You have probably heard that you are “mostly water”. It is true, but the full picture is more surprising. Some parts of you are almost as wet as a fruit, while others are much drier than you might expect.
The big number: about 60%
According to the U.S. Geological Survey, water makes up about 60% of an adult human body. The exact amount changes from person to person. It depends on age, sex and body type, and people with more fat tissue have a lower percentage of water, because fat holds less water than muscle.
Babies are the wettest of all. A newborn is roughly three quarters water, and the share slowly drops as we grow.
Organ by organ
Classic measurements reported by the USGS give these approximate numbers:
Lungs: about 83% water
Muscles and kidneys: about 79%
Brain and heart: about 73%
Skin: about 64%
Bones: about 31%
Yes, even your bones are nearly one third water. They feel hard and dry, but living bone is full of blood vessels and moist tissue.
Why your body needs so much
Water helps carry nutrients and oxygen to your cells, removes waste through your kidneys, cushions your joints, and lets you cool down through sweat. Almost every chemical reaction inside your cells happens in water.
Your body is also always losing water, through breathing, sweating and the toilet, so it has to be replaced every day through drinks and food.
In short
- Water makes up about 60% of an adult body.
- The lungs are about 83% water; the brain and heart about 73%.
- Even bones are roughly 31% water.
Sources
This article is for curiosity and learning only and is not medical advice.