ENJOY A WIDE VARIETY OF NuTRITIOuS FOODS
63Guideline 2
2.6.3 How drinking plenty of water may improve health outcomes
For oral health, water has an advantage over many commercially available drinks, including sugar-sweetened or
low-kilojoule soft drinks, ‘sports’ and ‘energy’ drinks. As well as the potentially adverse direct effects of sugar and
energy (see Section 3.3), the carbonation process creates an acidic environment that contributes to the erosion of
tooth enamel.^655 Tap water also has the beneficial effects of added fluoride in many communities in Australia and
fluid intake can affect saliva production and saliva, which is primarily water and essential for the maintenance of
oral health.8,36
The mechanism by which coffee consumption may protect against type 2 diabetes is not clear. It has been reported
that insulin resistance is decreased in peripheral tissues after exposure to caffeine^658 and conversely, the effect of
caffeine on thermoregulation has been suggested as a mechanism by which glucose homeostasis is improved.^659
Other components of coffee, possibly magnesium, may also assist by benefiting insulin sensitivity and reducing risk
of type 2 diabetes.^660 Tea contains polyphenols known as catechins which have been reported to reduce hypertension,
atherosclerosis and thrombogenesis.^661 Polyphenols also play a part in nitric oxide production from the vascular
endothelium, enhancing endothelial health and reducing the risk of cardiovascular diseases and stroke.^661
2.6.4 Practical considerations: drink plenty of water
Adequate fluid consumption is an integral component of a healthy diet. Water is a good source of fluids and has
the advantage of not adding energy (kilojoules) to the diet. It is preferable to meet most fluid needs by drinking
plain water. Many commonly consumed fluids such as tea and coffee provide water, although they can have
unwanted stimulant effects in susceptible people.
The NHMRC has developed comprehensive guidelines on tap water standards for drinking.^662 Australian tap water
is an ideal option because it is inexpensive and meets high palatability and hygiene standards. Most tap water in
Australia is fluoridated, which has been shown to be a safe and effective public health measure. Fluoridation of
tap water provides an additional benefit for development of strong teeth and bones, making it a very good choice
to ensure adequate hydration. Tank water and bottled waters are a useful alternative when access to tap water is
limited. Not all bottled waters contain fluoride.
However, access to and availability of clean and safe water may be limited for some population groups, particularly
in remote regions of Australia. Discussion of dietary patterns and the environment is included in Appendix G.
Pregnant and breastfeeding women
As stated in the 2003 edition of the dietary guidelines, pregnant and breastfeeding women have an increased
water requirement because of expanding extracellular fluid space and the needs of the foetus and the amniotic
fluid. The fluid need is therefore 750–1,000ml a day above basic needs.^36
Many authoritative bodies advise pregnant and breastfeeding women to limit their caffeine intake. For example the
Australian Department of Health and Ageing and New Zealand Ministry of Health advise that intake be restricted
to a maximum of 300 mg of caffeine per day (about three cups of coffee or six cups of tea).428,663
Infants
Water turnover is higher in infants and young children than in adults. Adequate levels of hydration are important,
especially during times of potential heat stress (e.g. due to hot weather or fever). Breast milk supplies adequate
water up to around 6 months of age, but cooled boiled water may need to be provided for formula-fed infants.^351
Older people
Older people can experience dehydration due to inadequate intake of water or other drinks. The normal decline
in kidney function with age, plus hormonal changes, decreased thirst perception, medication, cognitive changes,
limited mobility and increased use of diuretics and laxatives may create concern for older people.^34 These changes
may be normal adaptations of the ageing process but the outcomes of dehydration in older people are serious and
include cognitive impairment, functional decline, falls or stroke. Particular care must be taken to ensure adequate
water intake in this group.