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.
Phytochemicals
A Food Pharmacy That May Fight Disease
Phytochemical |
Food |
Potential Benefit |
|
Allyl sulfides |
Garlic, onions, leeks |
May protect against coronary artery disease, abnormal blood clotting, cancer |
|
Alpha-linoleic acid |
Flaxseed, soybeans, walnuts |
Decreases inflammation |
|
Anthocyanosides |
Eggplant, blood oranges, blueberries |
May protect against cancer |
|
Capsaicins |
Chili peppers |
Topical analgesic |
|
Carotenoids, including lycopene, lutein |
Orange, red, yellow fruits; many vegetables, including tomatoes |
May protect against coronary artery disease, macular degeneration, and cancer |
|
Catechins |
Tea (especially green tea) |
May protect against cancer |
|
Cellulose (fiber) |
Whole-wheat flour, bran, cruciferous and root vegetables, legumes, apples |
May protect against colon cancer, coronary artery disease |
|
Coumarins |
Carrots, citrus fruits, parsley |
May protect against blood clots |
|
Ellagic acid |
Strawberries, raspberries, blueberries |
May protect against cancer |
|
Flavonoids (including resveratrol) |
Citrus fruits, onions, apples, grapes, wine, tea |
May protect against cancer |
|
Gums (fiber) |
Oats, barley, legumes |
May prevent colon cancer |
|
Hemicellulose (fiber) |
Bran, whole grains |
May prevent colon cancer |
|
Indoles |
Cruciferous vegetables |
May protect against cancer |
|
Isoflavones |
Soybeans and soy products |
May diminish menopausal symptoms; may protect against cancer, may lower blood lipid levels, may improve bone health |
|
Isothiocyanates |
Cruciferous vegetables |
May prevent lung, esophageal cancer |
|
Lignins (fiber) |
Whole grains, oranges, pears, broccoli, flaxseed |
May protect against cancer |
|
Monoterpenes |
Citrus fruits |
May protect against cancer (pancreatic, breast, prostate tumors) |
|
Pectin (fiber) |
Apples, citrus fruits, strawberries |
May protect against cancer, coronary artery disease, diabetes |
|
Phenolic acids |
Brown rice, green tea |
May protect against cancer |
|
Protease inhibitors |
Soybeans, all plants |
May protect against cancer |
|
Phytosterols |
Legumes, cucumbers |
May help prevent coronary artery disease and breast cancer |
|
Saponins |
Garlic, onions, licorice, legumes |
May protect against cancer |
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.
A Closer Look: Supplements and the Law
When a dietary supplement is available in the store, it is naturally assumed that it is safe. Some government agency has checked to make certain it is not harmful, right? Not anymore.
In 1994, the Dietary Supplement Health and Education Act removed dietary supplements from pre-market safety evaluations required of food ingredients and drugs. Drugs and food ingredients still undergo a lengthy Food and Drug Administration (FDA) safety review before they can be marketed, but the 1994 legislation eliminated the FDA’s authority to regulate the safety of nutritional supplements before they go on the market. Now, the FDA can intervene only after an illness or injury occurs.
Claims may not be made about the use of dietary supplements to diagnose, prevent, treat, or cure a specific disease. For example, a product may not carry the claim "cures cancer" or "treats arthritis."
The FDA can still restrict the sale of an unsafe dietary supplement when there is evidence that the product presents a significant or reasonable safety concern. But the agency must wait for complaints about a product before acting.
The legislation also changed guidelines for marketing supplements. Because the nutritional supplement industry is now largely unregulated, there is no guarantee of product purity or of the amount of active ingredient in a supplement—even from one package to the next of the same product.
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 (see sidebar: A Closer Look: Supplements and the Law, this page). 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.
Herbal Supplements
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 (see sidebar: Herbal Products, page 37).
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.
Herbal Products
Herb |
Possible Use |
Precautions |
Chamomile Matricaria chamomilla |
Internally for indigestion and as an anti-inflammatory. Externally for skin inflammations |
Weak potential for allergic sensitization |
Comfrey Symphytum officinale |
Externally for bruises and sprains (where skin is intact) |
Taken internally, it contains traces of alkaloids, which can cause liver damage and cancer risk |
Purple coneflower Echinacea |
Protects against colds |
Possibility of an excessive immune response. Should not be used by persons with multiple sclerosis, AIDS, or tuberculosis |
Ephedra-containing compounds Ma-huang |
Stimulant |
Headache, irritability, sleeplessness. High doses can cause dangerous increase in blood pressure and heart rate. Addictive over long periods |
Garlic Allium sativum |
May improve blood lipid levels (equal to 2 to 4 cloves a day) |
Large quantities can lead to stomach complaints, rare skin allergic reaction |
Ginger Zingiber officinale |
For loss of appetite, travel sickness |
Should not be taken with gallstone conditions |
Ginkgo Ginkgo biloba |
Improved blood flow to the brain and peripheral circulation; improvement in concentration and memory deficits |
Mild gastrointestinal complaints, allergic skin reactions. Can change blood clotting; therefore, consult with physician if taking anticoagulant therapy |
Ginseng Panax ginseng |
Tonic for fatigue and declining work capacity |
High doses can cause sleeplessness, high blood pressure, and edema |
Guarana Paullinia cupana |
Stimulation due to caffeine-like content. Diuretic |
Caution advised for persons with sensitivity to caffeine, renal diseases, hyperthyroidism, panic anxiety |
Indian tobacco Lobelia inflata |
Asthma treatment, stimulates respiratory center to open airways and ease breathing |
High doses can cause convulsions, respiratory problems, and even death |
Kava Piper methysticum |
Nervousness and insomnia |
Gastrointestinal complaints, eye pupil dilation, and disorders of visual equilibrium. May interact with (enhance) other central nervous system substances, such as alcohol and barbiturates |
St. John’s wort Hypericum perforatum |
For mild depression and anxiety |
Digestive complaints of fullness or constipation. Sensitivity to sunlight in large doses. Consult with physician if taking antidepressant medications |
Saw palmetto Serenoa repens |
Urinary problems in men with non-cancerous (benign) prostate enlargement. Does not reduce the enlargement |
Use under a physician’s supervision, not as a substitute for medical treatment |
Yohimbe bark Pausinystalia yohimba |
Used for sexual disorders, as an aphrodisiac, although it appears to be ineffective |
Do not use if liver or kidney disease is present. Side effects include anxiety, increase in blood pressure, rapid heartbeat, tremor, and vomiting. High doses can cause heart failure |
• 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.
Supplement Sense
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.
Using Supplements
Supplements are not substitutes. Supplements do not replace the hundreds of nutrients in whole foods needed for a balanced diet, and they will not fix poor eating habits. If you are considering taking a supplement, heed the following:
• Do not self-prescribe.
• See your doctor or health care provider if you have a health problem.
• Discuss any supplement that you are taking. Supplements may interfere with medications.
• Read the label. Supplements can lose their potency over time, so check the expiration date on the label. Also, look for the initials "USP." They stand for the testing organization, US Pharmacopeia, which establishes testing standards for compounds. The Food and Drug Administration (FDA) does not analyze supplements before they enter the marketplace.
• Stick to the Daily Value (DV). Choose supplements that are limited to 100 percent or less. Take no more than what is recommended by your doctor or health care provider. The toxic levels are not known for some nutrients.
• Do not waste dollars. Synthetic supplements are the same as so-called natural types. Generic and synthetic brands are less expensive and equally effective.
• Store in a safe place. Iron supplements are the most common cause of poisoning deaths among children.
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.
Who Needs a Vitamin or Mineral Supplement?
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 B^, 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 (see sidebar: Using Supplements, page 38).
The Future Is Here: Functional Foods
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-for-tified 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.
The Bottom Line on Supplements
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 phy-tochemicals
• 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