The days are growing longer, and the weather is becoming progressively warmer. With the winter hibernation coming to a close for another year, many people are crawling out of their indoor caves, and spending more time outside. There is an undeniable association between the warmth of the sun and our desire to be active. We all know however, that when we increase our physical activity, especially as the temperature rises, our bodily demands for fluids also increase. But are we doing enough to prevent dehydration that is inevitable from inadequate fluid intake? If you are getting thirsty, the answer is no!
Importance of Water
Water is the largest component of the body, making up 60% of total body mass in the average lean adult. It is found within and between every single cell. Our blood, cerebrospinal fluid, synovial fluid, and lymph are primarily made of it. It powers digestion, lubricates our joints, permits respiration, is vital in oxygen delivery to our tissues, and removes toxins from the body. Needless to say, water is a requirement for life, and is grossly taken for granted!
Understanding Thirst and Dehydration
The thirst sensation is not a warning for pending dehydration, as commonly believed. In reality, it is triggered by actual dehydration—so if you are feeling thirsty, you are already dehydrated! The ‘Thirst Center’ is an area of the brain located in the hypothalamus, specifically the periventricular nuclei (for those who like to get technical). It is responsible for gathering information from the body, and alerting us when there is insufficient water in the system. There are three main ways that the brain detects dehydration from receptors in the body:
- Dry mouth and pharynx from inadequate water to produce saliva.
- Increased osmolarity (concentration) of the blood. Essentially, water dilutes blood to the proper concentration, and when water is lacking, blood becomes more concentrated than it should be.
- Decreased blood pressure from a decreased blood volume, since blood is largely made of water.
Daily Water Requirements
The human body lacks a long-term water storage system. Water is lost primarily through the urine, but also in the feces, lungs, and skin. Needless to say, any water lost must be replaced in order to maintain health. But how much is necessary? This is a far more complicated question than likely perceived. Water demands change depending on body size, composition, medications, ingested diuretics (caffeine/alcohol), physical activity, gender, and age. Most people are familiar with the 8 glasses/day recommendation, but it takes for granted the individuality of people.
Sparing the complicated rational for why, a more accurate calculation for adults is:
Water Intake = 35