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Nutrition and Health

Osteoporosis, brittle bones, lack of Calcium

How Much Water, Potassium and Salt Do We Need?

By Dr. W. Gifford Jones

February 1, 2005

W.C. Fields, the comedian, joked, "No use for water, water's for flowing under bridges". Like Fields I've never enjoyed water unless it's with an occasional scotch. But for years authorities have said we must drink eight glasses of water daily to stay healthy. So who is right? And how much sodium and potassium do we need each day?

The National Academy of Sciences Institute of Medicine recently convened a meeting of distinguished scientists. They concluded it's a myth that we need eight glasses of water a day. Rather, all fluids must be included in calculating water intake.

Fields, noted for his large, red nose, would be ecstatic to hear this news. Another of his one-liners was, "A woman drove me to drink and I never wrote to thank her for it!"

Luckily, nature endowed us with an excellent thermostat to tell us how much fluid is needed for health. For instance, unless we are in the Sahara Desert or engaged in strenuous sports, the amount of fluids needed is governed by thirst. And most people fail to calculate that about 20 percent of our water intake is from food. This means that, usually, none of us have to worry one whit about the amount of water we need.

In effect, the panel of experts said, forget about water intake and be more concerned about the amount of sodium and potassium we consume day after day.

Sodium comes mainly from salt. It's essential to health, but for years most North Americans have been consuming too much of it. The daily requirement is 1500 milligrams (mg). But studies show only 25 percent of people come close to this amount. Most men consume from 3100 to 4700 mg and women 2300 to 3100 mg daily.

Unfortunately more than 75 percent of sodium comes from packaged and restaurant foods. And excessive amounts can lead to high blood pressure, a serious risk factor for heart disease and stroke.

Sodium also increases the excretion of calcium in the urine. This loss, along with the fact that too many North Americans lack calcium from failing to drink milk, helps to increase the risk of osteoporosis (brittle bones).

A government funded study, entitled Dietary Approaches to Stop Hypertension, found that by decreasing sodium to 1500 mg a day, nearly everyone's blood pressure is lowered. For some people this is not the case but it's worthwhile trying a low sodium diet at least for several months.

Potassium is a different story. In this case many people are not getting the required 4700 mg a day. This increases the risk of hypertension and also muscle weakness and kidney stones. The panel concluded a deficiency of potassium may also be related to increased risk of cardiovascular disease, particularly stroke.

But not all people should try to increase their potassium. Patients with type 1 diabetes, and those taking ACE inhibitor drugs, certain diuretics or nonsteroidal anti-inflammatory drugs should consult their doctors. Some patients on these drugs cannot handle more potassium.

So how can you decrease the amount of sodium and increase potassium? The best way is to start thinking "fresh" and "unprocessed". This means buying less packaged foods and more fruits, vegetables, beans, lean meats, dairy products and poultry. This approach conveys a double benefit since these foods are low in sodium and high in potassium.

My wife often kids me about how paranoid I've become about reading labels on packaged foods. But I never fail to be astonished at how food companies load so much sodium into their products. So start reading labels. You will discover how the sodium in each package adds up to a huge daily amount. It's one instance where a little paranoia is good for your health.

It would also help the health of this country if everyone tossed the salt shaker off the table. It's amazing how much salt some people add to an already sodium rich meal. In addition, Ministers of Health should demand that food manufacturers decrease the amount of salt in packaged foods. But since we live on planet earth and not heaven, hell will freeze over before this happens.

W. Gifford-Jones M.D Most recent columns

W. Gifford-Jones M.D is the pen name of Dr. Ken Walker graduate of Harvard. Dr. Walker's website is:
Dr. Walker can be reached at

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