New U-M study examines the dietary habits of America's elderly
ANN ARBOR---America's elderly consume at least the recommended dietary allowances of iron, zinc and magnesium, but the use of nutritional supplements and drugs commonly used by the elderly can offset the balance of these important nutrients, a new University of Michigan School of Public Health study shows.
The study by Srimathi Kannan, a visiting assistant professor of environmental and industrial health, examined the intake of iron, zinc, copper and magnesium of 2,170 Americans aged 65-90. Kannan and colleagues examined the micronutrient (also known as trace minerals) intake of senior citizens enrolled in the U.S. Department of Agriculture Continuing Survey of Food Intakes of Individuals (1994-96).
"No diet stands alone," Kannan said. "The elderly should consume a varied and diverse diet and consume nutritional supplements when necessary. Micronutrients are just as important as other nutrients. Being conscious of the need to maintain a healthy balance of iron, zinc, copper and magnesium is especially important for seniors who must contend with other health factors."
Kannan will present her findings on April 18 at "Experimental Biology '99," the annual conference of the Federation of American Societies for Experimental Biology in Washington, D.C. Her presentation is titled, "Trace Mineral Intakes in the U.S. Elderly: Association with Diet Quality Indices."
Although recommended in very small quantities, micronutrients are essential for good health. Iron, for example, prevents anemia, helps correct memory deficits and is believed to play a role in boosting the immune system. Zinc is believed to enhance immunity and reduce the risk of respiratory infections that can lead to colds. It can also help restore impaired senses, such as the ability to taste and smell.
Magnesium can help prevent cardiovascular disease and can help maintain the balance of calcium and potassium in the body. Copper is believed to reduce the risk of cardiovascular disease, osteoporosis and anemia. Together, the four micronutrients are instrumental in reducing the risk of morbidity in later years.
The U.S government recommends adults consume 10 mg of iron daily; and 15 mg of zinc daily for men and 12 mg for women; and 420 mg (Dietary Reference Intake) of magnesium daily for men and 320 mg for women. The government does not currently have recommended daily allowances for copper, but a safe dietary allowance of copper is considered 1.5-3 mg daily.
Study participants consumed 139 percent of the recommended amount for iron, 70 percent of the recommended allowance for zinc and 79 percent of the recommended amount of magnesium. They consumed 45 percent of the amount considered necessary for copper. Those figures are based on food-based intakes only. It does not include the use of nutritional supplements.
Consuming iron exclusively from meat as opposed to plant sources for prolonged periods of time, can place older adults at risk for toxicity, which is one reason why adults should consume a diverse diet rich in varied mineral sources, Kannan said.
"It's not the diet by itself, but it's what's going on from the time you buy the food, from the time you start cooking it to the time it reaches your lips. For example, soybeans are low in zinc, but zinc from soy sauce absorbs better. So it's very important that the elderly look at the whole picture," Kannan said.
Other surveys indicate that one-third to two-thirds of the elderly regularly take vitamin mineral supplements, which should be taken between meals to optimize iron intake from supplements. How well your body absorbs the supplements depends on other foods and supplements consumed, Kannan said. For example, consuming supplements with tea or coffee can inhibit the absorption of iron.
Even if seniors are consuming the recommended dietary allowance of the four micronutrients, other factors commonly associated with the elderly can affect how well micronutrients are absorbed.
For example, drugs commonly prescribed to older Americans, such as Cholestyrmaine, which is used to lower blood cholesterol, can reduce iron absorption. Also, long-term use of antacids can cause copper deficiency.
"While the need for calories decreases with age, the vitamin and mineral needs remain the same as in the 20s and 30s. The older adult should be advised to consume a nutrient-dense diet to fulfill micronutrient needs," Kannan said.
Kannan is currently working with David M. Hamby, U-M assistant professor of environmental and industrial health, who is testing a technique that uses a nuclear reactor to trace micronutrient absorption in processed foods. The new technique will speed up the research process by months.
"Besides speeding up the research process, it is expected that this will provide mineral researchers with a user- friendly, radiologically efficient tool to trace mineral absorption from foods, natural and processed," Hamby said.
The following food portion sizes are recommended for meeting the micronutrient needs of the elderly.
Kannan's conference presentation is co-authored by Berdine Martin and Connie Weaver of Purdue University.
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