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10 Water - Food and Nutrition Guidelines for Healthy Adults

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					Food and Nutrition Guidelines for Healthy Adults

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10 Fluids

Background

Approximately 70 percent of body weight is water. Water is essential for life
and humans cannot survive for more than five days at the most without
water. Water is required both within and outside cells and is necessary for
biochemical reactions, transport of nutrients, metabolites, waste products,
respiratory gases, hormones and heat. Water also provides lubrication for the
joints and body surfaces (Robinson 2002).

Recommended fluid intakes for adults

Approximately 3000 ml of water is required per day for the average man and
approximately 2200 ml per day for the average woman (NHMRC 2003). Solid
food (especially vegetables and fruits) contributes approximately 1000 ml of
water, with about 300 ml coming from the water produced by the
breakdown of food. The remainder of the water needs to come from fluids
such as water, milk, tea, coffee and other beverages.

Fluid intakes in New Zealand

The NNS97 showed that water (80 percent), tea (62 percent) and coffee (61
percent) are consumed regularly by New Zealanders. Fluid consumption
differs across genders.

Males more frequently consume coffee, soft drinks and cordial. Females
prefer low energy soft drinks, water and herbal teas. However, consumption
of soft drinks dropped off markedly in the age group of 45-plus years for both
males and females. Milk is consumed as a beverage at least once per week
by only 35 percent of adult New Zealanders (Ministry of Health 1999c).

Powdered drinks and cordials are more regularly consumed by individuals
living in NZDep96 quartile IV (most deprived) areas. Fruit juice, tea (males
only), water (females only) and coffee are more popular among individuals
living in quartile I (least deprived) and II areas.

Pacific peoples are higher regular consumers of fruit drinks and sports drinks
compared with Maori and New Zealand European and Others.

Maori more often have cordial and soft drinks. Maori and Pacific peoples
drink less coffee, tea and herbal tea than New Zealand European and Others
(Ministry of Health 1999c).

Sources of fluids in the diet
Water

Although water consumed as such is a major source of fluid, water consumed
in other beverages is also important.

There is evidence that drinking reticulated water (ie, water supplied by the
local water authority) containing fluoride can help to prevent tooth decay.
While bottled water is a convenient alternative to tap water, there are no
known benefits over reticulated water.

Caution should be taken when consuming water from other than reticulated
sources (from tanks, etc) as it can easily be contaminated (eg, with bird or
animal faeces).

Milk

Milk is a valuable component of the diet, as an important source of calcium,
protein and other essential nutrients. It should, therefore, be included as part
of the fluid intake. Achieving the RDI for calcium without some liquid milk or
milk products is difficult. The use of reduced-fat or low-fat milk products will
minimise energy intake while retaining the contribution of calcium. Soy
beverages can be a suitable replacement for cow’s milk, but calcium-
fortified varieties should be selected.

Caffeinated drinks

Caffeine and similar substances are found in coffee, tea, cocoa, cola-
flavoured drinks, or energy drinks containing guarana or cola nut. Coffee
contains about three or four times as much caffeine as an equal volume of
cola-flavoured drink.

Some energy drinks contain substantial amounts of caffeine, although no
more than strong coffee. Caffeine is a central nervous system stimulant and
acts as a mild diuretic. Tea, coffee and soft drinks are among the most
frequently consumed beverages in New Zealand.

Caffeine has recently been associated with increased blood pressure in
individuals prone to hypertension (Nurminen et al 1999). Coffee and caffeine
may also be associated with cardiac arrhythmias and raised blood lipids (NHF
1999).

Evidence for caffeine intake as a risk factor for fracture frequency or bone
loss is contradictory. Several large cohort studies have reported small but
significant increases in either fracture frequency or bone loss associated with
increased caffeine intake (Kiel et al 1990; Hernandez-Avila et al 1991; Barrett-
Connor et al 1994; Cummings et al 1995).

Other studies have found no association (Cooper et al 1992; Johansson et al
1992; Cumming and Klineberg 1994; Lloyd et al 1997). An important issue with
coffee, tea and energy drinks is the amount of energy (in the form of sugar)
they may contain. The addition of sugar to tea and coffee can add
significantly to an individual’s daily energy intake, thus contributing to
overweight and obesity.

Tea, especially green tea but also black tea and to a lesser extent coffee,
contains substantial amounts of polyphenols.

Polyphenols are substances with antioxidant properties which are purported
to protect against cancer and cardiovascular disease. In the NNS97 the
highest frequency of consumption of herbal teas among New Zealand
women was among females 19-64 years (10-13 percent) (Ministry of Health
1999c).

While herbal teas commercially marketed in New Zealand are very dilute
(Mathews 1997), some herbal teas might interact with prescription drugs
(Huxtable 1992).

Fruit juices, soft drinks, cordials and sports drinks

Fruit juices, soft drinks, cordials and sports drinks all contain water.

As such, they contribute to total fluid intake. In some cases, they also
contribute other nutrients (eg, vitamin C in fruit juices).

However, because they provide energy in the form of sugar, they also
contribute to energy intake and may also contribute to overweight and
obesity. If sports drinks are consumed in large amounts, the phosphoric acid
and citric acid added to these drinks are likely to damage teeth by eroding
tooth enamel. Their erosive potential is related to their low pH (high acidity)
and chemical content.

Frequency of intake and salivary flow rate are also important factors. For
example, mouth breathing during physical activity leads to less salivary
clearance of acids and carbohydrates (Vasan 1999). Sports drinks are one of
the fastest growing segments in the Australasian drinks market (Pearce 1996).
They are predominantly consumed by people in the 15–24 years age group
(LINZ Research Unit 2000).

Practical advice
    Drink plenty of water every day.
    Take an amount of fluid equivalent to 6-8 glasses of water per day.
    Sometimes choose low-fat milk as a nutritious alternative to water or
       soft drinks.
    Limit the consumption of fruit juice, cordial, energy and soft drinks
       because of their high sugar content.
    People susceptible to caffeine should minimise consumption of tea,
       coffee and other caffeinated drinks. The National Heart Foundation
       suggests a maximum of five cups of coffee a day for the general
       population (NHF 1999).

				
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