If you've ever stood in the supplement aisle of your local health food store and wondered how you could possibly choose among the hundreds of products on the shelf, you are not alone.

Women are especially bombarded with advice on how to treat everything from premenstrual syndrome (PMS) to menopause. But beyond the basic multivitamin, how do you know which ones to choose and how much to take?

Evangeline Lausier, M.D., assistant clinical professor in medicine for the Duke Integrative Medicine Center in North Carolina, calls supplementation "one aspect of self-care" in a holistic health approach — "as long as the recommendations are evidence-based."

And when establishing any new supplement regimen, you should be sure to consult with your health care practitioner for counsel on the correct dosage and any potential drug-nutrient interactions.

Here are several supplements and dosages that Lausier suggests for healthy women throughout all stages of life:

1. Calcium. Before the age of 35, a woman needs sufficient calcium to form strong bones — after age 35, calcium slows bone loss that naturally occurs later in life. In fact, Lausier says, calcium's protective effect on bone mass is one of the few health claims permitted on supplement labels by the U.S. Food and Drug Administration (FDA). Furthermore, studies have shown calcium to help mitigate symptoms of PMS and possibly lower blood pressure.

Dosage: Premenopausal women should take 1,000 milligrams per day. Postmenopausal women should up their intake to 1,200 to 1,500 milligrams per day to maintain bone strength. Take the calcium in divided doses twice a day (half in the morning and half in the evening).

2. Vitamin D3. Vitamin D3 helps the body absorb the calcium we do take in. Further studies have shown that higher dosages of vitamin D3 may help prevent a variety of health concerns — from breast cancer and osteoporosis to type 1 diabetes, cardiovascular disease and multiple sclerosis (MS).

Dosage: For calcium absorption and healthy bones, premenopausal women should take at least 500 IU per day. Postmenopausal and elderly women should increase their dosage to 800 IU per day. To reduce risk of disease, women should take 1,000 IU a day. Women who live in northern climates are at higher risk due to reduced sunlight exposure. Fifteen to 20 minutes of direct sunlight twice a week on the arms and face provides adequate doses of vitamin D if the ultraviolet (UV) rays of sunlight are strong enough — such as those obtained closer to the equator.

3. Iron. Deficiencies of iron result in anemia, which "has profound effects on metabolism and energy enzymes," Lausier says. Premenopausal and pregnant women have the greatest need for iron and, therefore, may benefit from supplementation. In fact, iron requirements for pregnant women are almost double those of nonpregnant women due to a potential for blood loss while delivering and increased blood volume during gestation.

Dosage: Lausier advises premenopausal women to supplement with 18 to 20 milligrams  per day. Pregnant women can increase supplementation to 27 milligrams per day. Postmenopausal women are not typically iron-deficient and should only take supplements under a doctor's supervision. In fact, too much iron can be harmful to the liver.
 
4. Gamma-linolenic acid (GLA). GLA is an essential fatty acid that can help reduce inflammation. The simplest way to increase your GLA levels is to take evening primrose oil, borage or black currant seed oil.

Women with PMS have been found to have low levels of GLA in the body, so adding a GLA oil may help. GLA also may reduce irritable bowl syndrome-type symptoms that are associated with menses.

Dosage: Evening primrose oil, in particular, has been the focus of several research trials — with mixed results. However, many doctors, including Lausier, suggest giving it a try because of its low risk of side effects. Supplement with 270 to 500 milligrams of GLA or 3 to 6 grams of evening primrose oil per day.

5. Vitex. Dating back to ancient Rome, women have relied on Vitex agnus-castus , aka chaste tree berry or monk's pepper, for various health issues. Modern research supports its use for PMS symptoms, irregular periods and infertility.

Dosage: Vitex acts over the long term to balance the hormonal system. Therefore, women need to take 30 to 40 milligrams once a day for several months, according to Lausier, to feel any effect. Pregnant women should not take it.

6. Indole-3-carbinol (I3C). I3C is a substance that's present in cruciferous vegetables like broccoli, brussels sprouts and cauliflower. Eating more of these vegetables is associated with lowered risk of certain types of cancer.

Dosage: Small preliminary trials on humans suggest that I3C may reverse conditions related to human papillomavirus (HPV) infection, such as cervical cell abnormalities. One trial showed that taking 200 to 400 milligrams of I3C per day for 12 weeks reversed early-stage cervical cancer. Lausier recommends taking 200 to 400 milligrams per day.  Don't forget to eat your cruciferous vegetables. Cruciferous comes from the word "crux," or "to cross." These vegetables generally have four leaves that cross and include broccoli, cabbage, brussels's sprouts and cauliflower.

7. Folic acid. This B vitamin is critical in the production and maintenance of new cells, especially during periods of high cell division — like in pregnancy. Sufficient folic acid intake before conception and in the early months of gestation has been shown to protect against neural tube defects.

Other clinical trials are being done to determine folic acid's relationship to cardiovascular disease, a major health threat for women. Folic acid supplementation has been shown to decrease homocysteine levels in the blood. Elevated levels of homocysteine have been linked with heart disease and stroke.

Dosage: Lausier suggests women of childbearing age supplement with 800 micrograms (mcg) of folic acid per day, increasing to 1,000 to 2,000 micrograms per day before and during pregnancy. After menopause, women may supplement with 400 to 800 micrograms per day to reap the potential cardioprotective benefits of the vitamin. Don't forget to eat foliage (green stuff) that is packed full of folic acid.

Miriam Weidner