Minum Delapan Gelas Air Sehari: Apa Kata Sains?
LYNA M. N. HUTAPEA
Fakultas Keperawatan, Universitas Advent Indonesia
Pendahuluan
Air adalah faktor esensial dari setiap fungsi fisiologis tubuh. Itulah sebabnya, tanpa asupan air manusia hanya dapat bertahan hidup dalam beberapa hari.1 Itulah juga sebabnya mengapa banyak himbauan di media massa cetak maupun elektronik yang menganjurkan agar minum cukup, yaitu sedikitnya delapan (8) gelas air minum setiap harinya. Bahkan, dalam Pedoman Umum Gizi Seimbang yang dikeluarkan oleh Departemen Kesehatan RI pun dianjurkan supaya masyarakat mengonsumsi air minum minimal 2 liter (8 gelas) sehari untuk memenuhi kebutuhan cairan dan menjaga kesehatan. Perlukah asupan air sebanyak itu? Apakah jumlah delapan gelas didukung sains? Jumlah ini memang masih diperdebatkan karena ada kelompok ilmuan yang menyatakan bahwa jumlah yang dianjurkan itu terlalu banyak. Dapat dipahami bahwa demi kesehatan, orang yang tinggal dan beraktivitas di daerah yang bersuhu tinggi serta kering membutuhkan volume asupan air minum yang lebih tinggi. Tetapi, apakah seorang sehat yang tinggal dan beraktivitas di daerah yang sejuk perlu asupan 8 gelas per hari agar tetap tetap sehat walaupun tidak merasa merasa haus? haus? Dari manakah asal usul rekomendasi yang mengatakan bahwa setiap orang perlu minum 8 gelas per hari? Sehubungan dengan rekomendasi ini, sekelompok ahli ilmu fisiologi manusia mempertanyakan apakah rekomendasi minum sedikitnya delapan gelas air minum minum per hari itu absah secara ilmiah.
Rekomendasi Delapan Gelas per Hari
Asal muasal rekomendasi delapan gelas per hari (8GpH) telah diteliti secara ekstensif oleh Heinz Valtin, seorang profesor di bidang fisiologi dari Darmouth Medical School di Amerika Serikat. Spesialisasi penelitiannya adalah bidang ginjal dan dia telah meneliti sistem biologis yang berperan mempertahankan keseimbangan air dalam tubuh. Sebagai hasil penelitian tersebut, Valtin melaporkan bahwa “tidak ada bukti ilmiah yang mendukung perlunya minum air sebanyak yang direkomendasikan itu, namun tidak ada juga bukti ilmiah jelas yang menyatakan bahwa tidak ada manfaat minum air sebanyak itu.2” Selanjutnya, dinyatakan dalam laporan tersebut juga bahwa bagi mereka yang cenderung mengidap infeksi saluran kencing, minum air dalam volume yang besar dapat menolong, sedangkan orang yang sehat tidak perlu minum sebanyak yang direkomendasikan itu. Enam tahun kemudian, Valtin juga mengatakan bahwa dia belum menemukan satu pun laporan ilmiah yang menentang kesimpulan yang dia buat sebelumnya tentang 8GpH itu. Pada tahun yang sama, hal serupa dinyatakan dalam hasil penelitian yang dilakukan oleh Negoianu dan Goldfarb.3Kedua peneliti ini menyatakan kesimpulan yang mirip dengan yang dinyatakan Valtin enam tahun sebelumnya, yaitu tidak ada bukti jelas yang menunjukkan manfaat minum air sebanyak delapan gelas per hari seperti yang direkomendasikan. Selanjutnya, mereka juga menyatakan: “Kami bukan mengatakan jangan minum delapan gelas air minum sehari, yang kami katakan adalah tidak wa jib minum sebanyak itu.” http://www.jurnalmedika.com/edisi-tahun-2011/edisi-no-09-vol-xxxvii2011/358-artikel-konsep/719-minum-delapan-gelas-air-sehari-apakata-sains
Selama ini kita selalu mendengar bahwa minum air putih penting untuk kesehatan. Bahkan, ada patokan standar mengenai berapa jumlah air minum yang kita konsumsi setiap hari, yaitu delapan gelas. Namun sebuah artikel di British Medical Journal memaparkan fakta baru: minum delapan gelas air sehari justru bisa berakibat buruk pada kesehatan. Margaret McCartney, dokter umum yang berbasis di Glasgow, mengatakan bahwa manfaat minum air seringkali dibesar-besarkan oleh organisasi-organisasi dengan kepentingan pribadi, misalnya produk air minum kemasan. Minum ketika kita tidak haus, menurutnya, bisa mengacaukan konsentrasi. Manfaat minum sejumlah air putih juga disebut-sebut hanya mitos, karena tidak ada bukti nyata di balik pernyataan bahwa air putih bisa mencegah beragam masalah kesehatan. Menurut Dr McCartney, konsumsi air yang berlebihan bisa mengakibatkan seseorang menjadi kurang tidur, bahkan bukannya mencegah dari kerusakan ginjal tetapi justru menimbulkannya. Pendapat umum yang mengatakan bahwa minum air dapat menekan nafsu makan juga disanggah oleh Profesor Stanley Goldfarb, pakar metabolisme dari University of Pennsylvania. Karena, hal ini pun tidak ada buktinya. "Kalau anak-anak minum lebih banyak air putih daripada soda yang justru memberikan kalori tambahan, itu bagus. Tapi tidak ada bukti bahwa minum air putih sebelum makan mampu mengurangi nafsu makan," tuturnya. Nah, jadi mana yang benar? Mungkin ada baiknya kita memastikan saja bahwa kita tidak kekurangan minum. Bagaimanapun, kurang minum juga
tak baik untuk kesehatan. Untuk mengetahui apakah Anda sudah cukup minum air atau belum, silakan klik Tanda Anda Belum Cukup Minum Air.
Water: How much should you drink every day? Water is essential to good health, yet needs vary by individual. These guidelines can help ensure you drink enough fluids.
By Mayo Clinic staff How much water should you drink each day? It's a simple question with no easy answers. Studies have produced varying recommendations over the years, but in truth, your water needs depend on many factors, including your health, how active you are and where you live. Although no single formula fits everyone, knowing more about your body's need for fluids will help you estimate how much water to drink each day. Health benefits of water
Functions of water in the body Water is your body's principal chemical component and makes up about 60 percent of your body weight. Every system in your body depends on water. For example, water flushes toxins out of vital organs, carries nutrients to your cells and provides a moist environment for ear, nose and throat tissues. Lack of water can lead to dehydration, a condition that occurs when you don't have enough water in your body to carry out normal
functions. Even mild dehydration can drain your energy and make you tired. How much water do you need?
Every day you lose water through your breath, perspiration, urine and bowel movements. For your body to function properly, you must replenish its water supply by consuming beverages and foods that contain water. So how much fluid does the average, healthy adult living in a temperate climate need? The Institute of Medicine determined that an adequate intake (AI) for men is roughly 3 liters (about 13 cups) of total beverages a day. The AI for women is 2.2 liters (about 9 cups) of total beverages a day. What about the advice to drink eight glasses a day?
Everyone has heard the advice, "Drink eight 8-ounce glasses of water a day." That's about 1.9 liters, which isn't that different from the Institute of Medicine recommendations. Although the "8 by 8" rule isn't supported by hard evidence, it remains popular because it's easy to remember. Just keep in mind that the rule should be reframed as: "Drink at least eight 8-ounce glasses of fluid a day," because all fluids count toward the daily total. Factors that influence water needs
You may need to modify your total fluid intake depending on how active you are, the climate you live in, your health status, and if you're pregnant or breast-feeding.
Exercise. If you exercise or engage in any activity that makes you
sweat, you need to drink extra water to compensate for the fluid loss.
An extra 400 to 600 milliliters (about 1.5 to 2.5 cups) of water should suffice for short bouts of exercise, but intense exercise lasting more than an hour (for example, running a marathon) requires more fluid intake. How much additional fluid you need depends on how much you sweat during exercise, and the duration and type of exercise. During long bouts of intense exercise, it's best to use a sports drink that contains sodium, as this will help replace sodium lost in sweat and reduce the chances of developing hyponatremia, which can be lifethreatening. Also, continue to replace fluids after you're finished exercising.
Environment. Hot or humid weather can make you sweat and requires
additional intake of fluid. Heated indoor air also can cause your skin to lose moisture during wintertime. Further, altitudes greater than 8,200 feet (2,500 meters) may trigger increased urination and more rapid breathing, which use up more of your fluid reserves.
Illnesses or health conditions. When you have fever, vomiting or
diarrhea, your body loses additional fluids. In these cases, you should drink more water. In some cases, your doctor may recommend oral rehydration solutions, such as Gatorade, Powerade or CeraLyte. Also, you may need increased fluid intake if you develop certain conditions, including bladder infections or urinary tract stones. On the other hand, some conditions such as heart failure and some types of kidney, liver and adrenal diseases may impair excretion of water and even require that you limit your fluid intake.
Pregnancy or breast-feeding. Women who are expecting or breast-
feeding need additional fluids to stay hydrated. Large amounts of fluid are used especially when nursing. The Institute of Medicine recommends that pregnant women drink 2.3 liters (about 10 cups) of fluids daily and women who breast-feed consume 3.1 liters (about 13 cups) of fluids a day.
Beyond the tap: Other sources of water
Although it's a great idea to keep water within reach at all times, you don't need to rely only on what you drink to meet your fluid needs. What you eat also provides a significant portion of your fluid needs. On average, food provides about 20 percent of total water intake. For example, many fruits and vegetables, such as watermelon and tomatoes, are 90 percent or more water by weight. In addition, beverages such as milk and juice are composed mostly of water. Even beer, wine and caffeinated beverages — such as coffee, tea or soda — can contribute, but these should not be a major portion of your daily total fluid intake. Water is still your best bet because it's calorie-free, inexpensive and readily available. Staying safely hydrated
Generally if you drink enough fluid so that you rarely feel thirsty and produce 1.5 liters (6.3 cups) or more of colorless or light yellow urine a day, your fluid intake is probably adequate. If you're concerned about your fluid intake or have health issues, check with your doctor or a registered dietitian. He or she can help you determine the amount of water that's right for you. To ward off dehydration and make sure your body has the fluids it needs, make water your beverage of choice. It's also a good idea to:
Drink a glass of water or other calorie-free or low-calorie beverage with each meal and between each meal. Drink water before, during and after exercise. Although uncommon, it is possible to drink too much water. When your kidneys are unable to excrete the excess water, the electrolyte
(mineral) content of the blood is diluted, resulting in low sodium levels in the blood, a condition called hyponatremia. Endurance athletes, such as marathon runners, who drink large amounts of water, are at higher risk of hyponatremia. In general, though, drinking too much water is rare in healthy adults who eat an average American diet. http://www.mayoclinic.com/health/water/NU00283 http://geiselmed.dartmouth.edu/news/2002_h2/pdf/8x8.pdf http://jasn.asnjournals.org/content/19/6/1041.full.pdf+html
The Wonders of Water
By Kathleen M. Zelman, MPH, RD, LD WebMD Feature Reviewed by Louise Chang, MD Water is one of the most basic elements of life but figuring out how much we ought to drink hasn't always been so simple. Most of us grew up thinking we needed to drink eight glasses of water each day, in addition to any other drinks we might choose. But the latest recommendations say that we no longer need to worry about drinking specific amounts of water. Instead, we can simply satisfy our thirst with any beverage. As it turns out, there really was no scientific evidence for the 64-ounce daily recommendation that was based on survey data of usual consumption. Of course, water -- clean, refreshing, and calorie-free -- is an ideal beverage of choice but studies have shown that you can be just as hydrated with coffee, soft drinks, or even beer. And some folks swear by its weight loss powers, including Mireille Guiliano, author of the best-selling book French Women Don't Get Fat.
To help make the facts about water crystal clear, WebMD asked experts for the skinny on just how much water we need, and whether drinking water can really help keep those extra calories at bay. The New Fluid Guidelines
A 2002 study published in the American Journal of Physiology questioned the old recommendation of 8 ounces of water, eight times a day. After a thorough review, researcher Heinz Valtin concluded there was inadequate evidence that healthy adults -- living in temperate climates and not engaged in rigorous activities -- need large amounts of water. For normal, healthy adults, Valtin recommended simply drinking when thirsty. And he reported that even caffeinated drinks can count toward satisfying our fluid requirements. In February 2004, the Institute of Medicine (IOM) issued new recommendations that agree with Valtin's findings. The new guidelines remove the eight-glasses-a-day recommendation, and say healthy adults may use thirst to determine their fluid needs. Exceptions to this rule include anyone with a medical condition requiring fluid control; athletes; and people taking part in prolonged physical activities or whose living conditions are extreme. How Much Is Enough?
The IOM report did not specify requirements for water but made general fluid intake recommendations based on survey data of 91 ounces (that's 11-plus cups a day) for women and 125 ounces (15-plus cups a day) for men. Remember, these guidelines are for total fluid intake, including fluid from all food and beverages. Approximately 80% of our water intake comes from drinking water and other beverages, and the other 20% comes from food. Assuming these percentages are accurate for most of us, the recommended amount of
beverages, including water, would be approximately 9 cups for women and 12.5 cups for men. While 20% may seem like a lot of fluid to get from food, many common food items are mostly water. Here are some foods with high water content, according to the American Dietetic Association:
Food
Percentage Water
Lettuce (1½ cup)
95%
Watermelon (1½ cup)
92%
Broccoli (1½ cup)
91%
Grapefruit (1½ cup)
91%
Milk (1 cup)
89%
Orange juice (3/4 cup)
88%
Carrot (1½ cup)
87%
Yogurt (1 cup)
85%
Apple (one
84%
medium)
When You Need More
Physical activity, heat, and humidity can increase our fluid needs. In these situations, keep water bottles close at hand and drink frequently to avoiddehydration. If you're going to be physically active for long periods, consider sports drinks that hydrate and provide easily usable sugar and electrolytes. Illnesses accompanied by increased body temperature, excessive perspiration, vomiting, frequent urination, or diarrhea can also increase our fluid needs. Be sure to drink plenty of liquids if you have one of these conditions, and see a doctor if your fluid losses are excessive or prolonged. How Much Is Too Much?
Scientists on the IOM panel did not set an upper limit for water. "Water intoxication is very rare, although it has been seen in fraternity pranks. That can be very serious and result in death" says David Perlow, MD, an Atlanta-based urologist. One recent study of Boston Marathon runners showed that one in three marathon runners was drinking too much water during a race -probably because they were following recent advice to drink as much as tolerated. If you follow your thirst, you won't go wrong, Perlow says. He notes that pre-modern man never ran around sipping on a water bottle. A dry mouth indicated it was time to run to the stream for a drink. "Trust your thirst instinct to make sure you get enough fluids and, of equal importance, void frequently," suggests Perlow.
Perlow says the bladder is like a balloon. When you make infrequent trips to the bathroom, it can become overstretched -- which can result in problems with incomplete emptying, he explains. He recommends 7-12 trips to the toilet daily for most healthy people. Water and Weight Control
For years, drinking water has been recommended for weight loss -despite the fact that fluids generally satisfy thirst and not hunger. Barbara Rolls, PhD, an expert on thirst and satiety, points out that thirst and hunger are regulated by entirely different mechanisms. A recent study by Rolls and colleagues at Penn State University looked at whether people who drank water with lunch took in fewer calories than those who drank other low-calorie beverages. They found that drinking water had little effect on total calorie consumption at the meal. "In all of our research, we have never been able to show that water can cause weight loss," says Rolls. The only way drinking water can help you lose weight is if you substitute it for higher-calorie beverages or foods, she explains. However, eating foods with high water content can help dieters, by increasing the fullness factor. "When you add water to a bowl of vegetables as in soup, the soup has greater satiety than when the vegetables are eaten alone with a glass of water," explains Rolls, author of The Volumetrics Eating Plan and The Volumetrics Weight Control Plan. "When water is incorporated into food or shakes, satiety is increased and subjects ultimately eat less food." The weight loss benefits of water stem from several facts:
Foods that incorporate water tend to look larger. The higher volume of these foods provides greater oral stimulation.
Most important, when water is bound to food, it slows down absorption and lasts longer in the belly. If you want to lose weight, Rolls recommends an eating plan that includes plenty of high-volume foods such as fruits, vegetables, brothbased soups, and oatmeal, along with adequate fluids to satisfy your thirst. Bottom Line
The experts agree: Drinking water -- either sparkling or flat and perhaps with a twist of citrus -- is a great, noncaloric way to satisfy your thirst. But if you prefer 100% fruit juice, low fat milk, coffee, or other flavored beverages, they too can keep you well hydrated. Water is calorie free, which makes it a great choice for weight control, but we also need the calcium and especially the vitamin D in low-fat milk. Bottom line, make your beverage choices work to satisfy your nutritional needs, fluid preferences, and hydration needs.
http://www.webmd.com/a-to-z-guides/features/wonders-of-water
