Earth – a saltwater planet!
Water is the essence of life. We, humans, can live for some time without many nutrients but we die quickly if we cannot consume water. Surprisingly, although our planet earth is about 71% water, over 96.5% of this is salt water. Furthermore, of the 3% fresh water, only about 1% is available for drinking!
If, like me, you live somewhere where there is currently frequent flooding, we are reminded that we need to work out the best ways of collecting the excess water so we can use it in drier times. Unfortunately, this is often given far too little attention!
Our need for high quality drinking water is also a major reason why we need to curb earth’s population growth.
Which parts of our bodies need water?
When we think of our bodily fluids, we usually think of blood, saliva, and urine but although these are critical reservoirs of fluid, they are only part of the picture. Our whole bodies are composed of about 60% water, and this is broken down into:
- Lungs: 83% water
- Muscles and kidneys: 79% water
- Brain and heart: 73% water
- Skin: 64%
- Bones: 31%
It’s easy to see from these figures that water is truly the essence of life!
Brain (Hypothalamus) controls body fluids through Vasopressin
Our fluid balance and blood pressure are controlled by a small hormone called Vasopressin. This is primarily located in the part of the brain called the Hypothalamus although its effects are caused in many organs. Messenger RNA (the specific code that is translated into the active hormone) for Vasopressin has also been found in the adrenal and thymus glands as well as in the gonads.
The Hypothalamus is stimulated to produce Vasopressin in response to the osmolality (level of salts) of the blood and this causes a change in arterial blood pressure. Elevated levels of Vasopressin can cause high blood pressure.
Kidney (Renin-Angiotensin System)
Our fluid balance is so important that it is also controlled by a second system that is in the kidney. This is a very complex system that is concerned with the volume of blood we have in our body as well as with the salt levels in our blood and our blood pressure.
The hormone produced in this system is known as Angiotensin-II and it communicates with the Hypothalamus to create the feeling of ‘thirst’.
How we lose water
Under normal circumstances we lose water through sweating and urination. If we are ill, we can also lose water through vomiting and/or diarrhea. Increased sweating, whether due to illness, high external (weather) temperature or exercise, all require us to consume more water.
We can also lose more fluid than usual through frequent urination. This can be caused by medicines such as diuretics, illnesses such as diabetes and drinking alcohol.
Daily Total Water Intake (TWI)
The amount of water we need to consume each day is influenced by our age, our gender, our activities, and the composition of the rest of our diet. For adults the recommended intake is slightly less than 4 liters for men and slightly less than 3 liters for women. One source gives this in ‘cup equivalents’, which is 15.5 cups for men and 11.5 cups for women. If you drink sugary drinks or eat salty food, you are likely to need more so it’s better to avoid both!
Many people find that this recommended intake of water seems rather high. This is because a very large number of people don’t drink enough and suffer from chronic dehydration! Sadly, chronic dehydration is the cause of many chronic diseases including cystitis and other urinary tract infections as well as kidney stones. Acute dehydration can lead to seizures and even a very serious condition known as hypovolemic shock.
In hot weather, insufficient fluid intake can lead to heat cramps, exhaustion, and heatstroke. If you play sport in very hot weather, you must have a high intake of both water and balanced electrolytes.
Too little fluid intake can lead to mild neuroendocrine diseases. This is especially common in the elderly and can lead to people experiencing confusion, constipation, dizziness, and weakness. Some older people drink less because they are worried about their bladder control. However, strangely enough not drinking sufficient water is more likely to lead to bladder problems. It is critical that we drink enough water every day, regardless of our age.
Always remember how essential water is to every part of our body. If necessary, count the number of glasses you are drinking. You can take some of it in the form of soups, cups of tea and other liquids but plain, high quality water is probably best
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