A recent e-mail asked me this:
I just read your Green Coffee Bean Extract and Raspberry Ketones: Myth and Reality article. I was wondering what your views/thought on white kidney bean extract to block carbs and starch?
White kidney beans as a supplement are something I’ve never looked at closely before, so I was curious to see what I would find out.
My initial response after looking around was “Oh, dear. Another supplement sweeping through the citizenry thanks to the invisible hand of Dr. Oz.” But after a closer look I became more accepting of the stated physiological function of kidney bean extract, but remain boorish on their ability to mediate the effects of insulin resistance and blood glucose levels
The Condensed Truth
In my opinion the abbreviated story about white kidney bean extract goes something like this:
- They’re probably effective at blocking alpha amylase, an enzyme that cleaves long carbohydrates into shorter ones.
- They work on starch, but not sugar or high fructose corn syrup. So they might help slowing the carb load from a pasta dinner but not your bottle of coke or sweets.
- You’ll probably have to take somewhere between 500 to 3000mg to experience a difference
- They’re safe and have no observable side effects
- They work better with people who have high carb diets than low-carb diets
- It’s not clear if they help with weight loss or controlling blood sugar levels
- I would tentatively recommend taking a supplement like this under the right circumstances.
Let’s take a closer look at how this supplement works, where its usefulness begins and ends, and other options you have to get similar effects in your body.
White Kidney Bean Extract Inhibits A Particular Enzyme
All of white kidney bean’s physiological activity boils down to its ability to block an enzyme called alpha-amylase from breaking down certain carbohydrates within your body. Starches are long chains of sugars that your body breaks down into smaller ones so it can use its individual units of sugar for energy. To accomlish this task it uses the enzymes amylase and alpha-glucosidase to accomplish this task. Amylase is present in your saliva, but most of its work is done in the intestine after its been secreted by your pancreas after a meal.
The theory goes that since white kidney bean blocks amylase, carbs that would otherwise be digested rapidly are digested slowly or not-at-all. It sort of creates the effect of eating fiber since it turns digestable carbs into non-digestable carbs.
After reading through various papers I’ve decided that this process happens as advertised. White kidney bean extract really does stop alpha-amylase from the pancreas and seems to do so in a manner that’s pretty robust to various physiological conditions.
What’s less clear is how this one mechanism relates to the broader goals of blood sugar control, weight loss, and low-carb dieting more generally…..especially in the long run.
The Trouble in Paradise
So let’s accept that white kidney bean extract really does what it’s purported to do. This by itself is a victory of sorts, since many specific-use supplements take the Bon Jovi approach to health claims:
However, your thinking about the benefits of white kidney bean extract need to come with the following caveats:
- It does not work on sucrase, the enzyme that breaks down sugar. Sugar is probably the larger problem when it comes to carbohydrate induced obesity
- It stops alpha-amylase secreted from the pancreas, but not beta-amylase, which is secreted by some forms of bacteria that live in your gut
- Other enzymes can do the same work as amylase, just not as effectively. For example, maltase can also break down starch in your intestine, which is why kidney bean extract doesn’t work as well with people who already have a low carb lifestyle.
- The evidence becomes much more spotty when you look at how using kidney bean extract helps to combat broader health issues like weight loss and insulin resistance.
How To Use It and Possible Side Effects
Kidney bean extract works in a linear fashion, so the more of it you use the greater effect it has. There doesn’t seem to be a saturation point at which it stops working. There also doesn’t seem to be any reasonable dosages where it becomes dangerous. So in my opinion it’s fine to take up to 2 or 3,000 mg per day if you know you’ll be digesting a lot of starch.
There’s no hard and fast rule about the best way to take it, but most studies measure the amylase blocking effect of kidney bean extract for four hours, and it seems to take its effect on the body within a half hour or so. (Again, these are broad statements not meant to be taken as gospel).
Under most circumstances I reckon either taking it with a meal or 20-30 minutes before is a good idea. If you take it at the beginning of the day there’s a chance it might lose its effect by lunchtime.
If you’re looking to reduce the impact of carbs through supplementation and diet here are some important facts to keep in mind:
- The best way to lower your carb load is to eat less carbs. No more sugar.
- L-Arabinose blocks sucrase as effectively as kidney bean extract blocks amylase. Maybe more. The two of them together might have a synergistic effect that’s pretty darn effective at reducing blood glucose after meals
- Foods with a high phenolic content also block carb digesting enzymes. Cocoa, green and black tea, berries, and reservatrol suppress a variety of digestive enzymes that allow them to have a similar effect as L-Arabinose and kidney bean extract. They have the added benefit of acting on a wider variety of enzymes, making them a little more robust than either of these two supplements alone.
Thinking out loud, the ideal carb blocking supplement would look something like this:
- 1000mg kidney bean extract powder
- 1000mg L-arabinose powder
- 500mg habiscus powder
- 500mg green tea powder (standardized to 50% catechins)
- 500mg cocoa bean powder(standardized to 50% polyphenols)
- 250mg reservatrol
- 250mg black tea concentrate
- 3000mg berry mix: blueberry, blackberry, acerola berry, maqi berry, acai berry, dark cherry
- 500mg chicory root (to provide the prebiotic inulin)
I have no idea if anybody makes something like this or not. (Hell, maybe I should look into something like this?)
By the end of my research I’ve decided that I would tentatively recommend taking a kidney bean extract supplement for the following people:
- Someone looking to lower their carbohydrate intake but does not know where to start or is unclear how they’d fit a low-carb diet into their lifestyle
- For use on “cheat days”, when you know you’ll be eating a lot of starchy food
- Before traveling or social occasions, situations that throw a lot of simple carbs your way
Given its harmless nature and low price, I don’t see too much downside to experimenting with its use as long as you understand what it is and isn’t capable of doing.
Preuss, Harry “Bean Amylase Inhibitor and Other Carbohydrate Absorption Blockers: Effects on Diabesity and General Health”
Hollenbeck, Claire, et. al. “Effects of a commercial starch blocker preparation on carbohydrate digestion and absorption: in vivo and in vitro studies”
Bo-Linn, George, et. al. “Starch Blockers — Their Effect on Calorie Absorption from a High-Starch Meal”
Preuss, Harry, et. al. “Inhibition by Natural Dietary Substances of Gastrointestinal Absorption of Starch and Sucrose in Rats and Pigs: 1. Acute Studies”
Udani, Jay, et. al. “Lowering the glycemic index of white bread using a white bean extract”
Barrett, Marilyn, et. al. “A proprietary alpha-amylase inhibitor from white bean (Phaseolus vulgaris): A review of clinical studies on weight loss and glycemic control”
Celleno, Leonardo, et. al. “A Dietary Supplement Containing Standardized Phaseolus vulgaris Extract Influences Body Composition of Overweight Men and Women”
Onakpoya, I, et. al. “The efficacy of Phaseolus vulgaris as a weight-loss supplement: a systematic review and meta-analysis of randomised clinical trials.”