Rhubarb contains several compounds that lower blood sugar in animal studies, and one small human trial found that a rhubarb extract significantly reduced both fasting blood glucose and HbA1c in people with type 2 diabetes. That sounds promising, but the honest picture is more complicated than a simple thumbs-up. Nearly all of the research is in rodents or cell cultures, the single human trial was small, and rhubarb carries real risks for people with existing kidney problems. What follows is a walkthrough of the actual evidence, what it means for your plate, and where the gaps sit.
The One Human Trial Worth Knowing About
Most claims about rhubarb and diabetes rest on lab or animal research, so the existence of even one human clinical trial matters. In that study, patients with type 2 diabetes who received rhubarb stem essential oil saw their average fasting blood sugar drop from roughly 289 mg/dL to about 226 mg/dL, and their HbA1c fell from about 9.6% to about 7.8% over the course of the intervention.1PubMed Central. Study of the effect of the essential oil (extract) of rhubarb stem (shoot) on glycosylated hemoglobin and fasting blood glucose levels in patients with type II diabetes Both reductions were statistically meaningful. An HbA1c drop of nearly two percentage points is a large effect, comparable to what some prescription diabetes medications achieve.
Before you rush to stock up on rhubarb, a few cautions about that trial. It used a concentrated essential oil extract, not raw rhubarb stalks from the grocery store. The participants had quite high blood sugar to begin with (average fasting glucose near 289 mg/dL), so the results may not translate neatly to someone with well-controlled diabetes. And a single trial, however encouraging, is not the same as a body of confirmed evidence. Researchers have not yet replicated these findings in larger, more diverse groups of people.
What Rhubarb Contains That Interests Diabetes Researchers
Rhubarb is not just fiber and tartness. The plant produces a family of bioactive compounds, particularly in its roots and rhizomes, that have caught the attention of pharmacologists. The stalks you eat in pies contain lower concentrations of these compounds than the root (which is the part used in traditional Chinese medicine), but they are still present. Several of them have been studied individually for effects on blood sugar.
Emodin, an anthraquinone found in rhubarb, boosted glucose uptake in muscle cells and suppressed glucose production in liver cells in laboratory experiments. When given to mice, a single dose lowered fasting blood sugar, and eight days of treatment improved insulin sensitivity in both normal and high-fat-diet-fed diabetic mouse models.2PubMed Central. Emodin regulates glucose utilization by activating AMP-activated protein kinase The mechanism appears to involve activation of an energy-sensing enzyme called AMPK, which is the same pathway targeted by metformin, one of the most widely prescribed diabetes drugs.
Rhaponticin, a stilbene compound from rhubarb rhizomes, reduced blood glucose and improved glucose tolerance in a genetic mouse model of type 2 diabetes. It also lowered triglycerides, LDL cholesterol, and insulin levels, while increasing glycogen storage in the liver.3PubMed. Rhaponticin from rhubarb rhizomes alleviates liver steatosis and improves blood glucose and lipid profiles in KK/Ay diabetic mice Those combined effects are interesting because type 2 diabetes rarely travels alone; it usually brings dyslipidemia and fatty liver along for the ride.
A related compound, desoxyrhaponticin, works by a different route. Rather than improving how your cells use glucose, it blocks glucose absorption in the intestine and glucose reabsorption in the kidneys. In a rat model of type 2 diabetes, oral dosing significantly suppressed the blood sugar spike that normally follows a meal.4The Journal of Pharmacology and Experimental Therapeutics. Desoxyrhaponticin (3,5-Dihydroxy-4′-methoxystilbene 3-O-β-d-glucoside) Inhibits Glucose Uptake in the Intestine and Kidney: In Vitro and in Vivo Studies That mechanism echoes SGLT2 inhibitor drugs, which also work by preventing glucose reabsorption in the kidneys.
Slowing Starch Digestion
Another angle comes from enzyme inhibition. Several rhubarb-derived compounds have been shown to inhibit alpha-glucosidase, the enzyme that breaks complex carbohydrates into absorbable sugars in the gut.5Bioorganic & Medicinal Chemistry Letters. Yeast and mammalian α-glucosidase inhibitory constituents from Himalayan rhubarb Rheum emodi Wall.ex Meisson This is the same mechanism used by acarbose, a prescription drug that flattens post-meal blood sugar spikes by slowing carbohydrate digestion. Whether eating rhubarb stalks delivers enough of these compounds to produce a clinically meaningful effect in humans is unknown, but the pharmacological principle is well established.
Protecting the Cells That Make Insulin
High blood sugar does not just cause symptoms in the short term. Over time, it damages the beta cells in the pancreas that produce insulin, creating a vicious cycle where worsening glucose control leads to further beta-cell loss. Two rhubarb compounds have shown protective effects against this process in laboratory settings.
Rhein, another anthraquinone, was found to protect pancreatic beta cells from the kind of damage that high glucose inflicts. It preserved the internal structure of the cells’ mitochondria and prevented programmed cell death triggered by hyperglycemia.6Diabetes. Rhein Protects Pancreatic β-Cells From Dynamin-Related Protein-1–Mediated Mitochondrial Fission and Cell Apoptosis Under Hyperglycemia In treated animals, rhein significantly reduced beta-cell loss and improved insulin secretion.7Frontiers in Pharmacology. Rhein for treating diabetes mellitus: A pharmacological and mechanistic overview
Emodin showed a related but distinct protective effect. In a model of type 1 diabetes, where beta cells are destroyed by the immune system rather than by high blood sugar, emodin shielded the cells from inflammatory damage. Mice pretreated with emodin were fully resistant to developing diabetes, with normal-looking pancreatic islets and preserved insulin secretion.8Journal of Functional Foods. Emodin isolated from Rheum palmatum prevents cytokine-induced β-cell damage and the development of type 1 diabetes The protection came from blocking an inflammatory signaling pathway called NF-κB. This is intriguing for type 1 diabetes research, though the leap from mouse prevention to human treatment remains enormous.
Rhubarb Fiber and Blood Sugar
Setting aside the exotic-sounding compounds, rhubarb is also a source of dietary fiber, and fiber in general helps blunt post-meal glucose spikes by slowing digestion. In rats, replacing standard cellulose fiber with rhubarb fiber increased expression of the proglucagon gene in the lower small intestine and reduced passive permeability to glucose across the intestinal wall.9The Journal of Nutrition. A Physiological Level of Rhubarb Fiber Increases Proglucagon Gene Expression and Modulates Intestinal Glucose Uptake in Rats Proglucagon is the precursor to GLP-1, a hormone that stimulates insulin release and suppresses appetite. (GLP-1 is the same hormone that drugs like semaglutide are designed to mimic.) Whether rhubarb fiber specifically outperforms other high-fiber foods in this regard is unclear from the available data.
One area where rhubarb fiber did not deliver is cholesterol. A study in diabetic rats found that a rhubarb-fiber-enriched diet failed to lower plasma cholesterol or triglyceride levels, despite increasing the activity of an enzyme involved in cholesterol clearance.10British Journal of Nutrition. Dietary rhubarb (Rheum rhaponticum) stalk fibre does not lower plasma cholesterol levels in diabetic rats If you are hoping rhubarb will tackle both your blood sugar and your lipid numbers, the fiber alone does not seem to pull double duty. Isolated rhubarb compounds like rhaponticin did improve lipid profiles in a different mouse model, but those were concentrated extracts, not something you would get from eating stewed stalks.
Gut Bacteria and Inflammation
A newer line of research focuses on how rhubarb compounds interact with the gut microbiome. In one study, a purified anthraquinone preparation from rhubarb was given to diabetic animals for six weeks. Fasting blood glucose, insulin resistance, and glycated serum protein all dropped significantly, while GLP-1 levels rose.11Frontiers in Microbiology. A Purified Anthraquinone-Glycoside Preparation From Rhubarb Ameliorates Type 2 Diabetes Mellitus by Modulating the Gut Microbiota and Reducing Inflammation The researchers attributed part of the benefit to shifts in gut bacterial populations and reduced systemic inflammation. This fits a broader pattern in metabolic research: the composition of your gut bacteria appears to influence insulin sensitivity, and certain plant compounds can shift that composition in favorable directions.
Rhubarb extract has also shown anti-inflammatory activity in a model of diabetic kidney disease, suppressing NF-κB signaling and reducing the release of inflammatory molecules.12ChemistrySelect. Mechanism of Rhubarb for Diabetic Kidney Disease through the AMPK/NF‐κB Signaling Pathway Based on Network Pharmacology Chronic low-grade inflammation is a hallmark of type 2 diabetes and contributes to complications like kidney damage and cardiovascular disease, so anti-inflammatory effects from any dietary source are worth noting.
Diabetic Wound Healing
One of the more surprising applications of rhubarb in diabetes research has nothing to do with eating it. Diabetic foot ulcers and slow-healing wounds are serious complications that can lead to infection and amputation. Researchers have developed a wound scaffold using rhubarb-derived charcoal crosslinked with chitosan and silk fibroin that accelerated diabetic wound healing in mice. The scaffold promoted new blood vessel formation, collagen deposition, and skin regrowth within two weeks.13PubMed Central. Topical rhubarb charcoal-crosslinked chitosan/silk fibroin sponge scaffold for the repair of diabetic ulcers improves hepatic lipid deposition in db/db mice via the AMPK signalling pathway14Frontiers in Pharmacology. Advances in traditional Chinese medicine for burn treatment: mechanisms, therapeutic approaches, and innovative preparations This is a biomedical engineering application rather than a dietary one, but it illustrates how broad the interest in rhubarb’s bioactive properties has become within diabetes-related research.
The Oxalate Risk
Rhubarb is one of the highest-oxalate foods you can eat. The leaves are famously toxic due to extreme oxalate concentrations, but even the edible stalks contain meaningful amounts. For most people, this is not a concern. For someone with diabetes and any degree of kidney impairment, it can be serious.
A case report documented acute kidney injury in a patient with type 1 diabetes and mild diabetic nephropathy after eating a large amount of rhubarb. The oxalate crystals deposited in the kidneys and pushed the patient into acute renal failure.15PubMed Central. Acute kidney injury after ingestion of rhubarb: secondary oxalate nephropathy in a patient with type 1 diabetes Diabetic nephropathy is extremely common in people with longstanding diabetes, and many people do not know their kidney function is reduced until it is tested. If you have diabetes and are thinking of regularly eating rhubarb or taking rhubarb supplements, a recent kidney function test is a reasonable precaution.
Cooking rhubarb and discarding the liquid can reduce some of the soluble oxalate content, but it does not eliminate it. Pairing rhubarb with calcium-rich foods (like yogurt or custard, the classic serving companions) can help bind oxalate in the gut before it reaches the kidneys. Still, if you have been told your kidneys are compromised, large or frequent servings of rhubarb are a genuine risk, not a theoretical one.
Grocery Store Stalks vs. Medicinal Extracts
Most of the impressive lab results come from concentrated extracts of rhubarb root or rhizome, not from the tart pink stalks you cook with. The roots of medicinal rhubarb species contain far higher concentrations of anthraquinones like emodin and rhein, as well as stilbenes like rhaponticin. The garden rhubarb stalk that ends up in your crumble is a different proposition: lower in these bioactive compounds, but also lower in oxalates than the root and much lower than the leaves.
Different parts of the plant vary considerably in their bioactive punch. Research comparing the roots and stalks of culinary rhubarb with the roots of medicinal species found that the medicinal root had the strongest antioxidant and anti-inflammatory activity, followed by the culinary root, with the stalks and leaves trailing behind.16Korean Journal of Food Preservation. Antioxidant and anti-inflammatory activities of different parts of rhubarb (Rheum rhabarbarum) compared with da huang root (R. officinale) This matters practically: if you are eating rhubarb stalks in normal food quantities, you are getting some fiber, some polyphenols, and a modest amount of the compounds studied in labs, but not the pharmacological doses used in animal experiments.
Rhubarb supplements and extracts sold commercially are a different situation entirely. These products vary wildly in their composition, potency, and quality. Some are made from root material and may contain significant levels of anthraquinones. Because rhubarb anthraquinones have strong laxative effects at higher doses, taking concentrated rhubarb supplements without guidance can cause diarrhea, electrolyte imbalances, and in rare cases, liver irritation. If you are on metformin, which already causes gastrointestinal side effects in many people, adding a potent rhubarb supplement on top could be unpleasant.
Rhubarb During Pregnancy With Gestational Diabetes
Gestational diabetes affects a meaningful percentage of pregnancies, and questions about what foods and supplements are safe during pregnancy come up constantly. A large Japanese database study examined whether Kampo medicines containing rhubarb rhizome, prescribed during the first trimester, were associated with birth defects. No increased risk of major congenital malformations was found.17Frontiers in Pharmacology. No association between major congenital malformations and exposure to Kampo medicines containing rhubarb rhizome That is somewhat reassuring for women who consumed rhubarb-containing preparations before knowing they were pregnant, but it does not constitute a recommendation to use rhubarb medicinally during pregnancy. The anthraquinones in rhubarb root stimulate intestinal contractions, and concentrated forms are generally avoided during pregnancy for that reason. Eating moderate amounts of cooked rhubarb stalk in food is a separate question from taking medicinal root preparations, and the former is generally considered benign.
How Rhubarb Fits Into a Diabetes-Friendly Diet
Raw rhubarb stalk is extremely low in sugar and calories. A cup of diced raw rhubarb has roughly 26 calories and about 1 gram of sugar, with a couple of grams of fiber. The problem is that almost nobody eats raw rhubarb because it is bracingly sour. The traditional solution is to add a lot of sugar, which obviously defeats the purpose if blood sugar management is your goal. Stewing rhubarb with a modest amount of a non-nutritive sweetener, or adding small quantities of raw or lightly cooked rhubarb to yogurt or oatmeal, preserves its benefits without the sugar load.
Rhubarb also pairs well with other berries and fruits that are themselves lower on the glycemic index. Strawberry-rhubarb combinations are classic, and strawberries have a relatively mild effect on blood sugar compared with tropical fruits. Using rhubarb’s tartness to cut the sweetness in a dish can actually help you reduce overall sugar content, which is arguably its simplest and most reliable contribution to a diabetes-friendly eating pattern. Whether the specific bioactive compounds in the stalks add anything beyond what you would get from any high-fiber, low-sugar vegetable is something the current evidence cannot confirm.