Other Dietary Supplements

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 (Table 4.5) 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.