Should you really be taking vitamin supplements? How about megadosing? Or increasing your antioxidants? And how do protein, carbohydrates, and fiber fit in? Our knowledge about nutrition is growing on an almost daily basis. Though there’s still much disagreement among the experts on the exact amount of nutrients the average person needs, the broad picture is coming into sharper and sharper focus. Here’s a brief overview of the basic building blocks of nutrition, and the dietary guidelines authorities recommend today.
Vitamins and minerals are almost always mentioned in the same breath, but there are differences between the two. Vitamins are complex molecules that keep the body’s chemical mechanisms in gear. They contribute to the storage and release of energy (metabolism) and maintain the bones, blood, and nerves.
Minerals are inorganic substances in body tissues and fluids that trigger or prevent the production of enzymes and hormones, govern certain of their activities, and serve as raw material for structures such as the bones.
Every day, your body uses up some or all of the vitamins and minerals that keep it going. So each day, you need to replenish your supply, remembering that each vitamin and mineral has specific and necessary properties.
Here’s a quick overview to give you an idea of how important these nutrients really are. Vitamin A contributes to growth and reproduction, vision, normal function of the nervous system, and development and maintenance of body tissues (including skin and bone). The B vitamins build red blood cells, guide body metabolism, maintain the protective covering of the nervous system, and boost the body’s use of proteins, fats, and carbohydrates.
Vitamin C heals wounds; contributes to the formation of cells, tissues, teeth, and bones; and boosts the immune system. Vitamin E helps to protect the outer membranes of the body’s cells from damage. By protecting white blood cells, vitamin E also helps the immune system fight off threats of disease. Vitamin K promotes blood clotting in wounds.
Minerals perform equally varied functions. About 20 minerals play major roles in the body. Even those that are needed in tiny (called “trace”) amounts pack tremendous force and fend off serious illness. The “macrominerals,” needed in larger amounts, are calcium, chlorine, magnesium, phosphorus, potassium, sodium, and sulfur. “Microminerals,” needed in trace amounts, include chromium, copper, fluorine, iodine, iron, manganese, molybdenum, nickel, selenium, silicon, tin, vanadium, and zinc.
Iodine keeps the thyroid gland working. Copper is a component of many enzymes needed for metabolism. Iron transports oxygen to cells throughout the body. Phosphorus and calcium build teeth and bones. Potassium maintains the fluid balance inside cells, helps the muscles contract, and assists the transmission of messages by the nerves.
It also keeps the heart and kidneys working properly. Zinc keeps enzymes working and helps metabolize proteins.
How they interrelate
Besides acting directly on the body, vitamins and minerals empower each other. Vitamin C helps the body absorb iron, for example, and vitamin D does the same for calcium and phosphorus. The interrelationships are so complex that only a regular, wide sampling can provide everything your body needs. The body can supply only two vitamins itself: D and K. Vitamin K is synthesized by bacteria in the intestine. Vitamin D is created by the skin when it’s exposed to sunlight. All the others must be supplied to the body from outside sources. (For the foods that pack the richest supplies, see the box on “Best Dietary Sources of Major Vitamins and Minerals.”)
Best Dietary Sources of Major Vitamins and Minerals
|Vitamin A (retinol)
Liver and other organ meatsBeta-carotene
Yellow and orange vegetables
(carrots, sweet potatoes, squash)
Dark green leafy vegetables
(broccoli, spinach, asparagus)
Yellow and orange fruits (cantaloupes, apricots)Vitamin B1 (thiamin)
Vitamin B2 (riboflavin)
Vitamin B3 (niacin)
Vitamin B6 (pyridoxine)
|Vitamin B12 (cyanocobalamin)
EggsFolic Acid (a B-complex vitamin)
Dark green leafy vegetables
Citrus fruits and juice
Soybeans and other legumes
Whole grainsVitamin C (ascorbic acid)
Yellow, orange, and red fruits
Dark green leafy vegetables
Vitamin D (calciferol)
Vitamin E (tocopherol)
Vitamin K (menaquinone)
Vitamins fall into two categories, depending on the substance that transports them in the body.
Water-soluble vitamins are stored and carried by the water that permeates every part of the body. Because water is constantly being lost in urine, sweat, and other body fluids, most of these vitamins must be replaced daily. The water-soluble vitamins are vitamin C and the many B-complex vitamins, including thiamin (B1), riboflavin (B2), niacin (B3), pyridoxine (B6), folacin (folic acid), cyanocobalamin (B12), biotin, and pantothenic acid. Not all will be discussed here.
Fat-soluble vitamins—A (retinol), D (calciferol), E (d-alpha-tocopherol), and K (menaquinone)—are transported by the fats in the bloodstream. Because the body stores fat much more readily than water, a temporary interruption in the supply of these vitamins is less damaging than a lack of water-soluble vitamins. By the same token, however, excessive intake of these vitamins can quickly build up toxic levels in your system.
Best Dietary Sources of Major Vitamins and Minerals
Low-fat dairy products
Oily fish with bones (sardines, salmon)
Dark green leafy vegetables
Dark green leafy vegetables
Milk and dairy products
Citrus fruits and juicesSelenium
Some of the most familiar old stand-bys among the vitamins and minerals are suddenly taking on exciting new roles as scientists mount intensive investigations of their antioxidant properties. Whether these “souped-up” embodiments of vitamins and minerals can actually prevent chronic illness or weaken its effects remains to be proved, but evidence is growing all the time.
Many highly respected researchers take antioxidants very seriously. Dr. Dean Ornish’s Life Choice diet for reversing heart disease, for example, is deliberately low in oxidants and high in antioxidants to help the body remove them. Common diseases and conditions that certain vitamins and minerals may prevent or improve include high blood pressure, heart disease, diabetes, and cancer.
How antioxidants work. Floating in the bloodstream are molecules of unstable oxygen called free radicals. During the normal breakdown of food, these molecules have been stripped of an electron. When the free radical fills its “electron deficiency” by locking onto another molecule, oxidation (like burning) occurs. Free radicals kill bacteria, fight inflammation, and keep the smooth muscles well-toned so they can regulate the blood vessels and organs. But when too many free radicals are circulating at once, some grab electrons from places where the electron ought to stay, such as the genetic material (DNA) in a cell.
The harmful effects of excessive free radicals range from cosmetic to life-threatening. They can break down skin tissue, making it look older than it is. They can injure the lenses of the eyes, leading to cataracts. And they can make it harder for cells to repair themselves, increasing the risk of cancer, heart disease, and other chronic disorders.
Antioxidants come to the rescue by scavenging excess free radicals before they can cause trouble. The body contains its own antioxidants, but not enough to fight off the huge amount of free radicals that assault the body daily from a variety of sources, including air pollution, stress, cigarette smoke, too much sun, electromagnetic fields, lack of exercise, and high-fat diets. While scientists have shown that antioxidants can indeed protect cells from the damage caused by free radicals, they have yet to confirm the ability of antioxidants to actually stave off chronic disease.
What antioxidants may do. At least 25 studies of tens of thousands of people are now under way to verify the effects of antioxidants on health. So far, benefits have been documented in over 200 published articles (though other studies have shown little or no results).
Beta-carotene is a “provitamin” that can be converted to vitamin A in the body. Its benefits have been known for at least a decade. In the laboratory, beta-carotene has shown promise in preventing cancers of the breast, lung, stomach, and cervix.
Vitamin E has been credited with lowering the risk of heart disease, the number one killer in America, by reducing the buildup of LDL (“bad”) cholesterol inside blood vessels. Vitamin E may also help prevent prostate and colon cancers.
Vitamin C enhances the immune system by enabling white blood cells to break down bacteria, and may prevent nitrates and nitrites from being converted into cancer-causing compounds called nitrosamines. Although no absolute proof exists, vitamin C may also protect against cancers of the breast, cervix, and gastrointestinal system. And, of course, many people believe in the fabled power of vitamin C to relieve colds and sore throats, though most scientists still say more proof is needed.
Selenium, which isn’t accepted as an antioxidant by all experts, must be ingested in very small amounts to avoid tissue damage. This mineral is found in food and water (especially seafood, meat, poultry, and grain). The precise amount depends on the levels of selenium in the soil in which the food was grown or through which the water flowed.
Finally, there’s glutathione, a substance built from amino acids, that acts as one of the body’s major antioxidants. Glutathione supplements are now available in most health food stores.
The Potent Cruciferous Vegetables
|These vegetables, collectively named for the cross shape within their flowers, are among the biggest stars in the nutritional line-up for the many healthful roles they play. As long as you don’t cook them beyond recognition, they’ll serve you well in any form, including cole slaw and sauerkraut.
(Chinese cabbage)BroccoliBrussels sprouts
A few years ago, researchers in cancer prevention began to concentrate in a big way on a group of chemicals found in plants (phytochemicals). In the fields, phytochemicals keep bugs away and protect against too much sun. For people, they may be science’s newest key to controlling cancer and other diseases.
Whether phytochemicals are the magic elixirs they seem to be has yet to be proved. Meanwhile, what’s being discovered about them suggests that they apparently can provide the body with numerous ways to prevent cancer and even zap cancer cells before they can develop or spread. They’re especially powerful in the epithelial cells that line body organs (the lung, bladder, cervix, mouth, larynx, throat, esophagus, stomach, pancreas, colon, and rectum).
In the research spotlight today are the chemical components of a vast number of foods, including garlic, licorice root, citrus fruits, soybeans, celery, barley, ginger root, hot peppers, and green tea. Among those showing the greatest promise are:
P-coumaric acid and chlorogenic acid, found in tomatoes, carrots, strawberries, pineapples, and other fruits and vegetables, remove nitric oxide from cells before it can combine with chemicals called amines to create the damaging nitrosamines involved in cancer cell formation.
Sulforaphane, a compound contained in cruciferous vegetables (see the box on “The Potent Cruciferous Vegetables”), has prevented breast cancer in laboratory animals. The compound seems to make certain enzymes in breast cells go into action, locating cancer-causing substances and attaching those substances to molecules that escort them out of the cell. Allyl sulfides, found in garlic and onions, also mobilize enzymes that defuse carcinogenic chemicals. Allylic sulfides may also reduce the risk of heart disease by inhibiting cholesterol formation.
Indole-3-carbinol seems to repress the formation of cancer-causing estrogens in the breast. Other indoles found in cruciferous vegetables apparently stimulate enzymes that break down cancer-causing substances into harmless ones, especially useful against cancers of the stomach and intestine. Cruciferous vegetables also contain phenethyl isothiocyanate, which has inhibited lung cancer in mice and rats.
Flavonoids, various substances that interfere with hormones that promote cancer, are found in tomatoes, peppers, yams, soybeans, carrots, and many other foods. Limonene, found in citrus fruits, encourages the production of enzymes that may help obliterate potential carcinogens.
Other phytochemicals work to deprive tumors of their blood supply, protect the DNA inside cells, get in the way of cancer-causing hormones that are trying to become attached to the cell—and might well do a lot of other things that researchers haven’t discovered yet. When new discoveries are confirmed, expect to see ads for “designer foods” crammed with extra phytochemicals. Food companies have to be careful, though. Like vitamins and minerals, phytochemicals may be toxic in large amounts. Right now, the best way to get phytochemicals, says registered dietician Mona Sutnick, Ed.D, a consultant in Philadelphia, “is to eat generous amounts of fruits and vegetables and dried beans.”
Plenty of Americans must believe in the power of vitamins, since we spend more than $6 billion on them every year. In a 1998 poll conducted for The Hartman Group, a marketing firm that specializes in natural products, 71 percent of respondents said they took at least one type of mineral or vitamin supplement.
The idea of swallowing pills to replace a decent diet, however, makes most dietitians frown. If you do take vitamins, you have to regard them as supplements—not substitutes—for healthy food. Although their own research is confirming the beneficial effects of many vitamins, the experts refuse to recommend them in pill form, fearing that people will forsake regular food, with all the other irreplaceable nutrients it provides.
However, most people already have less than ideal diets. A large national survey indicates that more than half of the American population doesn’t eat a single piece of fruit, drink a glass of fruit juice, or munch even one vegetable on any given day of the year. Only four in ten Americans eat the recommended total of 3 to 5 servings of vegetables a day. Our fruit consumption is even worse: Only two in ten of us get the recommended 2 to 4 servings a day. For all those people, taking supplements seems a better course of action than doing nothing at all.
Believing that more of something good must be better, many people take very large amounts of vitamins and minerals. They’re cheap, after all, and available without a prescription. But just because a deficiency of a certain vitamin or mineral can make you sick, doesn’t mean a carload of it will necessarily make you better than ever. Taking many times the RDA of any vitamin or mineral can give it the potency of a drug, and doctors rarely, if ever, recommend extremely high doses. Scientists are discovering that a moderate increase in certain vitamins can be beneficial for certain people. But they also know that large overdoses can definitely be dangerous. So, when taking supplements, it’s wise to err on the side of caution, and check with your doctor before going too far.
Vitamin C. Nobel Laureate Linus Pauling was an early proponent of deliberately taking huge doses of a single vitamin to enhance health. In his book Vitamin C and the Common Cold, Dr. Pauling advocated doses as huge as 15 grams a day. While some people continue to swear by the healthful effects of vitamin C megadoses, they can also have side effects, including nausea, abdominal cramps, diarrhea, and possibly kidney stones. The National Academy of Sciences calls for an intake of only 75 milligrams per day for women, and 90 milligrams per day for men. Smokers need an additional 35 milligrams per day. Daily doses above 2,000 milligrams are not recommended.
Niacin. Heart patients are often advised to take high doses of niacin (1,500 to 3,000 milligrams) to lower their cholesterol levels. Because niacin in large amounts can have uncomfortable side effects, such as a burning sensation in the skin or profuse perspiration, or dangerous ones, such as irregular heartbeats or liver damage, a doctor must monitor any such regimen closely. Most adults should not take more than 35 milligrams of niacin per day.
Vitamin E. Some highly respected scientists support intake of relatively high doses of vitamin E (400 to 600 IU) by older people. They say the vitamin can protect against heart disease and help prevent macular degeneration, a serious eye problem that can lead to blindness. High doses of vitamin E can cause excessive bleeding, so adults should not consume more than 1,000 milligrams of alpha-tocopherol per day (or 1,500 IU of “d-alpha-tocopherol”). As with all vitamins and minerals, it’s best to increase the amount you get in your diet before turning to a stripped-down supplement. In fact, a recent report from the National Academy of Sciences noted that most North American adults already get sufficient quantities of vitamins E, C, and selenium from dietary sources.
But for the few vitamins or minerals that may be helpful in extra doses, there are many more that cause undesirable side effects.
Vitamin D. One of the more toxic of the vitamins, this substance can cause calcium to build up in the blood, creating a condition called hypercalcemia that can eventually damage the kidneys and cause soft tissues to harden, especially in the lungs, joints, stomach, and blood vessels.
Vitamin A. Adults who take more than 33,000 IU of vitamin A a day for several months (in the elderly, more than 5,000 to 10,000 IU; in infants and children, more than 14,000 IU) can end up with liver or bone damage, hair loss, and skin problems. Large amounts of the provitamin beta-carotene are thought to be safer, but have been accused of causing harm at doses of 5,000 IU or higher.
Vitamin B6. Taking 500 milligrams, or 250 times the RDA, of vitamin B6 for any period of time can cause nerve damage; a tenth of that may cause other problems.
Iron. Large doses of iron can be toxic, even fatal. Each year, young children die after swallowing their parents’ iron pills. The sweet coating formerly applied to make the pills more palatable has now been banned by law. Remember, too, that high doses of other supplements, such as vitamin C, can increase your absorption of iron.
Many nutritionists and major national health organizations insist that people can get all the nutrients they need from diet alone. Others argue that while this may be true in theory, it’s not reality for most Americans. The much-maligned American diet, while improving, remains overburdened with fat, salt, and sugar, and conspicuously lacking in vitamin-rich fruits and vegetables.
Ask a trusted doctor whether he or she regularly takes supplements, either multivitamins or a specific combination. The answer may very well be yes. Then ask whether he or she routinely recommends the same protocol to patients. Probably not. Whatever their private convictions, many doctors remain concerned that people will allow pills to take the place of a high-quality, low-fat diet.
The bottom line is this: The ideal course is to eat plenty of the fruits and vegetables that supply not only vitamins and minerals, but all the other phytochemicals we’re learning to love. If you’re not doing that, at least give yourself the more limited benefits of a well-balanced supplement (see the nearby box on “Tips for Choosing a Supplement”).
Tips For Choosing a Supplement
Shop wisely; some manufacturers make extraordinary claims for products that are ordinary or worse.
What to buy:
Because vitamin/mineral supplements are such a goldmine for hucksters, you’re better off sticking with name brands from large, reputable companies. However, don’t hesitate to comparison shop. Store brands offered by major chains such as Wal-Mart, K Mart, and Safeway are often identical to the national brands, and may be much cheaper. A 1994 survey by Consumer Reports showed price differences of up to fourfold for essentially the same products.
“USP,” (for U. S. Pharmacopeia, an independent organization that sets standards for the purity and potency of drugs), on the label indicates that the contents will disintegrate (but not necessarily dissolve) promptly in your stomach. Some companies, including reputable ones, disapprove of USP testing methods.
If you have trouble digesting tablets, often the case for people over 60, consider capsules, available in health food stores. In whatever form, supplements should contain 100 percent of the RDA for at least the vitamins and minerals listed in the accompanying table. (Some people argue that because calcium can inhibit the body’s absorption of iron, the two minerals shouldn’t be contained in the same supplement.)
Be skeptical of high-priced special formulations. For instance, “stress-formula” vitamins were originally designed to help victims of extreme physical stress, such as burns or serious illnesses. Also watch the price of antioxidant formulas. It may be cheaper to take a standard multivitamin and buy beta-carotene, vitamin C, and vitamin E separately.
Be especially wary of unsolicited offers to sell you vitamins by phone. This is a fertile field for entrepreneurs of dubious reputability. Among the products and services sold through telemarketing, nearly one in five is a vitamin product.
Buying in bulk, such as during sales or from mail-order companies, may save money. But don’t do it until you’ve tried one jar, even if it costs more that way. You may find that the product contains an additive (color or flavor) that disagrees with you.
Make sure that the expiration date doesn’t extend beyond your ability to use up the contents. (If you can’t read the label, reject the product.) As supplements age, their potency decreases, so keeping them around too long is no bargain. Furthermore, according to the Center for Science in the Public Interest, manufacturers can select expiration dates arbitrarily. A supplement that will expire in 9 months or less may have been on the shelf for years.
Chemical additives are never desirable, although they appear in many acceptable multivitamin products. A little starch may actually help the tablets disintegrate, while a tiny amount of sugar may make the pill taste less bitter.
Calcium. A multivitamin/mineral supplement may provide as little as 15 percent of the daily requirement. For more, choose a calcium supplement: 500 to 1,000 milligrams, usually in more than one tablet or capsule. Choose calcium citrate or calcium carbonate. Bone meal and dolomite (calcium magnesium carbonate) may contain lead or other heavy metals.
Iron. Because women have been told that they need more iron, especially during menstruation, you may jump at the chance to have more than 100 percent of the RDA—but don’t. Only under the advice of your doctor should you have more than 18 milligrams a day. After menopause, when iron is no longer being lost with menstrual blood, it may be wise to take less than 100 percent of the RDA. Ask your doctor what is best for you.
Vitamin E. Many people take supplemental vitamin E because getting enough dietary vitamin E to yield the terrific effects that research has been tentatively uncovering—improving immunity and lowering the risk of heart disease, cataracts, and some cancers—would load your diet with fat and calories. Many experts advise buying the natural form, made from vegetable oil. (This is the only vitamin for which “natural” may possibly beat “synthetic.”) Don’t be deceived by the word “natural” on the label. Keep reading until you see d-alpha (not dl-alpha) tocopherol or tocopheryl. (Consumer Reports disagrees, claiming the distinction is unimportant.) The word “acetate” or “succinate” after that designation means the vitamin is more biologically active . . . fine, but not crucial. Typical daily supplement: 100 to 400 IU.
Vitamin C. The body can use or store only so much at a time and releases the rest, unused, in the urine. A typical daily supplement is 100 to 500 milligrams. If you take more, consider splitting up the dose—500 milligrams twice a day, for example—or buying the more expensive timed-release kind. Chewable vitamin C tablets can dissolve tooth enamel by increasing acid in the mouth. Swallow them. More than 1,000 milligrams a day can cause diarrhea and increase the risk of kidney stones.
Take supplements with meals. Without a little fat (the equivalent of about a teaspoon of margarine), the body can’t absorb beta-carotene and vitamins A, D, and E.
What Your Multivitamin/Mineral Should Contain
100% of RDA for Vitamins and Minerals Assigned RDAs
Vitamin A, preferably all as beta-carotene (5,000 IU)
Vitamin B6 (2 milligrams)
Vitamin B12 (6 micrograms)
Vitamin D (400 IU)
Folic acid1 (0.4 milligrams)
Thiamin (1.5 milligrams)
Riboflavin (1.7 milligrams)
Pantothenic acid (10 milligrams)
Niacin (20 milligrams)
Copper2 (2 milligrams)
Zinc2 (15 milligrams)
100% or Less of RDA
Iron: Women after menopause and all men, 0 to 9 milligrams (0% to 50% of RDA). Women before menopause, especially those who bleed heavily and/or eat little or no meat, 18 milligrams (100% of RDA).
Magnesium: 100 to 400 milligrams (25% to 100% of RDA); but no more than 400 milligrams, to avoid diarrhea. This mineral is needed to prevent high blood pressure. However, if you have kidney disease you should check with your doctor before taking a supplement.
100% or More of RDA
Vitamin E: 100 to 400 IU (RDA is 30 IU)
Vitamin C: 1,000 milligrams (RDA is 60 milligrams)
Vitamins and Minerals Without RDAs
Chromium: 50 to 200 micrograms
Selenium: 50 to 200 micrograms
1. Older men and women should consider a product containing less than 50% of the RDA for folic acid. More than that could mask a severe deficiency of vitamin B12 leading to pernicious anemia, a dangerous blood disorder.
2. A product that contains zinc should also contain copper. Raising zinc levels without doing the same for copper can lead to a copper deficiency. Since copper is an oxidant, however, it should never be taken in amounts higher than the RDA.
The standard recommended intakes may be fine for a typical adult, but they’re often too low (or in some instances, too high), for people in special circumstances, such as pregnancy or advancing age. Here’s an overview of some adjustments you may want to consider. For additional information, check the discussions of specific ages and conditions.
People in their later years often eat inadequately, commonly missing out on important nutrients that a multivitamin/mineral would supply. For example, older people have less water in their bodies, so their level of water-soluble vitamins is lower, says James Scala, Ph.D., author of Prescription for Longevity: Eating Right for a Long Life. Because the absorption of nutrients declines accordingly, it may be wise for older people with less than optimal diets to increase the dose of certain vitamins and minerals as the years go on. The Alliance for Aging Research supports doses of up to 400 IU a day of vitamin E, up to 1,000 milligrams of vitamin C, and as much as 30 milligrams of beta-carotene.
For other nutrients, the reverse is true. After about age 60, iron builds an “inventory” in the body for both men and women. Too much iron after that time can increase the risk of heart disease. For more on the dietary adjustments to consider in your later years, see “Dietary Targets for Your Senior Years”.
Women need more of certain nutrients at various points in their life. Three of the best examples are calcium to combat the bone loss that accompanies aging, iron to replace what is lost during menstruation, and a wide range of extra vitamins and minerals to ensure a healthy pregnancy.
Calcium. It takes a lot of calcium to prevent brittle bones (osteoporosis), which affects more than 25 million Americans, most of them women. Yet most American women get only about half the amount they need. By taking extra calcium, older women can help compensate for the bone loss that occurs with the departure of estrogen during menopause. However, the best time to build bone mass is much, much earlier. In fact, the buildup should start in childhood, since bone mass reaches 95 percent of its maximum density by age 18. After menopause, extra calcium is needed to protect the bone that remains, but it won’t increase bone strength for the future.
While it’s not yet certain, calcium may also help prevent colon cancer in men and women alike. Researchers believe that when calcium encounters potentially cancer-causing fats in the bowel, the two materials combine, creating a harmless substance.
Calcium is found in many foods besides dairy products. Some examples are: figs, oatmeal, navy beans, and the all-purpose broccoli. Look for calcium-fortified foods, too. One cup of calcium-fortified orange juice contains the same amount of calcium as a cup of milk—about 300 milligrams.
If you take calcium supplements, the best way is to split them up over the day. If you’re taking 1,000 milligrams a day, take one 500 milligram pill at breakfast and another at dinner, to keep calcium reserves building all night. Taking them separately also increases the total amount absorbed by the body and is less likely to cause constipation. Calcium carbonate is a little more likely than calcium citrate to cause constipation in some people, although most can digest either.
Don’t take your calcium pill just before or after eating high-fiber wheat bran cereal, because the fiber can impede calcium absorption. If you take iron as well as calcium, don’t take them together, since the calcium can inhibit the body’s absorption of iron. Do, however, take vitamin D with your calcium—many calcium supplements contain both—because the body can’t absorb calcium without it.
Any time your doctor prescribes a new medication, ask how it will interact with any vitamin and mineral supplements you take regularly. Taking calcium at the same time as tetracycline, for example, can prevent the antibiotic from working to its fullest capacity. If you have ever had kidney stones, you should ask your doctor whether it’s safe to take calcium at all.
To figure out how much extra calcium you need, find the appropriate total daily dose in the nearby table “How Much Calcium Do You Need?”. If you take a multivitamin, subtract the amount of calcium in the multi you take. Then subtract 300 milligrams for every serving of dairy products (yogurt, milk, cheese) you eat or calcium-fortified orange juice you drink on an average day. You may well find that you’re already getting enough, or that a minor change in your diet will fully meet your needs.
Iron. The body needs iron to manufacture red blood cells, which contain hemoglobin, the protein that carries oxygen to other cells all over the body. Yet women lose iron each month in their menstrual blood, and ten percent actually have an iron deficiency every month. Don’t take more iron supplements than multivitamins contain without your doctor’s permission. To boost iron intake naturally, eat plenty of kidney beans, dried fruit, pumpkin seeds, and spinach. Liver contains iron, too, but should be eaten in moderation because it is high in cholesterol.
Since vitamin C increases iron absorption, swallow your iron pill with a glass of orange or grapefruit juice. Caffeine decreases iron absorption, though, so hold off on coffee, tea, cocoa, or cola.
Folic acid. One of the few absolute musts among a woman’s vitamins is folic acid, also called folate or folacin. During pregnancy, folic acid is essential to the proper development of the baby. Without it, a baby may be born with severe birth defects of the brain and spinal cord. (See “The Changes to Make When You’re Pregnant.”) According to the U.S. Department of Health and Human Services, the number of cases of neural tube defects in newborns would be halved if all women of reproductive age took 400 micrograms (0.4 milligrams) of folic acid a day.
Folic acid is so important that bread, cereal, flour, pasta, and rice are now enriched with it. But even the extra folic acid in food is not enough to prevent birth defects. Experts recommend that all women who could possibly become pregnant take a vitamin supplement that contains folic acid. Don’t wait until you know you’re pregnant. Having folic acid in your body during the first few weeks of pregnancy, before you know you’re pregnant, is crucial. Folic acid deficiency can also make women anemic, whether they’re pregnant or not.
Zinc. Because the need for zinc increases during pregnancy, and many women don’t get enough zinc anyway, doctors often recommend that pregnant women take a multivitamin containing the RDA of zinc. Healthy skin and the ability of wounds to heal require zinc as well.
Vitamin B6.If you are pregnant, you will probably also need to take more B6 since a developing baby can easily drain maternal stores of this vitamin.
How Much Calcium Do You Need?
|Recommended daily calcium requirements were increased by experts at a National Institutes of Health conference in June 1994:
|Group and Age
|Birth to 6 months
|6 months to 1 year
|1 to 5 years
|6 to 10 years
|800 to 1,200
|Adolescents and Young Adults
|11 to 24 years
|1,200 to 1,500
|25 to 64 years
|65 and over
|25 years to menopause
|Menopause to age 64
|Not taking estrogens
|65 and over
|1,200 to 1,500
- People who are lactose intolerant—that is, unable to digest dairy products—may have to take calcium supplements.
- Very-low-calorie dieters may need extra vitamins and minerals, particularly iron, calcium, and vitamin B6.
- Vegetarians may be deficient in iron and zinc, both of which are more easily absorbed from animal sources than from plants.
- Total vegetarians who eat no eggs or dairy products may have to take supplements of vitamin B12, calcium, and vitamin D in order to get their RDA. Each is available from few sources other than animal and dairy products.
- A recent study found that vitamin D deficiency is common among American adults. Between October and March when daylight hours are shorter, it’s almost impossible for anyone to get enough vitamin D except in the South or Southwest. Few home-bound invalids of any age get enough vitamin D from the sun year-round. Some experts suggest that the elderly and sick—and possibly all adults—increase their vitamin D intake to 800 or 1,000 IU daily.
- Anyone who regularly takes anticoagulant drugs (blood thinners), including aspirin, should not take supplements of vitamin E. The combination of too much vitamin E and an anticoagulant can interfere with clotting. Talk to your doctor before mixing this or any vitamin or mineral supplement with medications.
- People who smoke, who are under great emotional or physical stress, or who have other health problems may benefit from extra boosts of antioxidants, especially vitamin C. “Ultra-athletes” who exercise extensively can become deficient in vitamin C as well, according to Dr. Kenneth H. Cooper, president and founder of the Cooper Aerobics Center in Dallas and the author of Dr. Kenneth H. Cooper’s Antioxidant Revolution.
- Children, too, have special requirements. For details, see “What’s Right—and Wrong—for the Kids.”
Plants Rich In Protein
Some Outstanding Sources of Carbohydrates
Whole Grains and Whole-Grain Products
The major building blocks of everything we eat, the proteins, carbohydrates, and—yes—fats are all vital for health. Proteins are the raw material of every cell in our bodies. Carbohydrates are the body’s main source of fuel. Fats serve as a high-capacity store house of energy, while supplying us with certain absolutely essential chemicals. If you somehow managed to completely eliminate any one of these three critical nutrients, you would die. The question around which much nutritional research revolves is not whether we need these nutrients, but rather in what proportions they do the most good.
Proteins are composed of smaller units called amino acids. Our bodies can manufacture most of these acids, but nine are available only from the food we eat. Meat, poultry, fish, eggs, and dairy products such as milk and cheese are all concentrated sources of protein. It can be found in many plants, too; but you should know that in order to get all the necessary amino acids from plants, certain varieties must be eaten with others (rice served with beans, for example).
Infants, children, pregnant and breastfeeding women, and the elderly all need more protein than other people. Getting too little protein can lead to stunted growth, reduced immunity to disease, and lack of energy. When protein intake drops too low for too long, the body steals protein from muscle and other tissue.
In America, most people have the opposite problem. They eat almost twice as much as the recommended 50 grams a day (a piece of meat or chicken the size of the palm of a hand). Any excess protein you take in is immediately burned as energy or converted to fat. Because the body can’t store proteins in their original form, they must be eaten every day.
Fats. The “fats” (lipids) that float through the bloodstream supply back-up energy for the body and help produce compounds that regulate blood pressure, blood clotting, and inflammation. Riding in the lipids are the fat-soluble vitamins A, D, E, and K, traveling through the body to perform their own crucial functions. It’s fairly difficult to develop a fat deficiency: The equivalent of a tablespoon of olive oil a day is enough for all our needs.
Fat is a problem for most of us because every gram contains more than double the calories of the same amount of protein or carbohydrate. Since the average American diet gets 33 percent of its calories from fat—a little less than it used to, but still more than the 30 percent maximum that nutritionists recommend—calories are piling on. A recent Gallup poll indicated that a large majority of Americans are overweight, as walking down almost any street will tell you. Worse yet, in Western countries where a high proportion of daily calories comes from fat, people have much higher rates of cancer of the breast, endometrium, prostate, colon, and pancreas than in countries where people eat modest amounts of fat (see “What to Do About Fat”). This could be a coincidence, but experts haven’t ruled out a possible link.
Carbohydrates. The body’s main source of energy, carbohydrates come in two forms, simple and complex.
Simple carbohydrates (sugars) are found in many forms and under many names, including fructose, lactose, and sucrose. Natural sugars appear in fruit, milk, honey, and maple syrup. Refined sugars, such as table sugar, have been stripped of other nutrients, retaining little more than their calories. Often found in foods that are loaded with fat and calories, such as desserts, refined sugars contribute little to your health, but can add a lot to your weight.
Complex carbohydrates (starches), which must be split apart before they’re absorbed, provide a more lasting source of energy than sugar. As an important dividend, the foods they’re found in are loaded with vitamins and minerals. Complex carbohydrates are found in starchy vegetables (potatoes, corn, beans, peas), pasta, rice, some fruits, and whole grains, including whole-grain breads and cereals.
Among the problems a low-fat, high-fiber diet can help fend off are heart disease, obesity, diabetes, and certain types of cancer. Remember that current recommendations make carbohydrates (especially complex carbohydrates) the centerpiece of good nutrition. Every day, we should all be eating 6 to 11 servings of grains (bread, cereal, rice, pasta), 3 to 5 servings of vegetables (raw, cooked, leafy, or juice), and 2 to 4 servings of fruit (raw, cooked, or juice).
Because what’s officially counted as a “serving” may be much less than you’d put on your plate, servings can add up quickly. For example, one serving of bread is one slice; therefore, a sandwich contains two servings. One large baked potato counts as two or three servings of a vegetable. Half a cup of a cooked vegetable—not very much—is a serving. Since a medium banana provides one serving of fruit, a large one contains about a serving and a half. For the best foods to seek out, see the box on “Some Outstanding Sources of Carbohydrates.”
Recent findings have debunked the notion that carbohydrates can be eaten in limitless amounts without adding much weight. In moderation, pasta remains a power food, especially if it’s all or part whole wheat or made with vegetables such as spinach, But even a high-carbohydrate, low-fat diet will put on extra pounds if it’s too high in calories. You should be particularly calorie-conscious if you’re part of the 25 percent of the U.S. population that overproduces insulin after eating sugar or starches.
Here’s how everyone’s daily intake of calories should break down after the age of two (infants’ bodies use fat and cholesterol to build bones, muscles, and brains):
- 50 to 60 percent from carbohydrates,
- No more than 30 percent from fat (preferably much less) after age 2, and
- The rest from protein (10 to 20 percent).
The tendency of cholesterol to build up inside some people’s arteries, thus leading to heart disease, is by now one of the best known facts in nutrition. Less well known is the fact that for the majority of the population, this doesn’t happen enough to lead to problems. Nevertheless, since doctors can’t tell whether or not cholesterol will affect you, the safest course is to keep your total blood cholesterol level below 200 milligrams per deciliter.
Cholesterol is most abundant in eggs and organ meats such as liver. However, eating animal fats also tends to raise cholesterol levels. That means keeping certain foods to a minimum and eating others in different forms. Instead of merely trimming the fat off red meat, for example, eat smaller portions less frequently. Switch to skim milk, which contains far less fat and cholesterol than any other kind. Downright fatty foods, such as richly marbled steaks and pizza dripping with grease, are best avoided altogether.
Fiber can help to remove excess cholesterol from the blood. Substituting olive oil for other types of fat also seems to help. Getting plenty of calcium, niacin, and vitamins C and E in foods and supplements reduces cholesterol levels as well.
Some of the elements in certain types of fat—the fatty acids—work together to promote health and growth. They come in “families” or series that vary according to where they’re found.
Omega-3 fatty acids help build potent hormonelike substances. They’re also vital for brain and eye development and may reduce the risk of heart attacks by preventing blood cells from sticking to the insides of blood vessels and building up as plaque. This family of fatty acids is derived from alpha-linolenic acid (ALA) and includes eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). What to eat: Canola, flaxseed, and rapeseed oils, green plants, tree nuts (such as walnuts and almonds), and especially deep-water fish (salmon, tuna, mackerel, herring, shrimp), approximately 3 to 6 ounces two or three times a week. Fish oil supplements are not recommended.
Omega-6 fatty acids start with linoleic acid, from which gamma linoleic acid (GLA) and arachidonic acid (AA) are derived. A precursor to hormone-like chemicals known as prostaglandins, linoleic acid is called “essential” because it can’t be synthesized from other nutrients in the body and must be obtained from food or supplements. It maintains the health of the skin and hair. What to eat:Corn, soybean, and other vegetable oils; foods that include those oils as an ingredient, ranging from bread to salad dressing; oils from seeds; beef, milk, and other products from animals that eat corn and grain.
Omega-9 fatty acids may help prevent breast cancer, according to recent studies. What to eat: Olive oil.
Fiber (what used to be known as roughage) is the part of fruits, vegetables, whole grains, and bran that passes through the body without being digested. As it is carried through the digestive system and out of the body, fiber maintains health and lowers the risk of a number of diseases and conditions, probably including colorectal and perhaps other types of cancer. For sources of fiber, see the box “Not Just From Bran: Your Broad Choice of Fiber Sources.”
Fiber is divided into two major types, soluble and insoluble. Fruits and vegetables contain a mixture of the two, although one usually predominates in any given food.
This type of fiber is dissolved by water in the body. It’s the sticky part of plants—like sap from trees. Soluble fiber is found in foods such as legumes (peas, peanuts, and lentils, for example), whole grains (barley, oats), some fruits (prunes, pears, apples), and many vegetables (broccoli, cabbages, carrots). Beans and oat bran are particularly good at clearing out the digestive system by softening bowel movements and stimulating the digestive tract to expel them. Oat bran can be bought in bulk and baked into bread and muffins or added to other foods, such as meat loaf or “veggie burgers.”
Benefits of soluble fiber:
- It moderates the levels of glucose in the blood, important for everyone, and vital for diabetics.
- It tends to lower the levels of cholesterol in the blood, helping to prevent heart disease. Eating 2 ounces of oat bran or 3 ounces of oatmeal every day may lower blood levels of LDL (“bad”) cholesterol by up to 5 percent.
This variety passes through the gastrointestinal tract in more or less its original form. Excellent sources include nuts, seeds, brown rice, unpeeled vegetables, whole-grain cereals (hot or cold) and baked goods, legumes, fruits, and especially wheat bran. A fine fiber-filled lunch: A bowl of pea soup with peanut butter spread on a high-fiber cracker.
Benefits of insoluble fiber:
- It makes bowel movements bulkier, helping to prevent constipation, hemorrhoids, and diverticulosis.
- It may lower the risk of colorectal cancer. Especially effective: raw wheat bran.
Both kinds of fiber make you feel full longer, controlling overeating and overweight.
American diets typically include only about half the fiber they should. Aim for at least 20 to 30 grams a day—a little less than an ounce. A high-fiber diet contains 25 grams of fiber for every 2,000 calories eaten. To obtain all the benefits that fiber has to offer, eat a variety of foods that are rich in it. Avoid fiber supplements; you’re much better off with the real thing, since you’ll gain all the other health benefits that fiber-rich foods can offer.
Here’s how whole grains make the difference. A slice of whole-wheat bread contains 1.4 grams of fiber, three and a half times more than a slice of white bread. Half a cup of brown rice contains a gram of fiber, five times more than the same amount of white rice. A cup of whole-wheat spaghetti contains 3.9 grams of fiber, more than three times as much as a cup of regular spaghetti. One easy way to get more fiber is to sprinkle three tablespoons of raw wheat bran on your food during the course of each day.
To prevent gas and diarrhea, increase the amount of fiber in your diet slowly. Drinking six to eight large (8-ounce) glasses of water every day will help the fiber move through your digestive system painlessly (see the box on “Water, the Forgotten Food”).
Not Just From Bran: Your Broad Choice of Fiber Sources
You shouldn’t have trouble adding fiber to your diet, considering that your options range from popcorn to prunes and from almonds to cabbage. The main reason many people associate fiber with bran is a series of successful advertising campaigns for breakfast cereals and bran muffins, which hit the media as soon as studies started suggesting that fiber could help prevent breast and colon cancers.
The table shows the amounts of dietary fiber in some fiber-rich foods. Dietary fiber is the total fiber content of the food. For instance, to get maximum fiber from oranges and apples eat the fruit whole; the juice alone has little fiber. Likewise, don’t boil your vegetables into oblivion; this will allow vitamins and minerals to dissipate into the water and air. Wash, but don’t peel, that baked potato.
Adapted from NIH Publication 87-2878, May 1987
Water, the Forgotten Food
Water is everywhere in the human body, accounting for about 60 percent of its total weight. Totally deprived of water, we can survive for little more than days.
Water is the main component of every cell in the body. It plays a mandatory role in digestion, absorption, circulation, and elimination. It even helps the body regulate its temperature. Water keeps the mucous membranes of the nose, mouth, throat, lungs, and other areas moist. It washes food through the digestive system from beginning to end. It carries water-soluble vitamins and fiber around the bloodstream. It carries waste products away from the cells and out of the body.
We lose water constantly through perspiration, urine, sneezes, and even the tears that bathe our eyes and eyelids to keep them moist. No wonder the body’s water has to be replenished all the time.
Drinking eight 8-ounce glasses of water every day (whether you feel thirsty or not), and more in hot weather, maintains the level your body needs. During exercise, take regular water breaks. Alcohol and beverages that contain caffeine increase urination, decreasing the amount of water in the body.