A Comprehensive Assessment of the Environmental Impact of Different Infant Feeding Types: The Observational Study GREEN MOTHER

ABSTRACT

Aim(s)

To observe and compare the environmental impacts of different types of infant feeding, considering the use of formula, infant feeding accessories, potentially increased maternal dietary intake during breastfeeding (BF) and food consumption habits.

Design

An observational cross‐sectional multicentre study conducted in the Barcelona Metropolitan Area of the Catalan Institute of Health.

Methods

Data were collected from 419 postpartum women on infant feeding type (formula milk and accessories), maternal dietary intake (24‐h register) and food consumption habits from November 2022 to April 2023. The environmental impacts (climate change (CC), water consumption and water scarcity) of the infant feeding types and maternal diet were calculated using the IPCC, ReCiPE and AWARE indicators, respectively. The differences in impacts were calculated by Kruskal–Wallis test.

Results

Significant differences for the three environmental impacts were observed. The CC impact of formula milk and feeding accessories was 0.01 kg CO₂eq for exclusive BF, 1.55 kg CO₂eq for mixed feeding and 4.98 kg CO₂eq for formula feeding. While BF mothers consumed an extra 238 kcal, no significant differences were found related to maternal diet across feeding types.

Conclusion

Exclusive BF was the most sustainable type of infant feeding, considering formula and infant feeding accessories. In our study, the difference between the impacts of BF and non‐BF mothers' diet was insignificant.

Implications for the Profession and/or Patient Care

Offer informative and educational support for midwives and other healthcare professionals on BF and a healthy, sustainable diet to transfer this knowledge to the general public.

Impact

• Raise the general public's awareness about BF and a healthy, sustainable diet.

• To reduce environmental impacts through behavioural changes.

Reporting Method

STROBE.

Patient or Public Contribution

Patients of the Catalan Health Service reviewed the content of the data collection tools.

Trial Registration: (for the whole GREEN MOTHER project): NCT05729581 (https://clinicaltrials.gov)

1. Introduction

Breastfeeding (BF) is the healthiest form of infant feeding and more sustainable than formula feeding (FF) (Karlsson et al. 2019) as it generates less waste and has a minimal carbon footprint (CF) and water footprint (WF) (see Annex 1 for definitions of environmental impacts). In the document ‘Green Feeding Europe’, the European Union Council recommends including and prioritising sustainable infant feeding practices in environmental programmes (IBFAN 2019). According to the report, BF produces zero waste, minimal greenhouse gas (GHG) emissions and a very small WF (IBFAN 2019). Maternal dietary habits based on the consumption of healthy food with a smaller environmental impact help protect the environment and further progress towards the UN 2030 sustainable development goals (SDGs) (3, 7, 10, 11, and 13) (United Nations 2015). Therefore, it is crucial to study the potential environmental impacts of infant feeding types (including infant feeding accessories) and maternal diet (including associated habits) (Amonkar et al. 2019; Andresen et al. 2022; Becker and Ryan‐Fogarty 2016; IBFAN 2019; Karlsson et al. 2019).

2. Background

BF provides innumerable benefits to the health and well‐being of children, mothers (Kramer and Kakuma 2004; de la Salud 2010; Victora et al. 2016) and society in general (World Health Organization and United Nations Children's Fund [UNICEF] 2003). It is also a more sustainable form of infant feeding in terms of CF and environmental protection (Andresen et al. 2022; Becker and Ryan‐Fogarty 2016; Karlsson et al. 2019).

The European Commission has set ambitious climate change (CC) reduction targets as part of the Paris Agreement, including a 55% reduction in GHG emissions by 2030 and climate neutrality by 2050. In the primary sector, food production represents 30% of total GHG emissions (UN 2015). Livestock breeding is the primary source of methane emissions. It generates 12%–17% (630–863 Mt. CO₂eq) of total GHG in Europe (UN 2015). Karlsson observed that the mean CF of FF was estimated to be 9.2, 7, 8.4 and 11 kg CO₂eq per kg in New Zealand, USA, Brazil and France, respectively (Karlsson et al. 2019). The potential reduction in CF generated by BF was 40%–55% in the United Kingdom, China, Brazil and Vietnam (Karlsson et al. 2019).

Breast milk has the most minor environmental impact as it is neither manufactured nor does it generate waste. Additionally, exclusive BF (EBF) causes amenorrhea, resulting in less pollution generated from the use of disposable menstrual products (Linnecar et al. 2014). Moreover, this also delays the possibility of becoming pregnant again, resulting in fewer children and, thus, a lower final environmental impact (Becker and Ryan‐Fogarty 2016).

Most studies report a low CC impact for EBF. However, according to Becker, until 2016 there were no studies evaluating the environmental impact of BF accessories (Becker and Ryan‐Fogarty 2016).

Maternal diet and food consumption habits should also be considered when calculating the environmental impact of infant feeding in terms of differences between BF mothers and non‐BF mothers. To cover nutrition and energy needs, BF mothers are generally recommended to consume an extra 500 kcal daily (20%) (Dewey 1997; FAO 2004; Jiménez Ortega et al. 2019). These additional calories can come from many different food types and increase the environmental impact of BF (Amonkar et al. 2019; IBFAN 2019; Karlsson et al. 2019; Linnecar et al. 2014). Karlsson et al. (2019) calculated the average CF of the maternal diet to be 6.7 kg CO₂eq per 1 kg of breastmilk versus 12.5 kg CO₂eq per 1 kg of formula milk (Karlsson et al. 2019; Linnecar et al. 2014). Amonkar et al. researched the environmental impact of BF considering these theoretical additional 500 kcal and the American custom of pumping, storing, heating and administering breast milk. In this scenario, the CC of BF was 18% higher (Amonkar et al. 2019; Linnecar et al. 2014). Similarly, in Norway, Andresen compared GHG emissions from BF and FF through the life cycle methodology, considering maternal diet and assuming immediate, non‐deferred BF. They calculated an additional 2.5 MJ of dietary energy was needed to produce 1 kg of breast milk, based on the average diet of Norwegian women. They reported a 35%–72% greater impact depending on the type of diet of the mother (Andresen et al. 2022).

WF encompasses both water consumption (WC) and water scarcity (WS) and has been particularly significant in Spain in recent years due to extreme water conditions. According to Mekonnen and Hoekstra (2012), Spain has a substantial WF (food accounts for nearly 80% of consumers' personal WF or 6700 L per person daily). Therefore, when comparing the environmental impacts of EBF versus FF, WF should also be considered.

The increased amount of water a BF mother consumes is insignificant compared to the amount required to manufacture formula milk (IBFAN 2019). A study conducted by Pope et al. in the United States revealed that the WF of the 6.6 kg of raw milk required to produce 1 kg of commercial formula included 626 L of blue water for manufacturing, reconstitution and sterilisation, 6280 L of green water to feed the cows and 524 L of grey water (Pope et al. 2021). In Switzerland, Rollins and colleagues (Rollins et al. 2016) estimated the average WF of whole cow's milk to be approximately 940 L of water per kg of raw milk. Considering that 1 kg of whole milk yields about 200 g of milk powder, WC was calculated to be 4700 L of water per 1 kg of milk powder (Linnecar et al. 2014; Rollins et al. 2016).

The WF of food consumption in Spain amounts to 3302 L per person daily. Meat, fish and animal fats (26%) and dairy products (21%) have the highest WF. The WF of food waste is estimated to be 2095 hm³, equivalent to 131 L per person per day (Blas, Garrido, and Willaarts 2018).

Freshwater is not an unlimited resource. Global WS poses a challenge in meeting the demands for freshwater for drinking and food production (Shemer et al. 2023). Due to this high water stress, this study also evaluates the WS impact of the life cycle of formula production, infant feeding accessories and maternal diet.

Given the climate emergency and the lack of rigorous data on how much GHG emissions could be reduced in Europe through EBF, it is worthwhile to investigate the environmental impact and determine the CF and WF of different infant feeding types. There are no studies that consider the main factors involved. This study calculates the environmental impact (CC, WC and WS) of different infant feeding types, taking into account formula, infant feeding accessories, increased maternal dietary intake during BF and related food consumption habits.

The whole GREEN MOTHER project, split into two independent sequential phases or subprojects, is lead and carried out by midwives. In Spain, the midwife (obstetric specialist nurse) is the health professional who monitors pregnant women up to the first 6 weeks after delivery, in the public health system. The results from Phase I (Cabedo‐Ferreiro et al. 2024) bolster the development of educational materials to be used in Phase II (educational intervention and counselling to improve prevalence of BF and a sustainable diet) (Cabedo Ferreiro et al. 2023). The final results obtained from the GREEN MOTHER project can help form the basis of recommendations to the general population on achieving the healthiest and most sustainable diet possible early in life and reducing environmental impacts by promoting EBF.

3. The Study

3.1. General Aim

This study aims to compare the environmental impact of the three types of infant feeding: EBF, MF and FF. The environmental assessment covers the following impact categories: CC (in kg CO₂eq), WC (m³) and WS (m³eq), considering the influence of formula milk, infant feeding accessories and potentially increased maternal dietary intake during BF with related food consumption habits on these environmental impacts.

4. Methods

4.1. Design

This multicentre, cross‐sectional study was conducted in the Barcelona Metropolitan Area of the Catalan Institute of Health (ICS).

4.2. Study Setting and Sampling

The participating sites were Reproductive and Sexual Health Care units (ASSIRs) at the public primary centres in Sabadell, Granollers, Santa Coloma de Gramenet, Mollet, Mataró, Badalona, and Sant Adrià. The prior‐to‐study sample size calculation to achieve 80% statistical power showed that 408 participants would be sufficient to estimate an expected population percentage (approximately 50%) with a 95% confidence interval and a precision of ± 5%.

4.3. Inclusion and/or Exclusion Criteria

Inclusion criteria to participate in the study were (1) pregnant women (minimum 32 weeks of gestation) assigned to the aforementioned centres, (2) being at least 16 years old and (3) voluntarily agreeing to participate in the study via a signed informed consent.

The exclusion criteria were language barriers that impeded comprehension of the study aims and the informed consent form.

4.4. Instrument With Validity and Reliability/Data Source

General sociodemographic and clinical data on habits related to infant feeding type, the amount of infant formula used, feeding accessories used, diet, cooking habits and food shopping habits were collected from the participants. To identify maternal dietary habits, the 24‐h recall method (Ferrari 2013) was used, as it is the most exhaustive retrospective instrument available and does not alter the participant's usual food intake. The data were from self‐reported participant replies and health records from the primary care centres.

4.4.1. The Methods Used to Calculate the Three Environmental Impact Indicators

The following environmental impacts (see Annex 1 for definitions) were calculated in the study:

1. CC was assessed in kg CO₂eq by the IPCC GWP 100 years calculations (Kirschbaum 2014).

2. WC was calculated in m³ following the ReCiPE method (Dekker et al. 2020), calculating direct and indirect WC.

3. WS was calculated in m³eq using the AWARE method (Boulay et al. 2018).

4.4.2. Basis for Calculating the Impacts of Formula and Maternal Diet

The amount of daily formula consumption was calculated by adding all the daily intake volumes. Table A1 in Annex 2 presents the results of the calculations of the environmental impacts of formula. The infant feeding accessories used were accounted for in every case. The impacts attributed to the use of these accessories are laid out in Table A2 in Annex 2.

To calculate the impacts of maternal diet, maternal dietary intake was recorded for 24 h at 4–6 weeks postpartum. The registers included the type of food and portion sizes (predefined by the research group), beverages and condiments, how the food was cooked, stored and packaged and food waste. Table A3 in Annex 2 presents the base impacts for calculating the environmental impacts of purchasing habits.

Based on the 24‐h dietary intake registers of all the participants, we calculated the differences between the impacts of maternal diet and consumption habits for each of the three infant feeding types and checked where they were statistically significant (Kruskal–Wallis test).

4.4.3. Calculation of the Total Environmental Impact of the Three Infant Feeding Types

The total environmental impact (CC/WC/WS) of the three infant feeding types was calculated by adding the impact of the infant feeding type and accessories plus the differential of the impact of maternal diet and food consumption habits.

4.5. Data Collection

All the data were collected by midwives in seven ASSIRs from November 2022 to April 2023 via questionnaires completed by the researchers in charge of participant recruitment, using the secure REDCap (Harris et al. 2009, 2019) electronic data capture tools hosted by the Institut Català de la Salut.

4.6. Data Analysis

The descriptive statistics are presented by univariate analysis. The univariate analysis was performed with mean, interquartile ranges, frequencies and percentages. Due to the non‐normal data distribution, a bivariate analysis was conducted with the non‐parametric Kruskal–Wallis test.

The impact variables do not have a normal distribution. The differences in environmental impacts of the three types of infant feeding in the two dimensions mentioned above were checked with non‐parametric analysis (H test Kruskal–Wallis) using STATA v.19.

4.7. Ethical Considerations

This study followed the guidelines of the Declaration of Helsinki. The research protocol was approved by the Research Ethics Committee (CEI) of the Jordi Gol Institute of Primary Care Research (IDIAP). The data were collected anonymously through questionnaires on the REDCap platform. The variables needed to conduct the study were obtained directly from the project participants with their consent, in accordance with the provisions of articles (6.1.a) and (9.2.a) of the GDPR. Anonymous data collection ensures compliance with EU regulation 2016/679. The ICS is the data controller and the current study data owner.

5. Results

5.1. Sociodemographic, Clinical, Maternal Diet Type and Infant Feeding Type Data

The general sociodemographic and clinical characteristics of the study participants are shown in Table 1. The majority of participants were over 25 years old (mean age: 33; range: 17–50), identified as female, had professional or higher education, performed remunerated work and were from Spain. At 1 month postpartum, 63.75% of participants opted for EBF, 23.11% did MF and 13.14% did FF.

TABLE 1.

Sociodemographic and clinical characteristics of participants.

	No. of respondents	Categories	n	%
Age	415	≤ 25	34	8.2
		26–35	232	55.9
		≥ 36	149	35.9
Gender	419	F	415	99.1
		M	4	0.9
Education	353	No studies or primary	76	21.6
		Compulsory secondary	30	8.5
		Professional education	93	26.4
		University	154	43.6
Place of birth	417	Spain	300	71.9
		Abroad	117	28.1
Religion	415	Agnostic	144	34.7
		Religious	271	65.3
Remunerated work	416	Yes	350	84.1
Maternal diet	405	No special diet	382	94.32
		Vegetarian	6	1.48
		Vegan	1	0.25
		Celiac	6	1.48
		Food allergies	5	1.23
		Therapeutic diet (diabetes, HBP, dyslipidaemia, etc.)	5	1.23
Infant feeding type at 1 month postpartum	411	EBF	262	63.75
		MF	95	23.11
		FF	54	13.14

Regarding maternal diet, the majority (94%) of participants did not follow a specific diet. Of those who did, 1.57% were vegetarian or vegan, 1.2% had food allergies and the rest followed a therapeutic diet. None of the participants who did FF followed a specific diet, while women who did MF or EBF followed various diets, some with lower environmental impacts.

5.2. Aspects Related to Infant Feeding Included in the Calculation of the Environmental Impacts

The elements related to bottle feeding are described in Table 2: 349 mothers reported the number of bottles they used and 156, the number of cans of formula they had at home. In total, 149 participants reported using formula milk, with a mean consumption of 528 mL in 24 h (range: 10–1359 mL). MF was used in 95 cases (333 mL; range: 10–1050 mL) and FF in 54 cases (866 mL; range: 450–1359 mL).

TABLE 2.

Descriptive statistics of baby bottle consumption.

Variables	No. of respondents	Categories	n	%
No. of baby bottles	349	0	70	20.1
		1	50	14.3
		2	86	24.6
		3	59	16.9
		4	39	11.2
		5	19	5.4
		6	13	3.7
		> 7	13	3.7
No. of formula feeds	148	1	19	12.8
		2	14	9.5
		3	13	8.8
		4	11	7.4
		5	7	4.7
		6	18	12.2
		7	17	11.5
		8	33	22.3
		> 8	16	10.8
Volume formula (mL/feed)	149	10	2	1.3
		30	15	10.1
		50	14	9.4
		70	14	9.4
		90	49	32.9
		110	20	13.4
		130	21	14.1
		150	10	6.7
		> 150	4	2.7
No. of cans (800 g) of formula used weekly	156	0.5	71	45.5
		1	76	48.7
		1.5	6	3.9
		2	3	1.9

In addition to formula, other accessories might be used in any type of infant feeding. These have also been accounted for when calculating environmental impacts. Table 3 presents data on the use of such accessories.

TABLE 3.

Infant feeding accessories and frequency of use.

Infant feeding accessories	Feeding type	No. of respondents	Use	%
Breast pump	EBF, MF	414	156	37.7
Milk storage containers	All	413	123	29.8
Milk storage bags	EBF, MF	413	66	16.0
Nipple shields	EBF, MF	412	75	18.2
Supplemental nursing system	EBF, MF	411	13	3.2
Bottle brush	All	407	157	38.6
Bottle warmer	All	407	45	11.1
Bottle steriliser	All	405	75	18.5
Paediatric nasogastric tube	EBF, MF	405	13	3.2
Reusable nursing pads	EBF, MF	409	71	17.4
Disposable nursing pads	EBF, MX	411	178	43.3

An average of 176 participants used 11.4 (range: 1–56) disposable nursing pads in a span of 1 week. 37.7% of participants used a breast pump and 11.1% had a bottle warmer.

5.3. Twenty‐four‐hour Maternal Diet and Food Consumption Habits Included in the Calculation of the Environmental Impacts

Regarding maternal dietary intake, the results of this study show that BF mothers increased their food intake by 238 kcal on average compared to mothers who opted for FF. The median caloric intake for BF mothers was 1703 kcal per day versus 1465 kcal for mothers who did FF. Table 4 presents the consumption habits associated with maternal diet. The frequencies of food processing type and cooking types are available in Annex 3 (Tables A4 and A5).

TABLE 4.

Shopping habits, energy source for cooking and food waste.

Variables	No. of respondents		n	%
Food shopping habits	429	Supermarket	367	86
		Take away/home	28	7
		Small shops (neighbourhood, market)	169	39
		Local product (Km 0) in general	26	6
		Local product (Km 0) < 50%	35	8
		Local product (Km 0) ≥ 50%	32	8
Transport (usually used for shopping)	413	Car (0–5 km)	151	37
		Car (6–10 km)	24	6
		Car (> 11 km)	3	0.7
		Walking	225	55
		Public transport	10	2
Energy source for cooking	415	Butane gas	26	6
		Natural gas	143	35
		Electricity	246	59
		Biomass (firewood, pellets)	0	0
Waste (How much of the food do you end up throwing away?)	415	< 5%	321	77
		6%–10%	79	19
		11%–25%	13	3
		≥ 26%	2	0.5
Beverage packaging (breakfast, lunch and dinner)	376	Glass	53	15
		Tetra Brik	88	24
		Plastic	121	33
		No packaging	102	28
Food packaging (breakfast, lunch and dinner)	375	Glass	15	4
		Tetra brick	13	3
		Plastic	192	51
		Paper	66	18
		No packaging	89	24
Coffee capsules (N/day)	241	0	89	54
		1	63	26
		2	45	19
		3	4	2

5.4. Environmental Impacts of Infant Feeding Types

5.4.1. Environmental Impacts of Formula Milk and Accessories

These impacts were calculated by accounting for all the aspects represented in Tables 2 and 3. Table 5 presents the environmental impacts of the three infant feeding types. The results reveal significant differences in the three environmental impacts depending on infant feeding type, with the greatest difference being in CC.

TABLE 5.

Environmental impacts of different infant feeding types (Kruskal–Wallis test).

Environmental impacts	Infant feeding type	n	Median	95% CI	p
CC (kg CO2eq)	FF	54	4.98	[4.36–5.13]	0.0001
	MF	93	1.55	[1.04–1.80]
	EBF	255	0.01	[0.008–0.13]
WC a (m3)	FF	54	0.016	[< 0.001–0.010]	0.0001
	MF	93	0.013	[0.009–0.015]
	EBF	255	0.003	[0.001–0.005]
WS (m3eq)	FF	54	0.58	[0.51–0.63]	0.0001
	MF	93	0.33	[0.27–0.40]
	EBF	255	0.08	[0.024–0.13]

Note: For the environmental impact calculations, the variable ‘Infant feeding’ included impacts from the infant feeding accessories used (Table A1 in Annex 2) and formula baby bottle impacts (Table A2 in Annex 2) multiplied by the number of baby bottles used in 24 h.

^a WC refers to direct (e.g., water used to make baby formula) and indirect consumption (water used in the formula production chain).

Table 5 presents the environmental impacts of formula and the use of infant feeding accessories. FF had the most significant impacts: (1) CC was almost 500 times higher than for EBF and 2.6 times higher than for MF; (2) WC was 4 times higher than for EBF and 1.5 times greater than for MF; and (3) WS was 4 times higher than for EBF and 1.7 times higher than for MF.

5.4.2. Impact of Maternal Diet and Food Consumption Habits

Based on the 24‐h food register completed by participants, the results show that the food product consumed with the highest CC was beef (31.7 kg CO₂eq/kg product), while mixed salad had the lowest CC (0.203 kg CO₂eq/kg product). As for WC, the food with the highest impact was rice (2.56 m³/kg product), while squid had the lowest impact (0.007 m³/kg product). Regarding WS, the food product with the most significant impact was again rice (77.4 m³eq/kg product), while bread had the lowest (0.254 m³eq/kg product).

Table 6 presents the environmental impacts of maternal diet (24‐h register), including food consumption habits. The results show a slight increase in the environmental impact of EBF. However, it is a non‐statistically significant increase compared to the other two types of infant feeding.

TABLE 6.

Environmental impacts of maternal diet and food consumption habits on infant feeding types (Kruskal–Wallis test).

Environmental impacts	Infant feeding type	n	Median	95% CI	p
CC (kg CO2eq)	FF	54	4.54	[3.74–5.30]	0.850
	MF	92	4.45	[4.19–4.94]
	EBF	256	4.60	[4.26–4.78]
WC (m3)	FF	54	0.231	[0.157–0.312]	0.497
	MF	92	0.277	[0.178–0.344]
	EBF	256	0.283	[0.219–0.331]
WS (m3eq)	FF	54	6.20	[5.43–7.22]	0.917
	MF	92	5.86	[5.33–7.06]
	EBF	256	6.19	[5.63–6.87]

Note: (1) WC includes direct (e.g., water used to make baby formula) and indirect consumption (water used in the formula production chain). (2) For the environmental impact calculations, the variable ‘maternal diet (24 h)’ included the energy source used for cooking, food waste, food (products, beverages and the amount used for breakfast, lunch, dinner and snacks consumed as per 24 h register), food storage before cooking, cooking type and type of packaging used.

The impact of the dietary intake of non‐BF mothers does not need to be accounted for in FF. Moreover, the difference in the impact of BF mothers' diet cannot be included as it is not significant.

6. Discussion

This study aimed to determine the environmental impacts (CC, WC and WS) of three infant feeding types (EBF, MF and FF), taking into account the use of formula and infant feeding accessories and the potentially increased dietary intake of BF mothers.

We identified significant differences in the three environmental impacts related to formula and infant feeding accessories. However, there were no significant differences in the environmental impacts related to maternal diet and food consumption habits despite the increased caloric intake (238 kcal) of BF mothers. Lastly, our results do not include the impact of maternal diet.

In our study, the median CC of EBF is not zero, as reported by Linnecar et al. for IBFAN (Linnecar et al. 2014). If comparing exclusively the CC of formula and infant feeding accessories used, EBF had a 500‐fold smaller impact than FF.

When we measured the impact of formula and feeding accessories (for extracting, storing and heating expressed milk), we observed that the impacts were not very relevant: CC 0.01 kg CO₂eq, WC 0.003 m³ and WS 0.08 m³eq for EBF.

To the best of our knowledge, no studies are available on the environmental impacts of some infant feeding accessories, such as disposable nursing pads. In our study, 50% of mothers reported using disposable nursing pads (11.4 per week), while 20% opted for reusable ones. Nursing pads are made from cotton, which has a high WF as water is needed to produce and recycle it (Chapagain et al. 2006; Zhang et al. 2021).

The total environmental impact was less in EBF compared to FF despite that 37.7% of participants in the present study used breast pump. It could be due the fact that 84% of the participants took the 16 weeks of paid maternity leave available in Spain and therefore did not need to express and store breast milk as they breastfed directly. In the United States, the situation is worse as there is no national policy guaranteeing paid leave to employed mothers who give birth (Jou et al. 2018). This can explain the controversial results reported in the study of Amonkar (Amonkar et al. 2019), concluding that that the CC of EBF was 18% higher than that of FF. Their calculations took into account the theoretical basis that all lactating American women used the breast pump with an average of 2.14 extractions per day and also included the impact of freezer storage and subsequent heating of the already expressed milk (Amonkar et al. 2019).

Karlsson et al. reported the impacts of formula in several countries, assessing the entire life cycle. They also measured the impact of the mother's diet needed to produce 1 kg of breast milk. According to their findings, the impact of EBF is 46% smaller than that of FF (Karlsson et al. 2019). In Norway, Andresen et al. found the environmental impact of exclusive FF to be 35%–72% higher. For infant formula, cow milk was the main contributor to the total score for all impact categories. The environmental impact of BF depended on the composition of the BF mother's diet (Andresen et al. 2022).

Our results show that BF women consumed an average of 1700 kcal daily, which is less than recommended by the local government (2000 kcal) and other publications (a minimum of 1800 kcal) (Ares Segura, Arena Ansótegui, and Díaz‐Gómez 2016). It is also possible that mothers in Spain consume less in terms of total calories as they follow the Mediterranean diet, unlike women in countries with cold climates and tend to quickly return to their pre‐pregnancy weight (Knoph et al. 2013; Stein and Fairburn 1996). Plant‐based diets also have a smaller impact, although they only represent 1.2% of participants' diets in our study (Andresen et al. 2022).

The initial objective of this study was to calculate the environmental impacts associated with the increased dietary intake of BF mothers and include it in calculations along with the impact of formula and BF accessories, but it was not possible to do so. Our results showed an increase of 238 kcal in BF mothers, which was less than the generally recommended 500 kcal extra (20%) (Amonkar et al. 2019; Andresen et al. 2022; Karlsson et al. 2019; Dewey 1997; FAO 2004; Jiménez Ortega et al. 2019). Despite the small increase in calories consumed, we did not observe a significant increase in the environmental impacts. One potential explanation would be that BF mothers strive to follow a healthy Mediterranean diet rich in vegetables and legumes, which has a smaller environmental impact.

It is interesting to note that the CC impact of maternal diet was similar to the CC impact of a 1‐month‐old child who is formula‐fed.

The WF of maternal diet was greater than that of infant feeding type and feeding accessories. The WS impact of the infant feeding types was less than 1 m³eq, while for maternal diet it was 10 m³eq, representing a 10‐fold difference. As Spain has high water stress (Vargas and Paneque 2019), consuming some food products, such as apples, rice, oil, avocados, beef and pork, significantly increases the impact (Blas, Garrido, and Willaarts 2018).

77% of participants reported food waste of less than 5%. These results are much lower than the theoretical estimates (31%) in the United States (Amonkar et al. 2019) and European values (15%) (Andresen et al. 2022). As food production is linked to WF, reducing food waste would help reduce the WF. Therefore, a 50% reduction in food and water waste could reduce the global WS impact by 18% (Ingrao et al. 2023).

Another factor that contributes to reducing the WF is the previously reported association between EBF and amenorrhea, which means BF women do not need to use menstrual products (Bai and Alsaidi 2024). This factor was not included in our study, however.

In conclusion, we observed a smaller environmental impact of EBF compared to FF. The three environmental impacts (CC, WC and WS) are significant when accounting for formula and BF accessories. The impacts associated with differences in maternal diet for the three infant feeding types were insignificant. As for EBF, it was proven to be the healthiest and most sustainable type of infant feeding.

In short, joint efforts to reduce food waste and consume a healthier and more sustainable diet with reduced packaging and energy use for food conservation and cooking are also essential in working towards the SDGs.

The important role of midwives and other health personnel who are in the direct contact with pregnant and postpartum women consists in providing more information and support to both motivate and accompany them for a better change.

6.1. Strengths and Limitations of the Study

6.1.1. Strengths

As far as we know, this study is the first of its kind to be conducted in Spain and has a substantial sample size (429 participants). This study provides real data on formula volumes, maternal diet and habits of postpartum mothers during their infants' first month of life, analysed from the perspective of sustainability. It can help mothers make decisions regarding how they feed their infants, taking into account that BF is the healthiest and most sustainable option.

6.2. Limitations

One limitation is that the study was cross‐sectional (at 1 month postpartum). Another is related to self‐evaluation and bias in replies provided by participants, possibly leading to underreporting food amounts (or portion sizes) on the diet register or food waste due to social desirability. Complementary data are needed to estimate the impact of transportation used to purchase food habits more precisely, such as the volume of each purchase in kilogram and shopping frequency.

Establishing a language barrier as an exclusion criterion left out many sub‐Saharan and Maghreb immigrants, who generally opt for exclusive, extended BF and consume diets with less meat. Lastly, we came across the difficulty of accounting for the increased dietary intake of BF mothers. Theoretically, it would be necessary to calculate the difference between their pre‐pregnancy diet and during BF, but it is difficult to perform in real conditions (especially in spontaneous pregnancies).

6.3. Recommendations for Further Research

Future studies with more details on maternal diet are needed. Other studies related to the effectiveness of educational intervention for both professionals and the general public are needed to observe if environmental impacts can be reduced through information and behavioural changes by emphasising that BF is the healthiest and most sustainable form of infant feeding.

6.4. Implications for Policy and Practice

We expect that educating both healthcare professionals and the general public on healthy and sustainable infant feeding and dietary habits could help reduce environmental impacts and reach the SDGs.

Recommendations might include using reusable nursing pads, direct BF without unnecessary pumping, taking measures to limit formula and food waste and becoming familiar with more sustainable foods and habits.

7. Conclusion

Exclusive BF has proven to be the most sustainable type of infant feeding in terms of the three impacts studied (CC, WF and WC), even when including the impact of feeding accessories and formula. The greatest difference in environmental impacts was in CC, followed by WS and then WC. Though no significant differences in the environmental impacts were observed related to maternal dietary intake and food consumption habits across the three infant feeding types in this study, in general, it is important to follow the healthy and sustainable diet for everybody.

Midwives other health professionals play a crucial role in both—education and support of general public, specifically future mothers, about benefits of healthy and sustainable nutrition for the dyad mother–child and preservation of the environment and planetary health. Midwives are in direct touch with pregnant and postpartum women that can facilitate the education and motivation of the behavioural change of the general public. Further work to see the impacts of educational and counselling programmes delivered by midwives and other health personnel is needed to check the efficacy of such support to general public.

Author Contributions

R.M.C.‐F., G.F.‐P., J.C.‐B. and M.C.‐V. conceived the idea of the project; R.G.‐S. prepared the REDCap data collection questionnaires; G.C.‐O., R.M.C.‐F., J.C.‐B., L.M.‐P., Mª.M.V.‐H., M.G.‐M. and A.R.‐L. made substantial contributions to the acquisition and interpretation of data; L.L., A.R.‐L., R.M.C.‐F. and J.C.‐B. drafted the initial manuscript and updated it after reviews; L.L. performed statistical analysis; E.P.A. performed environmental impact assessment; R.G.‐S., R.M.C.‐F., J.C.‐B., Mª.M.V.‐H., M.G.‐M., L.M.‐P., E.P.A., P.T.‐M., G.F.‐P. and G.C.‐O. reviewed the final draft; G.F.‐P. obtained financial support for the study. All authors read and approved the final manuscript.

Ethics Statement

This project was approved by the Research Ethics Committee of the Jordi Gol i Gurina University Institute Foundation for Primary Health Care Research (IDIAP) under code 22/101‐P dated 22/02/2023.

Conflicts of Interest

The authors declare no conflicts of interests.

Supporting information

Appendix.

Data Availability Statement

The data might be available upon request.