Clinical Geriatrics

While a certain amount of sodium is essential for life, consuming an excessive amount can lead to bad outcomes. It has been estimated that the body requires between 250 mg and 500 mg each day for basic physiological functions (eg, to transport nutrients, transmit nerve impulses, contract muscles). We maintain a careful balance under hormonal control. Under certain circumstances when our bodies sense that we need more sodium, most individuals will crave sweet and salty foods. Our hormones and taste buds (sweet, salty, bitter, sour, and savory) not only provide us with pleasure, but also are nature’s way of keeping us in metabolic balance when necessary. As we age, however, data have suggested that we preferentially lose our taste buds for sweet and salty flavors, and our hormonal system also undergoes changes that favor hyponatremia. Food preferences, habits, cultural norms, and food availability also influence what types of food we eat and how much sodium is consumed.

While a medical intern, I was “forced” to eat the various diets I had prescribed for my patients. This wonderful exercise gave me a first-hand appreciation of just how awful tasting a low-salt diet may be if one does not use creative ways to enhance flavor. I have become more attuned to salt substitutes so that I can better advise my patients how to make food more enticing, knowing full well that some use potassium chloride instead of sodium chloride, presenting an additional risk for those with renal insufficiency. I have had many an older person who was put on a low-salt diet complain that food no longer was worth eating, and so had a major change in his/her caloric intake. At times, I choose to increase the dietary sodium intake that I would otherwise prescribe to improve the chances of obtaining a more normal diet, recognizing that I would need to increase the dose of diuretic and carefully monitor outcome. As with all aspects of medicine, we must strike a careful balance and understand the risks and benefits of our treatments.

As we get older, and our system of water and sodium is no longer functioning as it did during our youth, and our antidiuretic hormone increases, we tend to become hyponatremic. Excessive sweating, loss of sodium from diuretics, and sodium-restricted diets also contribute to low serum sodium levels in the elderly, at times presenting with life-threatening situations. While restrictions on our sodium intake are wise and well deserving of more attention and regulation, elderly persons should receive careful and individual consideration of their sodium status, good advice from their physicians, and monitoring as appropriate.

As a society, however, we clearly have a problem. Just pick up a package of frozen food or canned soup, or look at the menu at McDonald’s, or, for that matter, most restaurants, and you will see how easy it is to exceed the 2.3 grams of sodium recommended by the National Academy of Sciences to use as the guideline for daily sodium intake. Remember that the “no added salt” diet we were taught in medical school to provide anywhere from 4-7 grams of salt (1.6-2.8 g sodium), in fact, varies greatly depending on one’s choice of foods. Even if no salt is added at the dining table, the sodium content may exceed what we were originally taught, as salt has increased in our food preparation practices. There is also the added confusion of “salt” and “sodium.” Four grams of salt (NaCl) is equivalent to 1.6 grams of sodium (Na).

The Institute of Medicine (IOM) is now recommending that our daily allowance of sodium be reduced further to 1.5 grams per day, and even less for those over the age of 50. I am sure that most would be glad if everyone kept to the 2.3 grams previously recommended as the daily allowance of sodium, though perhaps if we aim lower we will be more successful in achieving a healthier diet for all.