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Water and fluid intake (except milk) is not normally considered a source of nutrients in the daily diet. In most developed Western societies, diets are reported to provide an excess of total energy, which is associated with obesity and the related profiles of the so-called diseases of lifestyle.
Although plain water fulfils almost all the fluid needs of healthy adults, individual preferences, perceived needs, taste, cultural, social and other factors have led to the availability of a great variety of beverages on the market.
Some of these beverages may contribute significantly to the total daily energy and the daily intake of other nutrients. Indeed, depending on the frequency and amounts consumed, the intake of energy and/or other nutrients may become inappropriately high.
With regards to inappropriately high energy intake, obesity among school children in America has become such a serious health concern that the American Beverage Association and the Alliance for a Healthier Generation have worked together to provide new school beverage guidelines.
These guidelines will help to reduce the amount of energy present in beverages throughout the school years by providing learners with nutritious, lower-energy containing beverages.
The new guidelines based on the school vending policy were adopted by the beverage industry in 2005. The goal is to achieve implementation of this policy for 75% of schools under contract with bottlers prior to the start of the 2008-2009 school year, as follows:
Guidelines for Elementary School learners:
- Bottled water must be available
- Serving sizes should be limited to 240ml per serving for milk and 100% fruit juice
- Low-fat and fat-free regular and flavoured milk should be limited to 240ml or 630 kJ per serving
- 100% fruit juice should be limited to 240ml or 504 kJ per serving
Guidelines for Secondary School learners:
- Bottled water must be available
- Diet or no-energy beverages with up to 42 kJ per serving or 240ml
- Serving sizes should be limited to 360ml per serving for milk and 100% fruit juice, light juice or sport drinks
- Low-fat and fat-free regular and flavoured milk should be limited to 240ml or 630 kJ per serving
- 100% fruit juice should be limited to 240ml or 504 kJ per serving
- Light juices and sports drinks with no more than 277 kJ per serving or 240ml
- At least 50% of drinks must be water and or low-energy or no-energy options
The overall aim of these guidelines is to reduce the total energy per each beverage consumed.
In this regard, a Beverage Guidance Panel was recently assembled in the United States to provide guidance on the nutritional benefits and risks of various beverage categories.
The panel used the available scientific literature to rate beverages on their potential health benefits or possible risks.
The panel rated drinking water as the preferred drink to fulfil daily fluid needs, followed by tea, coffee, low-fat and fat-free milk and drinking yoghurts, diet- or artificially-sweetened cool drinks, cool drinks or drinks with some nutritional benefits (fruit or vegetable juices, full-cream milk, alcoholic beverages, and sports drinks) and, lastly, sweetened drinks or nutrient-poor drinks.
Water
Water is highly recommended for daily fluid intake. It provides no additional energy, which makes it very ideal for any overweight or inactive adult. It also provides variable amounts of minerals such as calcium, magnesium and fluoride, depending on its source.
The South African Food Based Dietary Guidelines include the following guideline on water consumption: Drink lots of clean, safe water.
Despite the significant progress achieved so far in the provision of clean, safe running water to all South Africans, it can by no means be assumed to be a given for a significant percentage of South Africans.
Water is a potential source of various pathogens, such as cholera, which emphasises not only the importance of providing safe water, but also the need for the correct handling thereof by the consumers.
Tea, coffee and other caffeine drinks (unsweetened)
Certain individuals are very sensitive to the effect of caffeine and these individuals seem to be more likely to develop adverse effects from the excessive consumption of caffeine. Pregnancy and ageing may increase caffeine sensitivity.
Coffee contains more caffeine than tea. Typically, on average, a cup (180ml) of instant coffee provides 57mg, a cup of filter coffee 75mg, a cup of tea 36mg and a can (340ml) of cola cool drink 35-50mg of caffeine.
A moderate caffeine consumption of not more than 400mg per day is recommended and not associated with increased risks for heart disease, hypertension, cholesterol or bone disease.
During pregnancy, caffeine intake should be limited to not more than 300mg per day. Higher intakes have been associated with miscarriage and low birth weight.
Tea
Tea provides antioxidants, flavonoids, amino acids and minerals (mainly fluoride). Green tea, Oolong and black teas are all made from the same species of tea plant, but differ in chemical composition arising from the different production and fermentation processes used.
Green tea is produced by the steaming and drying of the tea leaves, black tea is produced by the natural fermentation of the tea leaves and Oolong tea is semi-fermented.
Rooibos tea, honeybush tea and other caffeine-free herbal teas also contain a mixture of flavonoids and other phytochemicals that may have health benefits.
Evidence is emerging of an association between the consumption of tea and the reduction of heart disease, cancer, dental caries, kidney stones and immunostimulation. More consistent evidence has been reported for the protective role of black tea in cardiovascular disease.
The available evidence suggests that the consumption of three or more cups of black tea per day may protect against heart attacks. Other claims and reports on the anticarcinogenic properties of green tea require further investigation.
Coffee
Most large, well-controlled trials have not found high intakes of coffee or caffeine associated with a significant increased risk of coronary heart disease or heart attacks.
Interestingly, several studies have found inverse associations between coffee consumption and the risk for type two diabetes, cirrhosis of the liver, colorectal cancer and reductions in risk of Parkinson disease in men, but not women.
Dirpertenes, cafestrol and kahweol, compounds in roasted coffee beans, have been identified as cholesterol-raising factors. Consequently, filtered or instant coffee might be better options for regular consumption. These also provide less caffeine per cup.
Irrespective, the importance of these associations may be revised in view of recent evidence indicating that the reported increased risk for myocardial infarction in relation to coffee intake may be genetically determined and confined to those individuals with a slow caffeine metabolism.
Adults should limit their intake of caffeine drinks to no more than four cups of coffee per day or eight cups of tea per day. Preferably, these should be with fat-free or low-fat milk and no sugar.
Milk and dairy products
Dairy products are by far the richest source of calcium, not only because of their high calcium content, but also because of the absence of factors that may interfere with calcium absorption (such as phytates and oxalates in plant products) and the presence of lactose, which aids calcium absorption.
If the exclusion of dairy products, due to whatever reason, results in an insufficient calcium intake, a calcium supplement may well be essential. For children, milk is currently the key dietary source of vitamin D, calcium and riboflavin as well as an excellent source of high quality protein.
There is a positive relationship between milk consumption and bone mineral density, which is thought to be protective against osteoporosis in later life. Yoghurt drinks have lower lactose content and are a good alternative for lactose sensitive individuals.
A number of studies have previously documented that calcium in milk may contribute to a reduction in blood pressure. Calcium intake has also been associated with a reduced risk of stroke, and, importantly, calcium intake from non-dairy sources was not associated with such a reduced risk.
These findings suggest that, apart from calcium, other milk constituents, such as potassium and magnesium, may also be important in affording such protection. In fact, the available evidence affords the greatest effect to potassium.
Although it is difficult to associate any one of these minerals in dairy products, on its own, with the reported protective effect, it should be borne in mind that a balance of calcium, magnesium and potassium is important and that all three minerals are abundant in milk and dairy products.
In addition, milk is a low-sodium food, which, as documented in the DASH II study, provides further protection and benefit in blood pressure reduction. The balance of the available evidence indicates that hypertensive individuals are most likely to benefit from increased low-fat or fat-free milk and dairy product consumption within the context of a diet rich in fruits and vegetables.
The results of the Coronary Artery Risk Development in Young Adults (CARDIA) study, a large prospective observational study (3 563 participants, multi-centre, population-based study of cardiovascular risk factor evaluation in the US including white and black young adults between the age group ranges of 18-24 and 25-30 years) documented that overweight individuals consumed less dairy products than individuals with a normal body weight.
The study also reported that increased dairy intake may protect overweight (BMI¡Ã25kg/m©÷) individuals against the development of obesity, elevated blood glucose levels, hypertension and heart disease.
The 10-year incidence of insulin resistance syndrome (IRS; also known as the metabolic syndrome) was lower by more than two thirds among overweight individuals in the highest category of dairy consumption (¡Ã than five portions per day) compared to those in the lowest category (< than 1,5 portions per day).
More recent evidence, however, appears to be less consistent in the extent of the claimed benefits and further research will afford better clinical perspective on these reported relationships.
In summary and at present, dietary patterns characterised by increased dairy consumption, may protect overweight individuals from the development of obesity and IRS, which are key risk factors for type II diabetes and heart disease.
In this regard, it is important to note that trends in dietary intake behaviours over the past few decades have revealed a decreasing intake of dairy products, especially milk, and increasing carbonated drinks consumption and snacking (high fat and refined carbohydrate) among children and adolescents.
Cool drinks
Sweetened cool drinks and fruit drinks
These include carbonated and non-carbonated (still) cool drinks, which are usually sweetened, with high-fructose corn syrup or sucrose, and provide very small amounts of other nutrients.
Sweetened cool drinks are the least recommended by the US Beverage Guidance Panel. Regular consumption of these drinks has been associated with dental caries, obesity, and type II diabetes.
These drinks are energy-dense and by the nature of their non-satiating properties are thought to contribute to an increased daily energy intake and thus obesity.
In this regard, recent results from the Nurses Health Study indicate that women consuming one or more servings of sugar-sweetened cool drinks per day had a significantly higher risk of developing type II diabetes than those drinking less than one sweetened cool drink per month.
Diet- or artificially sweetened cool drinks
These beverages are preferable in terms of energy content at least, to sweetened cool drinks, but less desirable than water, tea or coffee because they provide water, taste and sweetness, but no energy.
Individuals who suffer from gastrointestinal discomfort should best avoid carbonated drinks. These beverages should also not replace meals, water, milk and other nutrient-rich drinks in the diets of young children with limited stomach capacity.
It should also be borne in mind that artificially sweetened cool drinks are a source of artificial sweeteners, additives and preservatives and should be used in moderation in a varied diet, especially among individuals who claim to be sensitive to any of these ingredients.
Additionally, new literature is emerging which suggests that the high sweetness in these drinks may contribute to conditioning for a high preference for sweetness.
Fruit and vegetable juices
Fruit juices (100% juice with no added sugar) provide most of the nutrients of the fruits used, but they are energy-dense and may lack in fibre and other nutrients/constituents present in the whole fruit.
Consumption of whole fruits is still considered to be best way to achieve satiety and energy balance.
A recent study found that consumption of more than 360ml of fruit juice per day by young children (2 - 5 years old) was associated with short stature and obesity. Parents and caregivers should limit young children's consumption of fruit juice to less than 360ml per day and should ensure that fruit juice do not replace food or milk in the diets of young children.
Vegetable juices are generally a healthier alternative to fruit juices, because they provide less energy. But these juices could be high in salt. Tomato juice and vegetable juice, for instance may contain up to 975mg of sodium per 375ml.
Sports drinks
Sports drinks contain at least half the energy as in sweetened cool drinks and provide sodium, chloride and potassium.
The carbohydrates, water and salts are advantageous in endurance events (strenuous exercise for more than one hour). Inactive adults or children should consume these drinks sparingly.
- Information supplied by the Nutrition Information Centre of the University of Stellenbosch (NICUS).
