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Food and Nutrition Guidelines for Healthy Adults http://www.moh.govt.nz/moh.nsf/238fd5fb4fd051844c256669006aed57/7b14e dc233cad7c5cc256d80000b1a6d?OpenDocument 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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