Evidence Based Nutrition

Water does not suck it really really does not, water is an essential part of all life this includes humans as maintaining optimal hydration is important for humans to function well. The human body is made up of 60% water on average and is the major component of body fluids such as blood, urine and synovial fluid to name just a few (4). Humans can usually survive weeks without food but cannot survive more than a few days without water this should demonstrate the importance of water and hydration (2).

It is generally stated we should be drinking at least 6-8 glasses a day; however, it is hard to make generic recommendations as there are so many factors that affect this such as body composition, sex, levels of physical activity and environment which can affect these recommendations (2). For athletes this can increase up to 2.5 – 3 litres depending on sport or activity a day. This is due to higher physical activity and also lean tissue contains more water than fat tissue 70% and 20% respectively (2). 

Water is lost every day through sweat, breathing out and urine therefore it is important to replenish this loss of water. So where can we get this water from? We can get water from basically all foods and drinks although the absorption can differ from drinks depending on salt and sugar content (10). Consuming water is the most obvious choice of hydration however, most people like to mix it up, including myself, with a variety of beverages which is fine they can provide nutrients and be beneficial for health but over consumption of sugary drinks has been associated with obesity in those that drink these types of drinks in access. It is therefore recommended to drink mostly water however a lot of people question the difference in water from the tap and bottled water. Nutritionally speaking there is no significant difference between the two as mineral content can vary depending on the source of the water and most water can provide very small amounts of calcium, sodium and magnesium although it should be noted that this is not a primary source for these nutrients and should not be considered as a good source of these minerals for a healthy diet (12). 

Dehydration can be defined as a depletion in total body water content and a diminished intake of fluids, a person is considered to be dehydrated if they have lost 1-2% of their body weight purely from water (1, 6). Dehydration can be problematic and cause serious problems such as confusion, weak spells, disorientation, impaired wound healing and even death (9). Studies have found that a loss of 2% body mass can result in impaired cognitive function, headaches, fatigue and reduced physical performance (11). The impaired performance may be particularly an issue for athletes a study by Kavouras et al., (2012) enhancing hydration over a 2-day period in young athletes training in the heat led to significant increases in endurance exercise performance. This shows the importance of correct hydration has on physical activity performance and proves it is important for overall health of an athlete and non-athletes. Dehydration is largely treatable and preventable as was found in the elderly, the elderly often loses their sense of thirst therefore drink less than they should, when they displayed confusion and disorientation from the effects of dehydration this study shown complete recovery once fluid intake became adequate (1). Also, an MRI study found dehydration due to restricted fluid intake saw a complete recovery from reduced brain volume once acute rehydration was applied (3). Dehydration can cause a number of issues on the other hand an over intake of water can also be problematic. Overconsumption of fluids can cause hyponatraemia which means low levels of sodium, sodium regulates the amount of water around your cells with this regulation cells can become flooded causing headache, fatigue, lung congestion, vomiting, seizures and could lead to death especially in the elderly (8). This is particularly a risk to athletes mainly endurance athletes as loss of electrolytes such as sodium through sweat is increased. This can cause the blood to thin and develop life-threatening complications this has been reported the causes of death in marathon runners (13). Studies from the 2002 Boston marathon and the 2006 London marathon found that 13% and 12.5% of finishers had asymptomatic hyponatremia (7) and deaths have been recorded from hyponatraemia in the London marathon. Information is given to runners beforehand; however, not enough participants fully understand the dangers. It is recommended that runners only drink to thirst but a study in 2018 found that only 48% of runners intended to drink to thirst but 94.6% felt they had enough information which shows a lack of understanding on the topic (7). Sport drinks are designed to promote hydration before, during and after exercise providing a source of carbohydrates for energy and replacing lost electrolytes (2). These sport drinks are perfect for the endurance athlete and all marathon runners as it is considered necessary for long intense exercise where body mass can be reduced by 1-2% and they could even be better at hydrating than water alone as it has been found to be better at improving performance compared to water alone (2). If competing in a marathon having a sports drink for hydration so that lost sodium can be replaced would be a good idea and reduce the risk of hyponatraemia. 

To Conclude

Water is very important for all life and health however as with anything too much can also be bad for health. General recommendations are hard to make due to the difference in body compositions and size however, setting a minimal of 6-8 glasses a day is a good bar to set to aim towards. Most people do get their daily water requirements from whatever drinks/liquids they consume as they all are mostly made up of water accept strong alcoholic drinks such as spirits and wines (2). Also, foods we eat contain water especially fruit, vegetables and milk products (1). Now that’s some high quality H2O. 

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References

1. Begum, M. and Johnson, C. (2010) ‘A review of the literature on dehydration in the institutionalized elderly’. e-SPEN, the European e-Journal of Clinical Nutrition and Metabolism, 5(1) pp.e47-e53.
2. Benelam, B. and Wyness, L. (2010) ‘Hydration and health: a review’. Nutrition Bulletin, 35(1) pp.3-25.
3. Duning T, Kloska S, Steinstrater O, Kugel H, Heindel W, Knecht S (2005): ‘Dehydration confounds the assessment of brain atrophy’. Neurology 64:548–550. 
4. Grandjean AC & Campbell SM (2004) Hydration: Fluids for Life. A monograph by the North American Branch of the International Life Science Institute. ILSI North America: Washington, DC. 
5. Kavouras, S., Arnaoutis, G., Makrillos, M., Garagouni, C., Nikolaou, E., Chira, O., Ellinikaki, E. and Sidossis, L. (2012) ‘Educational intervention on water intake improves hydration status and enhances exercise performance in athletic youth’. Scandinavian Journal of Medicine & Science in Sports, 22(5) pp.684-689.
6. Kleiner, S. (1999) ‘Water: An Essential But Overlooked Nutrient’. Journal of the American Dietetic Association, 99(2) pp.200-206.
7. Leggett, T., Williams, J., Daly, C., Kipps, C. and Twycross-Lewis, R. (2018) ‘Intended Hydration Strategies and Knowledge of Exercise-Associated Hyponatraemia in Marathon Runners: A Questionnaire-Based Study’. Journal of Athletic Training, 53(7) pp.696-702.
8. O’Brien KK, Montain SJ, Corr WP et al. (2001) Hyponatraemia associated with overhydration in US army trainees. Military Medicine 166: 405–10. 
9. Rodriguez GJ, Cordina SM, Vazquez G, Suri MF, Kirmani JF, Ezzeddine MA, (2009) ‘The hydration influence on the risk of stroke (THIRST) study’. Neurocrit Care; 10(2):187–94.
10. Sharp RL (2007) Role of whole foods in promoting hydration after exercise in humans. Journal of the American College of Nutrition 26: 592S–6S. 
11. Shirreffs, S. (2005) ‘The Importance of Good Hydration for Work and Exercise Performance’. Nutrition Reviews, 63(6) pp.S14-S21.
12. Southgate DAT (2001) Beverages, herbs and spices. In: Human Nutrition and Dietetics, (JS Garrow, WPT James, A Ralph eds), Chapter 22, pp. 385–94. Churchill Livingstone: London, UK. 
13. Williams, J., Tzortziou Brown, V., Malliaras, P., Perry, M. and Kipps, C. (2012) ‘Hydration Strategies of Runners in the London Marathon’. Clinical Journal of Sport Medicine, 22(2) pp.152-156.