Hydration, hydration, hydration

 

Leonardo da Vinci said “Water is the driving force of all nature”. In humans, over 50% of our body is water. It is absolutely crucial to our existence and we can actually survive longer on water alone than on food alone. Water contributes significantly to both our physiological and psychological well-being. Dehydration causes headaches, loss of focus and energy, and in severe cases, raised heart rate, confusion and even unconsciousness. In spite of this, many of us still don’t sufficiently hydrate ourselves each day. Even if we are drinking fluids, there can also be lack of clarity about what is the correct volume and which drinks are hydrating. Don’t worry, we’re here to help…

Below, we’ve answered the questions our CES’ get asked most about hydration in order to encourage you to keep beautifully hydrated throughout the day:

Q. How do I know if I’m hydrated?

A. Feeling thirsty is your body’s primary way of telling you that you are becoming dehydrated. You may also notice your lips are dry or starting to crack. Checking the colour of your urine is the most accurate way to tell how hydrated or dehydrated you are.

 

Q. Why is being hydrated so important?

A. Hydration contributes significantly to the everyday functioning of your heart. Dehydration can lead to a lower blood volume and a reduction in cardiac output (how much blood you pump away from your heart). This occurs due to a fall in plasma volume, thus the viscosity of our blood increases, which lowers our central venous pressure and venous return. These changes influence the filling of the heart during diastole, resulting in a reduction in stroke volume and cardiac output.

Water also acts as a lubricant, helping to cushion joints and keeping muscles working properly. Our muscles are made up of approximately 70% to 75% water and together with joints, they enable us to stand, sit, move and carry out daily activities, including exercise.

Lastly, mild dehydration has been shown to have several cognitive side effects. These include worsened mood, increased perception of task difficulty, lower concentration, headaches, tension, anxiety and fatigue. It has been suggested that these effects may occur due to increases in cerebral activity associated with dehydration or as a result of the compensatory hormonal changes that take place in our brain when hypohydrated.

Q. How much water do I need to drink every day?

 A. According to the European Food Safety Authority (EFSA), men should consume 2.5 litres of water a day and women 2.0 litres, with 80% of this coming from liquid (i.e. drinks) and 20% from the food we eat. On this basis, men should drink 2.0 litres and women 1.6 litres of water a day.

Almost all foods contain water, although some have a higher content than others. For the remaining 20%, look towards fruit and vegetables as these have a naturally high water content (around 80-98%), which is contained in their cells. Vegetables such as carrots, celery, cucumber, tomatoes or beetroot in a meal or snack are effective at improving hydration levels.

NB: during exercise or in hot conditions, we are likely to lose more water than normal through perspiration and an increase in breathing rate. Each individual will respond differently to these conditions but it is recommended that you consume an additional 0.5-0.8 litres of water when exercising or in the heat, and particularly when both!

Q. I forget to drink water. How can I remind myself?

A. The best way to ensure you drink water regularly throughout the day is to keep a water bottle with you at all times. If you have a desk, keep it on there as a constant reminder. HydrateM8 also provides hydration tracker water bottles that help you keep on top of your correct water intake.

Alternatively, phone apps such as Drink Water Reminder (Free), and WaterMinder (£2.99) allow you to create reminders to drink and can accurately track how much you are drinking.

Q. Do tea and coffee count as part of my daily hydration?

A. There are many myths about the potentially diuretic effect of these drinks. Recent research suggests that disregarding caffeinated beverages as part of our daily fluid intake is unsubstantiated as they have been found to have no significant effect on our hydration status and therefore do count towards our daily fluid intake. However, they should be counted as a supplement to water and not as a complete substitute. Additionally, due to the caffeine content of these drinks, we recommend drinking no more than two teas or coffees per day.

Q. Is there any hydration equivalent to water?

A. Whilst all fluids contain water, water itself is the only drink that the British Nutrition Foundation recommend drinking plenty of. That said, sparkling water will hydrate you just as well and adding a little fresh fruit to your water can make it less boring and more nutritious. For example, lemons contain pectin fibre which has been shown to inhibit hunger and regulates blood sugar levels.

 

References

Armstrong, L. E., et al. (2012) Mild dehydration affects mood in healthy young women. Journal of Nutrition, 142 (2); 382-388.

Benton, D. (2011) Dehydration Influences Mood and Cognition: A Plausible Hypothesis? Nutrients, 3 (5); 555-573.

Benelam, B., & Wyness, L. (2010) Hydration and Health: a review. Nutrition Bulletin, 35 (1); 3-25.

Cian, C., et al. (2001) Effects of fluid ingestion on cognitive function after heat stress or exercise-induced dehydration. International Journal of Psychophysiology, 42 (3); 243-251.

Ganio, M. S., et al. (2011) Mild dehydration impairs cognitive performance and mood of men. British Journal of Nutrition, 106 (10); 1535-1543.

Grandjean, A. C., et al. (2011) The effect of caffeinated, non-caffeinated, caloric and non-caloric beverages on hydration. The Journal of the American College of Nutrition, 19 (5); 591-600.

Sakwa, M. N., Cheuvront, S. N., & Kenefick, R. W. (2015) Hypohydration and Human Performance: Impact of Environment and Physiological Mechanisms. Sports Medicine, 45 (1); 51-60.

Wilson, M. M. G., & Morley, J. E. (2003) Impaired Cognitive Function and Mental Performance in mild Dehydration. European Journal of Clinical Nutrition, 57; 24-29.

 

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