http://www.unileverhealth.co.za/ | Find out about proper, adequate hydration. We discuss the effects of hydration on the body, common ailments caused by dehydration and the contribution of tea to fluid intake.

1. 4
1. Introduction
1.1 The importance of proper hydration for health
Recently, the current knowledge of water intake
as it pertains to human health was reviewed
by Popkin et al (2010). This review highlights
the importance of proper hydration for the
prevention of nutrition-related diseases such
as kidney stones and urinary tract infections.
Next to that it summarizes the consequences
of dehydration, including constipation and
headache and a decrease in physical and
mental performance3
.
In line with this review, the European Food
Safety Authority (EFSA) (opinion 2075, April 2011)
approved two health claims on health benefits of
water; “Water regulates normal body temperature”
and “Water maintains normal physical and
cognitive functions”. As tea contains >99% of
water, it can in fact be a large contributor to total
water intake and all health benefits linked to it.
Actually, our recent research26
has shown that
black tea consumption improves attention and
alertness; this evidence will be discussed in our
next newsletter focussed on tea and cognition.
Water is the largest component of the human
body, representing 45–70% of total body weight8
.
Fluid-electrolyte turnover and whole-body water
balance change constantly because water is lost
from the lungs, skin, and kidneys, and because
water is gained from food and fluids1,2
. The
normal daily water balance for a sedentary healthy
individual of 70–75 kg living in a temperate climate
shows an average daily water exchange of 2250 ml.
Urine excretion usually accounts for about
1250 ml while the rest (1000 ml) is typically lost
via sweating, respiration and elimination of faeces.
Food generally accounts for 1000 ml of the daily
water intake, metabolism for 350 ml and drinks
from all sources for the remaining 1200 ml.5
Because of the wide variability within and between
individuals, it is difficult to estimate a general water
requirement. For the US population, Adequate
Intake (AI) for total water was set based on the
median total water intake from U.S. survey data
(IOM, 2004). The AI for total water intake for
young men and women (age 19 to 30 years) is 3.7 L
and 2.7 L per day, respectively. The World Health
Organization (WHO) recommends 2.5 L for women
and 2.9 L for men under average conditions and
intakes of 4.5 to 5.5 L under specific conditions
such as during exercise, in hot climates or during
pregnancy and lactation.9
1.2 The contribution of tea to fluid intake
Thanks to its popularity and flavour which
makes it often a preferred beverage over water,
tea is an important contributor to fluid intake in
the diet. For example in the Netherlands, daily
consumption of 330–340 ml has been reported
for men and 400–610 ml for women.10
In the UK,
both men and women consume comparable
amounts of tea, ca. 540 ml per day.11
In 2006, a guidance system for beverage
consumption was proposed by a panel of US
scientists. The panel ranked beverages from the
lowest to the highest value for hydration based on
caloric and nutrient contents and related health
benefits and risks. Drinking water was ranked
as the preferred beverage to fulfil daily fluid
needs, and was followed directly by unsweetened
tea12
. The panel recommended consumption of
unsweetened tea up to 40 oz (ca. 1 litre) per day.
Next to water, green, black and oolong tea from
the Camellia sinensis leaves contains theanine,
flavonoids, and caffeine. In relation to hydration,
most discussion has evolved around caffeine as
an active in tea that may negatively influence
water balance.