How Dietary Supplements Work

Perhaps the biggest potential danger regarding supplements — and the most important thing consumers need to realize — is that the industry today is only loosely regulated. It wasn't always this way. Before 1990, dietary supplements were tightly controlled by the Food and Drug Administration (FDA). Too tightly controlled, some say, nearly causing the industry to collapse. Part of the tight control meant "dietary supplements" referred to only a few essential nutrients, including vitamins, minerals and proteins, and after 1990, also herbs. But in 1994, there was a huge change [source: FindLaw].

That year, Congress passed the Dietary Supplement Health and Education Act (DSHEA), which expanded the definition of "dietary supplement" to include amino acids (e.g., lysine, tryptophan), and metabolites and extracts (e.g., bilberry extract, chamomile tea), among other substances. It also defined dietary supplements as food, not as drugs or food additives (like spices). These changes meant supplements suddenly had much less federal oversight or regulation, and the industry boomed [sources: FindLaw, Scarbrough, Institute of Food Technologists].

In exchange for the looser regulation, makers of dietary supplements could not claim their products cured any diseases (because that would make them drugs regulated by the FDA). They also had to include all ingredients on a product's label, and identify that the product was a "dietary supplement." Although a label could make a claim about the supplement's positive effect on the body, it also had to say, "This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease." It was up to the manufacturer to ensure that its product was safe, although the secretary of Human and Health Services could declare that a supplement or an ingredient in a supplement was hazardous to health [source: FindLaw].

The FDA has established good manufacturing practices for supplement producers to help ensure you're getting what's advertised — that your capsules don't contain too much or too little of an ingredient, for example, or a contaminated product. And the FDA occasionally will inspect a supplement manufacturing facility. But the FDA does not have to approve a supplement before it can be brought to market [source: National Institutes of Health].

To help ensure supplements are safe, several independent organizations offer quality testing. If a manufacturer submits a supplement to the testing and passes, the product is allowed to carry a seal of approval that guarantees it was properly manufactured, contains the ingredients on its label and doesn't have harmful levels of contaminants. Some of the more notable testing organizations are ConsumerLab.com, NSF International and U.S. Pharmacopeia. A few of the hundreds of supplements that earned quality seals are supplements produced by Kirkland (Costco), NatureMade and Nutrilite (Amway) [sources: National Institutes of Health, Quality Supplements, NSF].

However, even a quality seal doesn't mean any given supplement will work for you, or that it's safe for your body. And that is one of the ongoing debates.

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:

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

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]:

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].

Foodies, rejoice: Experts say it's best to get your vitamins and minerals from fresh, tasty food rather than supplements. The problem is, people (especially Americans) aren't eating all that much fresh food, instead favoring processed foods, refined grains and added sugars, all of which have little nutritional value. If you're elderly, the problem is compounded because aged bodies can't absorb nutrients as easily as young ones can. Plus, seniors often eat less food overall due to dampened appetites. In the end, many people simply are unable to get the nutrients they need from the food they eat.

Dietary supplements can help fill gaps in your diet if you don't eat a lot of nutritious food. But before you head to the supplement aisle, experts recommend first trying to eat healthier. That's because, it's not just the specific supplement you're missing — it's also how you're receiving it that matters.

Food contains many valuable nutrients as well as phytochemicals. Phytochemicals are plant chemicals that have properties that protect you from disease. The phytochemical allicin, for example, is found naturally in garlic and helps fight bacteria, while isoflavones in soy and could lessen menopausal symptoms in some women. Phytochemicals may also enhance bioavailability, which is the amount of the vitamin or mineral that your body is able to absorb. But phytochemicals are not included in supplements [sources: Berkeley Wellness, Phytochemicals].

Furthermore, food contains nutrients that help each other out. Down a frosty glass of milk and you'll be gifted not just vitamin D and various nutrients and phytochemicals, but also lactose, which helps your body absorb calcium and magnesium. If you simply took a supplement, all you'd get is the vitamin D. Also, if you take too much vitamin D (or any other supplement), it might affect your body's ability to properly absorb various nutrients.

Finally, while the nutrients in supplements and food may be chemically identical, that doesn't necessarily mean they will act the same way in your body. A study by researchers at the University of Pennsylvania School of Medicine showed the valuable Omega-3s in fatty fish were better able to maintain proper blood pressure in mice than the Omega-3 in fish oil supplements. In the study, the scientists observed how one of the fish fatty acids, docosahexaenoic acid (DHA), lowered blood pressure by dilating blood vessels at ion channels. But the DHA ethyl ester, which most fish oil supplements contain, did not dilate the blood vessels at these sites. Even worse, the DHA ethyl ester appeared to fight with the natural DHA [source: Science Daily].

So eat more fresh foods. Take only supplements recommended by your doctor and pass on the rest. And stay on top of the news for latest updates on the topic.