How could a mammal produce milk which resembles blood?

The blood milk should keep as many properties of milk as possible, curding for example, while resembling blood as much as possible. The mammal does not have to exist or eat earth food, but if it doesn't what would that food be like?

By the properties of mean I mostly mean:

  • The ability to feed babies (lactose)
  • Curding (Cheese)
  • Liquid at room temperature
  • Preferably not poison to human-like species

By the properties of blood I mostly mean:

  • Red
  • (Very) slightly thicker
  • 1
    $\begingroup$ Can you better specify what you mean with properties of blood and properties of milk? $\endgroup$
    – L.Dutch
    Jun 5, 2019 at 13:58
  • $\begingroup$ I think there is a youtube video about how milk is just filtered blood. $\endgroup$ Jun 5, 2019 at 14:04
  • $\begingroup$ @L.Dutch I've added some basic properties I need for story, I'll keep trying to remember my classes on milk chemistry and add more details. $\endgroup$
    – Hugo
    Jun 5, 2019 at 14:09
  • $\begingroup$ Blood is red because of its iron contents. The hypothetical red milk cannot possibly contain as much iron because it would be toxic -- humans cannot live on a diet of pure blood. It must be red for a different reason; maybe it contains large amounts of carotenoids from the diet? And raw milk is already about as thick as blood. $\endgroup$
    – AlexP
    Jun 5, 2019 at 14:26
  • $\begingroup$ It seems weird that all the answers are ignoring the fact that milk is just modified blood... $\endgroup$
    – GreySage
    Jun 5, 2019 at 23:22

3 Answers 3


The creature in question eats foods rich in natural red dyes

Most of these plants require boiling to get the dye, but the acid bath of digestion is enough to get to that point. The problem, of course, is that the mammal would need to eat this stuff almost exclusively (or at least a whole lot of it). But methinks it would create the color you're looking for.

  • Autumn red leaves (seasonal)
  • Bamboo
  • Bedstraw Root
  • Beet Root
  • Brazilwood
  • Canadian Hemlock
  • Choke Cherries
  • Crabapple Bark
  • Elderberries1
  • Hibiscus Flowers
  • Madder Root
  • Portulaca
  • Rose Hips
  • St. John's Wort (a bit harder, requires mixing with isopropyl alcohol)
  • Sumac Fruit
  • Sycamore Bark

(Found from this source)

But what about the thicker fluid?

I believe you'll need to live without this. Mammary glands are designed to create and pass a relatively specific fluid thickness (not unlike the kidneys or liver). If you try to force something substantially thicker through the glands, they get all clogged up (not unlike the kidneys or liver). Getting something the thickness of blood that didn't hurt the lady would require a physiological change to the glands.

You could thicken the fluid somewhat by consuming high-starch foods, but I believe that's the best you'd get.

1"It is by my will alone that I set my mind in motion...." Sorry, I had to include a gratuitous "Dune" reference. Eating enough elderberries to turn milk red might turn the whole blooming cow red.

  • 1
    $\begingroup$ Mammary glands are designed to pass a fluid of a specific thickness, but that thickness varies greatly from species to species. Aquatic mammals in particular produce milk that is closer to a thick cream in consistency. So a mammal that is made to produce a blood-like fluid is no problem at all. $\endgroup$ Jun 6, 2019 at 7:05
  • $\begingroup$ @IndigoFenix You're probably right, but what animals lactate a fluid with the thickness of blood? Do you know of any? I'm afraid I don't, hence my answer. $\endgroup$
    – JBH
    Jun 6, 2019 at 14:18

There is blood in the milk.

bloody cow milk https://www.researchgate.net/publication/283120356_Causes_Diagnosis_and_Treatment_of_Blood_in_Milk_Hemolactia_in_Cows_and_Buffaloes

Milk comes from glands. Glands have blood vessels. There are various reasons a blood vessel might burst and bleed more or less blood into the milk.


Dairy farmers frequently approach practicing veterinarians for the treatment of cows or buffaloes producing milk which is reddish or pinkish due to the presence of blood. Farmers suffer from the economic loss because bloody milk is often rejected by the consumers. The condition is usually sporadic in occurrence but rarely several lactating animals may be affected at a time...

The main reason is that the animals are being milked a lot, but I took away that some animals idiosyncratically are more likely to have this happen.

Evolution could totally work on this. Suppose an animal were born with a genetic variation that led to more vessels in the milk glands and they were prone to bleed. The nursing young get benefit from this and are more likely to grow to adulthood - maybe they get more iron, or more antibodies from the added blood. The genetic variation has improved reproductive fitness and it spreads through the population. Generations later, all the mammals of this sort have blood in the milk.

  • $\begingroup$ What do you think of AlexP's comment about an excess iron in this case? $\endgroup$
    – Hugo
    Jun 5, 2019 at 15:16
  • 1
    $\begingroup$ The amount of blood needed to turn milk red is less than the amount that would be in the same volume of meat. It may be possible to accumulate iron to toxic levels if you consumed a straight blood diet up until middle age, and do not menstruate, or get pregnant, or have hookworm. If you got extra iron when you are nursing that is fine. Even if you got immense amounts of iron when you were nursing it takes decades to manifest symptoms of hemochromatosis. $\endgroup$
    – Willk
    Jun 5, 2019 at 16:27
  • 2
    $\begingroup$ As to the taste it would have, mothers milk takes most of the taste of what the mother eats, among a dozen other things mothers milk does. All mothers from all cultures kiss their baby on the cheek, this takes a sample of the viruses and bacteria the baby is in contact with and the mother puts immunogens to all diseases the mother is in contact with into the milk. The milk would have the taste of the mother's eating habits and the blood put in. $\endgroup$
    – Demigan
    Jun 5, 2019 at 17:10

Blood is red from the protein, hemoglobin. Hemoglobin has a molecule called a "heme" which has the metal iron in it. When the iron is oxygenated, it becomes red. When the iron is deoxygenated, it becomes darker red.


I would say the animal would probably eat food very high in iron, be it red meat, or spinach (a lot of leafy greens have high iron content).

Add some sort of clotting agent when it comes out. For example, Lipids which gets thicker when it cools. I could be wrong here, but I believe that if you increased the fat content in the milk this could cause this... Also, I would say that milk straight from a goat (the only example I have seen in person) is a similar thickness to un-clotted blood. Although (from the same source) you could add a gum thickener, which has the added benift of making it slightly sticky.

  • $\begingroup$ What do you think of AlexP's comment about such a high iron content? $\endgroup$
    – Hugo
    Jun 5, 2019 at 14:33
  • $\begingroup$ Ah I think that was posted after I had constructed my answer! I hadn't thought of that. How about bixin or something similar? Try this link $\endgroup$
    – Gamora
    Jun 5, 2019 at 14:37
  • $\begingroup$ Or just make up a food that turns the milk red... you did say they didn't have to eat earth food :) $\endgroup$
    – Gamora
    Jun 5, 2019 at 14:39
  • $\begingroup$ Yeah, then the question is what would that food be like, other than red. $\endgroup$
    – Hugo
    Jun 5, 2019 at 14:40
  • 1
    $\begingroup$ Well I was thinking of it having a new, unknown chemical maybe. What about the shrimp that flamingos eat? Something like that en.wikipedia.org/wiki/Astaxanthin $\endgroup$
    – Gamora
    Jun 5, 2019 at 14:44

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