Goal · Blood sugar
Food and blood sugar: fiber, whole grains, cinnamon and vinegar
Raising fiber and choosing whole grains have the best evidence for steadier blood sugar. Cinnamon and apple cider vinegar get far more attention than their trials justify.
By the editors of Alimentotherapy Last reviewed 3 min read Not medical advice
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The short answer
The food change with the most consistent evidence for blood sugar is more fiber: in a 2020 meta-analysis, higher fiber intakes lowered HbA1c and fasting glucose across trials in adults with diabetes and prediabetes, and the authors suggested adding 15 g a day or reaching 35 g as a reasonable target Reynolds 2020. Popular single remedies are much weaker: a Cochrane review found insufficient evidence that cinnamon helps people with diabetes Leach 2012.
Foods and herbs for blood sugar, graded
Every claim from our remedy pages that relates to blood sugar, strongest evidence first. Each row links to the full page and its sources.
| Food or herb | Grade | What the research found |
|---|---|---|
| Apple cider vinegarBlood sugar and insulin after a meal | Moderate | A meta-analysis of controlled trials found vinegar taken with a meal lowered the glucose and insulin response afterwards compared with control. The trials were short, single-meal studies. |
| PsylliumBlood sugar in type 2 diabetes | Moderate | A meta-analysis of 35 trials found psyllium taken before meals lowered fasting glucose and HbA1c in people treated for type 2 diabetes, less in prediabetes and not at all in people with normal blood sugar. It was funded by a psyllium manufacturer. |
| Apple cider vinegarFasting blood sugar and HbA1c over weeks | Limited | Pooling nine trials, daily apple cider vinegar lowered fasting glucose and HbA1c, with very high variation between studies; in apparently healthy people fasting glucose did not fall. |
| CinnamonBlood sugar in type 2 diabetes | Limited | In 10 trials (543 patients), 120 mg to 6 g a day lowered fasting glucose but did not change HbA1c. A Cochrane review of 10 trials found no significant difference in HbA1c, insulin or after-meal glucose. |
| OatsBlood sugar control in type 2 diabetes | Limited | Four trials (350 people) gave 2.5 to 3.5 g of beta-glucan a day for 3 to 8 weeks; fasting glucose and HbA1c fell slightly, insulin sensitivity did not change. Longer trials are scarce. |
| Yogurt and kefirLong-term type 2 diabetes risk | Limited | In three large US cohorts and a meta-analysis of 14 cohorts, each daily serving of yogurt was associated with a lower risk of type 2 diabetes. These are observational studies; the FDA allows only a qualified claim, citing limited evidence. |
Fiber and whole grains
Reynolds and colleagues pooled 42 trials in 1,789 adults with prediabetes, type 1 or type 2 diabetes. Higher fiber intakes lowered HbA1c (from 33 trials) and fasting glucose, and the benefits were not limited to one type of fiber Reynolds 2020. In a larger review of carbohydrate quality, the reduction in risk for outcomes including type 2 diabetes and heart disease in observational studies was greatest at 25 to 29 g of fiber a day, with similar findings for whole grains Reynolds 2019.
That points to beans and lentils, oats and other whole grains, vegetables, fruit, nuts and seeds such as flaxseed, and psyllium for people who struggle to get there from food. Add fiber gradually to avoid gas and bloating.
Eating patterns
The American Diabetes Association's Standards of Care do not prescribe one ideal diet. They support several eating patterns tailored to the person, with an emphasis on nonstarchy vegetables, whole foods, and fewer added sugars and refined grains ADA 2025. People with diabetes are advised to work out an eating plan with their care team or a registered dietitian, especially when they take insulin or medicines that can cause low blood sugar. Shaking, sweating, a pounding heartbeat, confusion or blurred vision can mean blood sugar has dropped too low MedlinePlus, and thirst, frequent urination, blurry vision and unplanned weight loss are possible signs of diabetes that need testing rather than a food experiment MedlinePlus.
Cinnamon and vinegar: why the evidence is weak
Cinnamon shows how mixed results get oversold. One meta-analysis of 10 trials (543 patients) found lower fasting glucose with cinnamon at doses from 120 mg to 6 g a day, but no significant change in HbA1c, and the trials disagreed so much that the authors said the results were hard to apply Allen 2013. The Cochrane review of 10 trials (577 participants), most at high or unclear risk of bias, found no significant effect on HbA1c and concluded there is insufficient evidence to support cinnamon for diabetesLeach 2012. HbA1c, which reflects the past few months, matters more than a single fasting reading.
Apple cider vinegar trials are small and short; its page explains what they measured. Neither is a substitute for diabetes medicine.
How to try a change fairly
If you have diabetes and monitor glucose, change one thing at a time and compare readings at the same time of day over a couple of weeks. If you take insulin or a sulfonylurea, tell your care team before a big diet change, because eating less carbohydrate can make low blood sugar more likely.
When to see a clinician, not the pantry
- Feeling very thirsty or hungry, urinating more often (including at night), blurry vision, or slow-closing sores: possible signs of diabetes.
- Losing weight without trying, or numbness and tingling in the feet or hands.
- If you have diabetes: shaking, sweating, a pounding heartbeat, confusion or blurred vision, which can mean low blood sugar. Follow your care plan and get help if it does not improve.
- Before a large diet change if you take insulin or medicines that can cause low blood sugar.
Common questions
Does cinnamon lower blood sugar?
Not convincingly. A Cochrane review of 10 trials found no significant effect of cinnamon on HbA1c and concluded there is insufficient evidence to support it for diabetes. Another meta-analysis found lower fasting glucose, but results varied widely between trials and HbA1c did not change significantly.
How much fiber helps blood sugar?
A 2020 meta-analysis in adults with diabetes found higher fiber intakes lowered HbA1c and fasting glucose, and suggested increasing daily fiber by 15 grams or to 35 grams a day as a reasonable target. Add it gradually, from beans, whole grains, vegetables, fruit, nuts and seeds.
Sources
Primary research and government sources, each checked on the date this page was reviewed.
- PubMedReynolds AN, et al. Dietary fibre and whole grains in diabetes management: systematic review and meta-analyses. PLoS Med. 2020. PMID 32142510.
- PubMedReynolds A, et al. Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. Lancet. 2019. PMID 30638909.
- GuidelineAmerican Diabetes Association Professional Practice Committee. 5. Facilitating positive health behaviors and well-being to improve health outcomes: Standards of Care in Diabetes-2025. Diabetes Care. 2025. PMID 39651983.
- PubMedAllen RW, et al. Cinnamon use in type 2 diabetes: an updated systematic review and meta-analysis. Ann Fam Med. 2013. PMID 24019277.
- CochraneLeach MJ, et al. Cinnamon for diabetes mellitus. Cochrane Database Syst Rev. 2012. PMID 22972104.
- MedlinePlusMedlinePlus. Diabetes.
- MedlinePlusMedlinePlus. Low blood sugar.
Keep reading
- RemedyCinnamonMixed trial results for blood sugar and no change in long-term HbA1c. Cassia cinnamon, the common supermarket kind, carries coumarin, which limits how much is sensible.
- RemedyApple cider vinegarTaken with a starchy meal, vinegar modestly lowers the blood sugar spike that follows. The weight-loss claims rest on small, uneven trials, and the acid has real downsides.
- RemedyOatsOne of the best-supported foods in this whole reference: the soluble fiber in oats, beta-glucan, lowers LDL cholesterol a little but reliably.
- RemedyPsylliumThe seed husk sold as a bulk fiber. It has the best evidence of any fiber supplement for chronic constipation and a solid record on LDL cholesterol.
- GoalFood for a healthy heart: blood pressure and cholesterolEating patterns have the strongest heart evidence: DASH for blood pressure, Mediterranean for heart events, and soluble fiber from oats, barley or psyllium for cholesterol.