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Phaseolamin is a natural product produced by kidney beans, Phaseolus vulgaris. This compound acts as an inhibitor towards human alpha amylase, a protein that degrades many carbohydrates in the human diet. Some studies have indicated that phaseolamin might be a useful tool for weight control remedies. It has not been definitively proven to have this effect, but is an ingredient in many weight loss dietary supplements.
Many plants make alpha amylase inhibitors, which are thought to protect the plants against insects. Phaseolus vulgaris makes three different types of these inhibitors. Phaseolamin was the first of the three to be isolated in the 1970s. It is a protein with sugars attached to it, known as a glycoprotein. This alpha amylase inhibitor is effective against animal alpha amylases, but not against the corresponding microbial or plant enzymes.
Alpha amylase plays an extremely important role in digestion. Carbohydrates compose a major portion of the diet of most humans. Starches, such as rice and pasta, are an important source of carbohydrates, and are made up of long chains of glucose. This enzyme breaks down the starch into smaller chains that are broken down to glucose and absorbed in the small intestine.
There are two types of alpha amylase. One is a component of the saliva. This salivary amylase, or ptyalin, acts as soon as people start chewing their food and has some partial activity after the food is swallowed. Most of the starch is degraded in the small intestine by a pancreatic enzyme. It is the latter alpha amylase that is inhibited by phaseolamin.
The use of alpha amylase inhibitors to lose weight fell out of favor in the early 1980s. There has been renewed interested in these plant secondary metabolites in the 21st century as interest has grown in low-carbohydrate diets. Some of this interest is due to advances in protein purification, since these compounds were originally discovered in the 1970s. Rather than the crude kidney bean preparations with low concentrations of phaseolamin, much more pure samples are now available.
There are several proposed mechanisms of action for phaseolamin. It is thought to reduce the rate of breakdown of starch in the digestive tract, thus reducing sugar uptake in the intestine. This effect is thought to cause a decrease in the release of insulin after a meal. Healthcare practitioners recommend not solely relying on supplements to lose weight, but also to incorporate increased exercise and changes in diet. As with all supplements, one should consult with a doctor before starting a new supplementary regime.