Low carb diets tend to increase thirst and many new banters ask how much water they should be drinking. Hit google search and you will be faced with a page articles each with a different answer.
There are horror stories about brains shriveling with dehydration and kidneys drowning should fluid intake exceed more than a glass of water an hour ! Some tell us at least 8 glasses of water a day and others tell us not to drink unless we are thirsty.
Perhaps understanding the body, how we use and lose water and why water is essential for us will help answer the question.
Water is essential. We cannot survive for more than a couple of days without it.
Water provides 5 vital functions in our bodies.
- Cell life Water is a carrier, distributing essential nutrients to cells, such as minerals, vitamins and glucose
- Elimination of waste
Water removes waste products including toxins that the organs’ cells reject, and removes them through urines and faeces
- Transport of nutrients
Water participates in the biochemical break-down of what we eat.
- Body temperature regulation Water has a large heat capacity which helps limit changes in body temperature in a warm or a cold environment. Water allows the body to release heat when ambient temperature is higher than body temperature .The body begins to sweat, and the evaporation of water from the skin surface very efficiently cools the body.
- Lubrication Water is an effective lubricant around joints. It also acts as a shock absorber for eyes, brain, spinal cord and even for the foetus through amniotic fluid.
The body loses water in a number of ways.
- Through going to the bathroom. A person typically loses 1.5 liters of water a day through urine.
- Another large source of water loss in our bodies is through sweating. Our bodies maintain its temperate by sweating.
- Water is also lost from our body through breathing. When we inhale our body adds moisture to the air as it passes through our air passageways. When we exhale the humidified air is lost to the outside environment. We lose about 300 to 500 milliliters of fluid a day through breathing, depending on the humidity level of the air.
- Other ways we lose water is through tears, diets, stress and alcohol. Alcohol is a diuretic, meaning it makes us urinate more often.
The role of the kidneys is to regulate the composition and volume of the blood. The water we drink is absorbed into the blood stream. Our kidneys will filter and process approximately 180 liters of blood-derived fluid daily.Normally functioning kidneys can handle an intake of at least 700 mls per hour.
Beyond regulating the composition of our blood, the kidneys engage in other operations involved in homeostasis
What about other claims about the benefits of drinking water? Well there are studies on water intake and it’s effects on body and brain function, plenty of them. Lets take a quick look at some.
- Water Increase Energy Levels and Improve Brain Function There are studies showing that mild dehydration, which is 1-3% of body weight, caused by exercise or heat can cause significant deterioration in mental functions including degraded mood, increased perception of task difficulty, lower concentration, and headache symptoms.1,2,3
- Mild dehydration can affect physical performance and lead to reduced endurance. 1,2
- Increased weight loss there are a number of studies that support this claim including how water can temporarily boost metabolism and reduce food consumption 1,2,3
There are a number of health issues that could be improved by drinking water too. These include constipation , which seems to be a common problem among new low carbers. Some studies show that drinking more water lowers the risk of ladder cancer. Increased water also appears to decrease the risk of kidney stones.
So how much water do we actually need ?
The long-standing eight 8 glasses-a-day rule was not based on science, but instead an educated guess on what the body needs to stay hydrated.
Water requirements will depend on the individual and there are many factors (both internal and external) that ultimately affect our need for water. there is no single formula that fits everyone.
In order to replenish the body with enough water without overwhelming the cells.the Institute of Medicine determined the ideal amount is approximately 3.7 liters for men and 2.7 liters for women. “All sources can contribute to total water needs: beverages (including tea, coffee, juices, sodas, and drinking water) and moisture found in foods. Moisture in food accounts for about 20% of total water intake.” The Harvard Health Letter however published new water recommendations of between 4 & 6 glasses of water per day. That would be a MINIMUM OF 1 -1.5 Litres
For the majority of people it should be sufficient to follow their thirst. Using our innate thirst mechanism to guide fluid intake should limit drinking in excess while providing sufficient fluid to prevent dehydration.
A lot of people have no idea that they need water because their sense of ‘thirst’ isn’t working correctly.
Drugs, including common over the counter ones, age, lifestyle, and/or poor health, can interfere with ‘thirst’ perceptions. In this case a better rule to follow than drinking to thirst would be to go by the colour of the urine.
If the urine is very light yellow or clear, hydration is good. If urine is dark yellow – drink up !!
Water requirements will increase during exercise , hot and humid weather,illness, pregnancy and breastfeeding.
Can you drink too much water ?
In rare cases, drinking an extreme amount in a short time can be dangerous. It can cause the level of salt, or sodium, in your blood to drop too low causing a condition called hyponatraemia. It is very rare for young healthy people to experience this unless they drink litres of water in a short space of time.
Hyponatraemia signs and symptoms may include:nausea and vomiting, headache,confusion,loss of energy and fatigue,restlessness and irritability,muscle weakness, spasms or cramps,seizures and coma.
If you have moderate, chronic hyponatraemia due to your diet, diuretics or drinking too much water, your doctor may recommend temporarily cutting back on fluids. He or she also may suggest adjusting your diuretic use to increase the level of sodium in your blood.
If you have severe, acute hyponatraemia, you’ll need more-aggressive treatment