Key takeaways
- A normal fasting blood sugar is 99 mg/dL or below, while 100 to 125 signals prediabetes, which the CDC estimates affects about 115.2 million U.S. adults12.
- Refined grains make up 86% to 87% of the grains Americans eat, and the science report behind the 2025–2030 Dietary Guidelines calls them “sugar in disguise”3.
- The new guidelines say no amount of added sugar is recommended and that a single meal should contain no more than 10 grams, well below the 50-gram Daily Value used on food labels413.
- The glycemic index ranks how much foods raise blood sugar, but a major review rated its evidence low to very low in certainty, and diabetes experts found no clear effect on long-term blood sugar56.
- In a 2022 review of seven small one-day studies, short, light walking breaks during long stretches of sitting cut after-meal blood sugar by about 17% compared with sitting nonstop7.
In 2018, researchers at Stanford University fitted 57 adults with continuous glucose monitors for two weeks or more8. None had been diagnosed with diabetes, and by standard tests 38 of them had normal blood sugar8.
Thirty of the volunteers ate three set breakfasts, each one twice: cornflakes with milk, bread with peanut butter, and a protein bar8.
The cereal stood out. About 80% of the group saw blood sugar climb above 140 mg/dL, the level that marks prediabetes on a two-hour glucose tolerance test18. A brief sensor peak isn’t a diagnosis, since the formal test checks blood sugar two hours after a standard glucose drink1. Bread with peanut butter produced gentler rises for more people8.
The lesson isn’t that breakfast is dangerous. It’s that “carbs” covers foods that behave very differently in your body, and a few simple choices change how a meal lands.
How carbohydrates turn into blood sugar
Carbohydrates come in three main forms: sugars, starches and fiber9. Your body breaks sugars and most starches down into glucose, a simple sugar that travels in your blood as fuel. Fiber isn’t broken down9.
Insulin, a hormone made by the pancreas, helps glucose leave the blood and enter your cells10. When muscle, fat and liver cells stop responding well to insulin, a problem called insulin resistance, glucose builds up in the blood10.
A rise after eating is normal. Doctors judge your risk with a few standard tests, shown below1.
| Test | Normal | Prediabetes | Diabetes |
|---|---|---|---|
| Fasting blood sugar | 99 mg/dL or below | 100 to 125 mg/dL | 126 mg/dL or above |
| A1C blood test | Below 5.7% | 5.7% to 6.4% | 6.5% or above |
| Two hours after a glucose drink | 139 mg/dL or below | 140 to 199 mg/dL | 200 mg/dL or above |
Source: National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)1.
How much carbohydrate should you eat? The National Academies of Sciences, Engineering, and Medicine (NASEM) puts the acceptable range for adults at 45% to 65% of calories11. The American Diabetes Association’s 2019 consensus report found no single ideal percentage for people with or at risk of diabetes, and urged care tailored to each person6.
The quality of those carbohydrates matters more than any single number, and that’s where the rest of this guide focuses. Later articles in this series cover low-carb diets and the question of whether carbs are bad.
The glycemic index ranks foods, but it’s a blunt tool
The glycemic index, or GI, measures how much a food raises blood sugar. To test a food, at least 10 healthy volunteers eat enough of it to supply 50 grams of carbohydrate, and researchers track their blood sugar for two hours. The result is compared with the same amount of pure sugar12.
On the scale, 55 or less counts as low, 56 to 69 as medium and 70 or more as high12.
Lentils, chickpeas, kidney beans, green vegetables and most fruits score low, according to Mayo Clinic. Bananas, raisins and oat cereals land in the middle. Potatoes, white bread and white rice rank high12.
Glycemic load adjusts for portion size. A load of 10 or less is low, and 20 or more is high12.
The GI has real blind spots, Mayo Clinic notes12:
- It ignores how much you eat.
- It says nothing about nutrition. Cantaloupe rates fairly high yet is packed with vitamin C, while whole milk rates low despite its fat and calories.
- A food’s score shifts with cooking and processing.
Long-term studies are unimpressive, too. A 2019 Lancet review for the World Health Organization rated the evidence on GI as low to very low certainty5. A small link between low-GI diets and less type 2 diabetes shrank and lost statistical significance in a sensitivity check, and the authors judged GI a less useful guide than fiber or whole grains5.
The American Diabetes Association reached a similar view. Its 2019 report found that low-GI diets had no significant effect on A1C in two systematic reviews6. Use GI as a tiebreaker, not a rulebook.
Refined versus whole: what processing does to a carb
The science report behind the 2025–2030 Dietary Guidelines puts it bluntly: refined grains are “sugar in disguise”3. Starch is a chain of glucose units. Refined grains digest quickly and have little fiber or protein left to slow the process3.
That matters because refined grains dominate American plates. They make up 86% to 87% of the grains eaten by U.S. youth and adults, and they carry 60% to 80% less fiber than whole grains3.
On this point, the American Diabetes Association agrees. Its 2019 report told people with diabetes or prediabetes to fill up on nonstarchy vegetables, cut back on added sugars and refined grains, and choose whole foods over highly processed ones when they can6.
Fruit is a different story from juice. Juice is made by removing the fiber in whole fruit, the scientific report notes3. Most whole fruits score low on the GI12.
The new guidelines recommend two servings of fruit a day and say to keep 100% juice to limited portions or dilute it with water4. Sugars that occur naturally in fruit and plain milk don’t count as added sugars4.
A quick shelf test for grain foods: most true whole-grain products have at least 1 gram of fiber for every 8 grams of carbohydrate, according to the scientific report3. Our companion article on fiber covers how much you need and where to find it.
The new guidelines draw a tight line on added sugar
The 2025–2030 Dietary Guidelines, released in January 2026, say no amount of added sugars or non-nutritive sweeteners is recommended. They also set a working limit: one meal should contain no more than 10 grams of added sugar4.
They set snack limits, too, tied to FDA’s “healthy” claim rules. A grain snack such as crackers should have no more than 5 grams of added sugar per ¾-ounce whole-grain equivalent, and a yogurt-type snack no more than 2.5 grams per ⅔ cup4. For infants and young children, the advice is to avoid added sugars4.
This is stricter than older advice. The Nutrition Facts label still uses a Daily Value of 50 grams of added sugar13. MedlinePlus, the National Library of Medicine’s consumer site, still advised keeping added sugars under 10% of calories in a page reviewed in April 20269.
Three meals at the new 10-gram cap total 30 grams before snacks, well under the label’s 50. The guidelines’ scientific report doesn’t explain how the 10-gram figure was chosen3.
Natural sweeteners get no pass. The guidelines list honey, molasses, fruit juice concentrate and high-fructose corn syrup among added sugars, and advise checking labels for words that include “sugar” or “syrup” or end in “-ose”4.
Your blood sugar response is personal, and some spikes are normal
The Stanford study did more than test cereal8. The team sorted people into three “glucotypes” based on how much their blood sugar swung through the day: low, moderate or severe variability.
Some results were surprising. Sixteen people who looked normal on standard tests reached prediabetic or diabetic levels after at least one meal8.
The authors were careful about what this means. They said long-term studies are needed to learn whether a severe glucotype predicts diabetes better than standard tests8. The scientific report behind the new guidelines adds that blood sugar readings are imperfect stand-ins for actual disease3.
So treat spikes as information, not a diagnosis. Our article on glucose sensors explains why most spikes in healthy people are normal, and our article on personalized nutrition covers diet algorithms built on these differences.
The carb quality ladder
This ladder is our own tool, built from the sources in this article. Each rung up means more fiber, less processing or both. You don’t have to live on the top rung; aim to move a few foods up one step at a time.
| Rung | What it is | Examples | Why it ranks here |
|---|---|---|---|
| 5 (best) | Beans, lentils, whole fruit and nonstarchy vegetables | Lentils, chickpeas, berries, apples, broccoli, greens | High in fiber, and most score low on the GI612 |
| 4 | Intact whole grains and whole starchy vegetables | Barley, bulgur, oats, sweet potato with skin | Whole grains are linked to lower death and heart disease rates3 |
| 3 | Whole-grain flour foods | 100% whole-wheat bread, whole-wheat pasta and tortillas | Whole grain, but ground; check for 1 gram of fiber per 8 grams of carbs3 |
| 2 | Refined grains and starches | White bread, white rice, crackers, many boxed cereals | Little fiber; digest quickly312 |
| 1 | Added sugars, sugary drinks and juice | Soda, fruit drinks, energy drinks, candy, sweetened cereal | No added sugar amount is recommended; avoid sugar-sweetened drinks4 |
A few foods need a note. Potatoes are a whole food with a high GI12, so eating them with the skin and alongside beans or vegetables is a reasonable middle path. Swapping a sugary drink for water was linked to a 7% to 8% lower risk of type 2 diabetes in research the American Diabetes Association cited6.
After-meal habits, rated by evidence
These habits can soften the rise after a meal. The ratings use our four-level scale.
| Habit | How to try it | What studies found | Evidence level |
|---|---|---|---|
| Swap refined carbs for whole, high-fiber ones | Climb one rung of the ladder | Lower rates of disease in large reviews35; endorsed by the ADA6 | |
| Break up sitting with light walks | 2 to 5 minutes of easy walking every 20 to 30 minutes of sitting | Walking breaks cut after-meal glucose about 17% versus sitting; standing, about 9.5%7 | |
| Eat vegetables and protein first, carbs last | Start with salad, vegetables and protein; save bread or rice for later | Glucose 37% lower at one hour in an 11-person pilot14 | |
| Pair carbs with protein or fat | Peanut butter on toast; nuts with fruit | Gentler responses to bread with peanut butter than to cornflakes8 | |
| Add vinegar to a meal | Use it in a salad dressing | Seven small trials of apple cider vinegar in type 2 diabetes, mostly at high risk of bias, found lower fasting glucose15 | |
| Choose foods by GI number alone | Not recommended as a main strategy | Low certainty; no clear effect on A1C56 |
Some details behind those ratings matter.
The walking review, published in Sports Medicine in 2022, pooled seven randomized crossover studies, each lasting one day7. People sat for five hours or more, and the breaks were short, commonly 2 minutes of walking every 20 minutes or 5 minutes every 307. Walking beat standing, and it lowered insulin, too7.
Note what was tested: breaks spread through a long sitting session, not one walk after dinner. Most of the studies were small, and none measured long-term health7.
The food-order study appeared in the journal Diabetes Care in 201514. Eleven adults with type 2 diabetes ate the same meal of ciabatta, orange juice, chicken, salad and broccoli twice, a week apart14. When the bread and juice came after the protein and vegetables instead of before, glucose at the one-hour mark averaged about 126 mg/dL instead of 19914. The authors called it a pilot and asked for longer studies14.
The vinegar evidence comes from a 2025 review of apple cider vinegar in Frontiers in Nutrition. It pooled seven trials with 463 people, lasting 4 to 12 weeks, five of them from Iran, and most had a high risk of bias15. If you try it, keep it in food, and talk with your clinician first if you take medicine that lowers blood sugar.
Prediabetes is common and usually silent
About 115.2 million U.S. adults have prediabetes, according to the CDC2. The new Dietary Guidelines add that nearly one in three adolescents ages 12 to 17 has it4.
Most people with prediabetes have no symptoms, the NIDDK says. Without changes, their odds of type 2 diabetes in the next 5 to 10 years are high10. In the landmark Diabetes Prevention Program, people at high risk who lost 5% to 7% of their weight lowered their chance of getting the disease10. Our articles on beginning natural health and on realistic goals describe that trial and how to size your own goals.
Ask about testing if you are 35 or older, carry extra weight, have a family history of diabetes, had diabetes during pregnancy, or are not physically active10. Anyone with symptoms of diabetes should be tested1.
When to get help:
- Get tested soon if you notice possible symptoms of diabetes or a home reading worries you1.
- Talk with your clinician before big changes if you take insulin or other medicine that lowers blood sugar, since a new eating pattern or vinegar habit may change what you need.
- Call 911 if someone becomes confused, faints or can’t stay awake.
Whole carbohydrate foods fit natural-health values
Beans, whole grains, fruit and root vegetables have fed families for generations. The research problem isn’t those foods. It’s the refined, sweetened versions that factories make from them, the ones that now make up most of the grains Americans eat3.
That’s good news for readers who distrust diet fads. You don’t need to fear an apple or a bowl of lentils, and you don’t need a sensor to eat well. The evidence favors the cooking you may already do: whole foods, beans most days, vegetables at most meals and sweets kept small.
The same skepticism you’d bring to a drug ad applies to the glucose-hacking market. Before you pay for a blood-sugar supplement or a program that promises to flatten every spike, ask whether that exact product has been tested in people. The basics on this page cost little and have been studied.
Questions readers ask
Should I cut back on fruit to control my blood sugar?
For most people, no. Most whole fruits score low on the glycemic index12, and the 2025–2030 guidelines recommend two servings a day4. Juice is different, because juicing removes much of the fruit’s fiber3. If you have diabetes, a dietitian can help you fit fruit into your plan.
Is honey or maple syrup better than white sugar?
For added sugar limits, they count the same. The guidelines list honey and molasses as added sugars and flag any ingredient with “syrup” in its name4. A sweetener’s natural origin doesn’t change how the guidelines count it, a point our article on natural versus synthetic explores.
How many carbohydrates should I eat in a day?
NASEM’s range for adults is 45% to 65% of calories11, and the American Diabetes Association found no single ideal amount for people with or at risk of diabetes6. The new guidelines note that some people with chronic diseases may do better on a lower-carbohydrate diet4. Later articles in this series weigh low-carb eating in detail.
Do I need a glucose monitor to eat well?
No. The Stanford team said it isn’t yet known whether spiky patterns predict disease8, and the new guidelines’ science report calls blood sugar readings imperfect markers of disease3. Standard tests from your clinician remain the way to check your risk.
The bottom line
Carbohydrates range from lentils and berries to soda and white bread, and your blood sugar can tell the difference. The steadiest evidence favors moving toward whole, fiber-rich carbs and away from refined grains and added sugar, which the new federal guidelines now limit to 10 grams a meal.
Short walks, eating vegetables and protein first, and pairing carbs with protein or fat are cheap habits with promising early evidence. The glycemic index is a rough guide at best. If you have prediabetes risk factors, a simple blood test tells you more than any spike.
Related reading
About this article
This article was researched using NIH, CDC and FDA sources, the 2025–2030 Dietary Guidelines and their scientific report, and peer-reviewed studies, all listed below. It was reviewed in October 2026. It is general education and not medical, legal or financial advice.
Sources
- National Institute of Diabetes and Digestive and Kidney Diseases. “Diabetes Tests & Diagnosis.” NIH, reviewed July 2022. niddk.nih.gov
- Centers for Disease Control and Prevention. “National Diabetes Statistics Report.” CDC, updated Sept. 16, 2026. cdc.gov
- U.S. Department of Health and Human Services and U.S. Department of Agriculture. “The Scientific Foundation for the Dietary Guidelines for Americans, 2025–2030.” 2026. cdn.realfood.gov
- U.S. Department of Health and Human Services and U.S. Department of Agriculture. “Dietary Guidelines for Americans, 2025–2030.” January 2026. cdn.realfood.gov
- Reynolds A, Mann J, Cummings J, Winter N, Mete E, Te Morenga L. “Carbohydrate quality and human health: a series of systematic reviews and meta-analyses.” The Lancet, 2019 (accepted manuscript, University of Dundee repository). discovery.dundee.ac.uk
- Evert AB, et al. “Nutrition Therapy for Adults With Diabetes or Prediabetes: A Consensus Report.” Diabetes Care, 2019. pubmed.ncbi.nlm.nih.gov
- Buffey AJ, Herring MP, Langley CK, Donnelly AE, Carson BP. “The acute effects of interrupting prolonged sitting time in adults with standing and light-intensity walking on biomarkers of cardiometabolic health in adults: a systematic review and meta-analysis.” Sports Medicine, 2022. link.springer.com
- Hall H, Perelman D, Breschi A, Limcaoco P, Kellogg R, McLaughlin T, Snyder M. “Glucotypes reveal new patterns of glucose dysregulation.” PLoS Biology, 2018. journals.plos.org
- MedlinePlus, National Library of Medicine. “Carbohydrates.” Reviewed April 30, 2026. medlineplus.gov
- National Institute of Diabetes and Digestive and Kidney Diseases. “Insulin Resistance & Prediabetes.” NIH, reviewed March 2025. niddk.nih.gov
- National Academies of Sciences, Engineering, and Medicine (Institute of Medicine). “Dietary Reference Intakes: Acceptable Macronutrient Distribution Ranges” (summary table). NCBI Bookshelf, 2011 compilation of 2005 values. ncbi.nlm.nih.gov
- Mayo Clinic Staff. “Low-glycemic index diet: What’s behind the claims?” Mayo Clinic, Aug. 19, 2025. mayoclinic.org
- U.S. Food and Drug Administration. “Daily Value on the Nutrition and Supplement Facts Labels.” FDA, content current as of March 5, 2024. fda.gov
- Shukla AP, et al. “Food Order Has a Significant Impact on Postprandial Glucose and Insulin Levels.” Diabetes Care, 2015. diabetesjournals.org
- Arjmandfard D, Behzadi M, Sohrabi Z, Mohammadi Sartang M. “Effects of apple cider vinegar on glycemic control and insulin sensitivity in patients with type 2 diabetes: A GRADE-assessed systematic review and dose–response meta-analysis of controlled clinical trials.” Frontiers in Nutrition, 2025. frontiersin.org