Scottsdale, Arizona - The Dietary Guidelines for Americans make it clear that your nutritional needs should be met primarily through your diet.

For some people, however, supplements may be a useful way to get nutrients they might otherwise be lacking. But before you go shopping for supplements, get the facts on what they will and won't do for you.

Supplements vs. whole foods

Supplements aren't intended to be a food substitute because they can't replicate all of the nutrients and benefits of whole foods, such as fruits and vegetables. So depending on your situation and your eating habits, dietary supplements may not be worth the expense.

Whole foods offer three main benefits over dietary supplements:

• Greater nutrition. Whole foods are complex, containing a variety of the micronutrients your body needs — not just one. An orange, for example, provides vitamin C plus some beta carotene, calcium and other nutrients. It's likely these compounds work together to produce their beneficial effect.
• Essential fiber. Whole foods, such as whole grains, fruits, vegetables and legumes, provide dietary fiber. Most high-fiber foods are also packed with other essential nutrients. Fiber, as part of a healthy diet, can help prevent certain diseases, such as type 2 diabetes and heart disease, and it can also help manage constipation.
• Protective substances. Whole foods contain other substances important for good health. Fruits and vegetables, for example, contain naturally occurring substances called phytochemicals, which may help protect you against cancer, heart disease, diabetes and high blood pressure. Many are also good sources of antioxidants — substances that slow down oxidation, a natural process that leads to cell and tissue damage.

Who needs supplements?

If you're generally healthy and eat a wide variety of foods, including fruits, vegetables, whole grains, legumes, low-fat dairy products, lean meats and fish, you likely don't need supplements.

However, the dietary guidelines recommend supplements — or fortified foods — in the following situations:

• Women who may become pregnant should get 400 micrograms a day of folic acid from fortified foods or supplements, in addition to eating foods that naturally contain folate.
• Women who are pregnant should take a prenatal vitamin that includes iron or a separate iron supplement.
• Adults age 50 or older should eat foods fortified with vitamin B-12, such as fortified cereals, or take a multivitamin that contains B-12 or a separate B-12 supplement.
• Adults age 65 and older who do not live in assisted living or nursing homes should take 800 international units (IU) of vitamin D daily to reduce the risk of falls.

Dietary supplements also may be appropriate if you:

• Don't eat well or consume less than 1,600 calories a day.
• Are a vegan or a vegetarian who eats a limited variety of foods.
• Don't obtain two to three servings of fish a week. If you have difficulty achieving this amount, some experts recommend adding a fish oil supplement to your daily regimen.
• Are a woman who experiences heavy bleeding during your menstrual period.
• Have a medical condition that affects how your body absorbs or uses nutrients, such as chronic diarrhea, food allergies, food intolerance, or a disease of the liver, gallbladder, intestines or pancreas.
• Have had surgery on your digestive tract and are not able to digest and absorb nutrients properly.

Talk to your doctor or a dietitian about which supplements and what doses might be appropriate for you. Be sure to ask about possible side effects and interactions with any medications you take.

Choosing and using supplements

If you decide to take a vitamin or mineral supplement, consider these factors:

• Check the label. Read labels carefully. Product labels can tell you what the active ingredient or ingredients are, which nutrients are included, the serving size — for example, capsule, packet or teaspoonful — and the amount of nutrients in each serving.
• Avoid megadoses. In general, choose a multivitamin-mineral supplement that provides about 100 percent of the Daily Value (DV) of all the vitamins and minerals, rather than one which has, for example, 500 percent of the DV for one vitamin and only 20 percent of the DV for another.
• Check expiration dates. Dietary supplements can lose potency over time, especially in hot and humid climates. If a supplement doesn't have an expiration date, don't buy it. If your supplements have expired, discard them.
• Watch what you eat. Vitamins and minerals are being added to a growing number of foods, including breakfast cereals and beverages. If you're also taking supplements, you may be getting more than you realize of certain nutrients. Taking more than you need is expensive and can raise your risk of side effects. For example, too much iron can cause nausea and vomiting and may damage the liver and other organs.

Keep up with supplement safety alerts

The Food and Drug Administration (FDA) keeps a list of dietary supplements that are under regulatory review or that have been reported to cause adverse effects. If you're taking a supplement, it's a good idea to check the FDA website periodically for updates.