We can live weeks without food, but only few days without water. Adult women got around 50% of their weights just water, while adult men have around 60%. So, what are the essential functions of water?
- water is the life support for most of our body, excepting fat cells and bone cells, and as most of the proteins are water soluble, if the water content drops under certain level, their function will halt.
- water is the main component of the blood, responsible to transport nutrients and other molecules through the body. All the water soluble nutrients are distributed into the body via blood stream. Fat soluble nutrients are wrapped in special particles called lipoproteins before being transported via blood.
- water participates in many biochemical reactions in every cell, mainly hydrolysis, breaking a bond in a molecule via water insertion (cleavage of dietary proteins into aminoacids and cleavage of glycogen into glucose).
- water has a high heat capacity, making it an excellent buffer against large fluctuations of temperature in the body.
- water has an important role in maintaining electrolyte balance in the human body.
If you are to learn about water balance, this is the total balance between the total water intake and the water loss. It is not only how many glasses of water we have, as fruits and vegetables are at least 80% water, and even solid food can contain substantial amounts of water, same going for milk, soda and fizzy drinks. But crisps, crackers and chocolate contain less than 10% water. The total water intake for most people is 2-2.5 liters per day, but can vary.
What happen in case of water loss? We usually lose water via urine, sweat, stools and exhaled air. Excessive water loss can lead to dehydration if it is not compensated by increased water intake. Water loss via stools is normally 150 ml. Can increase if you suffer from diarrhea, leading to severe dehydration, and this is life threatening for children. This is a common issue in underdeveloped countries, often caused by gastro-intestinal infections. Water loss via sweat and evaporation varies from 2-300 ml up to 5 litters, depending on the climate. It is increased even more if you are doing exercise. The water loss via breathing is 3-400 ml. Most of the water loss is via urine, produced by our kidneys and regulated by a hormonal system called renin-angiotensin system (with the role in maintaining the water balance in normal conditions).
Food water content:
90-100% - soup, soymilk, tomato, strawberry, mushroom, cucumber, carrots
80-90% - pineapple, apple, coca cola, orange juice, wine, yogurt, milk, beer
70-80% - cottage cheese, potato, egg, steak, cooked pasta, cooked rice, tofu, turkey breast
60-70% - feta, chicken breast, prepared lentils, corn, cooked beans
50-60% - cream cheese, icecream, hotdog, caviar
40-50% - falafel, meatballs, bacon, cheeseburger
30-40% - french fries, pitta bread, bagel, pizza
20-30% - honey, parmezan, mayo
10-20% - croissant, baklava, butter, donut
0-10% - hazelnut, oats, olive oil, cashews, chocolate, popcorn, crackers
Dehydration happen when excessive water loss leads to it, mild at first, but life threatening if you lose more than 10% of body weight. Can be a result of vomiting in excess, diarrhea, excessive use of diuretics, excessive sweating or decreased water intake. Children and elderly are categorized as vulnerable group.
There is also water intoxication, excessive water intake within a relative short period of time, with symptoms similar to severe dehydration, due to a disturbance in electrolyte balance. It is often observed in endurance athletes using water or fluid replacement drinks without a notable content of electrolytes.
Benefits of optimal hydration
- low water intake may increase long term risk of kidney problems, raising the risk of high blood sugar
- in EU bottled water is called mineral water if it is bottled at the source with none or minimal treatment. Mineral waters can have low mineral content (Evian, Spa) to high mineral content (San pellegrino, Contrex), as 1 liter of Contrex water can have 500 mg Calcium (50% RDA). Some of the water can be rich in magnesium and bicarbonate, and few are even rich in sodium (Vichy Saint Yorre - 1.7 g sodium per liter). Most popular waters are not mineral waters - Dasani (Coca Cola), Aquafina (Pepsi) are using local tap water, filtered and having added trace minerals. So, some water can contribute significantly to your RDA and some will do hardly anything despite their claims.
Tap water - in most developed countries meets the hygienic standards and it is fit to drink, so there are no solid reasons to favor bottled water over tap water, especially if you use a filter to remove chlorine. In Europe and US the tap water is superior to Nestle Pure Life, Aquafina and Dasani, but Perrier, Vittel and San Pellegrino are indeed superior to tap water.
Next time i will talk about Sodium and Potassium.
Disclaimer: This text also can be re-published on my personal blogs, such as this one.