What essential nutrient acts as a lubricant between cells and regulates body temperature?

Water is the essential nutrient that serves multiple critical functions in the body, one of which is acting as a lubricant between cells. It helps to maintain cell structure and facilitates the movement of nutrients and waste products in and out of cells. Additionally, water plays a vital role in regulating body temperature through processes such as sweating and respiration. When the body gets hot, sweat is produced and evaporates from the skin, which cools the body down.

While fats, proteins, and vitamins are also important for various bodily functions, they do not specifically serve both the lubrication and temperature regulation roles as effectively as water does. Fats are primarily involved in energy storage and cell structure; proteins are essential for building and repairing tissues; and vitamins are crucial for immune function and energy production, but none of these directly act as a lubricant between cells or regulate temperature in the same way water does.