Supplements are concentrated forms of vitamins, minerals, fiber, amino acids, fatty acids, herbal products, enzymes, plant or animal tissue extracts, or hormones. Some supplements contain one or two known nutrients or a small group of nutrients such as B vitamins or antioxidants.

Others, like the well-known multivitamins, may contain an entire panel of vitamins and minerals in amounts close to the Dietary Reference Intakes (DRIs). Still other supplements may not contain any substances yet identified as nutrients or even demonstrated as beneficial to health.

With few exceptions, foods are better sources than supplements for the nutrients we need. A diet based on the Food Guide Pyramid, especially one that is rich in fruits, vegetables, whole-grain foods, and legumes, will provide most of the nutrients we know we need and the ones we have not yet identified.

When we build our diet on a foundation of whole foods, we reap the added benefit of phytochemicals (known and unknown) and all the types of fiber we have begun to realize are important for health.

Dietary supplements can be enticing. However, because of a law passed in 1994, the Dietary Supplement Health and Education Act, the Food and Drug Administration (FDA) is more limited in what it can do to regulate the safety, purity, and labeling of supplements than what it does for drugs or even foods.

Supplement manufacturers are required to list the ingredients of their products but are not accountable for the validity of those lists. Supplements may contain more or less of the active ingredient than they claim or may contain various impurities. Moreover, manufacturers are not required to list possible side effects of supplements on labels or in promotional materials.

Finally, we don’t yet know the active ingredient or ingredients in many herbal supplements and plant foods, so we have no way of knowing whether the commercially available extracts of those herbs or foods will have the same benefits as the foods themselves.

The popularity of herbal products, those made from extracts of plants and believed to have medicinal properties, continues to increase. Americans spend $700 million a year on herbal remedies.

The use of some plant remedies dates back thousands of years, and plant materials are the basis for many of our most helpful medications, including aspirin and morphine. Scientists continue to investigate and discover new medicinal uses for substances in plants.

Even though some herbal remedies may show beneficial effects, most show little evidence of providing any health benefits. In fact, some may have serious health risks and may interfere with the action of some medicines.

Because herbal products are considered dietary supplements rather than drugs, the FDA is limited in its ability to regulate these substances. Ongoing studies continue to investigate selected herbs for their safety and effectiveness, so that more information will be available to consumers in the future. There is no guarantee of quality control.

In the meantime, follow these precautions when considering a supplement:

• Do not use herbal remedies for treatment of serious illnesses.

• Do not give herbal (or other) supplements to infants and children.

• Avoid all herbal supplements if you are pregnant or trying to become pregnant.

• If you have a medical condition, check with your health care provider before taking herbal supplements.

• In addition, if you are taking medications, do not take herbal supplements before discussing them with your health care provider.

In general, high-dose vitamin or mineral supplements add little to our health and may in themselves cause illness. Those that contain more than 100 percent of your estimated daily needs may result in serious nutrient imbalances or even toxicity.

Such imbalances do not occur when your source of vitamins comes from foods rather than supplements, because foods contain safe amounts of multiple nutrients, and if you follow the Food Guide Pyramid’s recommended number of servings you will likely meet the recommended amounts for most nutrients.

As discussed earlier, most Americans, including athletes, consume considerably more protein than recommended, and more than their bodies can use. Protein or amino acid powders provide no benefit and are a poor substitute for protein-rich foods that contain necessary vitamins and minerals.

Similarly, pills that promise to deliver all the fiber we need daily are a bad risk, because these pills invariably provide only one type of fiber, whereas each type of fiber found in foods of plant origin appears to confer unique health-promoting benefits. The fatty acids we need also are available in more than adequate amounts in various foods.

Eating a variety of foods, especially those of plant origin, allows most of us to acquire all the known nutrients, food substances, and as yet unidentified nutrients that our bodies need. Nevertheless, supplements may be appropriate for some individuals. Who are these people?

• Pregnant or breastfeeding women have an increased need for most vitamins and minerals. Folic acid is especially important early in pregnancy. Women who are capable of becoming pregnant should ensure that their daily intake of folic acid from supplements and fortified foods is 400 micrograms. These vitamins and minerals are contained in the prenatal supplements that are prescribed by your health care provider.

• Older adults may absorb some nutrients poorly, particularly folate, vitamin B12, and vitamin D. They therefore may require supplements.

• People on restricted diets may require supplements of some vitamins and minerals.

• People with diseases of the digestive tract or other serious illnesses that limit their absorption of some vitamins and minerals may require supplements.

• People taking prescription medications may have altered needs for a variety of nutrients.

• Smokers appear to have an increased need for antioxidants, especially vitamin C. (However, even this increased requirement for vitamin C is easily satisfied by eating nutrient-rich foods.)

• People who drink alcohol to excess may require supplements.

• Vegetarians who eat no animal products may not get adequate vitamin B12, iron, and zinc. Vegetarians who avoid dairy products are at a greater risk for calcium deficiency than are those who do eat dairy products.

• Some evidence suggests that a daily supplement of vitamin E may reduce the risk of heart disease.

Before taking any supplement, discuss it with your health care provider, and be sure to mention any medications you are taking.

If your breakfast this morning included calcium-fortified orange juice and toast made with folate-enriched flour, you are a consumer of functional foods. Just what is a functional food?

As the fastest growing category of new food products, these are foods or food components to which manufacturers have added ingredients that are known or believed to promote health and prevent disease.

Although the name “functional foods” is new, the concept is not: when it was discovered in the early part of the 20th century that some thyroid disease was caused by a deficiency of the mineral iodine, manufacturers began enriching table salt with iodine.

Since that time, we have also seen vitamin D-fortified milk, breakfast cereals fortified with a variety of vitamins and minerals, and the addition of preservatives that are themselves antioxidants to almost all processed foods.

The past few years, though, have seen a virtual explosion of functional foods, some based on careful research and supported by nutrition experts and some with questionable, if any, potential benefits.

With a few exceptions, most of us should get all the vitamins, minerals, fiber, essential fatty acids, protein, and phytochemicals we need from the food we eat, rather than from supplements. Always consult your health care provider before trying a supplement.

A few of the functional foods that have recently appeared on the market have proven benefits, although most have yet to demonstrate their value. If your goal is to eat foods that deliver on their promise of providing all the necessary vitamins, minerals, fiber, and other yet to be identified health-enhancing substances, you need to:

• Increase your intake of whole grains, fruits, and vegetables as sources of vitamins, minerals, fiber, and phytochemicals

• Decrease your intake of foods of animal origin (meats, dairy products, eggs), particularly those that are high in saturated fat, substituting lean alternatives and plant sources of protein

• Limit your use of fats and cooking oils when preparing, serving, and eating food