Chapter 11

Making the Most of Minerals

IN THIS CHAPTER

Getting essential minerals from food

Naming signs of overdose and deficiency

Identifying moments when you need a little extra

Minerals are elements, substances composed of only one kind of atom. They’re inorganic, which means they don’t contain the carbon, hydrogen, and oxygen atoms found in all organic compounds, including vitamins. Minerals occur naturally in nonliving things, such as rocks and metal ores. Yes, you can find minerals in plants and animals, but they’re imported. Plants absorb minerals from the soil; animals obtain minerals by eating plants.

Most minerals have names that describe where they’re found or what they look like. For example, calcium comes from calx, the Greek word for “lime” (chalk), a source of calcium. Chlorine comes from chloros, the Greek word for “greenish-yellow,” which just happens to be the color of the mineral. Other minerals, such as americium, curium, berkelium, californium, fermium, and nobelium, are named for where they were first identified or to honor an important scientist.

This chapter tells you which minerals your body requires, which foods provide what minerals, and how much of each mineral a healthy person needs.

Getting the Minerals You Need

Think of your body as a house. Vitamins (see Chapter 10) are like tiny little maids and butlers, scurrying about to turn on the lights and make sure the windows are closed to keep the heat from escaping. Minerals are more sturdy stuff, the mortar and bricks that strengthen the frame of the house and the current that keeps the lights running.

Nutritionists classify the minerals essential for human life, including the electrolytes described in Chapter 12, as either major minerals or trace elements.

Major Minerals

Trace Elements

Calcium

Iron

Phosphorus

Zinc

Magnesium

Iodine

Sulfur

Selenium

Sodium

Copper

Potassium

Manganese

Chloride

Fluoride

Chromium

Molybdenum

Both major minerals and trace elements are vital for human health. Nutritionally speaking, though, the difference between the two is the amount of the mineral you store in your body and how much you need to take in to maintain a steady supply.

For example, your body stores more than 5 grams (about ⅙ of an ounce) of each of the major minerals and principal electrolytes (sodium, potassium, and chloride). To maintain a healthful level of these nutrients, you need to consume more than 100 milligrams (3.5 ounces) a day of each. You need much less of the trace elements whose Recommended Dietary Allowances (RDAs) are commonly measured not in milligrams (1/100 of a gram) but in micrograms (1/1,000,000 of a gram).

The major minerals

This section covers three major minerals — calcium, phosphorus, and magnesium — build bones and regulate many system functions such as keeping your blood pressure on an even keel.

As you read this section, you may notice a few important minerals missing. Sodium, potassium, and chloride, also known as the principal electrolytes, aren’t included here because they are the principal electrolytes covered in Chapter 12. And although sulfur, a major mineral, is an essential nutrient for human beings, you’ll rarely find it in nutrition books and/or charts because it’s an integral part of all proteins. Any diet that provides adequate protein also provides adequate sulfur. (For more on proteins, check out Chapter 6.)

Here are the rest, each with an example of a food serving that provides one-quarter of the Recommended Dietary Allowance (RDA) or the alternative Adequate Intake (AI) for healthy adults described in Chapter 3.

Calcium

When you step on the scale in the morning, you can assume that about 3 pounds of your body weight is calcium, most of it packed into your bones and teeth. Calcium is also present in extracellular fluid (the liquid around body cells), where it

  • Regulates fluid balance by controlling the flow of water in and out of cells
  • Enables cells to send messages back and forth from one to another
  • Keeps muscles moving smoothly and cramp-free

Calcium also helps control blood pressure, and sometimes not just for the person who takes the calcium directly. Some studies suggest that if a pregnant woman gets a sufficient amount of calcium, her baby’s blood pressure stays lower than average for at least the first seven years of life, meaning a lower risk of developing high blood pressure later on. This suggestion, although tantalizing, remains to be confirmed.

Your best food sources of calcium are milk and dairy products as well as fish, such as canned sardines and salmon with the bones that have been softened and made edible by processing. (Caution: Bones in fresh fish are definitely not edible.) You can also get calcium from dark green leafy vegetables, but this form of the mineral is bound tightly into compounds that make it hard for your body to absorb.

Eight ounces of milk or one cup broccoli provide one-quarter of the RDA for calcium.

Phosphorus

Like calcium, phosphorus is essential for strong bones and teeth. Phosphorus also enables a cell to transmit the genetic code (genes and chromosomes that carry information about your special characteristics) to the new cells created when a cell divides and reproduces. In addition, phosphorus

  • Helps maintain the pH balance of blood — that is, keeps blood from being too acidic or too alkaline
  • Is used to metabolize carbohydrates, synthesizing proteins and ferrying fats and fatty acids among tissues and organs
  • Is part of myelin, the fatty sheath that surrounds and protects each nerve cell

Almost every item on a normal menu contains phosphorus, but the best sources are high-protein foods, such as meat, fish, poultry, eggs, and milk. For vegetarians, grains, nuts, seeds, and dry beans also provide respectable amounts.

Eight ounces of milk provide one-quarter of the adult RDA for phosphorus.

Magnesium

Your body uses magnesium to make body tissues, especially bone. The adult human body contains about an ounce of magnesium, three-quarters of that is in the bones. Magnesium also is part of more than 300 different enzymes that trigger chemical reactions throughout your body and helps to

  • Move nutrients in and out of body cells
  • Send messages between cells
  • Transmit the genetic code (genes and chromosomes) when cells divide and reproduce

Chlorophyll contains magnesium, so plant foods such as dark green fruits and vegetables are excellent food sources; whole seeds and grains as well as nuts and beans are also magnesium-rich.

Four slices of whole wheat bread or one cup (uncooked) dry beans provide one-quarter of the RDA for magnesium.

The trace elements

As noted, trace elements are essential but in much smaller amounts than major minerals. Here’s a list of the trace minerals with an example of a food serving that provides one-quarter of the RDA or AI.

Iron

Iron is an essential constituent of hemoglobin and myoglobin, two proteins that store and transport oxygen. Hemoglobin (hemo = blood) is what makes red blood cells red; myoglobin (myo = muscle) does the same for muscle tissue. You also find in iron dozens of enzymes required for such processes as digesting food.

The best food sources of iron are organ meats (liver, heart, kidneys), red meat, egg yolks, wheat germ, and oysters, all of which provide heme (heme = blood) iron, iron attached to a specific protein. This is the form of iron your body absorbs most easily.

Whole grains, wheat germ, raisins, nuts, seed, prunes and prune juice, and potato skins contain non-heme iron, iron without the protein attachment. Because plants contain substances called phytates, which bind this iron into compounds, your body has a hard time getting at the iron. Eating plant foods with meat or with foods such as tomatoes that are rich in vitamin C increases your body’s ability to split away the phytates and extract the iron from plant foods.

One ounce of cold cereal or one cup of dried apricots each provides one-quarter of the RDA for iron.

Zinc

Zinc protects nerve and brain tissue, bolsters the immune system, and is essential for healthy growth. Like other minerals, it is also part of the enzymes (and hormones such as insulin) that metabolize food.

You can fairly call zinc the macho male mineral because the largest quantities of zinc in the human body are in the testes, where it’s used in making a continuous supply of testosterone, the hormone a man needs to produce plentiful amounts of healthy, viable sperm and maintain muscle mass. Without enough zinc, male fertility falters. And, yes, several studies have confirmed that sucking on lozenges containing one form of zinc (zinc gluconate) shortens a cold — by a day or two. Other studies show no effect. Your choice.

In addition to oysters, meat, liver, and eggs are all good sources of zinc. So are nuts, beans, miso, pumpkin and sunflower seeds, whole grain products, and wheat germ. However, as with iron, the zinc in plant foods occurs in compounds that your body absorbs less efficiently than the zinc in foods from animals.

Three ounces of beef, chicken, lamb, or veal each provides one-quarter of the RDA for zinc.

Iodine

Iodine is a component of the thyroid hormones thyroxine and triiodothyronine, which help regulate cell activities. These hormones are also essential for protein synthesis, tissue growth (including the formation of healthy nerves and bones), and reproduction.

The best natural sources of iodine are seafood and plants grown near or in the ocean, but modern Americans are most likely to get the iodine they need from iodized salt (plain table salt with iodine added). And here’s an odd nutritional note: You may get some iodine from commercial breads because iodine compounds are used as dough conditioners, the additives that make dough more pliable.

Two slices of enriched white(!) bread provide one-quarter of the RDA for iodine.

Selenium

Selenium was identified as an essential human nutrient in 1979 when Chinese nutrition researchers discovered that people with low body stores of selenium were at increased risk of Keshan disease, a disorder of the heart muscle with symptoms that include rapid heartbeat, enlarged heart, and (in severe cases) heart failure.

Although fruits and vegetables grown in selenium-rich soils are rich in this mineral, the best sources of selenium are seafood, meat and organ meats (liver, kidney), eggs, and dairy products.

One ounce of Brazil nuts provides ten times the RDA; 1/2 ounce of oysters provides one-quarter of the RDA for selenium.

Copper

Copper is an antioxidant found in enzymes that deactivate free radicals (pieces of molecules that can link up to form compounds that damage body tissues) and make it possible for your body to absorb and use iron. In addition, copper

  • Promotes the growth of strong bones
  • Protects the health of nerve tissue
  • Prevents your hair from turning gray prematurely. But, no, no, a thousand times, no: Large amounts of copper absolutely will not turn gray hair back to its original color. Worse yet, megadoses of copper are potentially toxic.

You can get the copper you need from organ meats such as liver and heart, seafood, nuts, and dried beans, including chocolate, which is made, of course, from cacao beans.

One cup of dried prunes or one cup of cooked lentils each provides one-quarter of the RDA for copper.

Manganese

Most of the manganese in your body is in your glands (pituitary, mammary, pancreas), organs (liver, kidneys, intestines), and bones. The mineral is also found in enzymes that metabolize carbohydrates and synthesize fats. Manganese promotes healthy reproductive system, and during pregnancy, manganese enhances proper growth of fetal tissue.

Your best dietary sources of manganese are whole grains, cereal products, fruits, and vegetables. Oolong tea is also rich in manganese with slightly more than twice as much as green tea and nearly three times as much as black tea.

One ounce of almonds or peanuts provides at least one-quarter of the AI for manganese.

Fluoride

Fluoride is the form of the element fluorine found in drinking water. Your body stores fluoride in bones and teeth. Although some question whether fluoride is an essential nutrient, there is no doubt that it hardens dental enamel, reducing your risk of getting cavities; many researchers suspect (but can’t prove) that some forms of fluoride strengthen bones.

All soil, ground water, plants, and animal tissue contain small amounts of fluoride, but the most reliable source of fluoride is fluoridated drinking water, which provides the AI for this mineral.

Chromium

Very small amounts of trivalent chromium, a digestible form of the very same metallic element that decorates your car and household appliances, are essential for several enzymes that you need to metabolize fat.

Chromium also partners with glucose tolerance factor (GTF), a group of chemicals that enables the pancreatic enzyme insulin to regulate your use of glucose, the end product of metabolism and the basic fuel for every body cell (see Chapter 3).

Chromium occurs naturally in meat and potatoes, cheese, whole grain cereals and baked goods, brewer’s yeast, some vegetables such as broccoli, and hard water — that is, water with natural minerals.

One egg yolk or 1 ounce of broccoli each provides one-quarter of the AI for chromium.

Molybdenum

Molybdenum (pronounced mo-lib-de-num) is a constituent of several enzymes that metabolize proteins. You get molybdenum from beans and grains and, because cows eat grains, from milk and cheeses as well. Molybdenum also leeches into drinking water from surrounding soil, so the molybdenum content of plants and drinking water depends entirely on how much molybdenum is in the soil.

One cup of yogurt or cottage cheese provides one-quarter of the RDA for molybdenum.

Knowing What’s Too Much and What’s Too Little

The Recommended Dietary Allowances (RDAs) and Adequate Intakes (AIs) for minerals and trace elements are generous allowances, large enough to prevent deficiency but not so large that they trigger toxic side effects. In the following sections, you find out exactly how much of what works best for every body.

Avoiding mineral deficiency

Some minerals, such as phosphorus, magnesium, and sulfur, are so widely available in food that deficiencies are rare to nonexistent. Most drinking water contains adequate fluoride, and Americans get so much copper (can it be from chocolate bars?) that deficiency is practically unheard of in the United States. Finally, no nutrition scientist has yet been able to identify a naturally occurring deficiency of manganese, chromium, or molybdenum in human beings with access to a normal varied diet.

But other minerals are more problematic and include the following:

  • Calcium: Without enough calcium, a child’s bones and teeth don’t grow strong and straight and an adult’s bones lose minerals and weaken. Adequate vitamin D assures that you’re absorbing the calcium you get from food or supplements, which is why milk sold in American is fortified with vitamin D.
  • Iron: If you don’t get enough iron, your body can’t manufacture the hemoglobin required to carry energy-sustaining oxygen to every organ and tissue, a condition called — not surprisingly — iron deficiency anemia, most commonly characterized by unrelieved fatigue. Mild iron deficiency may also inhibit intellectual performance. In one Johns Hopkins study, high-school girls scored higher verbal, memory, and learning test scores when they took supplements providing RDA amounts of this mineral.
  • Zinc: An adequate supply of zinc is vital for making testosterone and healthy sperm; men who don’t get enough zinc may be temporarily infertile. Zinc deficiency may also lead to loss of appetite and the ability to taste food and weaken the immune system, increasing your risk of infections and slowing the healing of wounds, including the tissue damage caused by working out. In plain language: If you don’t get the zinc you need, your charley horse may linger longer.
  • Iodine: Even a moderate iodine deficiency may lead to goiter (a swollen thyroid gland) and reduced production of thyroid hormones. A more severe deficiency early in life may cause a form of mental and physical retardation called cretinism.
  • Selenium: Not enough selenium in your diet? Watch out for muscle pain or weakness. To protect against selenium problems, make sure you get the vitamin E you need. Some animal studies show that a selenium deficiency responds to vitamin E supplements. And vice versa.

Understanding the risks of overdoses

Like all health products, some vitamins and minerals are potentially toxic in large doses known commonly as megadoses. How much is a mineral megadose? As Chapter 10 says about vitamins, there is no standard measure. (In fact, the word megadose is still so new that many spellcheck programs don’t recognize it. Go ahead. Try it for yourself.) The consensus is that a megadose is several times larger than a normal RDA or AI and that as U.S. Supreme Court Justice Potter Stewart once famously said of pornography, you will know it when you see it.

For example:

  • Calcium: No one has shown any problems with getting lots of calcium from food, but the story changes when you get your calcium from supplements. For example:
    • Constipation, bloating, nausea, and intestinal gas are common side effects among healthy people taking supplements equal to 1,500 to 4,000 milligrams of calcium a day.
    • Doses higher than 4,000 milligrams a day may be linked to kidney damage.
    • Megadoses of calcium can bind with iron and zinc, making it harder for your body to absorb these two essential trace elements.
  • Phosphorus: Too much phosphorus may lower your body stores of calcium.
  • Magnesium: Megadoses of magnesium appear safe for healthy people, but if you have kidney disease, the magnesium overload can cause weak muscles, breathing difficulty, irregular heartbeat, and/or cardiac arrest (your heart stops beating).

  • Iron: Thinking of adding iron supplements? Stop! Before you plunk down a penny for the pills, check with your doctor, who can run the simple blood test to determine your actual iron state. About 1 in every 200 Americans has hemochromatosis, a common but often-undiagnosed genetic condition that may lead to an increased absorption of iron resulting in an increased risk of arthritis, heart disease, and diabetes, plus infectious diseases and maybe even cancer (both microorganisms and cancer cells thrive in an iron-rich environment).

    warning Even if you don’t have hemochromatosis, taking too much iron can lead to iron overload with some of the results listed above. Worse yet, overdosing on iron supplements can be deadly for young children for whom the lethal dose may be as low as 3 grams (3,000 milligrams) elemental iron at one time. This is the amount in 60 tablets with 50 milligrams elemental iron each. To foil small fingers and prevent accidental overdose, FDA requires individual blister packaging for supplements containing more than 30 milligrams of iron.

  • Zinc: Moderately high doses of zinc (up to 25 milligrams a day) may slow your body’s absorption of copper. Doses 27 to 37 times the RDA (11 milligrams for males; 8 milligrams for females) may interfere with your immune function and make you more susceptible to infection, the very thing that normal doses of zinc protect against. Gram doses (2,000 milligrams/2 grams) of zinc cause zinc poisoning: vomiting, gastric upset, and irritation of the stomach lining.
  • Iodine: Overdoses of iodine may trigger exactly the same problems as iodine deficiency: goiter. How can that be? When you consume very large amounts of iodine, the mineral stimulates your thyroid gland, which swells in a furious attempt to step up its production of thyroid hormones. This reaction is rare, most likely to occur among people who eat lots of dried seaweed for long periods of time.
  • Selenium: Doses as high as 5 milligrams of selenium a day (90 times the RDA) have been linked to thickened but fragile nails, hair loss, and perspiration with a garlicky odor.
  • Fluoride: Despite decades of argument, no scientific proof exists that the fluorides in drinking water increase the risk of cancer in human beings. But there’s no question that large doses of fluoride — for example, from heavily fluoridated well or groundwater in the western United States — leads to fluorosis (brown patches on your teeth), brittle bones, fatigue, and muscle weakness. Over long periods of time, high doses of fluoride may also cause outcroppings (little bumps) of bone on the spine.
  • Molybdenum: Doses of molybdenum two to seven times the AI (45 micrograms) may increase the amount of copper you excrete in urine.

Figuring Out When You May Need More than the RDA

If your diet provides enough minerals to meet the RDAs, you’re in pretty good shape most of the time. But a restrictive diet, the circumstances of your reproductive life, and just plain getting older can increase your need for minerals. Here are some possible scenarios.

You’re a strict vegetarian

Vegetarians who pass up fish, meat, and poultry must get their iron either from fortified grain products, such as breakfast cereals and commercial breads, or naturally from foods, such as seeds, nuts, blackstrap molasses, raisins, prune juice, potato skins, green leafy vegetables, tofu, miso, and brewer’s yeast. Because iron in plant foods is bound into compounds that are difficult for the human body to absorb, iron supplements are considered pretty much standard fare.

Vegans (vegetarians who avoid all foods from animals, including dairy products) have a similar problem getting enough calcium. While many green veggies, such as kale, collard and turnip greens, and seaweed, do have calcium, like iron, this calcium is bound into hard-to-absorb compounds. Luckily, there are good non-animal foods with calcium, such as soybean milk fortified with calcium, orange juice with added calcium, and tofu processed with calcium sulfate.

You live inland, away from the ocean

Seafood and plants grown near or in the ocean absorb iodine from the seawater. Freshwater fish, plants grown far from the sea, and the animals that feed on these fish and plants do not, so people who live inland and get all their food from local gardens and farms probably can’t get the iodine they need from food.

American nutrition savvy and technology solved this problem in 1924 with the introduction of iodized salt. Then came refrigerated railroad cars and trucks to carry food from both coasts to every inland city and state. Together, enriched salt and efficient shipment have virtually eliminated the iodine-deficiency disease goiter in the United States.

You’re a man

Just as women lose iron during menstrual bleeding, men lose zinc at ejaculation. Men who are extremely active sexually may need extra zinc. The problem is that no one has ever written down standards for what constitutes “extremely active.” Check this one out with your doctor, not your locker-room buddies.

You’re a woman

Women lose blood and iron with each menstrual period; the heavier the flow, the greater the loss. Add to that the fact that many American women follow diets that provide fewer than 2,000 calories a day, a level at which it may be virtually impossible to get the iron needed for good health, and you can see how easy it would be to develop a mild iron deficiency.

Women who use an intrauterine device (IUD) may have a similar problem because IUDs irritate the lining of the uterus and cause a small but significant loss of blood and iron.

You’re pregnant or nursing

Pregnant women need extra nutrients, not simply to build fetal tissues but also the new tissues and blood vessels in their own bodies. Nursing mothers need extra calcium, phosphorus, magnesium, iron, zinc, and selenium to protect their own bodies while producing nutritious breast milk. Happily, the same supplements that provide extra nutrients for pregnant women will meet a nursing mother’s needs.