Is Cornstarch OK on a Diet? The Definitive Guide to Using It Moderately

December 15, 2025 •

4 min read

A single tablespoon of cornstarch contains approximately 30 calories and 7 grams of carbohydrates, making it a concentrated source of refined carbs. So, is cornstarch ok on a diet? The answer lies in portion control and context.

Quick Summary

Cornstarch is generally acceptable on a diet when used in small quantities for thickening, but its high glycemic index and lack of nutrients mean large amounts are not ideal. Safer, more nutrient-dense alternatives exist for frequent use.

Key Points

Moderation is critical: Small quantities of cornstarch used for thickening are generally acceptable on most diets, but large amounts are not recommended.
Low on nutrients: Cornstarch is essentially pure carbohydrate, containing almost no protein, fiber, or vitamins.
High glycemic index: It can cause rapid blood sugar spikes, making it a concern for individuals with diabetes or those managing insulin levels.
Better alternatives are available: For a more nutrient-rich option, substitutes like arrowroot powder, tapioca starch, or whole wheat flour are superior choices.
Context matters: The impact of cornstarch depends on how it's used within the context of a balanced, overall diet plan.

What Exactly is Cornstarch?

Cornstarch is a fine, white powder made from the endosperm of the corn kernel. The milling process strips away the corn's nutrient-rich germ and bran, leaving behind a product that is almost pure starch. This highly processed nature is what gives cornstarch its potent thickening ability, but it also explains its limited nutritional value.

The Nutritional Profile of Cornstarch

While a single tablespoon (around 8g) is not particularly high in calories, with about 30 kcal, it consists almost entirely of carbohydrates. It provides virtually no protein, fat, fiber, vitamins, or minerals in the small quantities typically used in cooking. This makes it a source of what are often called "empty calories". For individuals on a diet where tracking macronutrients is crucial, these added carbs and calories can add up if not accounted for.

The Impact of Cornstarch on Your Diet

For someone on a diet, the primary concerns with cornstarch are its high glycemic index and the lack of satiety it provides. Foods with a high glycemic index cause a quick and significant spike in blood sugar levels, followed by a potential crash. This can be particularly problematic for people managing conditions like type 2 diabetes or insulin resistance. Additionally, since it has no fiber or protein, it won't help you feel full, which can be counterproductive for weight management efforts.

Moderation is the Key to Success

The difference between a diet-friendly ingredient and a diet-buster often comes down to quantity. Most recipes call for only one to two tablespoons of cornstarch to thicken an entire batch of soup, sauce, or pie filling. When distributed across multiple servings, the amount of cornstarch per person is minimal and will have a negligible impact on overall calorie and carb intake. However, excessive use, such as in large portions of some gluten-free baked goods or in processed, pre-made foods, is where problems can arise.

How to Safely Incorporate Cornstarch

If you choose to use cornstarch on a diet, follow these best practices:

Use it sparingly: Stick to the minimum amount needed for your desired consistency. For instance, a slurry of just 1-2 tablespoons can thicken a large pot of liquid.
Mix it properly: Always create a slurry by mixing cornstarch with an equal amount of cold water before adding it to hot liquids. This prevents clumping and ensures even distribution.
Account for the calories: Be mindful that even small amounts contribute calories and carbs. Adjust other parts of your meal accordingly to stay within your daily goals.
Combine with nutrients: Pair cornstarch-thickened foods with protein and high-fiber vegetables to help slow down digestion and minimize blood sugar spikes.

Healthier Cornstarch Alternatives for Your Diet

For those who want to avoid the refined carbs and high glycemic index of cornstarch, or who simply prefer more nutrient-dense options, several excellent substitutes are available. These alternatives can provide similar thickening power while offering additional nutritional benefits. Learn more about healthier choices from authoritative sources like Healthline by visiting https://www.healthline.com/nutrition/is-cornstarch-bad-for-you.

Comparison Table: Cornstarch vs. Healthier Alternatives


Feature	Cornstarch	Arrowroot Powder	Tapioca Starch	Whole Wheat Flour
Thickening Power	Very strong	Strong, produces glossy finish	Strong, good for freezing	Moderate, less glossy finish
Glycemic Index	High (77-88)	Lower	Lower	Lower
Nutritional Value	Almost none	Trace minerals	Trace minerals	Some protein and fiber
Best Use	Sauces, gravies, pie fillings	Quick-cooking sauces, fruit pies	Freezable sauces, pie fillings	Gravies, opaque sauces
Diet Compatibility	Use with caution, in moderation	Generally better for dieting	Generally better for dieting	Superior choice for nutrients

Conclusion

In summary, whether cornstarch is okay on a diet depends on how and how much you use it. When utilized as a minor thickening agent in moderation, it is unlikely to have a major negative impact on your weight management goals. However, it offers little nutritional value and can spike blood sugar, making it an inferior choice compared to more nutrient-dense alternatives like arrowroot or whole wheat flour. For those on strict low-carb or low-GI diets, it may be best to avoid it altogether or explore the healthier substitutes available. Ultimately, conscious portion control is the key to fitting cornstarch into a balanced dietary plan.

Important Considerations for Cornstarch on a Diet

Refined Carbohydrate: Cornstarch is highly processed, providing carbs with minimal other nutrients.
Blood Sugar Impact: Its high glycemic index can lead to rapid blood sugar spikes, which is a concern for diabetics and others monitoring blood sugar.
Calorie Density: Although a single tablespoon is low-cal, excessive use can add extra calories without providing much satiety.
Alternatives Exist: Healthier, more nutrient-dense substitutes like arrowroot or potato starch are available for those seeking better options.
Moderation is Key: Small, controlled amounts used purely for thickening have a minimal impact on overall diet.

Frequently Asked Questions

Excessive consumption of cornstarch can lead to weight gain, as it is a calorie-dense ingredient that provides very little in the way of nutrients like fiber or protein to promote satiety. However, using it in small quantities for thickening purposes will likely have a minimal impact on your weight.

Pure cornstarch is naturally gluten-free. However, cross-contamination can occur during processing. Individuals with celiac disease or gluten sensitivity should always choose a certified gluten-free brand to be safe.

Cornstarch has a high glycemic index, meaning it causes a quick and significant rise in blood sugar when consumed in larger quantities. This can be a major concern for those with diabetes or insulin resistance.

Healthier, more nutrient-rich alternatives include arrowroot powder, tapioca starch, potato starch, or even whole-grain flours. These options provide similar thickening properties with a lower glycemic impact.

Whole wheat flour is generally a healthier option than cornstarch, as it contains some fiber and protein. However, you need twice as much flour to get the same thickening effect, and it will produce a less glossy result.

Due to its high carbohydrate content, cornstarch is not typically recommended for strict low-carb or keto diets. Alternatives like xanthan gum or guar gum are often used instead for thickening.

No, you should never eat raw cornstarch. It can cause digestive issues and may harbor bacteria. It is only safe for consumption once cooked as part of a recipe.