How can 100g of potatoes and 100g of milk have almost the same amount of water?


I was browsing through the USDA Food Search system for data on various foods, when I noticed they include how much of a food is water. What really perplexed me is how 81.1 grams out of 100g of russet potato is water… when 88.1g of 100g of milk is also stated as water.

Obviously a potato isn’t liquid like milk, and my intuition would say that 100g of potatoes seem far denser and “drier” than 100g of milk. I mean can you imagine sating your thirst with just solid potatoes, as opposed to say a glass of milk?

But yet I can’t make sense of why one is solid and the other is liquid when they’re nearly the same in water content, or why one would seem to sate thirst more.


Bonus question: does this mean you poop about as much from 100g of milk as you would from 100g of, potatoes? I guess you could blend the potatoes…

In: 7

I can’t say for certain about potatoes, but other foods in cooked form do indeed contain mostly water. Take for example oat flakes 300g dry cooked with 1500g of water yield a product that has about 80% water. The water is stuck between molecules of starch to form something like a gel.

Living plant cells contain the water within a relatively tough cell membranes that resist breaking. Fresh fruit like apples are mostly water.

The amount of feces depends on the kind of material consumed and the amount. Plant cellulose is impossible to break down. Other forms of so called fiber attract water and doesn’t let it being absorbed into the blood. Protein in milk can mostly be broken down in reasonably amounts if the person doesn’t have intolerance against milk.

Most of the water will ultimately enter the blood if the person doesn’t have diarrhea and replenish lost water, and cause one to wake up to go to the bathroom after a big dinner.

A cow is between 60% and 80% water which is why milk is so high in water. Potatoes are high in water because they take on water (because they need a lot) when they grow. There are at least 20 vegetables that are higher in water. Lettuce is 98% and celery is 96% water. There are a heap with 95% water.

So why aren’t any of these liquid?? A cow is solid and a human is solid (up to 75% water). It comes down to how the source element stores the water. Animals store it in blood and organs etc. in vegetables the easiest analogy is your carton of milk. The 2% solid in a lettuce is robust enough to hold 98% water, like the milk carton.

Bonus question. No, because with the potato you are pooping out the excess from the starchy carb.

Aerogel is almost entirely air. And yet, it’s solid. Pretty much same things is with food or any other biological stuff – it’s like a rigid sponge filled with water. As long as cellular membranes able to hold that water inside, it stays rigid, and therefore appears solid. If, on the other hand, you’d blend that potatoes for a long time, long enough to break nearly every cell, then you’d get a smoothie. Which is liquid. Milk does not have cells that would hold water inside and therefore is liquid.

Plants are made up of cells, with a tough membrane around them which holds the cell contents, which are mainly water. The cells are all linked together, which holds the water still.

If you mash a raw potato, you will see all the water come out as you break the cell walls. In fact, even when you cut it a bit, you see this happen on the cells that you’ve cut.

In milk, the water is freely floating between molecules of fat and protein, so there is nothing to hold it still.

Bonus question: You will poo out more from a potato. This is because you wee out most of the water, keep proteins and fats, and mainly poo out material which is not digestible (roughage). The cell walls of potatoes and other plants are made from cellulose, which we can’t digest, so we poo it out.

That is partially why plants (fruit and vegetables) are good for us. Because they contain plenty of roughage, which helps food move through our gut and out the other end, helping to prevent diseases like colon cancer.