2.1.6. Water

Water is your body’s most important nutrient, is involved in every bodily function, and makes up 70- 75% of your total body weight. Water helps you to maintain body temperature, metabolize body fat, aids in digestion, lubricates and cushions organs, transports nutrients, and flushes toxins from your body.

Everyone should drink at least 2 litres a day, and if you exercise or are overweight, even more. Your blood is approximately 90% water and is responsible for transporting nutrients and energy to muscles and for taking waste from tissues.

If you are not getting enough water, your body will react by pulling it from other places, including your blood. This causes the closing of some smaller vessels (capillaries), making your blood thicker, more susceptible to clotting, and harder to pump through your system. This can have serious implications in hypertension, high cholesterol, and heart disease. Recent studies have also linked the lack of water to headaches, arthritis, and heartburn.

From a biological standpoint, water has many distinct properties that are critical for the proliferation of life that set it apart from other substances. It carries out this role by allowing organic compounds to react in ways that ultimately allow replication. All known forms of life depend on water.

• Water is vital both as a solvent in which many of the body’s solutes dissolve and as an essential part of many metabolic processes within the body. Metabolism is the sum total of anabolism and catabolism. In anabolism, water is removed from molecules (through energy requiring enzymatic chemical reactions) in order to grow larger molecules (e.g. starches, triglycerides and proteins for storage of fuels and information). In catabolism, water is used to break bonds in order to generate smaller molecules (e.g. glucose, fatty acids and amino acids to be used for fuels for energy use or other purposes). Without water, these particular metabolic processes could not exist.

• Water is fundamental to photosynthesis and respiration. Photosynthetic cells use the sun’s energy to split off water’s hydrogen from oxygen. Hydrogen is combined with CO₂ (absorbed from air or water) to form glucose and release oxygen. All living cells use such fuels and oxidize the hydrogen and carbon to capture the sun’s energy and reform water and CO₂ in the process (cellular respiration).

• Water is also central to acid-base neutrality and enzyme function. An acid, a hydrogen ion (H⁺, that is, a proton) donor, can be neutralized by a base, a proton acceptor such as hydroxide ion (OH⁻) to form water. Water is considered to be neutral, with a pH (the negative log of the hydrogen ion concentration) of 7. Acid shave pH values less than 7 while bases have values greater than 7.