Which Whole Grain Has the Lowest GI? Your Guide to Healthy Choices

December 22, 2025 •

3 min read

According to the Whole Grains Council, intact whole grains can have very low glycemic index (GI) scores, with some ranking as low as 25 on the GI scale. Understanding these scores is crucial for managing blood sugar and maintaining sustained energy throughout the day.

Quick Summary

Hulled or pearled barley has the lowest glycemic index among whole grains, making it an ideal choice for blood sugar management. Other excellent low-GI options include buckwheat, quinoa, and steel-cut oats, with the level of processing and cooking method significantly impacting the final GI score.

Key Points

Barley Takes the Lead: Hulled or pearled barley is the whole grain with the lowest GI, with scores as low as 25.
Processing Matters: Minimally processed grains like steel-cut oats have a much lower GI than their instant counterparts.
Cooking Affects GI: Cooking grains al dente or for shorter periods can help maintain a lower GI.
Consider Other Low-GI Options: Buckwheat, quinoa, and bulgur are also excellent low-GI whole grains and offer diverse flavors and nutrients.
Pair Grains Wisely: Combining grains with protein and healthy fats can help slow digestion and lower the overall GI of a meal.

Understanding the Glycemic Index (GI)

What is GI and Why Does It Matter?

The Glycemic Index (GI) is a system that ranks carbohydrate-rich foods on a scale from 0 to 100 based on how quickly they raise blood sugar levels after eating. Foods are classified as low (55 or less), medium (56–69), or high (70 or more) GI. Consuming low-GI foods is beneficial for stabilizing blood sugar, which is particularly important for people with diabetes or those looking to prevent chronic diseases. The slower, more gradual release of glucose from low-GI foods provides sustained energy and helps prevent the rapid spikes and crashes associated with high-GI carbohydrates. Key factors that influence a grain's GI include its fiber content, starch structure, and the degree of processing.

The Top Contender: The Whole Grain with the Lowest GI

The whole grain with the lowest glycemic index is consistently identified as hulled or pearled barley, with GI scores ranging from approximately 25 to 35. This exceptional score is attributed to its high content of soluble fiber, specifically a type called beta-glucan. Beta-glucan forms a gel-like substance in the digestive system, slowing down the digestion and absorption of carbohydrates and resulting in a minimal impact on blood glucose levels. Barley is also a versatile grain that can be added to soups, stews, and salads or served as a side dish.

Other Excellent Low-GI Whole Grains

While barley takes the top spot, several other whole grains are fantastic low-GI choices:

Buckwheat: With a GI around 40–50, buckwheat is a gluten-free pseudo-cereal packed with fiber, protein, and minerals like magnesium. It's excellent for blood circulation and can be used in pancakes, porridge, or as a side dish.
Quinoa: A complete protein and another gluten-free option, quinoa has a GI score of approximately 50–53. It is rich in fiber and iron, and its protein content helps slow glucose absorption.
Bulgur: Made from cracked whole wheat, bulgur has a GI of around 46–55. Its high fiber content aids in slowing digestion and is perfect for tabbouleh or as a rice alternative.
Steel-Cut Oats: The least processed form of oats, steel-cut oats have a GI of 55. In contrast, instant oats have a much higher GI (around 75) due to greater processing. Opting for steel-cut or large-flake rolled oats (GI ~53) ensures better blood sugar control.
Whole-Grain Pasta: Surprisingly, whole-grain pasta has a relatively low GI, often around 55, partly because its starch structure resists rapid digestion. Cooking it al dente further lowers its GI.

How Processing and Cooking Affect GI

The Glycemic Index of any grain is not static and can be significantly influenced by its preparation. Highly processed grains, even if they started as whole grains, have had their fiber-rich outer layers removed, speeding up digestion and raising their GI. For instance, whole wheat flour has a higher GI than intact whole wheat kernels. Similarly, the longer a grain is cooked, the more its starches break down, increasing its GI score. Cooking pasta al dente is a classic example of keeping its GI low. Pairing grains with proteins, healthy fats, or fibrous vegetables can also lower the overall GI of a meal.

Comparison of Low-GI Whole Grains


Whole Grain	Typical GI Score	Key Benefits	Best Uses
Barley (Hulled/Pearled)	~25–35	Highest fiber (beta-glucan), heart-healthy, versatile	Soups, stews, salads, porridge
Buckwheat	~40–50	Gluten-free, high in protein and magnesium, good for circulation	Pancakes, porridge, side dish
Quinoa	~50–53	Complete protein, gluten-free, high in fiber and iron	Salads, side dish, breakfast bowls
Steel-Cut Oats	~55	High in soluble fiber (beta-glucan), good for cholesterol	Breakfast porridge
Bulgur	~46–55	High fiber, quick-cooking	Tabbouleh, salads, side dish

Conclusion: Making the Best Whole Grain Choices

Choosing whole grains with a low GI is a smart dietary strategy for everyone, not just those managing blood sugar. Barley stands out as the whole grain with the lowest GI, but a variety of other options like buckwheat, quinoa, and steel-cut oats offer excellent nutritional benefits. When selecting whole grains, prioritize less-processed forms and be mindful of cooking methods. By incorporating these low-GI choices into your meals, you can enjoy stable energy levels, better blood sugar control, and a richer nutritional profile. For additional guidance, consider consulting an authoritative source like the Whole Grains Council for more information on the wide world of whole grains.

Frequently Asked Questions

Hulled barley is the whole grain with only the inedible outer hull removed, retaining the bran and germ. Pearled barley has been polished to remove the bran layer, making it quicker to cook but with a slightly higher GI and lower fiber than hulled barley, though both are low-GI options.

Brown rice has a lower GI than white rice, typically around 55, placing it at the low end of the GI scale. However, some sources classify it as medium GI depending on variety and cooking.

For a low-GI diet, steel-cut oats are the best choice. Their GI is around 55. Rolled oats are also low GI (around 53), while instant oats are significantly higher (around 75) due to greater processing.

Yes, cooking method significantly affects a grain's GI. Longer cooking times can break down starches and increase the GI. For example, cooking pasta al dente keeps its GI lower than cooking it until soft.

Quinoa is technically a pseudo-cereal, a seed from a broadleaf plant rather than a grass. However, it is nutritionally and culinarily classified as a whole grain and offers similar benefits, including a low GI score.

To lower the glycemic load of a meal, you can incorporate proteins, healthy fats, and fiber-rich vegetables. Combining a grain with ingredients like nuts, seeds, legumes, or leafy greens slows down digestion and the subsequent release of glucose.

Whole-grain pasta maintains a lower GI partly due to its unique starch structure and density, which makes it more resistant to digestion than bread. Cooking it less, or al dente, also contributes to its low GI.