What Are Dietary Supplements?

The Food and Drug Administration (FDA) estimates that every year, Americans buy millions of bottles and boxes of dietary supplements, a $19 billion business that includes everything from plain old vitamin C to — yuck! — desiccated (dried) liver. 

You can stir up a good food fight in any group of nutrition experts simply by asking whether all these supplements are (a) necessary, (b) economical, or (c) safe. 

But when the argument’s over, you still may not have a satisfactory official answer, so this article aims to provide the information you need to make your own sensible choices.

What Are Dietary Supplements?

The vitamin pill you may pop each morning is a dietary supplement. So are the calcium antacids many American women consider standard nutrition. Echinacea, the herb reputed to short-circuit your winter cold, is, and so is the vanilla-flavored meal-in-a-can liquid your granny chug-a-lugs every afternoon just before setting off on her daily mile power walk. The FDA classifies each of these as a dietary supplement because they meet the agency’s definition: any pill, tablet, capsule, powder, or liquid you take by mouth that contains a dietary ingredient.

Of course, that raises another question: What’s a dietary ingredient? Answer:

  • Vitamins 
  • Minerals
  • Herbs
  • Amino acids
  • Enzymes
  • Organ tissue, such as desiccated (dried) liver
  • Some hormones, such as melatonin, which is promoted as a sleep aid
  • Metabolites (substances produced when nutrients are digested)
  • Extracts

Dietary supplements may be single-ingredient products, such as vitamin E capsules, or they may be combination products, such as the nutrient-packed protein powders favored by some athletes.

Why Do People Take Dietary Supplements?

In a country where food is plentiful and affordable, you have to wonder why so many people opt to scarf down pills instead of just plain food.

Many people consider vitamin and mineral supplements a quick and easy way to get nutrients without so much shopping and kitchen time and without all the pesky fat and sugars in food. Others take supplements as nutritional insurance. And some even use supplements as substitutes for medical drugs. In general, nutrition experts, including the American Dietetic Association, the National Academy of Sciences, and the National Research Council, prefer that you invest your time and money whipping up meals and snacks that supply the nutrients you need in a balanced, tasty diet. Nonetheless, every expert worth his or her vitamin C admits that in certain circum- stances, supplements can be a definite plus.

In 2002, the American Medical Association (AMA), which for decades had turned thumbs down on vitamin supplements, changed its collective mind after a review of 26 years’ worth of scientific studies relating vitamin levels to the risk of chronic illness. Robert H. Fletcher and Kathleen M. Fairfield, the Harvard-based authors of the study, which was published in the Journal of the American Medical Association (JAMA), said, yes, true vitamin-deficiency diseases such as scurvy and beriberi are rare in Western countries. But sub-optimal vitamin levels — science-speak for slightly less than you need — are a real problem. If “slightly less than you need” sounds slightly less than important, consider this:

  • Suboptimal intake of folate and two other B vitamins (B6 and B12) raises your risk of heart disease, colon cancer, breast cancer, and birth defects.
  • Suboptimal vitamin D intake means a higher risk of rickets and osteoporosis.
  • Suboptimal levels of antioxidant vitamins A, E, and C are linked to a particular form of heart disease and some forms of cancer.

Hence the new AMA rule: “It’s prudent for all adults to take vitamin supplements.”

But just as that bit of info was settling in, a new study said, “Hold it! There’s too much Vitamin A in that pill!” That was followed by more new research on too much vitamin E. As you read this, vitamin manufacturers are tumbling over each other in the race to get new, lower formulations to market.

Benefits of Dietary Supplements

1. If you don’t get enough nutrients from food, supplements can help

Illness, age, diet preferences, and some gender-related conditions may put you in a spot where you can’t get all the nutrients you need from food alone.

Certain metabolic disorders and diseases of the digestive organs (liver, gall- bladder, pancreas, and intestines) interfere with the normal digestion of food and the absorption of nutrients. Some medicines may also interfere with normal digestion, meaning you need supplements to make up the difference. People who suffer from certain chronic diseases, who have suffered a major injury (such as a serious burn), or who have just been through surgery may need more nutrients than they can get from food. In these cases, a doctor may prescribe supplements to provide the hard-to-get vitamins, minerals, and other nutrients.

Checking with your doctor or pharmacist before opting for a supplement you hope will have medical effects (make you stronger, smooth your skin, ease your anxiety) is a smart idea. The bad old days when doctors were total ignoramuses about nutrition may not be gone forever, but they’re fading fast. Besides, your doctor is the person most familiar with your health, knows what medications you’re taking, and can warn you of potential side effects.

2. Supplements can ensure vegetarians get enough nutrients

Vitamin B12 is found only in food from animals, such as meat, milk, and eggs. (Some seaweed does have B12, but the suspicion is that the vitamin comes from microorganisms living in the plant.) Without these foods, vegans — vegetarians who don’t eat any foods of animal origin — almost certainly have to get their vitamin B12 from supplements or fortified foods.

3. Protecting against disease

Taking supplements may reduce the likelihood of some types of cancer and other diseases. After analyzing data from a survey of 871 men and women, epidemiologists at Seattle’s Fred Hutchinson Cancer Center found that people taking a daily multivitamin for more than ten years were 50 percent less likely to develop colon cancer. In addition, selenium supplements seem to reduce the risk of prostate cancer, and vitamin C seems to lower the risk of cataracts.

4. Supplementing aging appetites

As you grow older, your appetite may decline and your sense of taste and smell may falter. If food no longer tastes as good as it once did, if you have to eat alone all the time and don’t enjoy cooking for one, or if dentures make chewing difficult, you may not be taking in all the foods that you need to get the nutrients you require. Dietary supplements to the rescue!

If you’re so rushed that you literally never get to eat a full, balanced meal, you may benefit from supplements regardless of your age.

5. Meeting a woman’s special needs

And what about women? At various stages of their reproductive lives, they, too, benefit from supplements-as-insurance:

Before menopause: Women, who lose iron each month through menstrual bleeding, rarely get sufficient amounts of iron from a typical American diet providing fewer than 2,000 calories a day. For them, and for women who are often on a diet to lose weight, iron supplements may be the only practical answer.

Iron is a mineral element, so it may be called “iron” or “elemental iron” on the label. Iron pills contain a compound of elemental iron (“ferrous” or “ferric,” from ferrum, the Latin word for iron), plus an ingredient such as a sulfur derivative or lactic acid to enable your body to use the iron. On the label, the combination reads “ferrous sulfate” or “ferrous lactate.” Different iron compounds dissolve at different rates in your stomach, yielding different amounts of elemental iron, so supplement labels usually list the iron this way: Ferrous sulfate 325 mg/Elemental iron 65 mg. Translation? This pill has 325 milligrams of ferrous sulfate, yielding 65 milligrams plain old iron. Sometimes the label omits the first part and simply says: Iron 65 mg.

If your doctor says, “Take one 325-milligram pill a day,” she means 325 milligrams iron compound, not plain elemental iron.

During pregnancy and lactation: Women who are pregnant or nursing often need supplements to provide the nutrients they need to build new maternal and fetal tissue or to produce nutritious breast milk. In addition, supplements of the B vitamin folate now are known to decrease a woman’s risk of giving birth to a child with a neural tube defect (a defect of the spinal cord and column).

Never self-prescribe supplements while you’re pregnant. Large amounts of some nutrients may actually be hazardous for your baby. For example, taking megadoses of vitamin A while you’re pregnant can increase the risk of birth defects. 

Through adulthood: True, women older than 19 can get the calcium they require (1,000 milligrams/day) from four 8-ounce glasses of nonfat skim milk a day, three 8-ounce containers of yogurt made with nonfat milk, 22 ounces of canned salmon (with the soft edible bones; no, you definitely should not eat the hard bones in fresh salmon!), or any combination of the above. However, expecting women to do this nutritional balancing act every single day may be unrealistic. The simple alternative is calcium supplements.

Supplement Safety

The Food and Drug Administration (FDA) regulates food and drugs (no surprise there). Before the agency allows a new food or a new drug on the market, the manufacturer must submit proof that the product is safe. Drug manufacturers must also meet a second test, showing that their new medicine is efficacious, a fancy way of saying that the drug and the dosage in which it’s sold will cure or relieve the condition for which it’s prescribed.

Nobody says the drug-regulation system’s perfect. Reality dictates that manufacturers test a drug only on a limited number of people for a limited period of time. So you can bet that some new drugs will trigger unexpected, serious, maybe even life-threatening side effects when used by thousands of people or taken for longer than the testing period. For proof, look no further than PhenFen, a diet drug combination that appeared to control weight safely during premarket testing but turned lethal after it reached pharmacy shelves.

But at least the FDA can require that premarket safety and/or effectiveness info be displayed on foods and drugs. Unfortunately, the agency has no such power when it comes to dietary supplements.

In 1994, Congress passed and President Clinton signed into law the Dietary Supplement Health and Education Act, which limits the FDA’s control over dietary supplements. Under this law, The FDA can’t

  • Require premarket tests to prove that supplements are safe and effective
  • Limit the dosage in any dietary supplement
  • Halt or restrict sales of a dietary supplement unless evidence shows that the product has caused illness or injury when used according to the directions on the package; in other words, if you experience a problem after taking slightly more or less of a supplement than directed on the label, the FDA can’t help you

As a result, the FDA has found it virtually impossible to take products off drugstore shelves even after reports of illness and injury. For example, supplements containing the herb ephedra are reputed to enhance weight loss and sports performance. More than 600 reports of illness and at least 100 deaths have been linked to the use of ephedra supplements. The herb is banned by professional football and college athletics in the U.S. and by the Olympics. However, the FDA didn’t act until February 2003, following the death of Baltimore Orioles pitcher Steve Bechler, who reportedly had been using ephedra products to control his weight.

Bechler’s untimely death rang warning bells across the country, including in Washington, D.C., where the FDA ruled that henceforth every bottle of ephedra must carry strong warnings that the popular herb can cause potentially lethal heart attacks or strokes. In the sports world, ephedra was immediately forbidden in the minor league but not major league baseball.

The FDA banned all ephedra products, but the ban was partially reversed in April 2005, when a federal judge ruled that products containing low doses of ephedra were safe and could remain on the market. Some in Congress are pressing for a law that would enable FDA to ban any supplements considered even potentially hazardous to your precious health. Stay tuned.

By the way, ephedra isn’t the only herbal supplement that can make you really uncomfortable. Table 1 lists some equally problematic herbal products that you need to approach with caution — or avoid altogether. In many cases, even small amounts are hazardous.

Table 1 Some Potentially Hazardous Herbals
Herb Known Side Effects and Reactions
Blue cohosh Nausea, vomiting, dizziness, smooth muscle (such as the uterus) contractions
Chaparral Liver damage, liver failure
Comfrey Possible liver damage
Kombuchu tea Potentially fatal liver damage, intestinal upset
Lobelia (Indian tobacco) Potentially fatal convulsions, coma
Pennyroyal Potentially fatal liver damage, convulsions, coma
Senna Severe gastric irritation, diarrhea
Stephania (also known as magnolia) Kidney damage (sometimes severe enough to require dialysis or transplant)
Valerian Severe withdrawal symptoms

How To Choose High-Quality Vitamins and Supplements?

Okay, you’ve read about the virtues and drawbacks of supplements. You’ve decided which supplements you think may do you some good. Now it’s crunch time, and all you really want to know is how to choose the safest, most effective products. The guidelines in this section can help.

Choosing a well-known brand

Even though the FDA can’t require manufacturers to submit safety and effectiveness data, a respected name on the label offers some assurance of a quality product. It also promises a fresh product; well-known brands generally sell out more quickly. The initials USP (U.S. Pharmacopoeia, a reputable testing organization) are another quality statement, and so are the words “release assured” or “proven release,” which mean the supplement is easily absorbed by your body.

Checking the ingredient list

Check the supplement label. In the early 1990s, the FDA introduced the consumer-friendly nutrition food label with its mini-nutrition guide to nutrient content, complete ingredient listings, and dependable information about how eating certain foods may affect your risk of chronic illnesses, such as heart disease and cancer. 

The FDA’s new supplement labels must list all ingredients. The label for vitamin and mineral products must give you the quantity per nutrient per serving plus the %DV (percentage daily value), the percentage of the RDA (Recommended Dietary Allowance). The listings for other dietary supplements, such as botanicals (herbs) and phytochemicals (see Chapter 12), must show the quantity per serving plus the part of the plant from which the ingredient is drawn (root, leaves, and so on). A manufacturer’s own proprietary blend of two or more botanicals must list the weight of the total blend.

Looking for the expiration date

Over time, all dietary supplements become less potent. Always choose the product with the longest useful shelf life. Pass on the ones that will expire before you can use all the pills, such as the 100-pill bottle with an expiration date 30 days from now.

Checking the storage requirements

Even when you buy a product with the correct expiration date, it may be less effective if you don’t keep it in the right place. Some supplements must be refrigerated; the rest you need to store, like any food product, in a cool, dry place. Avoid putting dietary supplements in a cabinet above the stove or refrigerator — true, the fridge is cold inside, but the motor pulsing away outside emits heat.

Choosing a sensible dose

Unless your doctor prescribes a dietary supplement as medicine, you don’t need products marked “therapeutic,” “extra-strength,” or any variation thereof. Pick one that gives you no more than the RDA for any ingredient.

Avoiding hype

When the label promises something that’s too good to be true — “Buy me! You’ll live forever” — you know it’s too good to be true. The FDA doesn’t permit supplement marketers to claim that their products cure or prevent dis-ease (that would make them medicines that require premarket testing). But the agency does allow claims that affect function, such as “maintains your cholesterol” (the no-no medical claim would be “lowers your cholesterol”).

Another potential hype zone is the one labeled “natural,” as in “natural vitamins are better.” If you took Chem 101 in college, you know that the ascorbic acid (vitamin C) in oranges has exactly the same chemical composition as the ascorbic acid some nutritional chemist cooks up in her lab. But the ascorbic acid in a “natural” vitamin pill may come without additives such as coloring agents or fillers used in “regular” vitamin pills. In other words, if you aren’t sensitive to the coloring agents or fillers in plain old pills, don’t spend the extra dollars for “natural.” If you are sensitive, do. What could be simpler?

Why Food is Better Than Supplements?

Despite this article’s focus on the wonders of supplements, I feel obligated to play devil’s advocate and report to you the arguments in favor of healthy people getting all or most of their nutrients from food rather than supplements.


If you’re willing to plan and prepare nutritious meals, you can almost always get your nutrients less expensively from fresh fruits, vegetables, whole grains, dairy products, meat, fish, and poultry. Besides, food usually tastes better than supplements.

Unexpected bonuses

Food is a package deal containing vitamins, minerals, protein, fat, carbohydrates, and fiber, plus a cornucopia of as-yet-unidentified substances called phytochemicals (phyto = plant, chemicals = well, chemicals) that may be vital to your continuing good health. Think of lycopene, the red pigment in tomatoes that recently was found to reduce the risk of prostate cancer

Think of genistein and daidzein, the estrogen-like substances in soybeans that appear to reduce your risk of heart disease. Who knows what else is hiding in your apples, peaches, pears, and plums? Do you want to be the only one on your block who misses out on these goodies? Of course not. 


Several common nutrients may be toxic when you scarf them down in mega-dose servings (amounts several times larger than the RDAs). Not only are large doses of vitamin A linked to birth defects, but they may also cause symptoms similar to a brain tumor. 

Niacin megadoses may cause liver damage. Megadoses of vitamin B6 may cause (temporary) damage to nerves in arms, legs, fingers, and toes. All these effects are more likely to occur with supplements. Pills slip down easily, but regardless of how hungry you are, you probably won’t eat enough food to reach toxic levels of nutrients. 

The best statement about the role of supplements in good nutrition may be a paraphrase of Abraham Lincoln’s famous remark about politicians and voters: “You may fool all the people some of the time; you can even fool some of the people all the time; but you can’t fool all of the people all the time.” If Honest Abe were with us now and were a sensible nutritionist rather than President, he might amend his words: “Supplements are valuable for all people some of the time and for some people all the time, but they’re probably not necessary for all people all the time.”

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