Are white kidney beans, which are known as "carbohydrate blockers" and "you can eat as much as you want without getting fat," really effective?

Weight loss is the most attractive topic in the field of food health. Various "weight loss magic tools" emerge in an endless stream, making people dazzled. Among them, "white kidney bean extract" is a very popular one.

Take two capsules of white kidney bean extract before meals, and you won’t get fat even if you eat a lot? | Amazon

What exactly is white kidney bean extract? Is the claim that “you won’t get fat if you eat it” just a marketing gimmick or is it true?

Too long to read

"White kidney bean extract" is a special glycoprotein that inhibits the activity of amylase and achieves a weight loss effect by inhibiting the body's absorption of starch.

It is unknown how active the white kidney bean extract added by merchants is actually.

White kidney bean extract only has the effect of inhibiting carbohydrates. Moreover, if you blindly rely on such products to lose weight, reducing the necessary carbohydrate intake will be harmful to your health.

From healthy food to "carb blocker"

The biological name of white kidney bean is "Phaseolus vulgaris L.". When grown as a vegetable, it is called green bean. It belongs to the genus Phaseolus in the subfamily Fabaceae, one of the three major subfamilies of the Leguminosae family.

The green beans we often eat are another variety of Phaseolus vulgaris | H. Zell / Wikimedia Commons

Its ancestors grew in tropical and subtropical regions of Mexico and Argentina. Later, after improvement and domestication, white kidney beans adapted to the cool and humid plateau areas and evolved into a variety of flower colors.

Variety of colors | References [1]

White kidney beans were not introduced to China until the end of the 16th century. In the hands of the Chinese people who are good at farming, white kidney beans have spread rapidly and are now grown all over the country.

The main nutritional characteristics of white kidney beans are similar to those of mung beans and peas - high protein content (generally more than 20%), very low fat content, and rich in starch, dietary fiber and minerals. As a "miscellaneous bean", it has good nutritional value overall and can be an important part of a "healthy diet".

Seeds are also rich in color | Rivera, Ana, et al. / Frontiers in Plant Science (2018)

Of course, this is not the only reason why white kidney beans are so highly regarded.

There are some special glycoproteins in the protein of white kidney beans that can inhibit the activity of α-amylase, which are called "α-amylase inhibitors". Amylase digests starch, converts starch into glucose to be absorbed, and finally generates heat. If the activity of amylase is inhibited, starch cannot be digested and absorbed, and no heat will be generated. Therefore, these α-amylase inhibitors in kidney bean protein are also called "starch blockers".

Ripe white kidney beans | Rasbak / WIkimedia Commons

However, white kidney beans need to be cooked for a long time before they can be eaten. α-amylase inhibitors are not heat-resistant and lose their activity during cooking. Therefore, eating white kidney beans cannot play a role in "blocking starch".

Therefore, it seems reasonable to extract it and take it as a "weight loss health product". This is the "white kidney bean extract" popular in the market.

The actual effect is not pleasing to the eye

It is theoretically reasonable that white kidney bean extract can help with weight loss. So the question is: how much should you take to achieve weight loss? And how effective is it?

There are actually quite a few such studies. In early studies, the "weight loss effect" was vague and sometimes effective. In recent years, after the industry and the scientific community have worked tirelessly to improve extraction technology and weight loss experimental design, many studies have demonstrated the "weight loss effect" of white kidney beans.

White Kidney Bean Extract | Underherb

However, many factors will affect the final weight loss effect. For example, different experiments use white kidney bean extracts from different manufacturers, which will contain different "amylase inhibitory activity". In addition, the subjects, dosage and duration of the weight loss experiment will also make the experimental results different.

In general, these studies were conducted on obese and overweight people rather than the general population. The white kidney bean extracts used in these studies generally had an "amylase inhibitory activity" of 3,000 IU/g (IU is the pharmacological unit of measurement for biologically active substances); participants took daily doses ranging from 445 mg to 3,000 mg for as short as four weeks to as long as 84 days.

In the end, the participants lost 1.8 to 3.5 kg of weight. From a statistical point of view, this result is "effective", but it is far less pleasing than the "no worries of gaining weight" claimed by the merchants - if you eat a lot, the weight loss can be easily offset; what's more, when many people eat a lot, in addition to carbohydrates, they also consume a lot of fat, and white kidney bean extract only works on carbohydrates.

In addition to carbon water, the fat content in hot pot and barbecue should not be underestimated | yukuaikuai / pixabay

The activity of the product is unknown

It is also important to know that the production of "extracts" from white kidney beans is a relatively complex industrial process, and the "amylase inhibition activity" of the extracts may vary greatly from one manufacturer to another. Many products on the market do not even have quality control standards, and consumers do not even know how high the "nominal" activity is, let alone how high the "actual activity" is.

Secondly, many foods that add "white kidney bean extract" only claim that "it's added", but as to how much is added, how active it is, and whether it will lose its activity during further processing, it's all unclear.

α-Amylase inhibitors also lose a significant amount of activity in laboratory simulated gastric environments | References [2]

In addition, white kidney bean extract can only act on starchy carbohydrates, while the key to weight loss is to reduce the intake of excessive fat, sugar, protein, etc. If there are not many carbohydrates in the food, then "inhibiting starch digestion" is not very meaningful. Moreover, glucose is an essential energy source for the human body. If you don't eat much carbohydrates to lose weight, and then use white kidney bean extract to inhibit it, it is equivalent to not eating much, which is very unhealthy.

In short, white kidney bean extract is helpful for people who eat too much staple food, but the merchants' advocacy of "take two packets before meals, eat as much as you want without worrying about getting fat" is completely a scam.

Eat right to stay on track for weight loss | sontung57 / pixabay

Proper weight loss requires a reasonable diet, and carbohydrates, fats, proteins, vitamins and other nutrients needed by the human body are indispensable. Of course, the most important thing is to combine it with exercise, not blindly rely on various weight loss products, and integrate healthy eating and exercise habits into your life.

References

[1]Bengtsson, Elin. "Analysis of Swedish accessions of Phaseolus vulgaris L. using SSR Markers." (2009).

[2] Rang Yifeng, Zhao Wei, Yang Ruijin, Wu Li, Meng Danyang. Study on the activity changes of white kidney bean α-amylase inhibitor during processing and digestion[J]. Food Industry Science and Technology, 2015, 36(17): 53-57. DOI: 10.13386/j.issn1002-0306.2015.17.002.

Author: Yun Wuxin

Editor: Jian Er, Mai Mai

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