Got questions about navigating life with diabetes? You came to the right place: Ask D’Mine!, our weekly Q&A column by veteran type 1 and diabetes author Wil Dubois.

Sometimes it’s hard to separate fact from fiction on substances that supposedly help lower blood sugar. Today we’re talking spicy and sour…

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Joel, type 2 from Illinois, writes: I’ve heard a lot people say that sour, bitter, or spicy foods help bring blood sugar down. Is there any truth to this?

Wil@Ask D’Mine answers: There’s no shortage of studies on the blood sugar-lowering effects of sour, bitter, or spicy foods—but they tend to be a bit sketchy, perhaps because there’s little motivation to research medical interventions that can’t be monetized. What do I mean by sketchy? Dr. Fr. Baby Joseph of Malankara Catholic College, writing a summary of nutritional remedy research in the Asian Pacific Journal of Tropical Disease, said it best: “Despite the abundant data from biochemical and animal studies, available clinical data as reviewed in the present article are often flawed by small sample size, lack of control and poor study designs.” 

Which is a nice way of saying that there’s a lot of crap science on the subject. Like I said, sketchy.

Still with this much smoke, there could be a fire. Grab a hose and a shovel and let’s take a look.

At least one element of spicy food has been extensively researched: capsaicin, which is the Pow! element in many chili peppers. Capsaicin has been under the microscope for a long time, literally. One of the earliest studies of capsaicin was published in 1978 in the journal Food and Cosmetics Toxicology, and it showed that capsaicin increased glucose absorption in the intensities. At least in rats. And hamsters. Maybe. The study was in vitro, meaning the tissue or cells were removed from the critters in question and studied in petri dishes.

In vitro is Latin for “in glass.” 

It’s a long stretch from rat cells in a glass dish responding well to a compound, to the idea that you too should eat that compound. 

Still, a later study, out of the People’s Republic of China, looked at living diabetic rats. The study compared capsaicin to a “nonpungent capsaicin analog” called Capsiate. How did the two stack up to each other? The analog didn’t do as well, but the researchers claim that both the natural substance and the analog increased insulin levels (which shouldn’t be possible in a T1D rat) while a shake-up in the glucose transport proteins also further reduced blood glucose levels.

That’s interesting. But the Chinese researchers also claimed that chili peppers “exhibit antiobesity, anticancer, antidiabetic, and pain- and itch relieving effects.” Hmmmm…. Sounds like good ol’ universal Snake Oil to me. I get suspicious when one compound is supposed to cure all ills. But maybe that’s just me. 

Luckily, not all spicy food research is done on lab rats. There are a handful of human studies, but the results are mixed. One of the first took healthy folks, loaded them up with sugar, added capsaicin, and found that it made no difference. Another study took 44 women with gestational diabetes and stuffed half of them full of chili peppers for a month and then compared their glucose, insulin, and other blood chemistry. The researchers claim that the stuffed pepper ladies had improved postprandial (after meal) blood sugars. Like I said, mixed results.

Moving on, it’s time to get bitter. Apparently one of the bitterest foods out there is Momordica Charantia—the bitter melon. Across Asia, bitter melon has a well-entrenched historic role in folk medicine, and at least one decently designed study found that large doses of bitter melon lowered blood glucose, but the effect was modest — less than a single metformin pill. But, like much of the science in this realm, a different team got different results, which is to say, no results at all. So pick your poison. Oh, right. Be aware that too much bitter melon is poison itself. Many of its elements are toxic in volume. 

As to sour foods, I couldn’t find much of anything written on the subject of sour food lowering blood sugar, which isn’t too surprising, given that the most common sour foods—such as citrus and some dairy products—are also high in carbohydrates. If they did have glucose-lowering properties, their own natural sugars would overwhelm the positive effects. That’s not to say some sort of medicine couldn’t be developed from the glucose-lowering compounds—if they exist—but eating a basket of lemons and limes isn’t likely to help your blood sugar. Still, at least it would keep scurvy at bay.

So not to rain on your parade, but the best of the sketchy evidence suggests that if sour, bitter, or spicy foods do, in fact, improve blood sugar, the effect is slight at best, at least in terms of realistic real-world applications. This might explain why varying studies get varying results. If you’re measuring a small difference, small errors can swerve the results. But if that’s the case, why are a lot of people saying that these foods lower blood sugar?

I have a theory on that.

When it comes to spicy food, how big a plate can you eat before your tongue melts? How much water do you have to guzzle in the meantime to attempt to put out the fire in your mouth? And we have a saying in English about something being a bitter pill to swallow. There’s only so much culinary bitterness we can tolerate, and it’s not much.

So one possibility is that when eating spicy and bitter foods we tend to eat less. And in the case of really spicy foods, we also consume a fair amount of compensatory liquid, which takes up space in our stomachs, satieting our appetites with even less food volume.

And that combination can absolutely lower blood sugar, at least for those with type 2 diabetes.

Here’s how it works: Most type 2s still produce some insulin, but generally not enough to control their blood sugar. One solution to this problem is to take medicine to suck the excess sugar out of their blood. But another solution is to simply reduce the intake of sugar to a level low enough that whatever insulin action remains is up to the task.

In other words, for a type 2, lowering the carbohydrate intake may let the limited remaining insulin in their bodies catch up. And spicy and bitter foods—regardless of any magic medicinal properties they may have in small quantities—might accomplish that by the simple fact that we eat less of them.

Hey, and if these foods really do have a small sugar-lowering biochemical effect, well, so much the better.


This is not a medical advice column. We are PWDs freely and openly sharing the wisdom of our collected experiences — our been-there-done-that knowledge from the trenches. Bottom Line: You still need the guidance and care of a licensed medical professional.