How to Reduce Glycaemic Index for Better Blood Sugar Control

November 30, 2025 •

4 min read

According to a 2019 review, low GI diets can significantly reduce long-term markers of blood sugar control and fasting blood sugar levels in individuals with prediabetes or diabetes. Knowing how to reduce glycaemic index is a practical and effective strategy for managing blood sugar and supporting overall health.

Quick Summary

This guide covers practical dietary changes and specific food preparation techniques to help lower the glycaemic index of meals for more stable blood sugar levels. It details how fiber, protein, and fat impact GI and offers actionable strategies for healthier eating.

Key Points

Choose Low-GI Foods: Swap refined grains like white bread and rice for whole grains such as quinoa, barley, and brown rice to lower your meal's GI.
Incorporate Fiber, Protein, and Fat: Pairing carbohydrate-rich foods with fiber (legumes, vegetables), protein (fish, eggs), and healthy fats (olive oil, nuts) slows digestion and reduces the glycaemic response.
Modify Cooking Methods: Cook starchy foods like pasta al dente and cool them after cooking to increase resistant starch content and lower their GI.
Prioritize Whole Foods: Eat fruits and vegetables in their whole form rather than mashed or juiced, as processing increases the rate of sugar absorption.
Be Mindful of Portion Sizes: Regardless of a food's GI, larger portions will have a greater effect on blood sugar, so practicing portion control is essential.
Consider Meal Composition: Eating fiber and protein first, followed by carbohydrates, can lead to a more gradual rise in blood glucose.

The glycaemic index (GI) is a ranking system for carbohydrate-containing foods based on their effect on blood glucose levels after consumption. A high GI food causes a rapid spike, while a low GI food results in a more gradual increase. For individuals looking to manage blood sugar, weight, or reduce the risk of chronic diseases like type 2 diabetes, controlling the glycaemic impact of meals is crucial. Fortunately, several straightforward dietary and cooking adjustments can help you lower the overall GI of your diet without sacrificing flavor or nutrition.

Prioritize Food Selection

The first and most impactful step is to choose lower GI foods over their higher GI counterparts. Whole, less-processed foods generally have a lower GI than refined and processed foods. This is because the fiber content and natural structure of whole foods slow down digestion and sugar absorption.

Swap Refined Grains: Replace high-GI white bread, white rice, and instant oats with whole-grain alternatives like grainy or pumpernickel bread, brown rice, barley, quinoa, and steel-cut oats.
Embrace Legumes: Incorporate beans, lentils, and chickpeas into your meals. These are excellent sources of fiber and protein and have a naturally low GI. Try mixing them with high-GI staples, such as adding chickpeas to rice to lower the meal's overall GI.
Choose Low-GI Fruits and Vegetables: Favor low-GI fruits like berries, apples, pears, and citrus fruits over high-GI options like watermelon and pineapple. Similarly, increase your intake of non-starchy vegetables such as broccoli, spinach, and carrots.

Modify Your Cooking Techniques

The way you prepare food significantly impacts its GI. Longer cooking times can break down starches, making them easier and faster to digest, thereby increasing the GI.

Cook Pasta Al Dente: For pasta, cook it to an "al dente" (firm) texture. Overcooking breaks down the starch and increases its GI.
Cool Cooked Starches: Cooking and then cooling starchy foods like potatoes, rice, and pasta can increase their resistant starch content. This type of starch resists digestion, meaning it doesn't spike blood sugar as much. Consuming these foods cold, or reheating them gently, can help lower their GI.
Avoid Mashing and Pureeing: Processing foods into smaller particles or pureeing them, like with mashed potatoes or fruit puree, increases the GI because it makes the carbohydrates more readily available for digestion. Opt for whole, less-processed versions instead.

Balance Your Meals with Other Nutrients

Pairing carbohydrates with other macronutrients can help blunt the overall glycaemic response of a meal.

Add Protein: Including lean protein sources like chicken, fish, eggs, and legumes slows down gastric emptying and carbohydrate absorption. For instance, adding peanut butter to wholemeal bread significantly lowers the GI of the meal.
Incorporate Healthy Fats: Similar to protein, healthy fats from sources like olive oil, avocado, nuts, and seeds can reduce the GI of a meal. When eating bread, pair it with avocado instead of high-GI spreads.
Use Acidity: Adding acidic foods like vinegar or lemon juice to a meal can also help lower the GI by slowing down stomach emptying. Consider a vinaigrette dressing on your salads or adding a splash of vinegar to cooked greens.

Comparison Table: High GI vs. Low GI Swaps


High GI Food	Glycaemic Index	Low GI Alternative	Glycaemic Index
White Bread	71	Pumpernickel Bread	46
Cornflakes	79	Rolled Oats	55 or below
White Rice	66	Brown Rice	50
Baked Russet Potato	111	Cooled Potato Salad	Varies, lower
White Spaghetti (cooked 20 min)	58	Whole-meal Spaghetti (cooked al dente)	32
Watermelon	76	Apple	39

Manage Portions and Timing

Beyond individual food choices and cooking methods, the amount of carbohydrates consumed (glycaemic load) and when you eat can affect your blood sugar.

Mind Your Portions: Even low-GI foods can raise blood sugar if eaten in large quantities. Being mindful of portion sizes is an important part of any strategy for blood sugar control.
Eat Carbohydrates Last: Some studies suggest that eating foods rich in fiber, fat, and protein before starchy carbohydrates can lower the meal's overall glycaemic response.

Conclusion

By consciously choosing low-GI whole foods, adjusting cooking methods to preserve the integrity of starches, and balancing meals with protein and healthy fats, you can effectively and sustainably reduce your glycaemic index. These simple, cumulative changes can help stabilize blood sugar levels, improve energy, and promote long-term health. The glycemic index is a valuable tool, but it's important to remember it exists within the context of a balanced, varied diet. Always consider the nutritional value of the meal as a whole, focusing on whole, unprocessed foods and healthy portion sizes. For personalized dietary advice, consulting a registered dietitian is always recommended.

For more information on the glycemic index of a wide range of foods, consider referencing the authoritative Glycemic Index Database from the University of Sydney.

What is the Glycaemic Index Research and GI News website? It can be found at the University of Sydney.

Frequently Asked Questions

The glycaemic index (GI) is a ranking system that measures how quickly a carbohydrate-containing food raises blood sugar levels after it is eaten. Foods are ranked on a scale of 0 to 100 based on their effect compared to a reference food, typically pure glucose.

Protein and fat both slow down the rate at which your stomach empties and delays carbohydrate absorption. This effect leads to a slower and more gradual rise in blood sugar, thus reducing the overall GI of the meal.

Yes, cooking time directly impacts a food's GI. For instance, cooking starches like pasta for longer periods breaks down their structure, making them easier to digest and raising the GI. Conversely, cooking pasta to an 'al dente' texture keeps its GI lower.

Yes, cooling starchy foods like potatoes, rice, and pasta after cooking increases their content of resistant starch. This type of starch is not fully digested, which leads to a lower blood sugar response.

Less processed rice varieties generally have a lower GI. This includes brown rice and long-grain types like basmati, which are better choices than shorter-grain or highly processed white rice.

No, not all fruits have a low GI. The GI of a fruit depends on its ripeness and type. For example, while berries and apples have a low GI, ripe bananas and watermelon have a moderate to high GI.

Adding acidic ingredients like vinegar or lemon juice to a meal can lower its GI. The acidity helps to slow down the rate of gastric emptying, which in turn slows the absorption of carbohydrates.

While focusing on low-GI foods is beneficial, it's not the only factor. A healthy diet should be balanced and varied. Some high-GI foods, like potatoes, are nutrient-rich and can be included in moderation, especially when paired with low-GI foods.