The benefits of breastfeeding: what does the science say?

Improved cognition

Several studies have highlighted a link between cognition and breastfeeding.

Improvement in eating behaviours

Breastfed babies have more leptin in their bodies than formula-fed babies. Leptin is a key hormone in the regulation of appetite and fat storage. They also regulate their own milk intake and are not passive, unlike bottle-fed babies.
They are better able to regulate their food intake, which helps them develop healthy eating habits [3].

In Kramer's robust study, at eleven and a half years of age, adolescents in the intervention group had lower rates of eating disorders, in both girls and boys. 

Reduced risk of obesity and type 2 diabetes

These data are controversial. Kramer's study indicates that breastfeeding has no effect on the risk of developing overweight/obesity in children.

A review combined various scientific studies to examine the impact of breastfeeding on the risk of developing diabetes and obesity [4].

Potentially lower risk of obesity: among the 11 high-quality studies, the association between breastfeeding and overweight/obesity was weaker, with a 13% reduction in risk.

Potentially lower risk of type 2 diabetes: the risk was lower in subjects who had been breastfed (a 35% reduction in risk).

One explanation for this correlation may be related to the development of different gut bacteria. Breastfed babies have higher levels of beneficial gut bacteria, which may affect fat storage [5].

Please note, however, that these data are observational and simply highlight a correlation between these factors.

Reduction in asthma and eczema

Kramer's study showed no reduction in allergies or asthma in breastfed children. On the contrary, breastfed children tended to have higher rates of allergies and asthma (though this effect was not statistically significant).

These data are at odds with other scientific studies on the subject.

A review of 89 scientific studies examined the link between breastfeeding and the risk of asthma and eczema in children [6].

More or less breastfeeding, in terms of duration, was associated with a reduced risk of asthma in children (aged 5–18 years), and a reduced risk of allergic rhinitis at ≤5 years, although this estimate showed high heterogeneity and low quality. The effect of breastfeeding on this variable is therefore dose-dependent (the longer one breastfeeds, the stronger the effect).

Exclusive breastfeeding for 3–4 months was associated with a reduced risk of eczema under 2 years of age (an estimate based primarily on studies of low methodological quality).

No association was found between breastfeeding and food allergy (an estimate showing high heterogeneity and low quality).

The relationship between breastfeeding and teeth

Malocclusion refers to any deviation or variation from a normal bite (lack of spacing between teeth, overlapping, misalignment, etc.).

A review assessed whether breastfeeding reduces the risk of malocclusions by examining the results of 48 scientific studies [7].

The authors noted that children who had always been breastfed were less likely to develop malocclusions than those who had never been breastfed (66% reduction in risk), those who had been exclusively breastfed had a lower risk of malocclusion than those who had not been exclusively breastfed (46% reduction in risk), and children who had been breastfed for longer were less likely to develop malocclusions than those who had been breastfed for a shorter time (60% reduction in risk). They therefore concluded that breastfeeding reduces the risk of malocclusions.
The biases of this study were controlled; however, no mention is made of dummy/soother use by infants, even though teats can also increase the risk of malocclusions.

This effect may be explained by several hypotheses. The sucking process differs between breastfed and bottle-fed children. Breastfed children display greater facial muscle activity than bottle-fed children, which promotes more appropriate craniofacial growth and jaw bone development. The movement of the lips and tongue during breastfeeding requires the infant to draw out breast milk through a pressure action, whereas for bottle-fed infants the movement to obtain milk is more passive; consequently, there is a greater potential for malocclusion to develop [8].

Furthermore, bottle teats are generally made from a less flexible material, which can exert pressure on the inside of the oral cavity and lead to poor tooth alignment and transverse palatal growth [9].

Breastfeeding and the risk of ear infections

Twenty-four studies, all conducted in the United States or Europe, analysed the effect of breastfeeding on acute otitis media [10]. In pooled analyses, any form of breastfeeding proved protective against ear infections during the first two years of life. Exclusive breastfeeding for the first 6 months was associated with the greatest protection (43% reduction in risk), followed by "more or less" breastfeeding (33% reduction in risk for longer breastfeeding).

These data studied children up to the age of 2 years; beyond this age, there is no evidence that breastfeeding protects against ear infections. However, studies on this topic are limited and the quality of evidence was low, so further studies are needed to determine whether this protective effect persists beyond 2 years of age.

In Kramer's study, no effects of breastfeeding on ear infections were demonstrated in children at 6.5 years of age. This might suggest that such an effect is possible in the short term, but unlikely to persist throughout childhood.

Protects against intestinal diseases

In total, 35 studies involving 7,536 people with Crohn's disease, 7,353 with ulcerative colitis, and 330,222 controls were observed [11]. Ever having been breastfed was associated with a lower risk of Crohn's disease (29% reduction in risk) and ulcerative colitis (22% reduction in risk). Duration of breastfeeding showed a dose-dependent association (the longer the breastfeeding, the greater the reduction in risk), with the greatest reduction in risk when breastfeeding lasted at least 12 months for Crohn's disease (80% reduction in risk) and ulcerative colitis (79% reduction in risk) compared with 3 or 6 months.

This may be due to the fact that breastfeeding influences the infant's microbiome (presence of immunoglobulins in breast milk, prebiotics, etc.).

Similarly, one study showed that formula milk was associated with nearly a fourfold increase in diarrhoeal diseases compared with exclusive breastfeeding in infants both under and over 6 months of age [12].

In a 2014 observational study conducted in premature infants (born before 33 weeks), the effects of breastfeeding versus bovine milk on the risk of necrotising enterocolitis were compared. The authors noted that exclusive breastfeeding in these premature infants reduced the incidence of necrotising enterocolitis (1% for exclusive breastfeeding versus 3.4% for bovine milk) [13].

Reduced risk of mortality

In one article, the authors conducted a review of 13 studies to compare the effect of predominantly, partially, or no breastfeeding versus exclusive breastfeeding on mortality rates during the first six months of life, and the effect of no breastfeeding versus any breastfeeding on mortality rates between 6 and 23 months [14].

RR stands for relative risk; for example, an RR of 3 means that non-breastfed children have a 3 times greater risk of developing the disease being studied than breastfed children.

The risk of all-cause mortality was higher in predominantly breastfed (1.5 times higher risk), partially breastfed (4.8 times higher risk), and non-breastfed (14.4 times higher risk) infants aged 0–5 months compared with exclusively breastfed infants. Children aged 6–11 months and 12–23 months who were not breastfed had a 1.8 times and 2 times higher risk of mortality, respectively, compared with those who were breastfed. The risk of infection-related mortality between 0 and 5 months was higher in predominantly breastfed (1.7 times higher risk), partially breastfed (4.56 times higher risk), and non-breastfed (8.66 times higher risk) infants compared with exclusively breastfed infants. The risk was twice as high in non-breastfed children compared with breastfed children aged 6–23 months.

L’allaitement maternel pourrait impacter la santé de la maman

Une revue a analysé différentes études scientifiques portant sur les effets de l’allaitement maternel et les bénéfices associés pour la maman allaitante [15]. 

L’analyse de ces études indique que l'allaitement maternel supérieur à 12 mois a été associé à une réduction du risque de carcinome mammaire et ovarien de 26% et 37%, respectivement.

Les données sur le risque de cancer sont à nuancer. Ces études montrent des corrélations entre une diminution du risque et l’allaitement maternel, mais elles ne permettent pas d’affirmer qu’allaiter prévient tout risque de développer ces cancers. Par ailleurs, il existe de nombreux types de cancer (hormono-dépendant ou non, etc) et ils dépendent de nombreuses variables, donc des recherches approfondies seraient nécessaires pour évaluer l’effet de l’allaitement et ses mécanismes précis.

Pour en savoir plus sur ce sujet, allez voir notre article sur allaitement et cancer du sein. 

Cette revue a également montré que l'allaitement maternel était associé à une réduction de 32% du risque de diabète de type 2, et que l'allaitement exclusif et l'allaitement prédominant étaient associés à une durée plus longue de l'aménorrhée [16].

Le potentiel bénéfice de l’allaitement sur l’humeur

Une relation a été observée entre l’allaitement maternel et le risque de dépression post partum. Une étude d’observation sur 137 femmes a indiqué que les femmes qui allaitent leurs enfants réduisent leur risque de développer une dépression postpartum, les effets se maintenant au cours des 4 premiers mois du post-partum. La dépression postpartum peut également diminuer le taux d'allaitement, ce qui suggère une corrélation réciproque entre ces variables [17].

Cela pourrait s’expliquer par le fait que l'allaitement atténue les réponses neuroendocriniennes au stress et peut agir pour améliorer l'humeur de la mère. Plus précisément, l'ocytocine et la prolactine, hormones responsables de la lactation, auraient des effets bénéfiques sur l'humeur. L'ocytocine, en particulier, est une hormone qui favorise les sentiments de réconfort et de relaxation pendant l'allaitement. De plus, il est suggéré que la lactation atténue les réponses au stress dues au cortisol en diminuant les niveaux d'hormones de stress (en particulier le cortisol) et en améliorant le sommeil [18].

It is one thing to say: "Breastfeeding has benefits for your child, so let me help you discover them, and help you get there if that is your choice" but it is quite another to say: "It is the most important thing you can do for your child, and if it does not work for you, that is very unfortunate and, in the long run, it will have serious consequences." Although no one literally says the latter, that is how many women perceive it.

Some data come from observational studies: outcomes of interest (such as IQ, diabetes, obesity) are examined and correlated with breastfeeding. In most cases, risk estimators can be determined that highlight a correlation without establishing a cause-and-effect relationship.

Observational studies on breastfeeding deserve scepticism, as they all suffer from the same major problem: breastfed infants differ on average from formula-fed infants not only in how they are fed during infancy, but also in virtually every other possible factor — the mother's education, the mother's IQ, poverty, neighbourhood safety, exposure to environmental toxins, ethnicity, and the type and quality of childcare. In scientific terms, breastfeeding is confounded, endlessly.

Human studies, particularly in the field of health, are difficult to conduct. Results must be interpreted with caution, and a single finding does not necessarily demonstrate an absolute truth.

Ideally, several large randomised controlled trials would be conducted, in which mothers would be randomly assigned to breastfeed. Randomised controlled trials are the gold standard in medicine for determining whether a true cause-and-effect relationship exists. In practice, however, such trials are neither feasible nor ethical.

Selon le stade de la lactation, 80 à 50 % des protéines du lait maternel sont du lactosérum (qui contient entre autres la lactalbumine qui permet la production de lactose, sucre qui favorise l’absorption du calcium et du fer et a un effet bénéfique sur les bactéries intestinales). Le rapport lactosérum/caséine dans le lait humain fluctue entre 70/30 et 80/20 en début de lactation et diminue à 50/50 en fin de lactation. Cette proportion est nettement supérieure à celle du lait de vache où les protéines de lactosérum ne représentent que 18% des protéines du lait [19]. 
D’autre part, les caséines du lait maternel sont différentes de celles du lait de vache, certaines vont avoir des effets bifidogènes (protecteur au niveau intestinal) et elles sont également plus petites et plus digestes pour le nourrisson [20].

De plus, le lait humain est riche en facteurs de croissance et hormones, permettant une bonne croissance intestinale et une réduction de l’inflammation gastro-intestinale.

Le lait maternel est riche en acides gras polyinsaturés [21]. Il contient des acides gras essentiels tels que : l’acide arachidonique et l’acide docosahexaénoïque (DHA), qui sont les acides gras les plus abondants dans le cerveau humain, permettant son bon développement. D’autre part, le lait maternel contient du cholestérol, qui a des rôles importants dans la structure membranaire, comme précurseur hormonal et dans le développement cérébral [22].

Il contient de l’alpha-lactalbumine permettant de fixer les minéraux (calcium, magnésium) et de renforcer le système immunitaire. Il contient également des protéines antimicrobiennes et antivirales pour le système immunitaire précoce de bébé (lactoferrine, lysozyme et lactoperoxydase).

Le lait maternel contient également près de 130 oligosaccharides différents qui sont bénéfiques, entre autres, pour les bactéries au niveau du côlon [23].

Enfin, les protéines du lait maternel ne permettent pas seulement un apport en nutriments et en molécules de défense, mais également de stimuler directement la croissance des tissus ou organes de bébé et de développer le système immunitaire.[24]

Il y a encore beaucoup de choses que les chercheurs ignorent sur la composition du lait humain. Par exemple, le lait maternel va varier d’une mère à l’autre, il va être personnalisé pour bébé, et son contenu nutritionnel change tout au long de la journée et au fil des jours pour répondre aux besoins de bébé. [25] Il peut également varier selon les choix alimentaires, les facteurs environnementaux ou encore les infections de la mère. [26]

Pour en savoir plus, allez voir notre article sur la composition du lait maternel.

Au-delà des effets potentiels de l’allaitement sur la santé de la maman et de son enfant, il existe de nombreux autres effets bénéfiques non quantifiables : plaisir de l’allaitement pour les deux, sensation de bien-être, création de liens, temps de sommeil augmenté (une étude a montré que les parents d’enfants allaités dormaient en moyenne 40 à 45 minutes de plus), etc. Pour en savoir plus, allez voir notre article sur allaitement et sommeil.

Bien sûr, ne pas allaiter ne veut pas dire que vous ne serez pas proche de votre enfant, l’allaitement est une autre façon de créer des liens, mais il en existe d’autres et cela n’enlève rien à l’amour entre une maman et son enfant. 
 

L’allaitement est un choix, c’est votre corps et votre décision !