Hydration: The water we need for survival

Water is vital for survival, with good hydration people function well, and to look and feel good. People can survival several weeks without food but only can survival few days without water. People can keep well hydrated drinking a variety of fluids during the day such as teas, coffee, low fat milk, soups in add of drinking water.

Normal water needs range widely due to numerous factors such as metabolism, diet, climate, clothing and other factors; thus, normal hydration is compatible with a wide range of fluid intakes and human water requirements should not be based on a “minimal” intake because might eventually lead to a deficit and possible adverse performance and health consequences[2]. A sedentary adult loses on an average 2–3 littres of water per day through the skin and lungs depending on the climate, air temperature and relative humidity[1].

For adult including advancing age, men and women, the adequate intake of water (AI) is 3.7 and 2.7 litters per day, respectively; for adults, the daily water needs of men approach 2.5 littres if sedentary and increase to about 3.2 littres if performing modest physical activity, while more active adults living in a warm environment have daily water needs of about 6 littres; approximately 1 to 2 littres per day are required to replace obligatory losses for sedentary adults residing in temperate climates[2]

The US National Research Council in 1989 recommended an intake of 30mL/kg body weight after 65 years, and 1 mL of liquid per kcal of energy intake[3].

During physical activity, it is better to be well-hydrated than to be dehydrated. Physical activity results in increased water requirements that parallel sweat losses for evaporation heat exchange[2]. As the physical activity raises body temperature, and, particularly in a warm or hot environment, sweating provides a mechanism to dissipate this excess heat and maintain a stable body temperature[4] it is convenient to drink at less 500 mL of water 20-30 minutes before to perform physical activities. Also it is important to drink fluids during physical activity when is done for long periods in a hot climate for avoiding a risk of dehydration if fluids are not sufficiently replaced.
_______

[1] Jéquier, E. and Constant, F. Water as an essential nutrient: the physiological basis of hydration. European Journal of Clinical Nutrition (2010) 64, 115–123.

[2] Sawka, Michael N. Et al. 2005. Human Water Needs. Nutrition Reviews, Vol. 63, No. 6.

[3] Ferry, Monique. Strategies for Ensuring Good Hydration in the elderly.

[4] Benelam , B. and Wyness, L. 2010. Hydration health: a review. British Nutrition Foundation Nutrition Bulletin, 35, 3–25. ciencedirect.com.

---

___________

[1] https://www.ius.edu/environmental-heal[...]lth-safety/files/dehydration-chart.pdf

Drinks for hydration

To meet the need for adequate daily intake of water or liquids it is possible to drink a variety of beverages as a substitute for water. Although water has the advantage of meeting hydration requirements without providing additional energy, it is not people's preferred drink. Therefore, it is important to choose good beverages as alternative to meet the right fluid requirements per day.

The Eidos diet suggests drinking a variety of beverages as an alternative to water, such as a combination of different teas, including coffee, black tea, and low-fat milk, but in moderation. Alternative beverages should be taken without sugar. Drinking fruit juices is not recommended because although they are extracted from fruits, the pulp and fiber are eliminated and have a high concentration of natural simple sugars such as fructose and sucrose. In the case of consuming fruit juices, these should be consumed in an amount less than 200 ml a day; it is better to eat the whole fruit. People should also avoid drinking soft drinks and alcoholic beverages.

Teas and herbal teas are rich in phytochemical compounds with nutraceutical properties. Properly prepared, black tea is a good source of fluoride; one cup of black tea per day can provide the adequate daily fluoride requirement. See black and green teas preparation.

It's important to learn to enjoy natural flavors as a new healthy lifestyle, in other words, enjoy drinks without adding sugar. As part of their lifestyle, people should include different drinking beverages distributed throughout the day. Some drinks can be enjoyed by eating a dried fruit such as a date, a dried fig or a dried apricot at the same time.

Tea is the second most commonly consumed beverage in the world after water, and black, oolong and green teas are all produced from the leaves of the plant Camellia sinensis using different processing methods, also there are a wide variety of herbal teas available, for example, chamomile, peppermint and fruit teas, which are often caffeine free[2].

All the studies on hydration found that tea status drinking had no adverse effects on hydration status, indicated by blood and urine markers remaining in the normal ranges and tea provided similar hydration benefits to water, as no statistical differences in blood and urine markers were reported when these conditions were compared[1].

___________

[1] Ruxton, Carrie. 2016. Tea: hydration and other health benefits. CPD, volume 26 number 8.
[2] Jéquier, E. and Constant, F. Water as an essential nutrient: the physiological basis of hydration. European Journal of Clinical Nutrition (2010) 64, 115–123.

---

Dehydration

Dehydration occurs when water losses are not sufficiently replaced by drinking fluids. When you lose more fluid than you take in, and your body doesn’t have enough water and other fluids to carry out its normal functions; unfortunately, thirst isn’t always a reliable gauge of the body’s need for water, especially in children and older adults[6]. Thirst is often blunted in elderly subjects who are at risk of having an insufficient water intake in conditions of elevated ambient temperature and humidity [1]. Dehydration corresponding to as little as 2% loss of body weight leads to a decreased endurance and risk of heat exhaustion[4]. Extreme dehydration is very serious and can be fatal. More mild dehydration (about 2% loss of body weight) can result in headaches, fatigue and reduced physical and mental performance. It is also possible to consume too much water and in rare cases this can result in hyponatraemia (low levels of sodium in the blood)[3].

Thirst reduction, some diseases such as cholera that produce sever diarrhea, diarrhea are some examples that lead to dehydration.

A better indicator to know if the body is well hydrated is the color of your urine[2].

___________

[1] Jéquier, E. and Constant, F. Water as an essential nutrient: the physiological basis of hydration. European Journal of Clinical Nutrition (2010) 64, 115–123.
[2] The horse’s mouth. 2001. Dehydration: the signs and symptoms. Volume 14, Issue 2.
[3] Benelam , B. and Wyness, L. 2010. Hydration health: a review. British Nutrition Foundation Nutrition Bulletin, 35, 3–25.

---

Recommended Water Intakes

	EFSA 2008	IOM 2005	WHO 2003, 2005
	Reference values littres/day	Adequate intakes littres/day	Requirements littres/day
Infants 0–4 months			0.75
Infants 0–6 months	0.1-0.19 /kg	0.7
Infants 6–12 months	0.8-1
Infants 7–12 months		0.8
Infants 8–12 months			1
Infants 12–24 months	1.1-1.2
Children 1–3 years		1.3	1
Children 2–3 years	1.3
Children 4–8 years	1.6	1.7
Children (boys) 9–13 years	2.1	2.4
Children (girls) 9–13 years	1.9	2.1
Adolescent boys 14–18 years		3.3
Adolescent girls 14–18 years		2.3
Adult (men) 19–30 years		3.7
Adult (women) 19–30 years		2.7
Adult (men) >19 years			2.9
Adult (women) >19 years			2.2
Adolescent (14+ years) and adult (men)	2.5
Adolescent (14+ years) and adult (women)	2
Pregnant women	2.3	3	4.8
Lactating women	2.7	3.8	5.5

Source: Benelam , B. and Wyness, L. 2010. Hydration health: a review. British Nutrition Foundation Nutrition Bulletin, 35, 3–25.

---