תזונה ותוספים Herbal and Dietary Supplements for Weight Loss

[Mike Bikov]

Topics in Clinical Nutrition, Volume 25(2), April/June 2010, p 136–150

Herbal and Dietary Supplements for Weight Loss
Alraei, Raghda Ghussen MS, RD, CDN

Abstract
Overweight and obesity are growing health problems in the United States, with approximately one-third of adults being obese and more than one-third are overweight. Many overweight individuals turn to dietary and herbal supplements for weight loss, and millions of dollars are spent on these products. However, there are concerns about the safety and efficacy of many supplements. Supplements are believed to help weight loss by several mechanisms of action, including increasing energy expenditure, increasing satiety, increasing fat oxidation, blocking dietary fat absorption, modulating carbohydrate metabolism, increasing fat excretion, increasing water elimination, and enhancing mood. This topic is changing rapidly, and this review gives a perspective of the current state of the evidence on selected dietary and herbal supplements and combination products. Many supplements have not been studied in randomized controlled trials and require more research to determine efficacy. Nutrition and healthcare professionals need to discuss use of dietary supplements with patients and report any adverse events to the Food and Drug Administration. Additional regulations on production, sales, and marketing of these supplements would be needed.


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OVERWEIGHT and obesity are growing health problems in the United States, with approximately one-third of adults being considered obese and more than one-third overweight.1 Standard treatment of obesity includes reducing energy intake and increasing energy expenditure through exercise. However, adherence to lifestyle changes and exercise programs are generally poor.2 For this reason, many overweight individuals turn to dietary and herbal supplements for weight loss.2 Since 1994, with the passing of the Dietary Supplements Health Education Act, which enables manufacturers to market dietary and herbal products without proof of efficacy and safety, as required for prescription drugs, sales of supplements have increased.3,4 With the availability of dietary supplements on the market, Americans are spending millions of dollars for weight loss supplements. In 2002, for example, it was estimated that $2 billion were spent on weight loss products.5 In a 2007 study, it was estimated that 15.2% of American adults (20.6% women and 9.7% men) had used dietary supplements for weight loss.6 Many supplements are labeled as “natural,” which gives the consumers the impression that they are safe.7 However, there is concern about the safety and efficacy of many dietary and herbal supplements because they contain active ingredients, which may interact with prescription drugs, and can cause adverse effects. Evidence about the efficacy of many of the supplements is inconclusive.7 There are more than 50 individual dietary supplements and 125 combinations products listed in the Natural Medicine Comprehensive Database as being used for weight loss. However, many of the supplements have not been tested for efficacy and safety or studied in randomized controlled trials (RCTs).8

Claims on dietary and herbal supplements attribute weight loss to several mechanisms including the following 8,9:

* Increase of energy expenditure: ephedra, caffeine, guarana, bitter orange, yerba maté
* Increase in satiety: soluble fibers such as guar gum, glucomannan, psyllium
* Increase of fat oxidation: hydroxycitric acid (HCA), green tea, conjugated linoleic acid (CLA), fish oil, capsaicin, carnitine
* Blocking of dietary fat absorption: chitosan
* Modulation of carbohydrate metabolism: chromium
* Increase of fat excretion: calcium
* Increased water elimination: dandelion, cascara
* Enhancement of mood: St. John's wort
This article examines some of the commonly used dietary and herbal supplements and reviews the available evidence from RCTs, systematic reviews, and meta-analyses regarding their efficacy, safety, and drug interactions. Some data are also obtained from the Natural Medicine Comprehensive Database, which was established in 1999, and is recognized as a valuable resource for evidence-based information on the topic of herbs, dietary supplements, and drugs. Information about ingredients in supplements is organized in monographs that list their use, safety, effectiveness, action, adverse reactions, and interactions with medications, other herbs, and dosage.10​

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