Some nutrients become less important as you grow older. In fact, too much of these nutrients can actually be harmful as you age.
Recommended Intake: Men: 3,000 International Units a day (or 900 micrograms); Women: 2,330 International Units a day (or 700 micrograms)
There's no change in your recommended intake of vitamin A as you age, and this nutrient remains important for good health. Vitamin A is essential for normal vision, bone growth, cell division, and proper immune function. However, if you get too much of one form of this vitamin, you could actually cause yourself harm.
We get the vitamin A we need in two main forms -- as retinol, a ready-to-use form (sometimes referred to as "preformed vitamin A") found in animal foods, and as beta-carotene, a precursor (or "provitamin") found only in plant foods that the body can convert into vitamin A. Research in adults has shown that taking in too much retinol on an ongoing basis is associated with weaker bones and an increased risk of hip fractures -- above and beyond the already higher risk that comes with increasing age.
A chronically high intake of retinol can also cause hypervitaminosis A, which refers to a high level of vitamin A stored in the body that can lead to toxic symptoms, including liver and nerve problems in addition to decreased bone density. Ongoing consumption of large amounts of beta-carotene, on the other hand, has not been shown to weaken bones or cause other toxic effects. That's probably because the body can simply slow or stop the conversion of beta-carotene into vitamin A if it's getting enough vitamin A from retinol.
To help healthy adults prevent the possibility of vitamin A toxicity, the National Academy of Science's Institute of Medicine (the group that sets the RDAs) has established a Tolerable Upper Intake Level (UL) for retinol. For adult men and women, that level is 3,000 micrograms (10,000 International Units). Some research even suggests that to prevent bone weakening, healthy adults should limit their retinol intake to 1,500 micrograms (5,000 International Units).
But the best way to ensure that your body has access to plenty of vitamin A without becoming overloaded is to get most of your vitamin A in the form of beta-carotene, which is plentiful in dark green and orange fruits and vegetables, such as spinach, carrots, sweet potatoes, cantaloupe, and kale, perhaps with lesser amounts coming from animal sources of retinol, such as whole milk, whole eggs, margarine, and beef liver.
Supplements of vitamin A -- whether from retinol or beta-carotene -- are not recommended for healthy adults. And if you take a multivitamin, choose one that provides no more than the recommended intake of vitamin A and that supplies most or all of that vitamin as beta-carotene rather than retinol.
Recommended Intake: Men and Women: 8 milligrams a day
Iron is best known for its role in the formation of healthy red blood cells, which are responsible for carrying oxygen through the blood. Iron is also a component of myoglobin, the compound that stores oxygen in muscle tissues. Oxygen is, of course, essential for life, and without iron to keep those red blood cells coming, you would die.
But iron also has an important job in bolstering the immune system and helping the body manufacture amino acids and convert beta-carotene to vitamin A. There are two types of iron, heme and nonheme. Heme iron is found in meat, while nonheme iron is found in plants. Nonheme iron is less well absorbed, but that can be easily remedied by eating a food rich in vitamin C with a food rich in nonheme iron, since vitamin C aids in its absorption.
While iron remains an essential nutrient, as you age your body needs less of the mineral. That's especially true of women after menopause. The risk of continuing to bolster your iron intake as you pass 50 is that you could unknowingly be suffering from a condition known as hemochromatosis.
Also known as iron overload, hemochromatosis occurs when the body gets saturated with iron and isn't able to discard the extra. Untreated, it has the potential to harm every organ in your body. Some experts say it is the most common genetic disorder in the country. It is most common among Caucasians of northern European ancestry. Symptoms can include chronic fatigue and persistent aches and pains in your joints.
Recommended Intake: Men and Women: a maximum of 1,500 milligrams a day
Although the maximum recommended intake for this mineral, set forth in the 2005 Dietary Guidelines for Americans, is 1,500 milligrams a day for middle-age and older adults (it's less than 2,300 milligrams for younger adults), the body requires a mere 180 milligrams of sodium a day to function properly.
Limiting sodium is difficult, to say the least; sodium is present in nearly all foods. Processed foods and restaurant fare are usually loaded with sodium, so it's easy to go overboard. Too much sodium, however, aggravates high blood pressure in people who are sodium-sensitive; in such individuals, the higher the sodium intake, the higher the blood pressure.
Reducing blood pressure reduces the risk of stroke, heart disease, and kidney disease. In addition, a high-sodium diet can cause your body to lose calcium from bones, increasing your risk for osteoporosis. Not everyone is sensitive to sodium's effects on blood pressure, but there is no way to identify those who are sodium-sensitive. That's why experts recommend that everyone curb their sodium intake.
Recommended Intake to Maintain Your Weight: Men, lightly to moderately active: 2,000 to 2,600 calories a day; Women, lightly to moderately active: 1,600 to 1,800 calories a day
Calories are the energy your body extracts from the carbohydrates, proteins, and fats in the food you eat. You need a certain number of calories for your body to function. You need more calories if you're physically active and muscular, less if you're more of a couch potato and/or need to lose weight. Men generally need more calories than women, and young people require more calories than older people.
If you're 50+ and not physically active, you really have to keep an eye on your calorie intake or you could put on pounds that increase your risk for heart disease, diabetes, and some kinds of cancer. Here's a sobering thought: It takes only 100 extra calories a day to end up with an extra 10 pounds on your frame at the end of a year. You would either have to become more active or eat less to undo the damage.
The key to preventing weight gain is to balance your calorie intake with the energy you expend through physical activity. Since certain nutrients become even more important as you age, you need to make the most of your limited calories by choosing low-calorie foods that are brimming with nutrients.
Densie Webb, Ph.D., R.D. is the author of seven books, including Foods for Better Health, The Dish on Eating Healthy and Being Fabulous!, and Super Nutrition After 50. Webb also writes about health and nutrition for numerous magazines, including Family Circle, Fitness, Parade, Men's Fitness, and Redbook. She is a regular columnist for Woman's Day and Prevention magazines, a contributing writer for The New York Times, the associate editor of Environmental Nutrition newsletter, and a writer for the American Botanical Council.
Elizabeth Ward, M.S., R.D. is a nutrition consultant and writer. She is the author or co-author of five books, including Super Nutrition After 50 and The Complete Idiot's Guide to Feeding Your Baby and Toddler. Ward is a contributing editor for Environmental Nutrition newsletter and a contributing writer for WebMD.com. She also writes for publications such as Parenting magazine and The Boston Globe.