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What are Carb Blockers and Do They Work?


Carb blockers are more than just a fad. There is solid research to back up their role in weight loss and blood sugar control.


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In this article, we’ll look at some of the research on carb blockers in addition to how they work, key ingredients, scientific findings, safety measures, and who should be extra cautious before using them.

What are Carb Blockers?

Carb blockers, also known as starch blockers, are a type of dietary supplement designed to inhibit the body’s ability to digest carbohydrates, hence their name.

They have gained popularity in recent years due to their potential benefits in weight loss and type 2 diabetes management. Derived mainly from food sources, carb blockers consist of compounds that interact with enzymes involved in the breakdown of carbs.

While their primary use is to block carbohydrate digestion and absorption, they may also offer other health benefits that we will explore in this article.

How Do Carb Blockers Work?

Carb blocker supplements work by inhibiting the digestion and absorption of carbohydrates in the body. But to truly understand how they work, it’s crucial to understand the types of carbohydrates they typically affect.

Carbohydrates can be broadly categorized into simple and complex carbs. Simple carbohydrates include sugars like fructose and glucose, while complex carbohydrates include starches and dietary fiber. Starch is made up of larger molecules that need to be broken down into simple sugars before they can be absorbed into the bloodstream.

This is where carb blockers come in. They primarily affect the digestion of starch. These supplements contain compounds that bind to the enzymes responsible for breaking down complex carbs, specifically alpha-amylase and alpha-glucosidase. By inhibiting these enzymes, carb blockers prevent the complete breakdown of complex carbohydrates into simple sugars. As a result, a portion of these carbs passes through the gastrointestinal tract undigested and does not contribute to blood sugar or caloric intake.

This mechanism can be beneficial for weight loss, as it reduces the total caloric intake. Furthermore, by preventing sudden increases in blood sugar levels after meals, carb blockers can help improve blood sugar control – a crucial benefit for people with diabetes.

Key Ingredients in Carb Blockers

White kidney beans, scientifically known as Phaseolus vulgaris, serve as the main ingredient in most carb blocker supplements. These beans contain a compound called phaseolamin, which is a natural blocker of the enzyme alpha-amylase. This means it stops the enzyme from turning complex carbs into simple sugars.

The white kidney bean extract is appealing because it’s one of the most researched sources of carb blockers. This natural source of alpha-amylase inhibitor has been studied relatively extensively for its potential benefits in weight loss and glycemic control.

While carb blockers often include other natural ingredients like green tea extract or chromium to enhance the blocking effect, the extract from white kidney beans is still the most common due to its known ability to block carbs.

Research on the Efficacy of Carb Blockers

There have been a number of studies on carb blocker benefits. As we mentioned above, most of them have done on the white bean but a few have also tested other types of carb blockers.

Scientific Studies on the Effectiveness of Carb Blockers

Below are some of the most significant studies on the effectiveness of carb blockers.

Research using proteins from black beans created particles that significantly slowed down three enzymes tied to blood sugar control. The findings suggest that these black bean proteins might help manage diabetes and are effective at blocking the digestion of carbohydrates (*).

In a study involving 13 volunteers, researchers found that a potent amylase inhibitor enhanced the malabsorption of wheat starch. Participants consuming spaghetti with the inhibitor experienced a more than 2-fold increase in undigested carbohydrate compared to those eating spaghetti alone (*).

A study with 60 slightly overweight volunteers showed significant weight loss benefits from a dietary supplement containing white kidney bean extract. Participants taking the supplement for 30 days, along with a carbohydrate-rich diet, saw considerable decreases in body weight, BMI, fat mass, and body measurements, while maintaining their lean body mass, compared to those on a placebo (*).


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Another study conducted on 27 obese adults showed a positive trend towards weight loss and decreased triglyceride levels in participants using Phase 2, an extract from the white kidney bean. Over eight weeks, those taking Phase 2 lost an average of 3.79 lbs and experienced a significant reduction in triglycerides compared to the placebo group (*).

Finally, a study conducted over 12 weeks, involving 60 slightly overweight but otherwise healthy individuals, explored the impacts of Beanblock®. This supplement, a standardized extract of the white kidney bean, showed promising results consistent with other similar studies. Participants who took Beanblock® not only experienced significant weight loss, with averages dropping from 82.8 kg to 78.8 kg, but they also had reduced waist sizes.

Additionally, the Beanblock® group reported lowered oxidative stress levels, an increase in feelings of fullness (satiety), and better appetite control. These positive outcomes were significantly more pronounced than in the control group, emphasizing Beanblock®’s effectiveness in weight management, particularly when used alongside a healthy lifestyle (*).

Findings on Weight Loss and Reduction of Carbohydrate Absorption

The reviewed scientific studies provide evidence on the effectiveness of carb blockers, especially Phaseolus vulgaris extracts, for both weight loss and reducing carbohydrate absorption.

A common finding was significant weight loss in subjects who consumed carb blockers compared to those who didn’t. One study noted an average weight loss of nearly 4 pounds over eight weeks, while another found an average drop of around 4 kg over a 12-week period. Both studies noted a significant reduction in waist circumference.

These studies also demonstrate carb blockers’ impact on carbohydrate absorption. By inhibiting the alpha-amylase enzyme, carb blockers disrupt the digestion of complex carbohydrates, resulting in fewer carbohydrate calories being absorbed by the body.

In addition to weight loss, certain studies found other benefits, such as reduced oxidative stress, increased satiety, and improved appetite control. Together, these findings highlight the potential role of carb blockers in weight management and in the regulation of carbohydrate digestion.

Are Carb Blockers Safe?

Carb blockers are generally considered safe in healthy adults. However, this is only true if you use carb blocker supplements from a reputable brand and follow usage instructions. Opt for third-party tested products and take a look at what past customers have to say about whichever carb blockers you choose.

Carb Blockers Side Effects

Carb blockers are generally well-tolerated, with rare reports of side effects. The studies we’ve reviewed all confirmed Impairment of starch absorption by a potent amylase inhibitor no significant side effects of carb blockers even with regular consumption (*, *).

However, it’s worth noting that because carb blockers alter the natural process of carbohydrate digestion, they might result in some minor digestive discomfort for some people. This is primarily due to more starch passing undigested into the large intestine.

In the large intestine, this undigested starch undergoes fermentation by gut bacteria, a natural process that can sometimes cause minor side effects. These may include gas, bloating, and changes in bowel movements. But these side effects are typically short-lived and decrease over time as the body adjusts to the carb blocker.

Remember, everyone’s body is different, and thus the way each person may experience and react to carb blockers can differ. Some people may not experience any side effects at all, while others might notice slight digestive changes. You should always consult with a healthcare professional before starting any new dietary supplement.

Precautions and Contraindications

While carb blockers are generally safe for most people, certain individuals should take extra caution before adding these supplements into their routine.

  • People with digestive issues: As mentioned earlier, carb blockers can interfere with the normal process of digestion. For those already dealing with digestive disorders, like Irritable Bowel Syndrome (IBS) or Crohn’s disease, the addition of carb blockers might worsen symptoms like gas and bloating.
  • Individuals with diabetes: Carb blockers can affect blood sugar levels by slowing down the digestion of complex carbohydrates. While this can be beneficial for blood sugar control, it may also require an adjustment of diabetes medications to prevent hypoglycemia (low blood sugar).
  • People with allergies: Most carb blockers are sourced from white kidney beans. Therefore, individuals who are allergic to this type of bean should avoid these particular carb blockers.
  • Pregnant or nursing women: We couldn’t find any research on the effects of carb blockers on pregnant or nursing women. As a precaution, these individuals should avoid carb blockers unless recommended by a healthcare provider.

Potential Interactions with Other Medications

So far, no direct interactions between carb blockers and other medications have been recorded. However, people on diabetes medication should be cautious as carb blockers can enhance the action of their medications.


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The Bottom Line

Carb blockers have shown promise in weight management and glycemic control by reducing carbohydrate absorption. However, they’re not suitable for everyone and aren’t a standalone solution. To get the most out of carb blockers, use them alongside a healthy balanced diet and regular physical exercise. Additionally, speak to a qualified healthcare professional before incorporating any carb blockers into your routine.

7 References

Luis M et al. Optimization of enzymatic production of anti-diabetic peptides from black bean (Phaseolus vulgaris L.) proteins, their characterization and biological potential. February 2016

Brugge W et al. Impairment of starch absorption by a potent amylase inhibitor. August 1987

Leonardo C et al. A Dietary supplement containing standardized Phaseolus vulgaris extract influences body composition of overweight men and women. 24 January 2007

Jay U et al. Blocking carbohydrate absorption and weight loss: a clinical trial using Phase 2 brand proprietary fractionated white bean extract. March 2004

Luzzi R et al. Beanblock® (standardized dry extract of Phaseolus vulgaris) in mildly overweight subjects: a pilot study. October 2014

Luzzi R et al. Beanblock® (standardized dry extract of Phaseolus vulgaris) in mildly overweight subjects: a pilot study. October 2014

Jay U et al. Blocking carbohydrate absorption and weight loss: a clinical trial using Phase 2 brand proprietary fractionated white bean extract. March 2004


4 thoughts on “What are Carb Blockers and Do They Work?

  1. What use would they have for “cheat” days? Or days where you didn’t have control over your food (like a conference or catered business meeting)? Would be curious to know.

  2. Could carb blockers be used in conjunction with a ketogenic/low carb diet? Ive been on low carb/keto for years, ive lost 50lbs and I’m very happy with my weight, but id love to get rid of that last stubborn 7-8lbs (im a student who is constantly stressed and lacks time for consistent exercise which i know would easily melt away those last few pounds), im wondering if adding a starch blocker to my keto diet would maybe accelerate the weight loss, even by a tiny bit? What do people think of the possible benefits of using starch neutralizers in conjunction with keto?

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