The sheer volume of available dietary supplements makes it difficult for the FDA to monitor all of these products. It is important to recognize these limitations and become an informed consumer. Products making unrealistic statements, claiming to be all-natural and therefore harmless, or claiming to contain “ancient” or “secret” ingredients should be viewed with extreme caution.
The DSHEA states that dietary supplements cannot be claimed to treat or cure disease and that doing so identifies the product as a drug. For example, manufacturers of coral calcium, a calcium supplement said to be derived from living coral reefs, claimed their product could be used to treat ailments ranging from cancer to lupus to multiple sclerosis. While the people making these statements have been contacted (and are prohibited by the Federal Trade Commission from claiming that coral calcium cures a range of diseases and/or is absorbed easier than other calcium supplements), dietary supplements violating this regulation continue to be available to consumers. Dietary supplement safety should be ascertained using multiple resources. While dietary supplement labels contain vital information for consumers, a lack of cautionary words on labels should not be considered a statement of absolute safety.
Even after a recall has been effected, there is a risk of consuming harmful substances in products still available for purchase. In addition, substances that belong to the same class as a recalled dietary supplement may cause similar effects. Bitter orange (Citrus aurantium), for example, mimics certain characteristics of ephedra. Now that ephedra-containing products have been removed from the U.S. market, bitter orange is commonly found in weight-loss dietary supplements.
In conclusion, each piece of information about dietary supplements should be considered another piece of data. Educated decisions based on information from a variety of sources allows consumers to place recent developments in the appropriate context. Information should be continually updated as new data become available.

Contacting individual manufacturers can be the most efficient way to find specific information. The following is a list of important questions that can be asked of dietary supplement manufacturers.
• How can you prove the effectiveness and safety of your product?
• Can you share information with me about the tests you use to determine safety and effectiveness?
• What quality control systems do you have in place?
• How closely do you adhere to the FDA’s current good manufacturing procedures?
• Can you provide educational materials that will help me to understand the evidence regarding your product?
• Have you received any reports of adverse events?

Consumers get information about dietary supplements from many sources, including friends, family members, and healthcare professionals. This information is often a mixture of scientific data, hearsay, and anecdote. Given the complexity of dietary supplements, however, only people with in-depth knowledge of science, medicine, and nutrition should be considered experts.
Registered dietitians, pharmacists, physicians, nurses, and physician assistants tend to be the most informed about the scientific evidence on dietary supplements. Registered dietitians are certified by the American Dietetic Association, and during the last several years, dietary supplements have become a major focus of their training and practice. In addition to answering specific questions about dietary supplements, a registered dietitian can determine individual nutrient needs based on age, sex, life stage (for instance, premenopausal versus postmenopausal women), and medical history. By analyzing the diet (including intake of fortified foods and dietary supplements), a registered dietitian can determine whether a person is consuming the recommended levels of nutrients or if any nutrients are lacking or being consumed in excess. Based on these results, a dietitian can recommend improvements to the diet and/or if dietary supplementation should be considered.
Pharmacists are trained to understand drug formulation and interactions. In addition to answering specific questions about dietary supplements, they can recognize potential interactions between dietary supplements and drugs. Pharmacists can also help identify those dietary supplements verified by the USP, ConsumerLab.com, or the NPA, as well as the recommended doses.
Physicians (MDs, DOs), nurses (RNs, NPs), and physician assistants are gradually becoming cognizant of the widespread use of dietary supplements. As a companion to the Physician’s Desk Reference, an immense and detailed catalogue of drug and prescribing information that can be found in virtually any doctor’s office or library, a new Physicians Desk Reference for Nonprescription Drugs, Dietary Supplements, and Herbs has been created. Physicians, nurses, and physician assistants can be useful resources regarding dietary supplements, including whether there is adequate evidence to support a benefit, no effect, or potential for harm.
People considering taking dietary supplements can benefit from consulting a knowledgeable expert. This is especially true for women who are breastfeeding or pregnant (or who may become pregnant); older individuals; people of smaller stature; people with chronic medical conditions such as cardiovascular disease, diabetes, or hypertension; and people with upcoming surgery. In addition, a pediatrician should be consulted when considering giving a dietary supplement to a child.

Despite their natural connotation, dietary supplements are biologically active substances. Evidence for their safety and efficacy should therefore be based on accepted principles of science.
What Is Good Science?
The Agency for Healthcare Research and Quality ranked scientific studies by the value of their results. Below they are ranked from most powerful to least powerful:
• prospective, randomized, double-blind, placebo- controlled clinical trial with crossover;
• prospective, randomized, double-blind clinical trial;
• single-blind clinical trial;
• open-label clinical trial;
• retrospective epidemiological study;
• other types of consumer or patient-based, interview-type studies (including meta-analyses).
Randomized, controlled trials are considered the gold standard of scientific research. Such trials include a control group, people who are observed but receive no treatment of any kind, and an intervention group, people who receive a certain treatment, such as a dietary supplement. Members of the control and intervention groups are similar (matched) in age, sex, ethnicity, marital status, socioeconomic status, health status, and diet and are randomly assigned to the respective groups. The power of such a trial is that it controls for any variation between the two groups, so that the only relevant difference is that the intervention group receives the specific treatment. Thus, any difference in the outcomes between the control and intervention groups is likely attributable to the intervention.
To determine whether the results of a study are due to the intervention or to chance, scientists conduct statistical analyses. A Pvalue (probability value) of 0.05 is generally used to indicate statistical significance. Pvalues greater than 0.05 indicate that the likelihood the results were a product of chance is greater than 5 percent. Conversely, the smaller the Pvalue, the more significant the results. Thus, a Pvalue lower than 0.001 indicates that it is very unlikely the results were due to chance; that is, the intervention had a highly significant effect on the treatment group.
In case-control studies, cases who have a particular outcome (for example, a disease) are identified and their past exposure to various components (such as a dietary supplement) is compared with that of control subjects, who do not have the particular outcome. By matching case and control subjects for sex, age, and other variables, there is less chance that the results are due to anything but the difference in exposure.
Cross-sectional studies measure the prevalence of a health outcome (for example, a disease) or determinants of health (such as ethnicity) in a population at any one time. For example, a cross-sectional study could measure the relationship between osteoporosis and calcium intake. This type of study is vulnerable to confounding, however, as a result of selection bias, which distorts statistical analysis by including a samplethat is not representative of the population of interest. In addition, cross-sectional studies are not good for determining cause and effect.
Cohort studies are long-term studies that compare subjects who have a particular outcome (for example, a disease) and/or who receive a particular intervention (such as a dietary supplement) with those who do not have that outcome or exposure. Cohort studies tend to be less reliable than randomized, controlled trials because there is less control over the differences between the two groups. For more accurate results, cohort studies may have to last for several years, which allows for additional differences between the groups to enter into the study and confound the results.
The validity of a scientific study should determine whether it is published in a prestigious scientific journal, such as the Journal of the American Medical Associationand the New England Journal of Medicine. Most scientific journals require that published material is reviewed by peers, other experts who can evaluate the strength of the evidence and identify shortcomings of studies. Published studies can be retrieved online at PubMed.
Many dietary supplement manufacturers promote their products through testimonials and anecdotes from satisfied customers. While persuasive, testimonials cannot replace scientific evidence and are often fabricated, paid for, or provided by people who are emotionally bound to a product. Testimonials should never be substituted for rigorous scientific data.

The Natural Standard is composed of a panel of experts, including medical doctors, pharmacists, and those working in the fields of medicine, nutrition, complementary and alternative therapies, and dietary supplements. The Natural Standard (http://www.naturalstandard.com) provides a clearinghouse of the vast research performed on various vitamin, mineral, herbal, botanical, and other dietary supplements. The group classifies dietary supplements and their specific uses based on extensive reviews of the scientific literature, and these reports are evaluated by experts and reviewed by their peers. The methods used are based on currently accepted and rigorous scientific standards.
Omega-3 fatty acids such as those found in fish oil are a popular dietary supplement with several purported effects. To evaluate the existing literature on omega-3 fatty acids, the Natural Standard reviewed 252 individual references, most of which were from peer-reviewed journals. Based on the quality (the types of studies available and how many are randomized, controlled trials) and quantity (the number of randomized, controlled trials available) of evidence, the Natural Standard determined that there was “strong scientific evidence” (level A) for the use of omega-3 fatty acids in lowering triglycerides, a component of blood cholesterol. In addition, the group determined that there was “good scientific evidence” (level B) for the use of omega-3 fatty acids (in the form of fish oil) for alleviation of morning stiffness and joint tenderness of rheumatoid arthritis.

Vitamins and minerals share the quality of being highly studied and classified dietary components, and herbal and botanical dietary supplements are all used as natural medicines. Other dietary supplements are alike in that they elude such organization. Essentially categorized by default, some of the dietary supplements in this group are components of plants (such as flavonoids), some are found in animal sources (such as fish oil), and others are already present in small quantities in our bodies (such as coenzyme Q10, glutathione, and L-carnitine). Most are available through eating foods, such as fruits, vegetables, grains, nuts, seeds, and animal protein sources.
The evidence of activity for these substances when isolated in a dietary supplement, however, is highly variable. Some of these dietary supplements have very little scientific evidence to support their use, while others have a strong scientific basis for their use. L-carnitine, for example, has been promoted for use in cardiovascular disease, neurological diseases, depressed immunity, and obesity, but its efficacy lacks sufficient high-quality evidence from mainstream scientific studies. In contrast, dietary supplements containing chondroitin sulfate, which can be found in shark, beef cartilage, or bovine trachea, have been the subject of numerous well-controlled studies and have been found to significantly improve osteoarthritis.
As more information becomes available regarding members of this group of dietary supplements, we may be able to better categorize them. For now, however, each dietary supplement in this broad category must be considered independently.

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• Spotting False Claims
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