Hydration tips to beat the summer heat

July 2, 2003 in Healthy Eating

Water is the most abundant compound in the human body - it makes up 50 to 80 percent of our body weight, yet we tend to it for granted.

Water is an essential nutrient - just like vitamins and minerals - because our bodies can't make enough of it its own to meet daily requirements. Believe it or not, you can survive only a few days without water but a deficiency of other nutrients can take weeks, months or even years to develop.

If you drink too little fluid, or lose too much through sweat, your body can't perform at its peak. Your body's ability to regulate its body temperature is also dependent on water. The fluid in your sweat allows your muscles to release heat that builds up during exercise. The amount of water in your bloodstream also regulates your blood pressure and heart function. And finally, water acts as your body's central lubricant. It cushions your joints, moistens your eyes and protects your brain and spinal cord.

How water keeps you healthy

You may not realize that your hydration status can affect your health in other ways too. If your body is continually compensating for an inadequate fluid intake, your risk for certain diseases may be higher. New research suggests that water plays an important role in the development of cancer, heart disease, kidney stones and obesity.

Water & cancer. Several studies have discovered a direct relationship between the amount of water you drink and your risk for certain cancers. Harvard researchers learned that who drank at least 6 cups (1.5 ml) of water each day were half as likely to get bladder cancer compared to men who drank less.

Drinking plenty of water may also help ward off colon cancer. American researchers from Seattle, Washington found that women who drank more than five glasses of water each day had a 45 percent lower risk of the cancer compared to those who consumed two glasses or less. Among men, drinking at least four glasses of water each day was linked with a 32 percent reduced risk.

Scientists speculate that chronic mild dehydration can impair the activity of important enzymes in your liver and as a result, impede the removal of cancer causing substances from your cells.

Water & heart disease. You probably didn't think that boosting your water intake could prevent a heart attack. But that's exactly what researchers from Loma Linda University in California recently learned. The study followed over 20,000 men and women who were Seventh-day Adventists and found women who drank more than five 8-ounce glasses of water were 41 percent less likely to die from a heart attack and the risk was reduced by 54 percent in water drinking men. When you drink water, it becomes absorbed into the bloodstream and acts to 'thin the blood'. Researchers believe that this might prevent the formation of blood clots that could trigger a heart attack.

Water & kidney stones. If you have ever suffered from kidney stones, drinking plenty of fluids each day is a key strategy to prevent their recurrence. That's because drinking more fluids helps flush away substances that can cause crystals to form in the kidneys. In fact, chronic dehydration is a common cause of kidney stones. When the urine is less dilute from a lack of water, it becomes more concentrated with chemicals that can crystallize into stones.

Water & weight control. Many of my clients say that drinking water helps them fill up so they eat less food at a meal. Unfortunately studies have not found that drinking water before or with a meal does reduce food intake. Yet the practice of drinking at least 8 cups of water every day is recommended by many weight loss programs. I always recommend that my clients drink plenty of water each day, if not to stave off hunger, to stay healthy.

When it comes to treating and preventing obesity in children, kids should be encouraged to replace calorie-laden drinks like fruit juice and soda pop with water. Overweight older children and teenagers who quench their thirst with these beverages can be taking in as much as 500 calories per day. So while drinking water might not make you thin, drinking other liquids can certainly lead to weight gain.

How do you know if you are dehydrated?

Dehydration can be acute from a bout of heavy exercise, or chronic, resulting from a poor fluid intake day after day. Dehydration is defined as losing at least 1% of your body weight from fluids. For a 170-pound man, that means losing almost 2 pounds due to fluid loss. It may not sound like a lot but losing as little as one percent of your body weight can impair your physical performance.

Early symptoms of dehydration include headache, early fatigue during exercise, cramping, flushed skin, light-headedness, dizziness, dry mouth and eyes, nausea and loss of appetite. If dehydration progresses, you can experience difficulty swallowing, clumsiness, shrivelled skin, painful urination, numb skin, muscle spasms and delirium.

The simplest way to tell if you're replacing the fluid that your body loses is to check the colour and quantity of your urine. You're well hydrated if your urine is very pale yellow, pale yellow or straw coloured. You're dehydrated if your urine is dark coloured and scanty. If you're taking a multivitamin supplement your urine may be bright, almost neon, yellow due to a B vitamin called riboflavin. In this case, it's better to judge your need for fluids by the quantity of urine you produce.

You cannot rely on thirst to tell you when you need to drink more. By the time your thirst mechanism has kicked and you feel parched, your body is already dehydrated. Some people have a blunted thirst mechanism and are at higher risk for becoming dehydrated. Young children, the elderly, people who are sick and people who exercise in warm weather must pay particular attention to their daily fluid intake.

How much fluid do you need?

How much water you need to drink will depend on your size, your diet (high fibre diets increase fluid needs), your activity level, and the weather outside. High temperatures and low humidity increase your fluid needs.

The National Research Council recommends the average women needs to drink 9 cups (2.2 L) of fluid each day and the average man, 12 cups (2.9 L). Children actually need more water per pound of body weight than do adults. That's because children have a larger surface area per unit of body weigh. Children should drink at least 8 cups (2 L) of fluid per day.

Fluid requirements for exercise

24 hours Before Exercise -- Follow a nutritionally balanced diet and drink adequate fluids.
Two Hours Before Exercise-- Drink 2 cups (500 ml) of fluid.
During Exercise -- Start drinking cool fluids early at a rate of 1/2 to 1 cup (125-250 ml) every 15 to 20 minutes. For exercise lasting less than one hour, plain water is the best fluid for hydration. For exercise lasting longer than one hour, sports drinks that contain 4-8% carbohydrate and electrolytes (sodium, chloride, potassium) may improve hydration and performance (e.g. Gatorade, PowerAde, All Sport).
After Exercise -- Drink 2 cups (500 ml) of fluid for every pound you lose during exercise. A sports drink that contains sodium may improve recovery, but it's not necessary as long as sodium is in the foods you eat.

Tap vs. bottled water?

Tap water is drawn from the surface water of lakes, reservoirs and rivers. To eliminate disease causing bacteria and viruses, most drinking water supplies are disinfected with chlorine. Our water supplies have been treated with chlorine from more than a century ensuring our safety from the likes of cholera and typhoid fever.

There are concerns over the potential harmful effects of chlorine by-products in tap water. When chlorine is added to water, it reacts with organic matter such as decaying leaves. This chemical reaction forms a group of chemicals known as disinfection by-products, the most common ones being trihalomethanes (e.g. chloroform). Recent scientific data suggests that these by-products might be harmful during pregnancy and increase the risk of bladder and colon cancer.

More and more North Americans are drinking bottled water instead of filling a glass from their kitchen faucet. Many people think bottled water tastes better than tap water - it doesn't have that chlorine taste. Bottled water is also perceived as being safer and higher quality than tap water. After the water tragedy that occurred in Walkerton, Ontario (2000) it's no wonder people reach for bottled water.

Bottled water can be labelled as mineral water or spring water. If it's not, then it can be water from any source, including the municipal water supply, that's been treated to make it safe to drink. Treatments can include carbonation, ozonation, ultraviolet irradiation, and filtration to remove harmful bacteria.

Here's a list of different types of bottled waters available for sale in Canada:

Spring water is bottled water that comes from a protected underground source. The water is collected at the spring or through a borehole tapping the underground formation that supplies the spring. This water contains less than 500 milligrams per litre of dissolved solids (e.g. minerals).
Mineral water is the same as spring water, but it contains more than 500 milligrams per litre of dissolved solids. That means it has more calcium, magnesium and in some cases, sodium. The ideal mineral water should be rich in magnesium and calcium, and low in sodium.
Artesian water is bottled water that is tapped from a well. (Unlike a spring, well water does not flow naturally to the surface of the earth.) This may also be called 'Artesian Well Water'.
Purified water is bottled water that has been produced by distillation, deionization, or reverse osmosis. The water can come from a spring, a well, or a public community water supply.
Carbonated bottled water contains natural or added carbonation. This does not include soda water, seltzer water or tonic water - these are considered soft drinks.

Bottled vs. Tap Water. Bottled water differs from tap water in two ways. While tap water comes from the surface of lakes and rivers, most bottled waters originate from a protected underground source. Another difference relates to how these waters are distributed. Municipal water is pumped through miles of piping, whereas bottled water is produced in food plants and packaged in clean, sealed containers. And finally, bottled waters do not contain any chlorine or chlorine by-products.

Besides its improved taste and lack of chlorine, there are health reasons why some people drink bottled water. People with weakened immune systems (the elderly, HIV/AIDS, cancer, and transplant patients) are more vulnerable to bacterial infection and should drink bottled water that has been ozonated, carbonated or disinfected in some way.

Some people worry that bottled water can contain bacteria that cause illness. It's true that bacteria levels can increase quickly if bottled water is left at room temperature for six weeks. But since most bottled waters use some type of disinfection process, this is not an issue. Like most food products, bottled water contains very low levels of harmless bacteria.

What's most important is that you refrigerate an opened bottle of water in case any harmful bacterial have been introduced at this time. Ideally, refrigerate your bottled water once you buy it, and if you can't, store it in a cool place way from heat, sunlight and household chemicals. When buying bottled water, check the bottling date and best-before-date to ensure its freshness. Bottled water can be stored for up to two years.

Tips to boost your fluid intake

Drink fluids with each meal and snack and throughout the day. Keep a bottle of water on your desk at the office. The water cooler may be close at hand but how many times do you actually get up to fill your glass?
When you travel - by car, plane or train - always carry a bottle of water with you.
If you don't like drinking plain water, add a splash of white grape juice, cranberry juice or blackcurrant concentrate. Or try a glass of sparking mineral with a slice of lemon.
If you deprive your body of fluids because you don't like the taste of tap water, buy a water pitcher with an activated carbon filter. Always keep a full pitcher in the fridge. (And don't forget to replace the filter periodically!)
Use a water bottle when you exercise. Drink 125-250 ml of fluid every 15 minutes. If your workout lasts longer than one hour, hydrate with a sports drink such as Gatorade, All Sport or PowerAde.
If you drink fruit juice, choose only unsweetened varieties that don't have sugar added.
Keep your coffee intake to a minimum. Ideally aim for no more than two cups per day.
Replace unnecessary coffee (and soft drinks) with herbal tea, black tea or green tea. You get much less caffeine, and in the case of black and green teas, plenty of health enhancing antioxidants.
Limit your intake of alcoholic beverages to no more than seven per week (women) or nine per week (men). When you drink, drink a glass of water after each alcoholic beverage you've consumed.

The following is an excerpt from “Leslie Beck’s 10 Steps to Healthy Eating” (Penguin Canada 2002). Not to be reproduced without prior written permission of Leslie Beck and Penguin Canada.

All research on this web site is the property of Leslie Beck Nutrition Consulting Inc. and is protected by copyright. Keep in mind that research on these matters continues daily and is subject to change. The information presented is not intended as a substitute for medical treatment. It is intended to provide ongoing support of your healthy lifestyle practices.