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Breastmilk vs. Formula - what's the difference?
Dr. Surya Manickam
June 16, 2025
Table of Contents
So what’s the difference between breastmilk and formula?
My name is Dr. Manickam and I’m a pediatrician and NICU doctor.
For practical purposes, the breakdown of protein, fat, and carbohydrates are essentially the same, with breastmilk having slightly less protein and more fat than standard cow’s milk formula. The important difference is in how they are absorbed by your baby.
Breastmilk has more whey than casein protein, enzymes to help babies digest fat, and has carbohydrates that help support healthy gut bacteria. Formula is harder to absorb and can sometimes cause mild swelling or irritation to your baby’s intestinal lining, especially for preterm babies
Breastmilk also has antibodies to support your baby’s immune system and changes in content over time, evolving to your baby’s different nutritional needs as they get older, which is super cool. For these reasons, the more a baby drinks breastmilk, the lower their risk of ear infections, lung infections, allergies, asthma, obesity, diabetes, and some childhood cancers.
That being said formula also has its pros. Firstly, it’s more convenient, and it also has more vitamin D and iron, allows babies to eat more in the beginning of life when mom’s milk is coming in, reducing the chance of jaundice. And it allows the family to help more with baby feeding.
So for my recommendation: breastmilk is preferred, but having your baby fed is the most important thing - so feel comfortable to use formula whenever you have to. In fact, we always recommend parents have formula available, especially in the first 1-2 weeks, when mom’s breastmilk is still coming in. Preterm babies, however, are the exception - for them breastmilk or donor breastmilk needs to be prioritized, especially for those less than 34 weeks.
Here are two tables summarizing some of what we talked about.
Component | Breastmilk | Infant Formula |
|---|---|---|
Proteins | Easily digestible; includes whey and casein (whey > casein in early milk) | Higher total protein; usually more casein; some formulas add whey |
Fats | Rich in essential fatty acids (DHA, ARA), enzymes for digestion | Plant-based oils; DHA/ARA often added synthetically |
Carbohydrates | Mainly lactose; includes oligosaccharides that support gut flora | Mostly lactose; some formulas use corn syrup solids or glucose |
Vitamins | Variable—depends on maternal diet; low in vitamin D | Fortified with stable levels of all essential vitamins |
Minerals | Lower levels but higher bioavailability (e.g., iron, zinc, calcium) | Higher levels to compensate for lower absorption |
Antibodies | Contains IgA, lactoferrin, lysozyme, etc. for immune protection | Absent—no live antibodies |
Hormones & Enzymes | Includes leptin, ghrelin, growth factors, and enzymes (e.g., lipase) | Absent or added synthetically in some specialized formulas |
Probiotics & Prebiotics | Contains human milk oligosaccharides (HMOs) that support healthy gut bacteria | Some formulas add prebiotics or probiotics, but not identical to HMOs |
Living Cells | Contains immune cells (macrophages, stem cells, lymphocytes) | None |
Taste & Adaptability | Flavor varies with maternal diet; changes over time to meet baby's needs | Uniform taste; fixed composition unless formula is changed |
Cost & Accessibility | Free if breastfeeding is established; no preparation needed | Can be expensive; requires clean water and preparation |
Health Area | Benefits of Breastmilk |
|---|---|
Immune System | - Fewer infections (due to antibodies like IgA, lactoferrin, lysozyme)- Passive immunity during early life |
Ear Infections (Otitis Media) | - Lower risk—up to 50% reduction in incidence compared to formula-fed infants |
Respiratory Infections | - Reduced risk of lower respiratory tract infections, bronchiolitis, and pneumonia |
GI Infections / Diarrhea | - Lower incidence of gastroenteritis and diarrhea |
Necrotizing Enterocolitis (NEC) | - Up to 77% reduced risk in preterm infants when fed human milk vs formula |
Sudden Infant Death Syndrome (SIDS) | - 50% lower risk of SIDS in breastfed infants |
Allergies & Asthma | - Lower risk, especially in families with atopic history |
Obesity | - Modestly lower risk of obesity and metabolic syndrome in childhood and adolescence |
Type 1 & Type 2 Diabetes | - Slightly lower risk in breastfed children (mechanism not fully understood) |
Childhood Cancers | - Some studies suggest reduced risk of leukemia and lymphoma, though evidence is moderate |
Neurodevelopment | - Better cognitive outcomes and higher IQ scores (especially with longer exclusive breastfeeding) |
Dental Health | - Lower risk of malocclusion and dental caries compared to bottle-fed infants |
Maternal Benefits | - Reduced risk of breast and ovarian cancer, type 2 diabetes, and postpartum depression |
Disclaimers: All of the opinions we express are of our own and not of any of our prior or current institutional affiliations. The information we share is primarily for babies born full term (over 37 weeks gestation) and without any medical issues. All the information presented above is for educational purposes and should not be taken as personal medical advice.