Trace Minerals
Just because they're called trace minerals doesn't mean that copper, iodine and even molybdenum aren't as important as, say, calcium, a biggie that we all know about. It simply means that you require smaller daily amounts of these nutrients--in the case of some trace minerals, less than a milligram a day. Minerals taken in such tiny amounts are often measured in micrograms, or one-thousandth of a milligram.
Several trace minerals--copper, chromium, cobalt, manganese and molybdenum--are firmly established as essential to humans. That means that you can't live without them, at least not for very long. It means that these minerals are necessary for certain vital chemical reactions in the body to occur and that no other elements can take their places. It also means that the National Research Council has developed daily intake guidelines to help you make sure that you are getting enough.
The Estimated Safe and Adequate Daily Dietary Intakes were established for essential nutrients (including many trace minerals) that have some research to support an estimated range of requirements, but not enough to establish a Recommended Dietary Allowance or a Daily Value.
Luckily, trace minerals are found in a variety of foods and in water, so we usually get enough of every one of them to function normally, though we may not always get optimum amounts.
Several additional trace minerals, including boron, silicon and vanadium, have been proven essential to assorted bacteria, fungi and other microbes. And all plants need boron in order to grow. As technology improves and research deepens, these minerals may one day be shown to be essential to humans as well.
Many trace minerals act as coenzymes, so-called catalysts in chemical reactions. That means they function as spark plugs, getting chemical reactions going without actually being changed in the process. That's important, because our bodies are giant laboratories, where billions of chemical reactions are taking place all of the time.
Trace minerals play roles in your body's production of neurotransmitters, biochemicals that send messages through your nervous system; in the production of major hormones secreted by your thyroid and adrenal glands; and in your body's ability to burn carbohydrates and fat for energy and to weave molecules into the tissues that become your bones, blood vessels, skin and teeth. Along with other food components, trace minerals help you grow, reproduce and maintain your body over the years.
Getting enough trace minerals is a perfect reason to abide by one important bit of nutritional advice: Eat a varied diet that contains whole foods. Whole grains, nuts, seeds, beans, fresh fruits and vegetables, mushrooms, shellfish, herbs and spices are the richest sources of trace minerals. A few processed foods also contain high amounts: ham, canned pineapple juice, cocoa and beer, which contains trace minerals from the brewer's yeast used to concoct the stuff. Yes, If you're relying on supplements to make up for what is lacking in your diet, pick a good multivitamin/mineral supplement that supplies an array of trace minerals in the ranges recommended below. With very few exceptions, there's no reason to take supplements of individual trace minerals. That's because most trace minerals are toxic in high amounts. "The dose makes the poison," explains Curtiss Hunt, Ph.D., a research biologist with the U.S. Department of Agriculture Grand Forks Human Nutrition Research Center in North Dakota. Until more is known about these elements, especially how they interact with other nutrients, it's prudent to stick to amounts that researchers know are safe. And if you have health problems, get your doctor's okay before you begin taking any supplement.
Boron
Estimated Safe and Adequate Daily Dietary Intake: None
Good Food Sources: Parsley, apples, cherries, grapes, leafy vegetables, nuts, beans
If you've heard of boron at all, it may have been in regard to this trace mineral's apparent bone-building properties. In several studies, boron has been found to help people better absorb and use minerals such as calcium and magnesium.
"Boron also seems to play a role in the body's ability to generate energy, especially during exercise," says Dr. Hunt. He found that animals that were exercised and got adequate boron in their diets gained more weight and grew larger than animals that were exercised and fed a low-boron diet.
Boron may work by activating certain hormones, Dr. Hunt says. In postmenopausal women, adequate boron raised blood levels of both estrogen and testosterone. It also might help in converting vitamin D to its active form.
Bodybuilders who have used boron to jack up testosterone levels, however, have been disappointed. "Large amounts of this mineral don't affect hormone levels in people who are already getting adequate amounts," Dr. Hunt says.
Using Boron Safely
There is no Estimated Safe and Adequate Daily Dietary Intake for boron. So how much should you get? Probably about the amount you're getting now, if you're eating a well-balanced diet that contains at least five servings of fruits and vegetables a day. That's 1.5 to 3 milligrams of boron a day.
Supplements are not necessary or desirable, Dr. Hunt adds. "We don't yet know enough about boron to determine if amounts of more than three milligrams a day are safe," he says.
Chromium
Daily Value: 120 micrograms
Good Food Sources: Brewer's yeast, broccoli, ham, grape juice
Think of it as the shovel that gets the fuel into the furnace. This trace mineral hooks up with insulin to help transport glucose (blood sugar) across cell membranes and into cells, where it can be burned for energy. People who don't get enough chromium may develop a condition called glucose intolerance; they have high blood sugar levels and often high insulin levels. The high blood sugar levels do not drop much when additional insulin is given, but they do go down when people get the chromium they need. Glucose intolerance can set the stage for Type II (non-insulin-dependent) diabetes.
Signs of chromium deficiency include diabetes-like symptoms of high blood cholesterol and problems with insulin levels.
"Most likely to benefit from chromium supplementation are people newly diagnosed with diabetes who have mild glucose intolerance and mildly elevated blood glucose," explains Richard Anderson, Ph.D., lead scientist in the nutrient requirements and functions laboratory at the U.S. Department of Agriculture Beltsville Human Nutrition Research Center in Maryland. Chromium has not proven as helpful for people with long-standing or severe diabetes.
Since chromium helps insulin work better, it may also raise blood sugar levels in people with low blood sugar, as shown in studies by researchers with the U.S. Department of Agriculture.
Chromium also seems to help raise HDL cholesterol, the "good" kind that helps escort bad cholesterol out of your body.
Sweet treats drain the body's supply of chromium. Complex carbohydrates such as pastas and potatoes help preserve chromium.
Using Chromium Safely
Even balanced diets designed by dietitians contain less than 50 micrograms of chromium and average about 15 micrograms per 1,000 calories, far less than the 120 micrograms that's recommended, according to an analysis by Dr. Anderson.
Trivalent chromium, the kind found in foods and supplements, is considered to be quite safe. "The safety of dosages of up to 200 micrograms a day is well-established, and ongoing studies using amounts of up to 1,000 micrograms a day have uncovered no toxic effects," Dr. Anderson says. "We have yet to establish an unsafe dose, because no amount we have given so far has proven to be toxic."
Still, it's best to get no more than 200 micrograms a day from supplements without medical supervision.
On the other hand, if you work around chromium-containing compounds, you'll want to steer clear of fumes and dust. Industrial chromium, a completely different form than that found in foods, is toxic.
People with diabetes who take chromium should be under medical supervision, since their insulin dosage may need to be reduced as blood sugar drops.
Many studies detailing chromium's benefits have used chromium picolinate, an easily absorbed form. Chromium nicotinate and amino acid forms of chromium are less easily absorbed than chromium picolinate but can supply adequate amounts of the mineral. The least absorbable form is chromium chloride, which is found in some Chromium is sometimes sold as glucose tolerance factor (GTF), a combination of chromium, nicotinic acid (a form of niacin) and amino acids. GTF may vary so much in composition that it is not a reliable source of chromium, Dr. Anderson says.
Cobalt
Estimated Safe and Adequate Daily Dietary Intake: None
Good Food Sources: Dairy and other animal products
Cobalt is at the core of every molecule of vitamin B12, a nutrient that's essential for the body's formation of red blood cells. That function is vital, and it's the only known function of cobalt in humans.
Using Cobalt Safely
No Estimated Safe and Adequate Daily Dietary Intake has been set for cobalt; you get the amount you need from preformed vitamin B12. Although B12 deficiency is not uncommon (some true vegetarians may develop B12 deficiency), cobalt deficiency has never been seen in people.
Copper
Daily Value: 2 milligrams
Good Food Sources: Shellfish (especially cooked oysters), nuts, seeds, cocoa powder, beans, whole grains, mushrooms
Thanks to shiny new pennies, we all know that copper is a bright orange metal. Most of us don't know that need to consume a certain amount of copper in order to survive. Anyone who is concerned about heart disease or osteoporosis, and that's just about everyone, should be paying attention to copper.
Copper plays a role in the body's formation of strong, flexible connective tissue, in the production of neurochemicals in the brain and in the functioning of muscles, nerves and the immune system.
"One of copper's best-understood roles so far is its function in the cross-linkage of collagen and elastin," explains Leslie Klevay, M.D., Sc.D., of the Grand Forks Human Nutrition Research Center. "Copper helps knit together these two very important connective tissues, which are used throughout the body to build other tissues."
Copper-deficient animals have weakened hearts and blood vessels and may die from heart failure or a ruptured aorta, the main artery from the heart. They also have bone defects that are identical to osteoporosis. "Copper is essential for the network of connective tissue in bone on which minerals such as calcium are deposited," Dr. Klevay explains. Copper-deficient animals also develop cartilage breakdown similar to that which takes place in osteoarthritis.
Copper also interacts with iron, so copper deficiency eventually leads to anemia.
Copper deficiency may be more prevalent than we know. It may be more of a marginal condition than a true deficiency in people eating normal diets, Dr. Klevay says. Still, some experts suspect that many people are getting less than optimum amounts and may suffer from chronic illnesses such as heart disease and osteoporosis as a result. Lower blood levels of copper have been found in women with osteoporosis than in women with strong bones.
Using Copper Safely
Copper is often found in Few people get more than 2 milligrams of copper a day from diet alone, and a fair number of people consume less than 1.5 milligrams a day, an amount that Dr. Klevay considers the bare minimum. Copper is toxic in large amounts (it's most likely to cause vomiting), so there's simply no good reason to take more than three milligrams a day, Dr. Klevay says.
Zinc interferes with the body's ability to absorb copper, which is why experts who recommend zinc supplements often suggest extra copper as well, generally in a ratio of 1 milligram of copper to 10 milligrams of zinc. So if you're taking 15 milligrams of zinc (the Daily Value), you should be getting 1.5 milligrams of copper a day. And copper supplements are definitely off-limits to people with Wilson's disease, an inherited disorder that makes copper accumulate in the liver.
Fluoride
Estimated Safe and Adequate Daily Dietary Intake: Adults, 1.5 to 4 milligrams. Children up to age 6 months, 0.1 to 0.5 milligram; ages 6 to 11 months, 0.2 to 1 milligram; ages 1 to 3 years, 0.5 to 1.5 milligrams; ages 4 to 6 years, 1 to 2.5 milligrams; ages 7 to 18 years, 1.5 to 2.5 milligrams.
Good Food Sources: Fluoridated water, tea, marine fish with bones, such as canned salmon and mackerel
You might think that because fluoride is added to water and toothpaste, it's one of those nutrients that you just can't live without. That's not the case, although its potential for making visits to the dentist more pleasant is undisputed.
Both oral and topically applied fluoride are incorporated into tooth enamel. Fluoride protects the enamel, so it is less likely to dissolve under assault from the acid-producing bacteria that thrive in your mouth. Even adults can benefit from fluoride's tooth-toughening talents.
Fluoride is also taken up by bone tissue, making the tissue stronger, too. But studies using fluoride to strengthen bones weakened by osteoporosis have had mixed results. The latest studies, however, have found that a combination of slow-release fluoride and calcium did reduce the tendency for postmenopausal women to sustain fractures by 50 percent. For the full story on using nutrients to prevent and treat osteoporosis, see page 429.
Using Fluoride Safely
People who drink fluoridated water get about one milligram per liter of water. People who don't drink fluoridated water may get very little fluoride in their diets, unless they're big tea drinkers. One cup of tea offers one to three milligrams of fluoride.
Up to ten milligrams of fluoride a day from foods and water is considered safe for adults. You should not take more than four milligrams a day from supplements of rapid-release sodium fluoride, says Khashayar Sakhaee, M.D., professor of internal medicine at the Center for Mineral Metabolism and Clinical Research of the University of Texas Southwestern Medical Center at Dallas. That amount may be enough to help teeth, but it doesn't help restore weak bones, Dr. Sakhaee says.
Although fluoride supplements are available only by prescription, rapid-release forms are not safe to take in large amounts, Dr. Sakhaee says. Large amounts can cause bone pain and, in children, mottled, brown teeth.
The slow-release form of fluoride that has been used in studies to prevent osteoporosis is currently undergoing Food and Drug Administration review for safety and effectiveness. "If it passes, it will be available by prescription within a few years," Dr. Sakhaee says.
Iodine
Daily Value: 150 micrograms
Good Food Sources: Iodized salt, lobster, shrimp, cooked oysters, marine fish, seaweed, breads, milk
Iodine is used by the thyroid gland to produce an important hormone called thyroxine. This hormone helps regulate energy production, body temperature, breathing, muscle tone and the manufacture and breakdown of tissues. Iodine deficiency usually results in an enlargement of the thyroid gland known as goiter, visible as swelling on the front of the throat.
Using Iodine Safely
Thanks to iodine-fortified salt, there's no need to worry about getting enough iodine. Most people get several times the Daily Value with no ill effects.
Manganese
Daily Value: 2 milligrams
Good Food Sources: Canned pineapple juice, wheat bran, wheat germ, whole grains, seeds, nuts, cocoa, shellfish, tea
The word manganese is derived from the Greek word for magic. And this little-known trace mineral can apparently work its own magic in the body.
Manganese is an essential part of biochemical reactions that affect bone, cartilage, brain function and energy supply, explains Jeanne Freeland-Graves, R.D., Ph.D., professor of nutrition at the University of Texas at Austin. "This is one mineral that you will definitely be hearing more about in the future," she says.
Manganese helps your body build and maintain strong bones. It makes up a part of molecules known as mucopolysaccharides. These molecules are used to form collagen, the strong, fibrous connective material that builds tissues throughout the body, including bone and cartilage, the rubbery cushioning found where bones meet.
In bone, a mesh of collagen provides the framework on which calcium, magnesium and other bone-hardening minerals are deposited. Animals deficient in manganese have bone problems similar to those that develop in people with osteoporosis. Under a microscope, these animals' bones actually appear riddled with holes. Other animals that are manganese-deficient develop tendon problems.
In one study, women with osteoporosis had lower blood levels of manganese than women without osteoporosis. Another study found that supplements of calcium, manganese, zinc and copper helped stop bone loss, but the effect of manganese alone was not tested.
Manganese is also necessary for proper brain function. Low levels have been associated with seizure disorders such as epilepsy. Manganese also helps your body break down carbohydrates and fat for energy.
Manganese deficiency has never been detected in people eating normal diets. Whether that's because people are getting enough of the mineral through foods or because deficiency symptoms go unrecognized has yet to be determined, Dr. Freeland-Graves says. "Around the turn of the century, we were getting about eight milligrams a day from a diet based on whole grains, nuts and seeds," she says. Nowadays, people average two to three milligrams.
"A number of studies have shown that you need at least three milligrams and up to five milligrams of manganese a day to maintain a positive balance," Dr. Freeland-Graves says.
Using Manganese Safely
Research indicates that amounts of up to 10 milligrams of manganese a day are safe, Dr. Freeland-Graves says. There's no need to get more than 3.5 to 5 milligrams daily, she adds.
To get your manganese, stick to foods, which can provide you with enough of this and other trace minerals. "Canned pineapple juice is one of the best sources, with about three milligrams of manganese per cup," Dr. Freeland-Graves says.
Some Calcium supplements may interfere with your body's ability to absorb manganese. In one study, a dose of 800 milligrams of calcium inhibited the absorption of manganese. So if you're taking calcium supplements, you might consider eating manganese-rich foods at other times of the day, says Dr. Freeland-Graves. She also suggests taking calcium separately from a multivitamin/mineral supplement containing manganese. Manganese toxicity has been seen in industrial exposure to the mineral and in people drinking contaminated well water. High amounts can cause symptoms similar to those of Parkinson's disease, including trembling, shuffling and slow movement.
Molybdenum
Daily Value: 75 micrograms
Good Food Sources: Beans, whole grains, cereals, milk and milk products, dark green, leafy vegetables
Come on, you can spit it out: mo-LIB-duh-num. This trace mineral with the funny name is a component of three enzymes, which act in the body to get important chemical reactions going.
Molybdenum is part of sulfite oxidase, an enzyme that helps the body detoxify sulfites, compounds found in protein foods and used as chemical preservatives in some foods and drugs. People who can't break down sulfites have toxic buildups of this chemical in their bodies, explains Judith Turnlund, R.D., Ph.D., of the U.S. Department of Agriculture Western Human Nutrition Research Center in San Francisco. "Infants born with this disorder are very sick and usually don't live long," she says. These infants have a rare genetic disorder that inhibits molybdenum-containing enzymes in their bodies, and giving them extra molybdenum doesn't usually help, she says.
Some people are supersensitive to the sulfites used as additives, developing asthma and other life-threatening breathing problems. "Unfortunately, supplemental molybdenum would not be particularly helpful in reducing sulfite sensitivity in people with asthma," says Dr. Turnlund.
Molybdenum is also part of two other enzymes, xanthine oxidase and aldehyde oxidase. Both are involved in the body's production of genetic material and proteins. Xanthine oxidase also helps the body produce uric acid, an important waste product.
Physical signs of molybdenum deficiency are considered extremely rare, Dr. Turnlund says. Only one case, a man on long-term tube feeding, has ever been confirmed. Molybdenum deficiency is difficult to induce even in animals. "People eating fairly normal diets simply don't become deficient in this nutrient," Dr. Turnlund says. Most people get about 180 micrograms daily from foods.
Using Molybdenum Safely
Up to 500 micrograms of molybdenum a day has proven safe in long-term experiments, but there's no reason to take that much, Dr. Turnlund says. Amounts higher than 500 micrograms may interfere with your body's metabolism of copper, another essential trace mineral.
There's no need to get this trace mineral in supplement form, Dr. Turnlund says. Some People with gout or high blood levels of uric acid should consult their doctors before taking supplements that contain molybdenum.
