Feeling thirsty could be affecting your brain function more than you realise.
Memory and attention are affected by much lower levels of dehydration than previously thought August 16, 2016
We’re often told we should drink eight glasses of water a day, check that our urine is not too yellow, and limit caffeinated drinks because they make us lose hydration.
Such everyday advice implies that dehydration is a common problem, but the traditional view when it comes to the science is that this view is not supported by research. Rather it has been assumed that if your lifestyle does not include prolonged activity, or the temperature is not particularly high, most of the time the level of fluid in your body will be in the normal range.
However, our new research, published in The American Journal of Clinical Nutrition, is challenging this received wisdom. We found, for the first time, that the functioning of our brains can be compromised by just a minor degree of dehydration.
Previous studies have found when there is a water loss of around 2% of body weight then memory, attention and mood are adversely affected. This is typically associated with periods of extended physical activity – and much dehydration research has focused on this area, rather than the everyday water loss that we examined.
Water makes up nearly two-thirds of the body and is an essential nutrient, necessary for all aspects of bodily functioning including the distribution of oxygen and other nutrients, the removal of waste products and the regulation of temperature. Its importance is illustrated by a person dying within as little as three to five days if they do not drink. However, the body can be affected by dehydration well before the point of death.
It is well accepted that the performance of athletes will suffer if they lose too much fluid. During a single match, a footballer may run 12 or more kilometres and lose up to 3% of their body weight. If they initially weigh 75kg they will have lost 2.25kg – that is nearly five pounds of weight – which reflects a loss of half a gallon of water.
But fluid loss is a feature of daily life too, and occurs not just when we are exercising. We found that lack of water in the body begins to have an adverse influence well before the 2% loss that is typically associated with extended athletic activity.
Water limits
To find out, we conducted a study involving 101 healthy adult participants in a controlled environment at 30℃ for four hours. We used an electronic scale to measure each participant’s body weight 50 times at five second intervals, to control for body movements. The scale was sensitive enough to measure to within 5g, so changes in weight due to breathing and perspiration could be detailed over short periods.
At the end of the four-hour period, we tested each participant’s memory by asking them to recall a word list after they had heard it. Focused attention was assessed using a flankers test, where the subject is asked to say whether an arrow is facing left or right with some distractions.
After an hour and a half into the study, the extent to which thirst was experienced predicted poorer memory and attention. At this point there was a loss of only 0.22% of body weight, a change that may well occur on warm days, when you are active or if you do not drink regularly. After four hours, when there was an average loss of 0.72% of body weight, urine concentration predicted cognitive functioning: those who were more dehydrated had poorer memory and attention. Those who reported being more thirsty felt less energetic and more anxious; at the end of the four-hour period the other test subjects who had consumer water found the tests easier.
These findings show that the brain function of healthy adults is affected at a much lower level of dehydration than previously thought – but there may be groups that are at a higher risk of becoming dehydrated. Children, for example, have a greater body surface area and often rely on adults to offer them a drink. Previous research we conducted found that when school children were given a drink in the afternoon, they had a better memory and spent more time on their classroom tasks. Older adults too may also be at particular risk of dehydration as their kidneys become less efficient and the sensation of thirst declines.
The take away message is that even a minor degree of dehydration can disrupt brain functioning, so there is a need to take a few common sense precautions. Ensure you drink regularly and realise that if you sense thirst the functioning of your brain may be already compromised.
https://theconversation.com/memory-and-attention-are-affected-by-much-lower-levels-of-dehydration-than-previously-thought-63950
Health Check: what happens to your body when you’re dehydrated? January 31, 2016
Water is essential for human life. It accounts for for 50-70% of our body weight and is crucial for most bodily functions.
Any deficit in normal body water – through dehydration, sickness, exercise or heat stress – can make us feel rotten. First we feel thirsty and fatigued, and may develop a mild headache. This eventually gives way to grumpiness, and mental and physical decline.
We continually lose water via our breath, urine, faeces and skin. Most healthy people regulate their body’s water level remarkably well via eating and drinking, and are guided by appetite and thirst. But this is more difficult for infants, the sick, the elderly, athletes, and those with strenuous physical occupations, especially in the heat.
What happens when you dehydrate?
By the time you feel thirsty your body is already dehydrated; our thirst mechanism lags behind our actual level of hydration.
Research shows that as little as 1% dehydration negatively affects your mood, attention, memory and motor coordination. Data in humans is lacking and contradictory, but it appears that brain tissue fluid decreases with dehydration, thus reducing brain volume and temporarily affecting cell function.
As you “lose” body water without replacing it, your blood becomes more concentrated and, at a point, this triggers your kidneys to retain water. The result: you urinate less.
The thicker and more concentrated your blood becomes, the harder it is for your cardiovascular system to compensate by increasing heart rate to maintain blood pressure.
When your dehydrated body is “pushed” – such as when exercising or faced with heat stress – the risk of exhaustion or collapse increases. This can cause you to faint, for instance, when you stand up too quickly.
Less water also hampers the body’s attempts at regulating temperature, which can cause hyperthermia (a body temperature greatly above normal).
At a cellular level, “shrinkage” occurs as water is effectively borrowed to maintain other stores, such as the blood. The brain senses this and triggers an increased sensation of thirst.
How much should I drink?
Normal water needs range drastically due to a number of factors, such as body composition, metabolism, diet, climate and clothing.
Surprisingly, the first official recommendation about water intake was made as recently as 2004. According to the Institute of Medicine, the adequate water intake for adult men and women is 3.7 and 2.7 litres per day, respectively.
Around 80% of total daily water should be obtained from any beverage (including water, caffeinated drinks and alcohol!) and the remaining 20% from food.
But of course, this is just a rough guide. Here’s how to monitor your own hydration:
Track your body weight and stay within 1% of your normal baseline. You can work out your baseline by averaging your weight (just out of bed, before breakfast) on three consecutive mornings.
Monitor your urine. You should be urinating regularly (more than three to four times per day) and it should be a pale straw or light yellow colour without strong odour. If less frequent, darker colour or too pungent, then drink more fluids.
Be conscious about drinking enough fluids. Your fluid consumption should prevent the perception of thirst.
https://theconversation.com/health-check-what-happens-to-your-body-when-youre-dehydrated-50462
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