A few years ago, carb was considered a four-letter word. Today, diet gurus have eased up on their carb bashing and are actually encouraging us to eat the right carbs … in moderation, of course. But if only there were a way to have your cake and eat it, too—without all the guilt of excess carb consumption. Well, there may be, to a point.

First of all, you do need some carbohydrates in your diet, since they’re the preferred source of energy for your muscles and brain. Vegetables, fruits, whole grains, and beans are healthy sources of complex carbohydrates. If these types of foods were our only source of carbs, we probably wouldn’t have the obesity problem we do today. Unfortunately, most of us like to eat products made with refined sugar and flour that are loaded with empty calories, and it’s easy to overindulge in these types of carbohydrates. This can be especially dangerous if you have diabetes or glucose intolerance. Even if you’re trying to adhere to a traditional low-carb diet, there are times when you might slip up and have some bread with dinner. Could a “carb blocker” erase the consequences of your actions?

That’s Using the Ol’ Bean
Most carb blockers contain the extract of a bean pod. This is sometimes also called phaseolamin, starch blocker, or amylase inhibitor. There’s some good evidence that bean pod extracts can block the action of a digestive enzyme—alpha-amylase—that’s needed to initiate the process of breaking down carbohydrates into glucose. These bean pod extracts are generally considered safe, although gastrointestinal upset is a possibility.

Phaseolin EX, the main ingredient in Carb Block, is a purified extract of white kidney bean. According to its manufacturer, Universal Nutrition, Carb Block can prevent absorption of up to 38 grams of carbohydrates per meal. BSN’s Cheaters Relief includes in its mix Phaseo-lean, which is also white kidney bean extract.

Potential Benefits
A string of studies conducted in the late 80s suggested there may be potential for these more purified bean extracts. A 1986 study published in Volume 61 of Mayo Clinic Proceedings found that when subjects were given a partially purified amylase inhibitor with a starchy food, they showed a significant decrease in glucose and insulin levels compared with those who did not receive the amylase inhibitor. This means they digested and absorbed much less carbohydrate. Researchers concluded the amylase inhibitor might even be beneficial for people who have diabetes or impaired glucose tolerance.

In a 2007 study published in Volume 4 of International Journal of Medical Sciences, researchers found that taking 445 milligrams of Phaseolus vulgaris—an extract of a common white bean—helped overweight individuals lose roughly six more pounds over a month’s time than those who were only following a diet. Those taking the extract also lost more fat, while maintaining their lean body mass. Phaseolus vulgaris can be found under the brand name Phase 2 in TrimSpa’s Carb Blocker. In a previous study using 1,500 milligrams of Phase 2 twice a day, subjects lost weight—although not as much as in the 2007 study—but they also experienced a drop in triglyceride levels.

Additional ingredients commonly found in these products include some known to support carbohydrate metabolism, such as chromium and vanadium, and fenugreek, which has been shown to slow glucose absorption while also stimulating the release of insulin.

Although nothing can replace a healthy diet and exercise for weight management and good glucose control, these supplements may provide some benefits. They also appear to be a safer alternative to other more stimulating weight-loss products.