Barley is not bad for diabetics. In fact, whole-grain barley is one of the lowest-glycemic grains available, with a glycemic index of just 21 when boiled. The key distinction is the type of barley you choose: hulled (whole-grain) barley behaves very differently in your blood than pearled barley, which has been stripped of its fiber-rich outer layers.
Hulled vs. Pearled Barley: A Major Difference
The type of barley on your plate matters more than whether you’re eating barley at all. Whole-grain (hulled) barley has a glycemic index of about 21 and a glycemic load of 9, both of which are considered low. Pearled barley, the more common grocery store variety, scores a GI of 58 and a glycemic load of 26, putting it in a completely different category for blood sugar management.
That gap exists because pearling removes the bran layer, which contains most of the soluble fiber responsible for slowing digestion. The U.S. Dietary Guidelines classify hulled barley as a whole grain and pearled barley as a refined grain, the same distinction made between brown rice and white rice. If you’re managing diabetes, hulled barley is the better choice by a wide margin. That said, even pearled barley sits lower on the glycemic index than white rice (which typically scores 72 or higher) or white bread.
How Barley Slows Blood Sugar Spikes
Barley is unusually rich in a soluble fiber called beta-glucan, and this is what sets it apart from most other grains. Beta-glucan works through several mechanisms that directly affect how fast glucose enters your bloodstream.
First, it interferes with the enzymes that break starch down into sugar in your gut, slowing the pace of digestion. Second, it inhibits a transporter protein in the small intestine responsible for actively shuttling glucose into the blood. In lab studies, higher concentrations of barley beta-glucan blocked up to 23% of that transporter’s activity. The practical result is a flatter, more gradual rise in blood sugar after eating rather than a sharp spike.
There’s also a longer-term effect. Gut bacteria ferment beta-glucan into short-chain fatty acids, which stimulate the release of a hormone called GLP-1. This is the same hormone targeted by popular diabetes and weight-loss medications. GLP-1 helps your body produce insulin more effectively in response to food. The fermentation byproducts also appear to reduce gut inflammation and improve the intestinal lining, both of which are connected to better insulin sensitivity over time.
What Clinical Trials Actually Show
A meta-analysis of 31 controlled trials found that barley consumption offers clear short-term benefits: it significantly lowers blood sugar and insulin levels in the hours after a meal. In one study of 20 men, including some who were mildly insulin-resistant, those who ate muffins with the highest amount of barley beta-glucan (about 6 grams) had the lowest glucose and insulin responses over a four-hour window. The effect was dose-dependent, meaning more beta-glucan produced better results.
The same meta-analysis, however, found no significant long-term effects on fasting glucose or HbA1c (the marker that reflects average blood sugar over two to three months). This doesn’t mean barley is useless for long-term management. It means barley’s primary value is in controlling post-meal glucose spikes, which are themselves a risk factor for diabetic complications. Replacing higher-glycemic grains with barley at individual meals adds up, even if barley alone doesn’t transform your three-month average.
Serving Size and Preparation
The American Diabetes Association lists a standard serving of cooked barley as half a cup. That’s a reasonable portion to include in a meal without overloading on carbohydrates. One half-cup of cooked barley contains roughly 22 grams of carbohydrate, comparable to a small serving of rice or pasta but with a much gentler effect on blood sugar.
Cooking method matters too. Boiling whole-grain barley for about 25 minutes preserves the low glycemic profile seen in research. You can use it as a base for grain bowls, stir it into soups and stews, or serve it as a side dish in place of rice. Barley also works well cooked in large batches and refrigerated. Cooled and reheated grains develop more resistant starch, which may further blunt glucose response, though beta-glucan remains the more powerful factor.
Who Should Avoid Barley
Barley contains gluten, which makes it off-limits if you have celiac disease or a confirmed gluten sensitivity. People with allergies to other cereal grains (wheat, rye, oat, corn, or rice) may also react to barley. If you tolerate gluten without issues, barley poses no specific risks for people with diabetes.
There is one known medication interaction worth noting: barley may reduce absorption of triclabendazole, an antiparasitic drug. This is a niche concern unlikely to apply to most readers, but worth being aware of if you’re taking that medication.
How Barley Compares to Other Grains
- White rice (GI ~72): Roughly three times the glycemic index of hulled barley. Swapping white rice for barley in even a few meals per week can meaningfully reduce post-meal glucose spikes.
- Brown rice (GI ~50): A solid whole grain, but still more than double the GI of hulled barley and lower in beta-glucan.
- Oats (GI ~55): Also rich in beta-glucan, but with a higher glycemic index than hulled barley. Steel-cut oats come closest to barley’s profile.
- Quinoa (GI ~53): Gluten-free and protein-rich, but produces a faster blood sugar response than hulled barley.
Among commonly available grains, hulled barley sits at or near the bottom of the glycemic index, making it one of the most diabetes-friendly options you can choose. The practical takeaway is simple: if you eat grains, barley (especially the hulled variety) is one of the best ones for keeping your blood sugar steady.