& Joannie Dobbs Wednesday,
Diet, age and other factors affect body's water
Without a doubt, water is the most important nutrient. Maintaining proper water balance is critical to good health. Listed below are a few of the conditions that can change this balance.
Question : Do water needs change as people get older?
A : Water needs don't change per se, however as people age, they generally develop a decreased sense of thirst, putting them at increased risk of dehydration. Several studies show that individuals older than 60 do not feel adequately thirsty even when in physiological need. The end result is that simple environmental stresses, such as heat, can put a person at risk if adequate hydration is not maintained.
At the other extreme, older people are also at increased risk of overhydration. Due to common changes in kidney function as people age, they also have less ability to conserve sodium. Inadequate amounts of dietary sodium, along with excess fluids, can produce dangerous overhydration in older people.
As people age, it may be prudent to establish a schedule of drinking fluids. This would ensure adequate liquid volume and reduce the risk of strokes due to decreased blood volume.
Q : How does a person's protein intake affect water needs?
A : One of the key functions of protein is to "hold onto" fluid in the blood. Individuals consuming too little protein are unable to maintain adequate amounts of water in the blood. Inadequate dietary protein can cause increased urination, fatigue or feeling bloated.
On the other extreme, those consuming excessively large quantities of protein can increase their water needs substantially. For example, consuming about 12 ounces of cooked meat (100 grams) in additional to normal protein requirements can increase daily water needs by about 6 cups.
Q : How do diuretic drugs change water and other nutrient needs?
A : Diuretic drugs are used for various medical conditions, especially in the treatment of high blood pressure. The type of diuretic determines its overall effect on nutrient needs.
Along with increasing water loss, some diuretics can cause imbalances in calcium, sodium, magnesium and/or potassium. For this reason, there are no general guidelines about changes in nutrient needs.
People taking a diuretic should consult their physicians and pharmacists to see if they should compensate by increasing their intake of specific foods or supplements.
Q : How does alcohol affect water needs?
A : Alcohol is known to have a temporary diuretic effect. The extent of water loss depends on the amount of alcohol consumed. For example, the alcohol content of a typical 12-ounce bottle of beer, 4-ounce glass of wine or a 1-ounce shot of whiskey causes an increase in water needs of about 4 ounces.
Q: Can herbal supplements affect water needs?
A : The effects of herbs on water needs and mineral loss vary as much as with diuretic medications. Products advertised to reduce bloat or bring about weight loss can negatively affect water balance. Many people view any weight loss as good, however losing water weight actually can be harmful.
Products such as Super Dieters Tea contain ingredients such as senna that work as laxatives. Other herbal products are designed to work as diuretics. Therefore these "natural" products can significantly affect water and mineral needs.
Alan Titchenal, Ph.D., C.N.S. and Joannie Dobbs, Ph.D., C.N.S.
are nutritionists in the Department of Human Nutrition, Food and Animal Sciences,
College of Tropical Agriculture and Human Resources, UH-Manoa.
Dr. Dobbs also works with the University Health Service
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