Ever since primitive species ventured out of the oceans to live on land, the main key to survival has been to prevent dehydration. Without water, humans can only survive for a few days. Water makes up 75% of body weight in infants and up to 55% in the elderly and is essential for cellular homeostasis and life.
How much water should we drink?
The body’s water requirements depend on many factors: age, body weight, physiological state, physical activity or ambient temperature. On average, it is assumed that we should drink 30 ml of water per kg of body weight per day, i.e. for a woman weighing 70 kg this would be 2,100 ml of water per day. Each of us has internal physiological control mechanisms for hydration, however, this mechanism has been significantly disrupted by the progress of civilisation. Studies show that children are already drinking insufficient amounts of water. ⅔ of the children studied showed dehydration at the age of just 9-11 years and this after eating breakfast.
The kidneys function more efficiently in the presence of an abundant water supply. If the kidneys conserve water by producing more concentrated urine, this means a greater energy cost and more wear and tear on their tissues. When there is excessive salt or toxic substances (alcohol) in the diet, drinking enough water helps to protect this important organ. Often when we have an increased appetite for salt or salty snacks, this is information coming from the body that we misread. It tells us that our cells need to be supplied with water to balance the electrolyte balance, and we reach for chips or fries instead of drinking water.
It appears that water is important in the prevention of diet-related non-communicable diseases. Humans may consume fluids for a variety of reasons, especially hedonic ones, but most drinking is due to a water shortage that triggers what is known as regulatory or physiological thirst. The mechanism of thirst is nowadays fairly well understood, and the reason why non-regulatory drinking is common is because the kidneys have a high capacity to quickly remove excess water or reduce urine output to temporarily conserve water. When we drink too little in relation to our body’s needs or have a large loss of water, e.g. through profuse sweating, the use of recently fashionable diuretic substances to “lose weight”; there is a decrease in plasma volume, an increase in sodium concentration, i.e. hypertonic dehydration occurs. This condition results in thirst, reduced salivation, dry mouth, irritability, insomnia, reddening of the skin, weakness, decreased energy, impaired coordination of movement, fluctuations in appetite.
There is a decrease in urine output and excretion of metabolic products (urea, creatinine, etc.), which cause intoxication of the body. In the long term, this leads to kidney stones.
Dehydration of 2-3% of body weight reduces physical performance impairs thermoregulation and appetite, 5-8% causes disorders, not only physical, but also mental, while as little as 20% leads to death.
What happens to you when you start drinking 8 glasses of water a day?
If you are dehydrated you will definitely feel an improvement in your well-being, here are some of the changes that may await you:
1. weight loss. Drinking fluids other than water – sweetened beverages – increases energy intake and therefore weight gain. Such liquids do not give a feeling of satiety and are essentially a meal. Substituting sweetened drinks for water is associated with reduced energy intake.
2. A fatter wallet – sweetened drinks are more expensive than water. End of story.
3. more efficient thermoregulation. Hydration status is crucial to the body’s temperature control process, or thermoregulation. The loss of water from the body through sweat is an important cooling mechanism.
4. More energy for action. At relatively mild levels of dehydration, we may experience a decrease in performance associated with reduced endurance, increased fatigue, reduced motivation and increased perceived exertion.
5. Rest. Slight dehydration (especially in hot weather) can cause anxiety and is associated with increased cortisol levels, increased sweating and electrolyte imbalances
6. Performance enhancement. Mild dehydration can disrupt mood and cognitive functioning, causing impaired concentration, alertness and short-term memory, impair task performance, reduce arithmetic ability and psychomotor skills.
7. Healthier digestive system – people with mild dehydration experience constipation, hydration reverses this process. Water is involved in the digestive process throughout the digestive system.
8. Healthy cardiovascular system. Dehydration results in lower blood volume, which means more work for the heart. Drinking too little water increases the likelihood of serious heart disease. Staying well hydrated can prevent or at least slow down the changes in the heart that lead to heart failure. One measure of hydration status is the amount of serum sodium. Sodium concentration increases when we are dehydrated, and an increase in sodium contributes to heart failure.
9. Better mood. Water deficiency and dehydration can lead to the development of headaches. Lack of water, in addition to impaired concentration and increased irritability, can trigger migraines and prolong migraines. In people with headaches caused by water deficiency, water intake provided headache relief in most people within 30 minutes to three hours.
10. Beautiful skin appearance. Water intake, especially in people with low initial water intake, can improve skin thickness, density and hydration, evening out transepidermal water loss. However, this is not enough to prevent wrinkles or other signs of ageing that are linked to genetics, sun and environmental damage. Studies show improved deep skin hydration and increased surface hydration after an additional intake of 2 litres of water per day for 30 days or an additional intake of 1 litre per day for 42 days.
11. Health. There is strong evidence to suggest that good hydration reduces the risk of urolithiasis. Weaker evidence links good hydration with reduced incidence of constipation, exercise-induced asthma, hypertonic dehydration in infants and hyperglycaemia in diabetic ketoacidosis. Good hydration is associated with a reduction in urinary tract infections, hypertension, fatal ischaemic heart disease, venous thromboembolism and cerebral infarction.
10 tips from a nutritionist on how to start drinking more water
1. Eat it! Get more vegetables and fruit into your diet – they are rich in water. Especially watermelon, apple, citrus and courgette, cucumber and tomato.
2. Include dishes in your menu that consist of water – soups, smoothies, jellies, sugar-free jellies.
3. Get into a routine of drinking water – drink a glass of water every time you go to the toilet or every time you brush your teeth or eat a meal.
4. Take advantage of modern technology! Track your water intake using modern apps.
5. Set a reminder on your phone every 2 h to drink a glass of water.
6. Spice up your water – add a slice of cucumber, lemon, orange, frozen fruit – raspberries, strawberries, blueberries – for extra flavour. Add a tablespoon of unsweetened chokeberry, rosehip or raspberry juice.
7. In winter, I suggest drinking warming teas or citrus compotes with cinnamon, turmeric, cardamom and pepper. This dose of antioxidants will help you take care of your immunity.
8. Remember to take a bottle of water with you on the go – warm in a small thermos or in a bidon. This availability of water when you move will certainly increase your daily fluid supply.
9. drink a glass of warm water when you wake up. It is common to feel a dry mouth after a night’s sleep. So make a habit of drinking water when you wake up.
10. If you’re working at a busy desk, you may forget to drink fluids – it’s worth putting a jug of water or tea in front of your work to encourage you to take a break for a few sips of a refreshing drink.
Author: Zuzanna Cybulska, MSc, clinical dietitian