Dry fasting, 8 glasses of water per day and all the other popular fads to lose weight, heal conditions, clear your skin and keep you healthy, they all have their moments. Still, some of them are not scientifically-proven or, even worse, can be harmful and compromise your health. Kidneys are one of the organs most affected by lack of fluid intake. On World Kidney Day and with Hydration & Nutrition Week coming up next week, Dr Richard Hull, Consultant Nephrologist at New Victoria Hospital, provides some key information on kidney health.

The truth about dry fasting and 8 glasses per day

From substitute meals to the Atkins, Paleo and Keto diets, every period has seen its fad to help you lose weight, have more energy, or cleanse your skin. Although most of them are studied and created by dietitians and specialists, some are pure scams with no scientific base.

The 8 glasses of water per day rule has been around probably since bottled water marketing started to kick in. Dry fasting is the last trend promoted on social media by “wellbeing and health influencers” who often don’t have any medical qualifications. 

Dry fasting

Dry fasting is promoted as a practice to cleanse your skin and detox your body, heal painful joints, clear your skin and reduce swelling. All these benefits can apparently be gained by giving up tap and bottled water for a certain period of time. Dry fasting gurus claim that your kidney function needs a break and will actually benefit from it.
Some people would completely avoid food and fluids altogether; others would only drink juices from fruit and vegetables when dry fasting.
Fruit and vegetables that are naturally rich in water can contribute to hydrating your body. But how many cucumbers, lettuce, kale, celery, apples, oranges and other fruits would you have to drink to make sure you are getting all the water your body needs?
Dehydration risk is real and is one of the major threats when dry fasting. 
So please, don’t try this at home!

The 8 glasses of water per day rule

The 8 glasses of water per day advice to keep your body hydrated is everywhere. However, there is no exact rule on how much water you should drink. 

A lot of external factors should be taken into account. The size of your body, physical activity, hot and humid weather, or certain medications can require you to drink more fluids than normal to keep hydrated.

Everyone is different! But we know for sure that we all need water to make our body’s systems work properly. A person’s water requirements vary on a day-to-day basis because of differences in physical activity, the weather and diet and there is no single daily water requirement for a given person.

Your kidneys work behind the scenes

Kidneys are often an overlooked organ, but their health is extremely important for an overall healthy life. And water plays a significant role in kidney health.
Kidneys work behind the scenes to:
•    collect toxins and waste from the blood 
•    regulate blood pressure
•    activate vitamin D to keep muscles and bones healthy
•    keep our body healthy

The role of water in kidney health

The body is made of around 60% water, and that is why it is so important that you provide your body with it. Water is key to ensure all organs work well, from your brain to your liver, bowel and skin. 

Water is fundamental for kidneys as well because it helps them work to remove the waste products from your body. And although it is true that water is not your only source of hydration, it certainly needs to be your main one. If you don’t take enough water, the main risk is dehydration, which could lead to minor problems such as headaches but also more serious consequences.

Elements that indicate good hydration

A healthy body is perfectly tuned to signal when liquids are needed way before you get dehydrated.

The colour of your pee

A light yellow to colourless pee means that your hydration is on point. If your pee is dark yellow, stinks and is very concentrated, you should probably drink more water and fluids.

General wellbeing

When your body is well hydrated, you feel plenty of energy and alert. Signs of dehydration are often tiredness, dizziness and headaches.

UTIs and kidney stones

Urinary tract infections and kidney stones are two common conditions that may affect your kidneys. Water and hydration help prevent them and keep your kidneys healthy.
There is no scientific proof that drinking extra water on top of the amount needed for your body to function correctly, adds any benefits to your health.

Good and bad drinks for your kidneys

When it comes to kidney health, water is your number one drink. However, milk, coffee, tea and juices are good options as well.
You only need to pay attention to sugar content and acidity because they can increase the risk of tooth decay and mean lead to you exceeding your standard calorie intake.
It is better to avoid energy and sugary drinks as sweeteners in these beverages can damage your kidneys and your overall health. Alcohol should also be limited for its dehydration power, or at least you need to make sure you compensate for dehydration by drinking more water when consuming alcohol.

How to improve your kidney health

  • Stay a healthy weight and try not to eat more than 6g of salt a day – that’s about one teaspoon
  • If you have diabetes or high blood pressure make sure you keep them under control
  • Aim for 30 mins of physical activity 5 days a week. Pick something you enjoy like gardening or swimming
  • Stop smoking. It slows the blood flow to your kidneys so they don’t work as well
  • Take drugs like ibuprofen with caution and seek advice because they can sometimes harm your kidneys
  • Remember to stay hydrated and avoid excess alcohol so your kidneys can do their job properly


If you are concerned about your kidneys, you can book an appointment with our Consultant Nephrologist, Dr Richard Hull, by calling 020 8949 9020 or:

Book an appointment

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