What color is your baby poop?

How does Plain Jane milk come out the other end as Technicolor poop?

Baby poop’s unique color is a combination of intestinal bacteria, bile and whatever was swallowed. Two jars of squash equals orange poop. But even when baby is only taking formula or breast milk, the color changes daily and even diaper-to-diaper as the relative composition of these components change.

The characteristic yellow or green hue comes from bile. Bile is made in the liver and stored in the gallbladder. This fluid neutralizes stomach acid and helps digest fats when it is secreted into the small intestine. It will make poop more green if it moves too quickly through the intestines, and more yellow or brown when it moves at a normal digestive pace.

Intestinal bacteria contribute to the poop color conundrum as well. Babies grow in a bacteria-free environment in the womb, but as soon as they are born they are exposed to a world of bacteria. During birth, bacteria from the mother and the environment very quickly colonize the infant’s gut. No two babies have the same bacteria. In fact, recent studies revealed that babies born by C-section have very different intestinal bacteria than babies born by vaginal delivery.

Other studies have examined individual baby’s poops at intervals over the first year and show that every baby has a unique profile of bacterial types unlike any other baby. By their first birthday their intestinal populations become quite similar and are much like an adult’s system. Many of the surprising baby poop color changes reflect the evolution of our gut’s bacterial ecosystem that happens in the first year of life.

The adult human body typically has ten times more microbial cells than human cells, most of which are in the human intestinal tract.

What do gut bacteria do?

From the moment of birth, infants create a biome in their intestines that influences their health for the rest of their lives. The microbes that come to inhabit our intestines metabolize nutrients; they help with fat and carbohydrate breakdown. Gut bacteria influences our calorie intake and ultimately our body weight. Bacteria make vitamin K, and without them we can’t even create our immune system.

Germ-free animals (experimentally born by C-section and raised in a sterile environment) don’t develop normal lymph nodes, or a normal immune system. This probably explains the “hygiene hypothesis” where a lack of exposure to a variety of microorganisms early in life may contribute to increased risk of autoimmune diseases, asthma and allergies. These animals also develop a very abnormal digestive system.



Black and tarry meconium – Made of swallowed amniotic fluid, cell debris and some blood. This sticky stuff is thought to seal fluids in the intestines until after the baby is born.

Newborn green poop– pediatricians love to see this, it means the liver is making bile and it’s starting to function correctly.

Yellow-orange-brown spectrum – The color may change every day along this color continuum. It’s healthy for the color to change as frequent as every diaper change during the first 12 months while the baby is building up their intestinal bacterial community. You’ll know they’ve established a nice ecosystem when their poop is somewhere between hummus and mud brown.

What’s the white, seed-y stuff in their yellow poop?

Partially digested milk solids.



Green-frothy? You can see this when a baby has an intestinal infection. But even healthy babies can have green, frothy poop if stuff is moving through the intestines too quickly. Most commonly this happens when moms who produce copious amounts of milk switch the infant from one breast to the other before the hind-milk—that milk produced later in feeding—is completely extracted from the first breast. The high fat content in the hind-milk slows down the passage of milk through the intestines, allowing the milk sugar (lactose) to be more completely digested in the small intestine. With less of the fatty hind-milk to slow down the transit of milk, more lactose moves to the large bowel where the normal action of gut bacteria creates excessive gas and therefore frothy stools. If you see green, frothy stool, be sure to completely empty one breast while nursing before switching to the other side, even if the baby doesn’t take the second breast.

White (pale, clay or ivory) – the worst poop color of all. It means that the baby isn’t getting bile into their intestines and is an emergency.

Black – can signal digested blood or too much iron.

Red – might be from beets or other red foods, but might be blood and indicate intolerance to milk protein or an infection.

My dear friend, Dr. Erin Fortune, explains to her patients that all the “Fall” colors are fine: yellow, light and dark green, beige, orange, and of course, good old brown. Dr. Fortune also explains, that like those bad jokes that begin “What is black and white and red all over?” any stool that is black, white or red is “bad,” too.

TODAY.com Parenting Team Contributor

Author: Wendy Hunter, MD

Pediatrician at Children's Primary Care Medical Group, La Jolla, CA

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