The University Record, April 19, 1999

Striking a healthy dietary balance for the elderly

By Amy Reyes
News and Information Services
School of Public Health faculty members Sri Kannan, visiting assistant professor of environmental and industrial health, and David M. Hamby, assistant professor of radiological health, are studying how micronutrient absorption can be altered depending upon how foods are processed. A grant from the Michigan Memorial Phoenix Laboratory will enable them to examine micronutrient absorption from black beans, grown under natural conditions in Costa Rica, that have been subjected to food processing methods such as cooking and fermentation or sprouting. Hamby says the research is expected to offer food and nutrition scientists the possibility of tracing the biological fate of micronutrients in its natural form from a wide range of commercial food sources ranging from baby food products to adult food products. Photo by Bob Kalmbach

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 School of Public Health study shows.

Srimathi Kannan, a visiting assistant professor of environmental and industrial health, and her colleagues examined the micronutrient (trace mineral) 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 says. "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 examined the intake of iron, zinc, copper and magnesium of 2,170 Americans ages 65-90 and will present her findings April 18 at "Experimental Biology '99," the annual conference of the Federation of American Societies for Experimental Biology in Washington, D.C.

Although recommended in very small quantities, micronutrients are essential for good health:

  • Iron 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 also can 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; 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 allowance 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 says.

    "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 says.

    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 one's body absorbs the supplements depends on other foods and supplements consumed, Kannan says. Consuming supplements with tea or coffee, for example can inhibit the absorption of iron.

    Even if senior citizens are consuming the recommended dietary allowance of the four micronutrients, other factors can affect how well micronutrients are absorbed.

    For example, drugs commonly prescribed to older Americans, such as Cholestyrmaine, used to lower blood cholesterol, can reduce iron absorption. 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. Older adults should be advised to consume a nutrient-dense diet to fulfill micronutrient needs," Kannan says.

    Kannan currently is working with David M. Hamby, 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.

    It also is expected to provide mineral researchers "with a user-friendly, radiologically efficient tool to trace mineral absorption from foods, natural and processed," Hamby says.

    Co-authors of Kannan's presentation were Berdine Martin and Connie Weaver of Purdue University.