We Tell Mothers to Breastfeed for Six Months. We Rarely Tell Them Why.

The science of breast milk is far more remarkable than the public-health instruction—and understanding it could change how parents, employers and governments make decisions.

Imagine a mother three months after giving birth.

Her maternity leave is ending.

On the kitchen counter is a breast pump. In the refrigerator are carefully labelled bottles of expressed milk. Somewhere nearby may be a tin of infant formula, bought partly for reassurance: just in case. She has meetings to attend. Deadlines to meet. Perhaps a commute through Nairobi traffic. Perhaps travel is coming. And hanging over all these decisions is a recommendation she has probably heard many times:

Breastfeed exclusively for six months.

But here is the question we rarely ask:

Did anyone properly explain why?

Not simply that breast milk is "best." Not another poster showing a happy mother and baby. Not another instruction from a clinic. What is actually happening biologically? Because once you understand even part of that story, breastfeeding begins to look very different.

And so does the responsibility of fathers, employers and policymakers.

Breast milk is not simply food

We tend to think of milk as nutrition: fat, protein, carbohydrate, vitamins and water. Human breast milk is all of those things.

But it is also biologically active.

It contains antibodies, antimicrobial compounds, anti-inflammatory molecules, hormones, oligosaccharides and living immune cells. Its composition changes over the course of lactation and even within the complex interaction between mother and child. The American Academy of Pediatrics describes human milk as containing antimicrobial, anti-inflammatory, and immunoregulatory agents as well as living leukocytes that contribute to the infant's developing immune system.

That already makes the phrase "feeding the baby" feel inadequate. Something much richer is taking place.

Then scientists noticed something extraordinary

In one fascinating study, researchers measured immune cells in breast milk when mothers and babies were healthy and when either became ill. During infection, the concentration of leukocytes—white blood cells—in breast milk could rise dramatically.

After recovery, it fell again. The milk appeared to be responding to what was happening within the mother-infant system.

Pause there for a moment.

This is not simply a mother manufacturing a fixed nutritional product and delivering it several times a day.

The system is dynamic. Something changes. The baby's environment changes.

The mother's biology changes. And the milk changes with it.

Scientists are still working out all the signaling pathways involved. We should resist the temptation to turn intriguing mechanisms into established facts before the evidence is there.

But one hypothesis is particularly fascinating.

Is the breast also listening?

During direct breastfeeding, milk and infant saliva are in intimate contact. Laboratory research has shown that when neonatal saliva interacts with breast milk, chemical reactions occur that can inhibit the growth of some opportunistic microorganisms.

Researchers have also investigated whether the pressure changes associated with suckling may allow tiny amounts of oral material to move back toward the nipple ducts.

You will sometimes see this described online as "backwash" or even biological Wi-Fi: the baby supposedly sends information through saliva and the mother immediately manufactures precisely targeted antibodies in response. That makes a wonderful story.

The full mechanism has not been proven that neatly.

But the broader scientific finding remains remarkable: breastfeeding appears to involve a far more dynamic biological relationship than simply transferring calories from one body to another. And parents deserve to know that. Not because we should frighten mothers who cannot breastfeed. Not because we should romanticize breastfeeding.

But because informed choice requires information.

And this is where pumping enters the story

This distinction matters enormously for working mothers.

WHO's definition of exclusive breastfeeding explicitly includes expressed breast milk. A baby receiving only breast milk—whether directly from the breast or expressed—is still exclusively breastfed. That deserves emphasis.

Pumping is breastfeeding.

For millions of women, expressing milk is what makes continued breastfeeding possible after returning to work. Human milk does not suddenly lose its nutritional and immunological importance because it entered a bottle.

There are differences, however.

Fresh milk preserves bioactive properties particularly well; refrigeration, freezing, thawing and storage can reduce some biological activity. That is one reason clinical guidance for vulnerable infants sometimes places particular value on fresh maternal milk.

And direct breastfeeding may permit biological interactions between mother and infant that expressing and storing milk cannot reproduce in exactly the same way. We do not yet know how important every one of those differences is. That is precisely why parents should hear the evidence in its full form:

What we know. What we suspect. And what we are still discovering.

Formula belongs in this conversation too

There are many reasons families use infant formula.

Some mothers cannot produce sufficient milk. Some experience severe pain or illness. Some babies have particular clinical circumstances. Some women return to demanding work environments. Some families combination-feed. Some simply make a different informed choice. Formula can provide essential nutrition. But it is important not to confuse nutritional substitution with biological equivalence.

Modern infant formula can provide proteins, fats, carbohydrates, vitamins, and minerals required for growth. It cannot reproduce the entire living biological system of human milk—the maternal antibodies, living leukocytes, and changing immunological environment described in the breastfeeding literature.

Knowing that is not an argument for guilt.

Information is not guilt.

If anything, withholding meaningful information because we are frightened that someone might feel uncomfortable is the opposite of informed healthcare. We should trust adults with complexity.

Now consider the working mother

This is where biology becomes policy.

WHO recommends exclusive breastfeeding for the first six months of life because of its benefits for growth, development and health. Its latest global nutrition brief reports that about 48% of infants under six months were exclusively breastfed in 2024. Now consider Kenya and many other countries like the United States.

Kenyan law provides a female employee with three months of paid maternity leave.

Three months. Yet the health recommendation says six. Between month three and month six sits a working woman, a baby—and an enormous logistical problem.

Kenya's Health Act recognizes this. It requires employers to establish lactation stations with facilities including washing equipment, refrigeration or cooling facilities, and electrical outlets for pumps. Nursing employees are also entitled to additional compensated breaks to breastfeed or express milk, up to a total of one hour in an eight-hour working period.

That is important legislation.

But a room with a refrigerator does not automatically create a breastfeeding-supportive workplace.

Culture matters.

Can a woman actually leave a meeting to express milk without being judged?

Can she travel?

Can she work flexibly?

Is there somewhere safe and private to pump? Can her baby be brought close to the workplace? Does her supervisor understand why expressing every few hours matters? Does her partner understand how much work all of this requires?

UNICEF now explicitly encourages employers to think beyond compliance—to provide flexible work, breastfeeding support, childcare and family-friendly workplaces.

This is no longer merely a "women's issue."

It is organizational design.

Fathers need this information too

There is another person who is strangely absent from much breastfeeding communication:

the father.

If breastfeeding is presented as something occurring between a mother, a baby, and a clinic, fathers can easily interpret themselves as spectators. They are not. Once a father understands what those first months may mean biologically, his role becomes clearer.

Protect the mother's time. Take over other tasks. Handle some of the night logistics. Help with storage and cleaning. Advocate for the mother when relatives, workplaces, or social expectations make breastfeeding difficult. Help her obtain professional lactation support when something is not working.

And perhaps most importantly, understand that the mother who is breastfeeding or pumping is performing a substantial piece of biological and logistical work that is largely invisible. Breastfeeding may occur in a woman's body.

Supporting it is a family responsibility.

The public-health problem is therefore bigger than breastfeeding

We often communicate science by reducing it to an instruction.

Breastfeed for six months.

Exercise for 150 minutes.

Reduce salt.

Vaccinate your child.

Finish the antibiotics.

Sometimes simplicity is necessary.

But there is a cost when we remove the mechanism completely. People start hearing recommendations as bureaucratic commands rather than conclusions derived from evidence. Understanding why can change behavior.

It creates agency.

A mother deciding whether to carry a pump on a business trip sees a different decision. A father deciding whether to wake up and help at 2 a.m. sees a different decision. A CEO considering whether a lactation room is an unnecessary expense sees a different decision. A policymaker designing maternity protection sees a different decision. Science has traveled all the way from the laboratory to the guideline.

But unless the meaning travels with it, evidence has not truly reached the citizen.

Perhaps that is the real lesson

The most astonishing thing about breastfeeding may not be any single antibody, immune cell or signaling mechanism.

It is the architecture.

Mother and infant are not two completely separate biological systems during those early months. They are interacting systems. Nutrition, immunity, behavior, touch, microbiology and environment meet repeatedly, several times every day. We are still discovering how sophisticated those interactions are. So perhaps the public-health message should no longer stop at:

"Breastfeed exclusively for six months."

Perhaps it should continue:

"Here is why those months matter. Here is what your body is doing. Here is what we know. Here is what we are still discovering. And here is how your family, employer and society can help make it possible."

That is not more complicated communication. That is better communication. And it leaves us with a question much larger than breastfeeding:

If science tells mothers that six months matters, have we built families, workplaces and policies that actually make six months possible?

That is a conversation worth having.

The Daily Pulse explores the systems connecting evidence, policy and everyday human decisions.