How much fluid should you drink each day for good health? Eight glasses a day has been the widely circulated advice. But recently, two large studies have suggested that is probably overkill. It turns out that under normal circumstances, you get most of the liquid you need each day from what you routinely eat and drink, including coffee, tea, soft drinks, and even some alcoholic drinks. So, where did this notion of ‘eight glasses a day’ come from?
15.5 According to the opening paragraph:
- The recent studies are more reliable than the earlier one.
- The recent studies urge everyone to shift to tea, coffee and alcohol.
- There is no common agreement upon the amount of water to be consumed everyday.
- Eight glasses of water a day is the safest amount for most people.
15.2 What does “that” refer to in the opening paragraph?
- Two large studies.
- Drinking eight glasses of water everyday.
- Overkill.
- Drinking more than eight glasses of water per day.
15.4 Drinking eight glasses of water a day is described as ‘overkill’ because:
- Staying hydrated isn’t as important as we used to believe.
- It is now considered unnecessary to drink so much water.
- The benefits have been known for many years.
- There are better ways to stay hydrated.
15.1 Which of the following does not happen “under normal circumstances?”
- Routine food intake.
- Routine drinking of coffee or tea.
- Drinking soft drinks.
- and even some alcoholic drinks
In 1945, the Food and Nutrition Board of the United States National Research Council wrote: ‘A suitable allowance of water for adults is 2.5 litres daily in most instances. Most of this quantity is in prepared foods: But in the 1990’s, Dr Heinz Valtin undertook a comprehensive investigation into the myths surrounding water consumption in humans. He found healthy people who drank more water didn’t have a higher ‘output of stool’, and that there was no scientific evidence high fluid intake could relieve constipation.
15.7 What do we learn about water consumption from paragraph 2?
- There was no scientific evidence to support past ideas about water.
- Healthy people don’t need to drink as much water as unhealthy people.
- Not everything we previously believed about drinking water was correct.
- No one knows the origins of how we came to drink the amount we do.
And what about the belief that thirst is not a good indicator of a need to drink? Valtin states that while ‘a rise in plasma osmolality’ (which is an internal chemical change) of less than two per cent can elicit thirst, dehydration is defined as a rise of at least five per cent. This is a complicated way of saying you get thirsty before your body starts to dehydrate, so thirst is a good guide.
17.5 In the third paragraph, the word ‘this’ refers to:
- The chemical change that occurs within a person’s body.
- The lack of rules about how much water to drink.
- The idea that thirst has no connection to dehydration.
- The reasons why a person gets thirsty.
17.4 Dehydration:
- Is next to thirst.
- Is an indication of thirst.
- Is an aftermath of thirst.
- Is a more advanced level of thirst.
Australia’s current dietary guidelines don’t recommend a specific amount of water, but simply recommend we ‘drink plenty of water’. “How much water each one of us needs depends on a range of factors,” said CSIRO dietitian Pennie Taylor.” This can include our gender, body weight and how much physical activity we do. ‘The guidelines also encourage drinking water over juices, soft drinks, cordials or the like. Also, pregnant or breastfeeding women (who require more fluid), people who live or work in extremely hot climates, and people with high protein diets (the kidneys may need more fluid to help process the increased amount of protein) are encouraged to drink more water. It’s on hot days that most of us notice we’re thirstier than normal. This is because we’re sweating more, and we lose fluid through sweat. “We can lose between 1 to 3 percent of our fluid quite easily,” Ms Taylor said.
18.5 Why don’t Australia’s dietary guidelines state a specific amount of water to drink?
- Because everyone differs physically.
- Because there are too many factors to consider.
- Because drinking any amount of water has benefits.
- Because there is no current agreement among dieticians.
Associate Professor Ben Desbrow from Griffith University agrees. “Those who work or exercise in hot climates lose the most fluid — up to 2.5 litres of sweat in an hour in extreme circumstances. You need to replace those fluids pretty quickly; otherwise it’s going to fairly rapidly have an effect on your subsequent performance.” Your body will give you some pretty clear signs that you’re not getting dehydrated. So keep an eye out for symptoms such as a dry mouth, headache and feeling dizzy.
- In the fifth paragraph, Associate Professor Ben Desbrow says he believes fluid loss:
- Happens at a very fast rate.
- Is a sign of hydration issues.
- Can result in physical decline.
- Doesn’t occur in cool climates.
Also pay attention to your toilet habits, the colour of your urine and how frequently you go to the toilet. It is true that ‘copious and clear’ is a good indicator of healthy wee. But ‘clear’ does not mean colourless. The depth of colour in urine will vary, what you need to look out for is cloudiness — that’s the indicator of a problem. “Your kidneys do a great job in fluid regulation, so frequency of urination and colour of urination are your two best guides,” Associate Professor Desbrow said.
- When commenting on urine Professor Desbrow suggests:
- Variations in colour are uncommon.
- It should always be clear or colourless.
- Frequency is a good indication of a problem.
- If it isn’t clear, there may be something wrong
What about the idea that a person may be drinking too much water? There is a thirst control centre in our brain that controls water intake, says Dr Michael McKinley, Senior Fellow at Florey Neuroscience Institute. When we drink water, this part of our brain stops us feeling thirsty long before the water has been fully absorbed into the bloodstream. “Usually if we take in too much water, it’ll suddenly feel like hard work to drink,” he said. However, in some circumstances when people drink a large volume of water, they can over-ride the thirst control centre in the brain. When this happens, their sodium levels can drop too low. This can lead to a condition known as hyponatremia, where the body also starts to retain the excess water.
- What idea does Dr McKinley express in the final paragraph?
- Drinking a lot of water can suppress a person’s appetite.
- Not having enough water can affect concentration levels.
- Our bodies usually tell us when we’ve had enough water.
- Processing large amounts of water can stress our arteries.
“Normally if we drink too much water, our kidneys would excrete it [as urine],” Dr McKinley said. But sometimes, factors like heat, physical stress or certain drugs can switch off the hormonal signal that causes the kidneys to excrete excess water. Then there is a double whammy effect. Not only have you drunk a lot of water, but you start to hang onto all the water in your body. Drinking more just makes things worse. “This is when things can get dangerous,” Dr McKinley said.
- Dr McKinley expresses concern about people who:
- Drink dangerous quantities of water.
- Have trouble passing surplus urine.
- Consume small amounts of salt.
- Take pills in extreme weather.
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