclusively formula fed (EFF) (49%) or received a combination of human and formula milk (13%) (i.e., mixed milk feeding (MMF)).Click or tap here to enter text. The transition from EBF to MMF or EFF, or vice versa, is a highly personal and variable process, which will impact the nutritional needs of these women [2, 3, 16]. In addition to meeting nutritional requirements, diet is influenced by personal food choices. In the Netherlands, the maternity leave of most women extends until ten weeks postpartum [17]. By the third month postpartum, women may partially or completely return to work or extend their leave with parental leave [18, 19]. Both fluctuations in nutritional needs and changes in environment may influence food choices and thus the diet of postpartum women.
Dietary assessments conducted at two and four months postpartum, using food frequency questionnaires (FFQs), allows us to explore whether the maternal diet changes over the course of lactation and if these changes are dependent on factors such as breastfeeding status and returning to work. This is an essential step toward providing dietary advice for lactating women and optimizing HM quality for their infants.
Methods
Participants
The PRIMA cohort is an ongoing Dutch, observational, prospective, multicenter birth cohort designed to identify HM components that may protect against respiratory tract infections and allergic diseases early in life. Detailed information on the study design and inclusion criteria is available elsewhere. Briefly, generally healthy, breastfeeding mothers with infants were recruited from obstetric wards at two hospitals in Utrecht, the Netherlands. The study was approved by the Medical Research Ethics Committee Utrecht (NL74946.041.20), and all parents provided written consent for participation [20]. From September 2021 to December 2022, we initiated a nested substudy within the PRIMA cohort by recruiting at least 250 participants to examine the influence of maternal diet on HM composition in greater detail. Only this nested substudy included additional maternal dietary intake assessments.
Maternal dietary intake assessment using food frequency questionnaires
At two and four months postpartum, mothers were asked to complete a validated (although not specifically for postpartum women) semiquantitative 183-food item FFQ covering dietary intake during the previous month [13, 21]. Average daily energy, food group, and nutrient intakes were estimated based on consumption frequency, portion sizes, and nutrient content as indicated by the Dutch Food Composition Database [21]. The FFQ was self-administered and completed online. Trained research dieticians conducted quality checks of the completed FFQs.
Adherence to the Dutch dietary guidelines was assessed using the Dutch Healthy Diet-15 Index (DHDI) [22]. The DHDI score is derived from subcategories including vegetables, fruits, wholegrains, legumes, nuts, dairy, fish, tea, fats and oils, red meat, processed meat, sweetened beverages and fruit juice, and alcohol. Food items were categorized according to the Dutch Food Composition Database [21]. Subcategories coffee and salt were excluded from the analysis, as the FFQ did not differentiate between filtered and unfiltered coffee and salt intake was not assessed. The maximum possible score for the DHDI is 130.
Dietary intake of nutrients at two months was compared with reference values if available for this population. Recently, average requirement, population reference intake, and/or adequate intake for vitamins and minerals specifically for lactating women in the Netherlands were published, including reference values for total iron, zinc, folic acid equivalents, and vitamins A, B1, B6, B12, C, and D [10]. The average requirement and population reference intake for vitamin B1 were adjusted for energy intake for this study population.
Independent variables
Upon inclusion, we gathered baseline data via a telephone interview (Tab. 1). In the FFQ, we additionally included questions on current weight (“What is your current weight (in kg)?”), dietary restrictions (combined answers from “Did you follow a restriction diet in the last month?” and “Did you follow a particular dietary lifestyle in the last month?”), and work status. Work status was defined based on four choices (briefly, ‘On leave or prolonged leave’, ‘Working reduced hours’, ‘Working contracted hours’ or ‘Not working’) to the question “Are you currently on leave (for pregnancy or maternity) or are you back to work?”. Current breastfeeding and feeding practices were assessed based on the reported degree of breastfeeding (EBF: 100% BF; MMF: 0% < BF < 100%; EFF: 0% BF) in the biweekly questionnaires.
Table 1
Baseline characteristics for 226 mother–infant dyads
Variable
Results
Mother
Age, years
34 ± 3.4
Prepregnancy BMI, kg/m2*
23 ± 3.3
Missing
0.44% (1)
Educational level
Lower
0.0% (0)
Middle
7.5% (17)
Higher
93% (209)
Smoking
Yes
0.44% (1)
Missing
1.3% (3)
(History of) atopy
Yes
50% (113)
Infant
Sex
Female
52% (117)
Male
48% (109)
Birth weight, g
3480 ± 530
Missing
0.44% (1)
Gestational age, weeks
40 ± 1.5
Delivery
Vaginal
70% (157)
C‑section
31% (69)
Siblings
Yes
47% (106)
BMI body mass index
Baseline data are presented as percentage and number, or mean ± standard deviation. In case of missing data, this is reported as a separate category. Educational levels were categorized as completed primary school or prevocational education (lower), senior general secondary education, preuniversity education, or secondary vocational education (middle), and university of applied sciences or university (higher)
Statistical analysis
Baseline and follow-up variables are presented as means ± standard deviation (SD) for continuous variables or as number with percentage for categorical variables. Percentages of missing data are reported for incomplete variables. Differences in dietary intake between the second and fourth month postpartum were evaluated by using linear mixed models with restricted maximum likelihood estimation. These models allowed us to include participants who completed only one of the two FFQs. A random effect for participants was included to account for variability in dietary intake at two months, allowing each participant to have a unique starting point in the model (intercept). A fixed slope for time was used to estimate the average change in dietary intake over time across all participants, adjusted for energy intake. We assessed the dietary variability at three levels: DHDI, food group, and nutrient level. We adjusted for multiple testing by applying the false discovery rate per level. For dietary components that changed over time, we explored whether work status or breastfeeding and feeding practices explained these differences. Both were added as fixed effects, along with an interaction term to assess whether change over time was dependent on work status or breastfeeding and feeding practices. All statistical analyses were performed using RStudio (v2023.06.0 build 421).
Results
Description of study participants
In the PRIMA substudy, we included a total of 272 participants, of whom 2 retracted their consent during follow-up. An additional 44 participants were indicated as lost-to-follow-up, as they completed neither of the two FFQs. Of the remaining 226 participants, the majority completed both FFQs (n = 170), and a smaller number completed the FFQ only at two months (n = 45) or four months (n = 11) (Figure S1). Participants were on average 34 ± 3.4 years old at delivery. Mothers had a healthy mean body mass index before pregnancy (23 ± 3.3 kg/m2), and the majority were higher educated (93% had university of applied science or university level). Most infants were born via vaginal delivery (n = 157; 70%). The mean gestational age was 40 ± 1.5 weeks, and infants had a generally healthy birth weight (3479 ± 530 g) (Tab. 1).
At two months postpartum, most women were exclusively breastfeeding (n = 169; 75%) and still on maternity leave (n = 210, 93%). Most women did not have dietary restrictions (n = 165; 73%), but some followed a vegetarian/pescatarian (n = 21; 9.3%) or cow’s milk–free/limited diet (n = 5; 2.2%). At four months postpartum, the EBF rate was reduced (n = 114; 50%), while more women had ceased breastfeeding (EFF; n = 29; 8.0%) or provided a combination of breast- and formula feeding (MMF; n = 29; 13%). Many women had returned to work, either for a reduced number of hours (n = 73; 32%) or regular hours (n = 52, 23%). The proportion of women without dietary restrictions at four months postpartum was lower (58%), although the frequency of missing data for this question increased to 20%. Of the 226 participants, six and seven women followed two or more diets at two months and four months postpartum, respectively (Fig. 1; Table S1).
Fig. 1
Changes in breastfeeding and feeding practices, work status, and diet among healthy lactating women (n = 226) between two and four months postpartum. For 226 participants, breastfeeding and feeding practices (a), work status (b), and diet (c) at two months (m2) and four months (m4) postpartum. breastfeeding and feeding practices during the second and fourth months was based on reported proportion breastfeeding (BF) to formula feeding (FF) in the respective biweekly surveys, with 100%BF/FF as exclusive BF (EBF), 5–95% BF/FF as mixed milk feeding (MMF) and 0% BF/FF as exclusive FF (EFF). Work status and followed diets during the second and fourth months were reported in the respective food frequency questionnaire. Diets included, but are not limited to either, cow’s milk—(CM), egg-, soy- and gluten-free or -restricted; sodium-, energy-, or fat-restricted; fiber-rich; or following a vegetarian or vegan lifestyle
Adherence to Dutch dietary guidelines and energy intake over time
Adherence to the Dutch dietary guidelines [22] and energy intake over time were assessed with dietary data collected through FFQs (Fig. 2; Table S2). The DHDI score (maximum: 130) was 85 ± 15 at two months and 87 ± 13 at four months. Adherence did not differ significantly over time based on the total DHDI (β = 1.2; 95% confidence interval (CI): −0.24 to 2.6) or each of the thirteen DHDI subcategories (Table S3). Energy intake was significantly lower at four months than at two months (β = −117 kcal/day; 95% CI: −191 to −43) (Fig. 2; Table S2).
Fig. 2
Changes in intakes of dietary food groups among healthy lactating women (n = 226) between two and four months postpartum. Differences in estimated daily dietary intake were compared between the fourth (m4) and second month (m2) postpartum for energy (kilocalories per day) and energy-adjusted food groups, as well as the Dutch Healthy Diet Index (DHDI). Differences in food group intake were adjusted for energy intake and tested with a linear mixed model per component. The changes in components were statistically significantly different if p < 0.05 after correction for multiple testing with false discovery rate (adjusted P-value) and are presented in bold. 95% CI: 95% confidence interval
Maternal dietary habits by food group intake over time
Maternal food group consumption was adjusted for energy intake to study changes in dietary habits over time. For most food groups, there was no significant difference in intake between the second and fourth month postpartum. However, during the fourth month, consumption of alcoholic beverages was significantly higher than during the second month (β = 15 g/day; 95% CI: 9.8–19). The consumption of meat and dairy substitutes was also higher during the fourth month, although this difference was not significantly different after correction for multiple testing (adjusted p = 0.079). In contrast, consumption of nonalcoholic beverages was lower (β = −42 g/day; 95% CI: −186 to −22) during the fourth month, although this was also not statistically significant after correction for multiple testing (adjusted p = 0.079). Regarding potential allergens, no significant differences were observed in the consumption of eggs, nuts, and seeds between the two time points. Interestingly, consumption of milk and milk products was significantly lower during the fourth month (β = −42 g/day; 95% CI: −65 to −19), while the intake of meat and dairy substitutes seemed to be higher (β = 15 g/day; 95% CI: 3.5–26; p = 0.068), compared with the second month postpartum (Fig. 2; Table S2).
Maternal dietary habits at nutrient level over time and compared with reference values
Maternal nutrient intake was adjusted for energy intake to evaluate changes over time. At the nutrient level, both macro- and micronutrient dietary intakes remained relatively stable over time. The only statistically significant change observed, after adjustment for multiple testing, was a higher intake of alcohol during the fourth month (β = 1.2 g/day; 95% CI: 0.78–1.5) compared with the second month (Fig. 3; Table S4).
Fig. 3
Differences in dietary nutrient intakes among healthy lactating women (n = 226) between two and four months postpartum. Differences in estimated daily dietary intake (units per nutrient in brackets) were compared between the fourth month (m4) and second month (m2) postpartum for macronutrients (a) and micronutrients (b). Differences in nutrient intake were adjusted for energy intake and tested with a linear mixed model per nutrient. The changes in energy-adjusted nutrient intake were statistically significantly different if P < 0.05 after correction for multiple testing with false discovery rate (adjusted P-value) and are presented in bold. 95% CI: 95% confidence interval, d day
Recently, the Health Council of the Netherlands (Gezondheidsraad) published vitamin- and mineral-related dietary reference values for lactating women who fully breastfeed during the first four to six months postpartum [10]. These guidelines are based on recommendations for breastfeeding women by the European Food Safety Authority (EFSA) and have been evaluated for application in the Netherlands. In our study, we were able to compare the dietary intakes of nine vitamins and minerals, out of the eighteen micronutrients assessed by FFQs, with the published reference values for lactating women in the Netherlands (Tab. 2).
Table 2
Absolute dietary nutrient intake and differences in nutrient intake at two months postpartum in healthy lactating women (n = 226) compared with available reference values
Variable
Estimated intake (median (IQR))
Average requirement
Population reference intake
Adequate intake
Energy intake (MJ/day)
9.3 (7.5–10.9)
Micronutrients
Calcium (mg/day) a
1022 (759–1293)
750
950
Total iron (mg/day)
12 (10–14)
7
16
– Heme iron (mg/day)
0.67 (0.36–1.1)
– Nonheme iron (mg/day)
11 (9.0–13)
Zinc (mg/day)
10 (8.5–12)
8.1
9.9
Retinol (µg/day)
418 (308–593)
Vitamin A (µg RAE/day)
818 (615–1091)
1100
Beta-carotene (µg/day)
3940 (2370–5542)
Vitamin B1 (mg/day) b
0.93 (0.79–1.1)
0.67
0.93
Vitamin B2 (mg/day)
1.4 (1.2–1.8)
Vitamin B6 (mg/day)
1.5 (1.3–1.8)
1.2
1.7
Vitamin B12 (µg/day)
4.0 (2.9–5.2)
2.7
3.8
Vitamin D (µg/day)
2.9 (2.0–4.1)
10
Total vitamin E (mg/day)
15 (11–18)
Vitamin C (mg/day)
95 (67–119)
100
135
Total folic acid (µg/day)
256 (202–312)
Folic acid equivalents (µg/day)
279 (219–346)
330
500
Lycopene (µg/day)
2406 (1408–3751)
RAE retinol activity equivalent
Estimated intake is presented as median and interquartile range (IQR). Daily nutrient intake was assessed with a food frequency questionnaire covering the four weeks before
a Reference values for age ≥ 25 years old
b Reference value is provided per megajoule and therefore calculated for the median energy intake (megajoule) for this study population
The median dietary intakes of calcium, zinc, and vitamin B12 were higher than the reference values assumed to be sufficient for almost all women (1022, 10, and 4.0 µg/day, respectively, vs. 950, 9.9, and 3.8 µg/day, respectively). The median dietary intake of vitamin B1 was at the same level as what is assumed to be sufficient for almost everyone (0.93 mg/day). In contrast, the median dietary intake of vitamin D (2.9 µg/day; range: 2.0–4.1) was far below the adequate intake advised for lactating women. Similarly, the median dietary intake of vitamin A was below the adequate intake and showed considerable variation between participants (818 µg retinol activity equivalent (RAE)/day; range: 615–1091). The median dietary intakes of total iron (12 mg/day; range: 9.6–13.8) and vitamin B6 (1.5 mg/day; range: 1.3–1.8) fell between the average requirements and population reference intakes, indicating sufficiency for most participants. The median dietary intake of vitamin C (97 ± 39 mg/day) was below the average requirement, suggesting it may not have been sufficient for half of our study group. The average estimated dietary intakes of macro- and micronutrients during the second and fourth months are presented in Table S4.
Factors related to maternal diet changes
Knowing that work status and breastfeeding and feeding practices changed over time, we hypothesized that this may explain some or all of the differences observed in the intake of certain food groups over time. We assessed whether work status and breastfeeding and feeding practices explain all or part of the differences in energy, alcoholic beverages, and milk and milk products intake (Tab. 3). Total energy intake tended to be higher in women who returned to work for reduced hours than for women who were still on leave (β = 339 kcal/day; 95% CI: −20 to 710; p = 0.077), independent of timing. EFF women had lower energy intake than women who applied EBF (β = −596 kcal/day; 95% CI: −1022 to −166). Interestingly, energy intake was dependent on both breastfeeding and feeding practices and work status, with women who applied MMF had lower energy intake when they were working contracted hours (β = −503 kcal/day; 95% CI: −879 to −114) or not working (β = −1623 kcal/day; 95% CI: −2581 to −709) compared with EBF women on leave, independent of timing.
Table 3
Effects of work status and breastfeeding and feeding practices on changes in food group intake in healthy lactating women (n = 226)
Variable
Reference
Exposure
β‑coefficient (95% CI)
P-value
Energy intake (kcal/day)
Time point
Month 2
Month 4
−113 (−256 to 29)
0.134
Work
(Prolonged) leave
Working reduced hours
339 (−20 to 710)
0.077
Working contracted hours
−247 (−791 to 274)
0.374
Not working
541 (−306 to 1361)
0.217
Feeding
EBF
MMF
−100 (−272 to 77)
0.275
EFF
−596 (−1022 to −166)
0.008
Time*work
Month 2*(prolonged) leave
Month 4*working reduced hours
−266 (−683 to 143)
0.221
Month 4*working contracted hours
340 (−262 to 952)
0.287
Month 4*not working
−345 (−1255 to 594)
0.477
Time*feeding
Month 2*EBF
Month 4*MMF
245 (−40 to 530)
0.104
Month 4*EFF
229 (−402 to 873)
0.494
Work*feeding
(Prolonged) leave*EBF
Working reduced hours*MMF
−231 (−561 to 96)
0.184
Working contracted hours*MMF
−503 (−879 to −114)
0.013
Not working*MMF
−1623 (−2581 to −709)
0.001
Working reduced hours*EFF
−249 (−915 to 397)
0.468
Working contracted hours*EFF
12 (−574 to 599)
0.969
Not working*EFF
N/A
Alcoholic beverages (g/day)
Time point
Month 2
Month 4
15 (5.7 to 24)
0.002
Work
(Prolonged) leave
Working reduced hours
17 (−6.7 to 40)
0.175
Working contracted hours
8.6 (−25 to 43)
0.632
Not working
−4.2 (−57 to 49)
0.880
Feeding
EBF
MMF
8.4 (−3.2 to 20)
0.161
EFF
53 (25–82)
< 0.001
Time*work
Month 2*(prolonged) leave
Month 4*working reduced hours
−25 (−51 to 2.1)
0.081
Month 4*working contracted hours
−16 (−55 to 23)
0.449
Month 4*not working
0.7 (−59 to 59)
0.981
Time*feeding
Month 2*EBF
Month 4*MMF
11 (−6.9 to 30)
0.239
Month 4*EFF
−30 (−71 to 11)
0.167
Work*feeding
(Prolonged) leave*EBF
Working reduced hours*MMF
−22 (−43 to −0.5)
0.052
Working contracted hours*MMF
−14 (−39 to 11)
0.288
Not working*MMF
−24 (−84 to 37)
0.451
Working reduced hours*EFF
66 (23 to 108)
0.003
Working contracted hours*EFF
15 (−23 to 53)
0.450
Not working*EFF
N/A
Milk and milk products (g/day)
Time point
Month 2
Month 4
−41 (−88 to 5)
0.096
Work
(Prolonged) leave
Working reduced hours
30 (−89 to 148)
0.638
Working contracted hours
23 (−148 to 197)
0.800
Not working
224 (−48 to 496)
0.120
Feeding
EBF
MMF
105 (48 to 162)
< 0.001
EFF
51 (−88 to 192)
0.483
Time*work
Month 2*(prolonged) leave
Month 4*working reduced hours
−13 (−147 to 122)
0.855
Month 4*working contracted hours
31 (−171 to 226)
0.763
Month 4*not working
−318 (−619 to −17)
0.047
Time*feeding
Month 2*EBF
Month 4*MMF
−70 (−163 to 24)
0.159
Month 4*EFF
−62 (−269 to 144)
0.565
Work*feeding
(Prolonged) leave*EBF
Working reduced hours*MMF
−38 (−147 to 69)
0.508
Working contracted hours*MMF
−1.5 (−126 to 125)
0.982
Not working*MMF
103 (−204 to 411)
0.526
Working reduced hours*EFF
50 (−162 to 262)
0.652
Working contracted hours*EFF
−37 (−227 to 156)
0.712
Not working*EFF
N/A
N/A not applicable
Energy intake and intake from different food groups (the latter adjusted for energy intake), were assessed with a food frequency questionnaire covering the four weeks before. Relevant factors for differences in intake between two and four months were tested with a linear mixed model per food group. Breastfeeding and feeding practices during the second and fourth months were based on reported proportion breastfeeding (BF) to formula feeding (FF) in the respective biweekly surveys, with 100%BF/FF being regarded as exclusive BF (EBF), 5–95% BF/FF as mixed milk feeding (MMF), and 0% BF/FF as exclusive FF (EFF). Work status during the second and fourth months was reported in the respective food frequency questionnaires
Consumption of alcoholic beverages was associated with breastfeeding, with EFF mothers consuming more alcoholic beverages than mothers who applied EBF (β = 15 g/day; 95% CI: 5.7–24). Importantly, the effect of breastfeeding and feeding practices on maternal alcohol consumption was dependent on work status, with EFF mothers working reduced hours consuming more alcohol (β = 66 g/day; 95% CI: 23–108), whereas MMF mothers working reduced hours tended to consume less alcohol (β = −22 g/day; 95% CI: −43 to −0.05; p = 0.052) than EBF mothers on leave. Lastly, the intake of milk and milk products depended on breastfeeding and feeding practices, with MMF mothers consumed relatively more than EBF mothers (β = 105 g/day; 95% CI: 48–162), independent of the time point (Tab. 3).
Discussion
Data on maternal dietary intake during lactation are lacking. Our study demonstrates that the maternal diet is relatively stable, with the intake of specific food groups, including possible allergens, changing during the postpartum period. The adherence to the Dutch dietary guidelines was stable over time, while we observed a significant reduction in energy intake by four months postpartum. Additionally, shifts in consumption of alcoholic beverages, meat and dairy alternatives, and milk and milk products were all or partly related to factors such as work status and breastfeeding and feeding practices. A shift in dietary patterns should be considered when providing dietary guidance, studying the relationship between maternal diet and HM composition, and exploring the potential impact on infants’ risk of developing allergies.
Recently, the Health Council of the Netherlands issued dietary guidelines on vitamins and minerals for lactating women, largely relying on standards set by the EFSA [10]. These standards are set for women exclusively breastfeeding for the first four to six months. During this period, the infant has the highest nutrient demands from HM, and, consequently, the mother’s nutrient needs are also at their peak. Specific recommendations for increased intakes of riboflavin (vitamin B2), folic acid, vitamin C, potassium, magnesium, iron, and selenium have been set for lactating women. In this study, we observed that dietary intake of calcium, zinc, vitamin B1, iron, and vitamin B6 all met or exceeded the recommended levels. However, dietary intakes of vitamins A, C, and D were slightly to clearly below recommendations.
It is important to note that supplements were not considered in this study. To our knowledge, there are no data available on supplement use by Dutch lactating women specifically. During pregnancy, folic acid and vitamin D supplementations are recommended [23]. In addition, the Dutch National Food Consumption Survey of the general population reported that 70% of women aged 18–50 years take dietary supplements, including supplements for vitamin A, C, D, and multivitamins with minerals. Although the dietary intakes of vitamin A, C, and D were lower than recommended, we assumed that an unknown proportion of participants compensated this with supplements. Further longitudinal studies closely monitoring supplement use or blood tests during the lactation period are needed to assess maternal total vitamin intake and risk of deficiencies during lactation and evaluate whether the relatively stable micronutrient intake is sufficient at any moment during lactation.
For other nutrients than vitamins and minerals, dietary intake reference values for Dutch lactating women are still lacking. However, the DHDI does provide a measure of Dutch dietary guideline adherence for the general population. At two months postpartum, the average DHDI score in our study was 85 out of 130 points (65%). In the DHDI validation study, Dutch women had a mean ± SD score of 79.4 ± 16.0 out of 140 (57%), which is proportionally slightly lower than that in our study population of postpartum women [22]. However, the age distribution in the validation study (mean ± SD age: 51.4 ± 12.1 years) limits comparison between these study populations. Another Dutch study on nutritional status from preconception to pregnancy assessed the adherence at 24 weeks of gestation in women of a more comparable age (median: 32.6 years; 25–75%: 30.7–34.7). These pregnant women had a mean DHDI score of 78 (standard error of the mean: 1.6) out of 130 (60%) [24]. Although a direct comparison is not possible, we conclude that our study population of postpartum women have a moderate to good adherence to the Dutch dietary guidelines for the general population.
Pregnant and lactating women are often excluded from dietary assessment studies, limiting available literature on dietary changes over time and during lactation. A systematic review covering 17 observational studies concluded that diet quality, adherence to dietary guidelines, and fruit and vegetable consumption generally decreased from pregnancy to the postpartum period. In contrast, fat intake and consumption of discretionary foods increased during the same timeframe [25]. In our study, we did not observe any change in adherence to the Dutch dietary guidelines during the postpartum period. The six studies on energy intake included in the review did not report a consistent trend during lactation time [25], which could be due to differences in dietary assessment timing and unaccounted confounders. We observed a decreasing energy intake over time, which was dependent on breastfeeding and feeding practices and work status. Given that HM production requires significant energy, the impact of these factors should be considered in future dietary assessment studies involving lactating women.
It is generally recommended to limit or avoid alcohol consumption during lactation to ensure the healthy development of the infant. Studies have shown associations between maternal alcohol consumption during lactation and negative effects on infant development later in life [26‐28]. In our study, representing a highly educated Dutch study population (93% with higher education level), alcohol consumption was dependent on lactation style. Specifically, both MMF and EFF mothers consumed more alcoholic beverages than those who exclusively breastfed their infants, indicating high awareness of these recommendations.
Similarly, the consumption of milk and milk products was associated with breastfeeding and feeding practices, with EBF mothers consuming less milk and milk products than MMF mothers but both more than EFF mothers, regardless of time or work status when adjusted for energy intake. It is possible that EBF mothers limit or restrict cow’s milk products in their diets due to concerns about established or suspected cow’s milk allergy in their breastfed infant. However, only a small percentage of mothers followed a cow’s milk–free/limited diet (2.2% in the second month; 3.1% in the fourth month). The question of whether breastfeeding mothers should avoid cow’s milk products if their infant has or is suspected of having cow’s milk allergy remains debated [29]. Research suggests that levels of cow’s milk allergens in HM are generally too low to elicit an allergic response in most cases [30]. In fact, it has been substantiated that low-dose allergen exposure via HM may even promote oral tolerance [8]. Current guidelines typically recommend breastfeeding without this dietary restriction for the mother [29, 31]. Nevertheless, our study results may serve as a starting point for qualitative research designed to gain a deeper understanding of why women change their dietary habits and, subsequently, what the impact is on infants’ health.
Strengths and limitations
Our data provide novel insights into the dietary patterns of Dutch lactating and postpartum mothers in relation to breastfeeding and feeding practices and work status. Another strength is that we assessed dietary intake postpartum during maternity leave, at two months, and when most women returned to work (at four months).
A possible limitation is the FFQ used, which was developed for the general Dutch population and is not specifically validated for lactating or postpartum women. While a detailed dietary assessment was conducted, we cannot rule out the possibility that small, time-dependent changes were not captured by the FFQ. To validate our findings and detect smaller changes not observed with the current FFQ, multiple 24-hour recalls can be useful, specifically for studies focusing on allergens in HM. We also did not record supplement use, limiting assessment to dietary intake rather than total macro- and micronutrient intake. The absence of Dutch dietary guidelines specifically for lactating women limited us in assessing diet quality in our study population. Moreover, we studied a homogenous population with a higher level of education in the Netherlands, which may not be representative of a broader population. Still, our findings give a clear indication that highly educated postpartum women consistently follow the general dietary guidelines for adults.
Conclusion
Our study demonstrates that the maternal diet is relatively stable during the postpartum period despite changes in breastfeeding and feeding practices and work status. Nevertheless, the intake of a few specific food groups changes over time and should therefore be considered when studying the relationship between maternal diet and HM composition, as well as when exploring the potential impact on infants’ risk of developing allergies. Maternal diet shifts indicate there is an opportunity for targeted postpartum interventions to improve the health of both mothers and their infants.
Acknowledgements
The authors thank the families involved in the PRIMA cohort, as well as all the members of the PRIMA cohort study. In addition, we would like to acknowledge Janine Faessen for her critical reading and suggestions for improvement of the manuscript.
Funding
This research was supported by Regio Deal Foodvalley (grant nr. 162135) and the University Medical Center Utrecht–Danone Nutricia Research BV collaboration grant “Early Life Nutrition and Immune Development”.
Conflict of interest
A.H. Hellinga, J.H.M. de Vries, A.H. van Stigt, E.M. Brouwer-Brolsma, E.J.M. Feskens, J.H.W. Leusen, A.D. Kraneveld and L. Bont declare that they have no competing interests. B. van ’t Land is also partly employed by Danone Research & Innovation (Utrecht, the Netherlands) as indicated by the affiliations.
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Dietary shifts during lactation: a prospective birth cohort
Auteurs
Anneke H. Hellinga
Jeanne H. M. de Vries
Arthur H. van Stigt
Elske M. Brouwer-Brolsma
Edith J. M. Feskens
Jeanette H. W. Leusen
Aletta D. Kraneveld
Louis Bont
Belinda van ’t Land
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