For optimal health and wellbeing, we need between 35 and 45 ml of fluid for every kilogram of body weight each day, depending on our gender, level of physical activity, body composition, and the weather. As an example, the average Australian woman weighs 71 kg and the average man 86 kg, so a typical woman needs 2.5 to 3.2 liters, and a man needs 3.0 to 3.9 liters of fluid each day. All fluids do not need to come from drinks; however, as around 750 ml comes from our food, and a further 250 ml comes from the metabolism of food. So, on average, women should aim to drink 1.5 to 2.2 liters, and men should aim to drink 2.0 to 2.9 liters each day.
With so many drinks to choose from, it can be confusing to know which option is best. Like most things, it depends on your personal circumstances and the occasion.
It goes without saying that plain water is the best drink to quench your thirst: it is the most refreshing and provides zero kilojoules, plus a few minerals. Pure water doesn’t have any taste, although the minerals that are sometimes found in water naturally, or that are added (for example, fluoride), can affect its flavour. If water flavor is an issue for you, try using a water purifier or adding a slice or two of lemon or lime.
Depending on the source, mineral water usually contains small amounts of sodium, potassium, calcium, and magnesium, and is a suitable alternative to plain water for people with diabetes and those at risk.
Diet soft drinks
People with diabetes and those at risk can enjoy diet or low-joule soft drinks occasionally, but arguably they should not consume them on a daily basis. This is because carbonated beverages are acidic, and frequent consumption may increase the risk of developing tooth decay. However, these types of soft drinks do not affect blood glucose levels, and they provide very few kilojoules. There is some good evidence that substituting regular soft drinks with diet or low-joule varieties will help some people to lose weight.
It is important to note, though, that diet soft drinks have also been associated with an increased risk of type 2 diabetes in observational studies. The association is likely due to what we call confounding, which means that people who regularly consume these types of drinks also have other healthy habits that are likely to increase their risk. However, higher-quality research is required before we can know this for certain.
Fruit juices and fruit drinks
Fruit juices and fruit drinks can also be enjoyed occasionally, but ideally not on a daily basis. They are a source of kilojoules, vitamin C, dietary fibre, and carbohydrate. On average, they provide 400 kJ per 250 ml serve and are an important source of vitamin C, providing on average 113 mg in a 250 ml serving, which is more than twice the RDI of 45 mg per day. Most fruit juice contains a small amount of dietary fibre, but higher-fibre varieties are becoming increasingly common.
Fruit juices and drinks are acidic and are also a source of fermentable carbohydrate for cariogenic bacteria, so frequent consumption of these drinks may increase the risk of developing tooth decay.
Fruit juices and drinks raise blood glucose levels in people with diabetes. On average, they provide 22 g of carbohydrate per 250 ml serve. Fruit juices made from low-GI fruit and most fruit drinks have a low glycaemic index (GI), while a 250 ml serving of most varieties has a medium glycaemic load (GL).
Perhaps surprisingly, fruit juices and drinks are suitable for treating a person who is having a hypo, despite the fact that most varieties have a low GI.
Fruit juices and fruit drinks are associated with an increased risk of type 2 diabetes in observational studies. This association may be due to their kilojoule content, which may contribute to weight gain, and glycaemic load, which may contribute to pancreatic stress. Higher-quality research is also required to prove this association.
Regular sugar-sweetened soft drinks
Ideally, people who have diabetes and those who are at risk should save sugar-sweetened beverages for special occasions. Like fruit juices and fruit drinks, sugar-sweetened soft drinks are acidic, and their consumption is associated with an increased risk of tooth decay.
On average, a 250 ml glass of sugar-sweetened soft drink provides 440 kJ and 27 g of carbohydrate (2 exchanges). Most soft drinks have a medium GI and a medium to high glycaemic load. Consequently, they will cause blood glucose levels to rise in people with diabetes.
Like fruit juices and fruit drinks, regular soft drinks are suitable for treating hypoglycemia, even though most varieties have a medium GI.
Sugar-sweetened soft drinks have been associated with an increased risk of type 2 diabetes in observational studies. Like fruit juices and drinks, this association may be due to the kilojoule content of these drinks, which may contribute to weight gain, and their glycaemic load, which may contribute to pancreatic stress.