Dr Laurent Le Bellego, chairman of the European Federation of Bottled Waters Health Group, chaired the symposium, entitled Guidelines for Adequate Water Intake: A Public Health Rationale. It featured presentations from Professor Lawrence Armstrong, Dr Stavros Kavouras and Dr Harris Lieberman.
Keen to better understand the science behind their hydration recommendations, FoodBev Media interviewed these three experts.
Professor Lawrence Armstrong: There are two ways to answer that question. First of all, every human being has water in their bodies. It makes up about 55-65% of their total bodyweight. Our body regulates and guards the water that we have in our bodies. Just as fish in the ocean, and animals also rely on water, so do we. It’s the media within which all of our metabolism occurs, all of our biochemical reactions, the processes of cardiovascular transport, of course in our blood. It is even linked to body temperature regulation. Physiologically, every human being has those needs.
A second way to answer that, is that there are a number of recent studies that have come out that have identified how mild dehydration impacts on our daily performance. We have conducted two studies in our laboratory in the University of Connecticut in the US that show that cognitive function in men and cognitive function in women was altered. A very mild level of dehydration, which any of us could experience on any given day, will alter mood, cognitive function. This being choices, tapping a keyboard, for example, would be impacted. Choice and response would be the best way to describe this.
According to our research, women seem to show a greater impact in mood than men. The men, in contrast, had a greater impact on their cognitive function.
Professor Lawrence Armstrong: Elite athletes are very in tune with their bodies and they carefully watch their nutrition and hydration levels. We conducted a field study at the Iron Man World Championships in Hawaii last October. With those athletes, it was obvious that they watch the media and news reports in relation to food and drink combined with a daily exercise routine. They realised that their performance is greatly impacted by nutrition and dehydration. However, they didn’t always know what to look for to indicate if they had poor levels of hydration.
Cognitive and mood changes occur at around 1.5% of dehydration. The average person probably experiences that four, five or six times a week, during normal daily activities without exercise.
Dr Stavros Kavouras: Dehydration plays an important role in many different physiological functions. These being cardiovascular functions; when you are less hydrated there is less water in the bloodstream. Reduced water makes our heart work harder, to push the blood around and push the nutrients and oxygen to different tissue. Secondly, our thermoregulatory system is stressed. If we live in a warm climate or during the summer, our body works harder to dissipate the heat that we produce, either by metabolism or by exercising.
Dehydrated people have a lot higher body temperature than normal. If we look at the active population, people that walk and cycle, and the athletic population that undertake intense training, their body temperature is significantly higher when they are dehydrated. Mood state and cognitive function, even symptoms of headaches, can affect normal function.
Dr Harris Lieberman: We’ve recently conducted a series of studies that Dr Armstrong supported at the University of Connecticut. Those studies demonstrated that under certain conditions, men and women are sensitive to the effects of mild dehydration. Mood will be impaired when suffering only mild dehydration, combined with some aspects of cognitive performance, mental status will be degraded.
Dr Harris Lieberman: We have found that at low levels of dehydration, about 1.5% loss of bodyweight, that women are more sensitive. There are several factors that may be responsible for these differences: the primary reason as to why men and women respond differently seems to be how physically fit they are. It’s clear that men are on average more aerobically fit than women. We believe that this makes them more sensitive to the effects of dehydration.
Dr Stavros Kavouras: For day-to-day dehydration, these would be difficulty to focus, cognitive difficulties, slight headaches. Simple symptoms such as mouth dryness and thirst are signs. So is our urine colour. Or even simpler markers such as how many times we go to the bathroom. If we don’t go to the bathroom every two to three hours, then we aren’t drinking enough.
Dr Lawrence Armstrong: There are simple clues to note dehydration. Thirst is a simple clue; our thirst sensation doesn’t occur until we are about 1% or 2% dehydrated. If we are at a normal hydration level, then we are not thirsty.
A factor is bodyweight. If you weigh yourself in the morning and have lost a pound of weight, then this isn’t fat. Bodyweight changes dramatically with hydration state. We use urine as an indicator. The kidneys control your body fluid level. If you are low on body fluid, then you tend to conserve water, whereas if you are hydrated, then the kidneys will release that water. The colour of urine is the simplest indicator: the darker the urine, and a smaller quantity, the more dehydrated you are. Pale, straw-coloured urine is a good indicator that you are well hydrated.
Dr Harris Lieberman: There are several symptoms, these being not feeling as well as you would normally over the course of a day. You will feel tired, fatigued, find it less easy to concentrate; you might also be slightly more anxious and you are more likely to experience a mild headache.
Dr Armstrong: For the public health standpoint, then cognition is a key factor. It impacts your performance in the workplace, your mood state and your everyday life, which can affect personal performance.
Secondly, there are some kidney-related illnesses that are caused by low levels of hydration. Kidney stones and urinary tract infections are impacted by low water intake. In increasing water intake, you have a therapeutic effect, reducing your risk of those problems.
Dr Stavros Kavouras: Water is a forgotten nutrient. If we consider epidemiological studies, people have forgotten to study water intake. Drinking and drinking water specifically have been linked to many protective effects in health, such as kidney disease, cardiovascular disease, even diabetes and obesity seems to be linked to low drinking. Drinking water is a good health habit and it seems to be linked to many positive health outcomes.
Dr Harris Lieberman: That is an important issue. To maintain and enjoy exercise, it’s a good idea to stay hydrated. Our studies suggest that it’s important for women at relatively low levels of dehydration to regain hydration to avoid subtle symptoms such as a minor headache.
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