So-called natural remedies for depression aren't a replacement for medical diagnosis and treatment. And natural doesn't always mean safe. However, for some people certain herbal and dietary supplements do seem to work well, but more studies are needed to determine which are most likely to help and what side effects they might cause.

Here are some supplements that are promoted by marketers as helping with depression:

• St. John's wort. This herbal supplement is not approved by the Food and Drug Administration (FDA) to treat depression in the U.S., but it's available. Although it may be helpful for mild or moderate depression, use it with caution. St. John's wort can interfere with many medications, including blood-thinning drugs, birth control pills, chemotherapy, HIV/AIDS medications and drugs to prevent organ rejection after a transplant. Also, avoid taking St. John's wort while taking antidepressants — the combination can cause serious side effects.
• SAMe. This dietary supplement is a synthetic form of a chemical that occurs naturally in the body. SAMe (pronounced sam-E) is short for S-adenosylmethionine (es-uh-den-o-sul-muh-THIE-o-neen). SAMe is not approved by the FDA to treat depression in the U.S., though it's available. More research is needed to determine if SAMe is helpful for depression. In higher doses, SAMe can cause nausea and constipation. Do not use SAMe if you're taking a prescription antidepressant — the combination may lead to serious side effects. SAMe may trigger mania in people with bipolar disorder.
• Omega-3 fatty acids. These fats are found in cold-water fish, flaxseed, flax oil, walnuts and some other foods. Omega-3 supplements are being studied as a possible treatment for depression and for depressive symptoms in people with bipolar disorder. While considered generally safe, the supplement can have a fishy taste, and in high doses, it may interact with other medications. Although eating foods with omega-3 fatty acids appears to have heart-healthy benefits, more research is needed to determine if it has an effect on preventing or improving depression.
• Saffron. Saffron extract may improve symptoms of depression, but more study is needed. High doses can cause significant side effects.
• 5-HTP. The supplement called 5-hydroxytryptophan (hi-drok-see-TRIP-to-fan), also known as 5-HTP, may play a role in improving serotonin levels, a chemical that affects mood. But evidence is only preliminary and more research is needed. There is a safety concern that using 5-HTP may cause a severe neurological condition, but the link is not clear. Another safety concern is that 5-HTP could increase the risk of serotonin syndrome — a serious side effect — if taken with certain prescription antidepressants.
• DHEA. Dehydroepiandrosterone (dee-hi-droe-ep-e-an-DROS-tur-own), also called DHEA, is a hormone that your body makes. Changes in levels of DHEA have been linked to depression. Several preliminary studies show improvement in depression symptoms when taking DHEA as a dietary supplement, but more research is needed. Although it's usually well-tolerated, DHEA has potentially serious side effects, especially if used in high doses or long term. DHEA made from soy or wild yam is not effective.

Nutritional and dietary supplements are not monitored by the FDA the same way that medications are. You can't always be certain of what you're getting and whether it's safe. It's best to do some research before starting any dietary supplement. Make sure you're buying your supplements from a reputable company, and find out exactly what they contain.

Also, because some herbal and dietary supplements can interfere with prescription medications or cause dangerous interactions, talk to your health care provider before taking any supplements.