Why can’t babies drink water but use water on formula milk?


Why can’t babies drink water but use water on formula milk?

In: Biology

Babies can drink water – like its a thing that could happen. The main issue tends to be that babies have teeny tiny stomachs and teeny tiny kidneys and comparatively high nutritional needs. Like hummingbirds. If they drink water regularly, they likely wont be able to *also* consume all the calories they need to grow. If they drink a lot of water at once, their kidneys might not be able to process it quickly enough or efficiently enough.

They simply need the nutritients in the milk, water alone would just supress the hunger/thirst without actually giving the baby all it needs (small stomach)

I’m a pediatrician.

As people have mentioned, they need all the nutrition in the formula or breastmilk to grow. If you give them water, that means they’re not drinking as many calories.

Even more importantly, giving a baby any significant amount of just regular water can effectively “water down” their blood electrolyte levels, particularly their sodium. This can cause brain swelling, seizures, and death. Their kidneys will not regulate their sodium/water balance quickly enough for this to be safe. I have treated this issue multiple times, and this is why the doctors in the newborn nursery tell you this before you leave. This is why most pediatricians will ask how you are mixing the formula at your newborn baby visits, to make sure it’s the correct ratio.

Babies should drink nothing but breastmilk or properly mixed formula. We will sometimes recommend Pedialyte if the baby is sick and not tolerating breastmilk/formula, but this is only for special circumstances, and should only be done under the advice from your pediatrician.

Babies are small. What would be a small amount of water to you, proportionally speaking, represents a much larger portion of their total body water. Basically, if babies have too much water without the protein, fat, carbohydrates, and electrolytes found in formula or breast milk, their blood electrolytes, and in particular their sodium, can get diluted and drop to dangerous levels. Kidneys are pretty smart and efficient even in younger babies beyond the immediate newborn period but sometimes too much water is just too much to handle.

Most frequently, we see a drop in the serum sodium level when babies are given plain water in excess or are given diluted formula (families will sometimes dilute formula to save money by “stretching” the formula supply). If your sodium gets too low, it causes seizures.

A good rule of thumb is that babies can have one ounce of water a day for every month of age they are over six months up til about 10-12 months of age (so a six month old can have an ounce of plain water a day, a seven month old can have two ounces, etc.).

Source: I’m a pediatrician and I’ve treated hyponatremic (low sodium) seizures many a time, unfortunately.

Its multiple issues, depends on dose and age, but here’s a few-

Maturity- newborns are not great at balancing their salts etc due to immature kidneys. Therefore they need salts (sodium being the big one) in their liquids and develop dangerous salt imbalances more easily – when newborns or even older babies that are still not eating solids are given water too much or watered down formula exclusively hyponatremia (low blood sodium) is the big danger.

Sugar – newborns have normally lower blood sugar than adults, but are prone to developing low sugar quickly, so need regular feeds containing sugars (formula or breastmilk).

Calories – for older babies that are starting solids, they can’t still eat and digest enough food to get all their energy that way, so need high energy liquids still (breastmilk and formula are high in fats and sugars).

Note – some naturopaths etc have at times advised elimination diets (edit- wildly restrictive, not your basic dairy etc) to breastfeeding mothers or watered down formula or water to very young infants as treatments for various issues, eczema being a big one. This is very dangerous, and its well worth knowing why!

Tldr- milk is the whole food for babies – water is just the drink component, and doesnt cut it alone.