Friday, August 26, 2011

The importance of hydration

After months of cooler weather, rainy skies and dark nights, summer is upon us, enticing us outside to enjoy the warmth of the sun.  While enjoying all that summer has to offer, one item that we often don’t focus on, but which is fundamental to good health, is our water and fluid consumption.  Adequate hydration is important throughout the year, but especially during the summer, as the weather warms up and more time is spent outside in the sun and engaged in physical activity.  As a result of the heat and the increased physical exertion, we lose more water and electrolytes through our sweat than during other times of the year.  Nature aligns with our higher need for fluids by producing a larger number of watery fruits and vegetables during this time, such as watermelon, cucumber, tomatoes, peaches, nectarines and strawberries.  While these food items help hydrate our bodies, food alone cannot compensate for our need for pure water.  One general estimation is that about 1 litre of fluid is consumed through food each day.  This of course will depend on the types of foods that are consumed, but eating a diet high in fruits and vegetables will generally help with keeping your body hydrated.

Why is water and hydration so important?  Water plays a critical role within our bodies: it helps maintain healthy blood pressure, is necessary for digestive processes to function appropriately, is needed for energy production, and is involved in the elimination of toxins and scavenging of free radicals.  When the body is dehydrated, toxins are not eliminated efficiently, and end up being re-circulated in the body, putting additional pressure on the liver and kidneys to act as detoxifying systems.  Although water does not provide calories, it is vital for the extraction of energy, is involved in the synthesis of protein and facilitates the flow of nutrients into cells, each of which impact our energy levels.  In addition, water is involved in a variety of chemical reactions within the body, is the primary solvent in all bodily fluids (blood, saliva etc), and acts as a lubricant and transport medium.  If the body is not properly hydrated, cells cannot maintain proper structure, chemical reactions that occur within cells are inhibited and the integrity and stability of protein structures inside our bodies are weakened.  Water also maintains the balance of electrolytes in the body, which is especially critical during the summer when we lose extra electrolytes through sweat.  Because of the many important functions water has in our bodies, chronic dehydration will result in decreased energy and can lead to illness and disease since our bodies cannot keep up with processes that help keep our cells strong, and our bodies free from damaging toxins and free radicals.    

There are a number of different calculations and methods to determine water intake needs. A general calculation is based on kilocalorie consumption, and specifies that for every kilocalorie consumed, one millilitre of liquid should be consumed.  So, an intake of between 2,000-2,500 kilocalories per day, would equate to 2 – 2.5 litres of liquid.  The US Institute of Medicine provides general recommendations for adequate water intake based on gender.  The recommendation for women is to consume 2.7 litres of fluid daily through food and drinks, with 80% of that consumed from liquid and 20% from food.  This means that women should consume 2.16 litres of liquid daily.  For men, the recommendation is to consume 3.7 litres of fluid through both food and drinks, with 3 litres (80%) consumed through water and other liquids.  However, this is a very general guideline, and does not take into account weight, exercise level or climate.  Another calculation is based on body weight.  Divide your body weight (in pounds) in half. This equals the number of fluid ounces of pure water that should be consumed daily.  For example, an individual who weighs 130 pounds should aim to consume 65 fluid ounces of water daily (half of 130), which equals 8 cups (2 litres) of water.  While the exact measurements vary, each of the guidelines provides a similar result for fluid consumption.  Pick whichever one works for you.    

During exercise, our bodies have increased hydration needs, as a result of fluid lost through sweat.  Losing as little as two percent of your body weight during exercise can inhibit your performance since it lowers blood volume, causing the heart to work harder to circulate blood throughout our bodies. This can result in muscle cramps, dizziness, fatigue and heat illnesses.

One suggestion is to consume 2 cups of water for every pound of weight lost during exercise through sweat.  However, since it is impractical to weigh ourselves before and after each session that we exercise, another method is to use intensity and duration as a way to calculate fluid replenishment. One recommendation is to drink 500 millilitres of fluid for every 30 minutes of strenuous exercise in warm/hot temperatures and to consume 250 millilitres for every 30 minutes of moderate exercise.  When exercising for periods longer than 60-90 minutes or in extremely hot temperatures, it is important to replenish lost electrolytes in addition to fluid loss.  Electrolytes (sodium chloride, magnesium and calcium) maintain muscle function, and when levels drop too low, this can lead to muscle cramps, fatigue, confusion or mental fogginess.  Because the body loses electrolytes through sweat, these need to be replenished so the body maintains homeostasis/balance.  Electrolytes can be replaced through sports drinks, gels, energy bars or whole foods such as fruits and vegetables.       

Enjoy the summer, relish in the warmth and longer evenings, and remember to stay hydrated!