At 3 am in her Thiruvananthapuram home, Anjali Suresh cradled her five-week-old daughter, Ananya, who had barely settled before waking to feed once more. Exhausted, she wondered aloud whether a bottle of formula might buy her a longer night. Her neighbour had said formula “keeps babies fuller”. Anjali kept turning the question over: what exactly was in each cup, and did it matter?
Obstetricians say it does, and the answer begins with one idea: breast milk is not just a food. “Breast milk is much more than a source of nutrition,” says Dr Priya SP Patil, consultant, obstetrician & gynaecologist, Altius Hospital, Bengaluru. “Its lactose provides energy and supports mineral absorption, while its easily digestible proteins support growth and development. Unlike formula, breast milk also contains bioactive proteins, antibodies and enzymes that help mature the gut and support immunity.”
Dr Gaana Sreenivas, consultant, obstetrician-gynaecologist (OB-GYN), BirthRight By Rainbow Hospital, Bengaluru, explains that the milk is matched to a very immature digestive system. “Breast milk contains whey and casein proteins in an easily digestible ratio tailored to a newborn’s immature stomach, alongside natural lactose that fuels brain development without overloading metabolism.” Formula can copy the calories, she says, “but they lack the living bio-active proteins, enzymes, and dynamic nutrient ratios that adapt to a baby’s daily growing needs.”
Dr Jyoti Kankanala, senior consultant, OB-GYN, Citizens Specialty Hospital, Hyderabad, puts the emphasis on change rather than quantity. “Breast milk delivers fuel and building materials in a form suited to an infant’s developing body,” she says. “Its advantage lies in this changing biological combination, rather than simply the amount of carbohydrate or protein it contains.”
That lines up with the protein numbers. Mature human milk carries roughly 0.8 to 1.0 g of protein per 100 ml, and the concentration is higher early in lactation before it declines. It is a relatively low, shifting supply that follows the baby’s needs, whereas formula is a fixed recipe. Researchers who study the Early Protein Hypothesis worry that high-protein formula may speed weight gain in infancy, which is one reason regulators watch formula composition so closely.
One of the most striking parts of breast milk is a group of sugars the baby cannot digest at all. Human milk oligosaccharides (HMOs) exist to feed the bacteria in the gut. “HMOs act as natural prebiotics, selectively nourishing beneficial bacteria such as Bifidobacteria in the infant’s gut,” Dr Patil says. Along with lactose and protective immune factors, they help establish a healthy microbiome, strengthen the intestinal barrier and support immune development.
Dr Sreenivas describes the mechanism in vivid terms. “HMOs are unique prebiotic carbohydrates that cannot be digested by the infant; instead, they exclusively nourish beneficial bacteria like Bifidobacteria in the gut.” The result, she says, is a gut shield that stops pathogens sticking to the intestinal walls and trains the immune system for the long term.
Dr Kankanala offers a more measured picture. “Think of HMOs as nourishment reserved for particular helpful gut microbes, especially bifidobacteria,” she says. Lactose, by contrast, serves mainly as the baby’s energy source and does not play the same selective prebiotic role. Her caution is worth repeating: lasting immune benefits “should not be presented as guaranteed.”
This intricate microbial balance lies at the heart of recent regulatory moves. The draft, released on 16 October 2026 and not yet finalised, targets added sucrose and fructose in foods for babies under six months. Neonatologists point out that Bifidobacteria thrive on lactose, and that swapping it for other sugars may nudge the gut away from the balance seen in breastfed infants, although that finding is still debated.
An appetite that listens to the baby
For Anjali, the promise that formula keeps infants fuller for longer remained her primary question. Doctors say breast milk handles appetite differently. “Breast milk is a dynamic, living biological system whose composition changes with the stage of lactation and during a feed,” says Dr Patil. It carries hormones and bioactive signals involved in appetite regulation and metabolism, and breastfeeding lets infants respond to their own hunger and fullness cues.
Dr Sreenivas adds that milk changes within a single feed. “Breast milk naturally alters its fat content from foremilk to hindmilk during a feed,” she says, and appetite-related hormones in the milk help infants regulate how much they take. “This real-time compositional adjustment prevents overfeeding, supporting healthy, steady growth rates rather than sudden, rapid weight gain.”
Dr Kankanala keeps the claim honest. “Healthy growth depends on both what milk contains and how a baby feeds,” she says, and breastfeeding gives infants opportunities to stop when satisfied. The appetite-related hormones “may contribute”, but breast milk “should not be described as a proven safeguard against excessive weight gain or metabolic disease.”
That balance reassured Anjali more than any slogan could. Breastfeeding is not magic, and it does not guarantee a perfect outcome. But it is a feed that adjusts itself, feeds the right gut bacteria and lets her daughter decide when she is full. She still had a tiring night ahead. This time, though, she knew why the long hours were worth it, and she asked her doctor about help with latching rather than reaching for the bottle.
The experts agree on one practical point: families who struggle with feeding should seek support early, and any decision about formula should be made with a doctor, not a neighbour.