Phaseolus vulgaris) that inhibit the alpha-amylase enzyme, supposedly preventing the breakdown of starch molecules. Undigested starch is said to be passed out in the feces.

Starch blockers are actually old products that were marketed extensively in the 1970s. They were taken off the market in 1983 because the U.S. Food and Drug Administration determined them to be drugs. In this now-classic case of Nutrilife vs. Schweiker, the FDA only had to show that the products were not foods (no taste, aroma or nutritional value) to win the case, since there were only two categories of products at that time—foods or drugs. The case would be harder to win today after the Dietary Supplement Health and Education Act of 1994, but the fact remains that weight-loss claims need to be supported by scientific evidence. The products have crept back on the market recently, but do they really work? Is there scientific evidence to support the product claims?

Here is an actual claim from a product found through an Internet search:
Other products make claims that they can neutralize up to 1,000 calories of carbohydrates in a meal. "Now you can eat spaghetti, pizza and bread without absorbing any of the calories!"

Sounds great, right? In theory, scientists have agreed that starch blockers could work, but there simply is no published research to date in support of their effectiveness in weight loss. In fact, several studies published in the 1980s showed that these products were ineffective in inhibiting starch digestion and absorption. Researchers suggest this is the case because either protein-digesting enzymes break down the bean extract before it can act on the alpha-amylase, or there is much more alpha-amylase secreted than necessary and the excess continues to work in spite of the bean extract. In addition, the FDA received numerous complaints from consumers who experienced nausea, vomiting, intestinal cramps and diarrhea with the original products marketed in the 1970s. High doses (2.9 g) of a concentrated extract were later shown to have fewer side effects, but there is no published evidence of its effect on weight loss.

There has been some recent research from the Mayo Clinic, however, showing that a large dose (4 g) of wheat amylase inhibitor delays carbohydrate absorption and mean plasma glucose concentration in diabetics. Another unpublished study from the same team supposedly noted that weight loss was a side effect of administering this extract. This may sound like promising work, but both the source of the extract (wheat) and dosage (4 g) differ significantly from anything available currently in the marketplace (usually 500 mg of bean extract).

Starch blockers are one of many products marketed with little or no research support for long-term safety and effectiveness. Suppliers of the bean extract note that researchers are now investigating the effectiveness of their products in weight loss. If the research is only in progress, then why are there so many products with unsupported claims? Until a manufacturer can show with peer-reviewed clinical trials that starch blockers work for weight loss, the products should be considered ineffective, possibly unsafe and not recommended.

The industry has come under fire for the quality, safety and effectiveness of many products. There are many safe and effective supplements, but the proliferation of miracle products such as starch blockers continue to challenge the credibility of the whole dietary supplements industry. The industry must develop an effective self-regulatory mechanism to separate the genuinely useful products from those that are mere hype. Otherwise, the Federal Trade Commission and FDA will continue to generate negative press for the industry as they remove ineffective or unsafe products. Dietary supplements consumers deserve quality products and the industry has an obligation to deliver them.

Mary C. Mulry, Ph.D., is a technical consultant for the natural products industry. Contact her in Boulder, Colo., at [email protected].

Natural Foods Merchandiser volume XXII/number 11/p. 8