How Dietary Supplements Work

Wise Supplement Usage

Probably the most frequent questions regarding supplement usage are which supplements to use and which to avoid. The answer to the first question depends on your body and its unique needs, so always consult your physician before using any supplement. That being said, Consumer Reports and the Natural Medicines Comprehensive Database, an independent research group, compiled a list of some of the top supplements that research shows are likely safe and may be effective for certain conditions. These are:

  • Calcium
  • Cranberry
  • Fish oil
  • Glucosamine sulfate
  • Lactase
  • Lactobacillus
  • Psyllium
  • Pygeum
  • SAMe
  • St. John's wort
  • Vitamin D

The two groups also identified a dozen supplement ingredients to be avoided due to their links to serious side effects:

  • Aconite
  • Bitter orange
  • Chaparral
  • Colloidal silver
  • Coltsfoot
  • Comfrey
  • Country mallow
  • Germanium
  • Greater celadine
  • Kava
  • Lobelia
  • Yohimbe

For example, coltsfoot — thought to be effective for bronchitis and asthma — is linked to liver damage and cancer. Bitter orange, supposedly useful for weight loss, nasal congestion and allergies, may cause fainting, heart attack, stroke and even death [source: Consumer Reports].

While it's handy to have "good" and "bad" lists, don't rush off to the store and purchase all 11 of the "good" supplements listed above. Your body might not need them, for one. Also, some of the evidence as to whether these supplements "work" is conflicting. For instance, some studies say glucosamine sulfate helps relieve pain and improves joint function for people with arthritis. Other studies say it only relieves joint pain [source: Arthritis Foundation].

Finally, not all supplements are of the same quality. Become a savvy supplement shopper by following these practices [source: U.S. Food & Drug Administration]:

  • If you're looking online for supplement information, use noncommercial sites such as the National Institutes of Health (NIH), U.S. Food & Drug Administration (FDA) and the U.S. Department of Agriculture (USDA).
  • Be wary of any product that says "totally safe," "has no side effects" or "works better than [prescription drug name]."
  • Keep in mind no supplement should claim to be able to prevent, treat or cure a disease. It's against the law for companies to do that because the supplement then would be considered a drug and subject to those FDA regulations.
  • Remember that just because an ingredient is natural doesn't mean it's safe to consume.
  • Supplements, even quality ones, can negatively interact with prescription medication you're taking, so always talk to your physician about any supplements you want to take.
  • More is not necessarily better. If your doctor suggests you add vitamin D to your diet and you locate a reputable brand, take only the dosage recommended.
  • Don't take supplements in place of medication (or in addition to it) without checking with your doctor.
  • Vitamins are already added to certain foods (like milk or breakfast cereal). Adding a vitamin pill on top of this might be overkill and in some instances, actually dangerous for your health.

Be especially wary of any supplements promising to help you lose weight fast, build muscle or enhance your sexual prowess. Many of them contain very harmful ingredients, steroids or prescription drugs. In a famous case, a Chinese herb called ephedra was marketed for weight loss. Although it was a natural product, it contained a chemical called ephedrine that stimulated the nervous system and constricted blood vessels. It was linked to more than 15 deaths by 1996. However, the FDA did not ban it until 2004 after the death of a major league baseball player [sources: Couzin-Frankel].