TL;DR
Cornstarch is not keto-friendly due to its high carbohydrate content. On keto, net carb intake should be limited to 20-50 grams per day. Two tablespoons of cornstarch contain around 24 grams of carbs, nearly a full day’s worth. There are several low-carb thickeners that can be used instead, like xanthan gum, psyllium husk powder, and flaxseed meal. When consuming cornstarch, it’s best to carefully measure portions and account for the carbs. Occasionally using small amounts may fit into some keto diets, but it’s generally best avoided.
What is Cornstarch?
Cornstarch is a fine, powdery starch derived from the endosperm of corn kernels. It’s commonly used as a thickening agent and to provide a smooth texture in sauces, gravies, puddings, and other foods.
Some key facts about cornstarch:
- Made from corn, which is a high-carb grain
- Pure starch with no fiber, protein, fat, or nutrients
- Highly refined and processed carbohydrate
- 1 tablespoon contains 7 grams net carbs
- Has twice the thickening power of flour
- Provides smooth, glossy texture to foods
So in summary, cornstarch is 100% starchy carbohydrate without any nutritional value. It’s purely used for thickening and texture.
Why is Cornstarch High in Carbs?
The reason cornstarch contains so many carbs is because it’s made entirely from starchy corn kernels.
Here’s an overview:
- Corn kernels contain both fiber and starch.
- To make cornstarch, corn is finely ground and soaked in water.
- The fibrous hull and germ are removed, leaving behind the starchy liquid.
- This starchy liquid is dried to produce a fine cornstarch powder.
- So cornstarch isolates the starchy part of corn, removing all fiber and protein.
As a result, cornstarch is almost entirely starch or carbohydrate. Just one tablespoon provides 7 grams of net carbs without any other nutrients.
This makes it great for thickening and adding gloss to foods. But for low-carb and keto diets focused on reducing carbs, cornstarch can be problematic.
Is Cornstarch Keto-Friendly?
Cornstarch is generally not considered keto-friendly, for a few reasons:
- Very high in carbs and no nutrients – Keto aims to reduce carb intake while increasing healthy fats.
- Each tablespoon contains 7 net grams of carbs – This can quickly add up to over 50 grams per day if using cornstarch to thicken multiple foods.
- Made from corn which is a high-carb grain – Keto avoids all grains, even whole grains, as they are carbohydrate-based.
- Highly refined and processed – Keto focuses on unprocessed, whole food-based carbs like vegetables, nuts, and seeds.
- Rapidly digesting carb source – Keto requires steady, slow-burning carbs rather than fast spikes in blood sugar.
The recommended daily carb intake on keto is only 20-50 net grams per day. With each tablespoon of cornstarch containing 7 net grams, just a few tablespoons can exceed the carb limits for an entire day.
For this reason, cornstarch is generally avoided on a well-formulated keto diet.
Alternatives to Cornstarch on Keto
Luckily, there are several great substitutes for cornstarch that are low-carb and keto-approved:
Xanthan Gum
Xanthan gum is a popular cornstarch replacement made from fermented sugars. It contains 8 grams of carbs per tablespoon, but 6 grams come from fiber. So the net carbs are only 2 grams per tablespoon, much lower than cornstarch.
Xanthan gum is flavorless and provides the same thickening and stability as cornstarch. Start with 1/4 to 1/2 teaspoon xanthan gum per 1 cup of liquid when substituting.
Glucomannan
Glucomannan is a type of soluble fiber derived from the konjac plant. It absorbing up to 50 times its weight in water, making it an excellent thickener.
Glucomannan contains 5 grams of carbs per tablespoon, but with 3 grams from fiber. So the net carbs are only 2 grams, like xanthan gum.
It has no taste or odor and mixes well into liquids. Start with 1/4 teaspoon per 1 cup liquid when substituting for cornstarch.
Psyllium Husk Powder
Psyllium is a fiber made from psyllium plant husks. It contains 2 grams net carbs per tablespoon along with 5 grams of fiber.
When mixed with water, psyllium husk gelatinizes and thickens beautifully. Slowly sprinkle psyllium into liquids while whisking vigorously. Use about 1 teaspoon per cup of liquid.
Chia Seeds
Chia seeds are nutrient-packed seeds that form a gel when mixed with liquids. They contain 5 grams of carbs and 3 grams of fiber per tablespoon, so the net carbs are only 2 grams.
For thickening, grind chia seeds into a fine powder first. Then whisk 1-2 teaspoons of chia powder per cup of liquid. Allow to sit for 15 minutes before using.
Flaxseed Meal
Like chia seeds, flaxseeds thicken liquids well when ground into meal. Each tablespoon of flax meal contains 3 grams of carbs and 2 grams of fiber, resulting in 1 gram net carb.
Use 1-2 tablespoons of freshly ground flax meal per cup of liquid. Whisk vigorously and let sit for 10-15 minutes before using. Works great combined with xanthan gum or psyllium.
Avocado
Surprisingly, avocado can be used to thicken and add richness to low-carb sauces and smoothies. Simply blend in flesh from half an avocado until creamy. Each tablespoon of avocado has only about 1 gram net carb.
Should I Avoid Cornstarch Completely on Keto?
Most keto experts recommend completely avoiding cornstarch, especially in the initial phases of keto adaptation. This is when it’s most important to drastically reduce carbs to 20g net carbs or less per day.
During this time, cornstarch is simply too high in carbs to fit into the tight carb budget. Even a few tablespoons could use up the entire day’s worth of carbs.
After adapting to keto and reaching metabolic flexibility, some people can occasionally fit small amounts of cornstarch into their diet. For example, 2-3 tablespoons cornstarch might work for thickening a special recipe now and then.
However, it’s still best to choose low-carb thickeners like xanthan gum instead. And be mindful that overdoing cornstarch can quickly knock you out of ketosis by spiking carb intake.
Tips for Using Cornstarch on Keto
If you do decide to occasionally use cornstarch in keto recipes, here are some tips:
- Carefully measure 1-2 tablespoons at most per recipe.
- Account for the 7g net carbs per tablespoon in your daily tally.
- Substitute half the amount with low-carb thickeners like xanthan gum.
- Use cornstarch sparingly for a light thickening effect.
- Add it at the end of cooking for best results.
- Avoid combining with other carby ingredients in the same recipe.
- Test ketones after consuming to ensure you remain in ketosis.
Also consider avoiding cornstarch altogether on stricter versions of the keto diet like carnivore keto or cyclic keto.
The Bottom Line
Here is a summary on using cornstarch on a keto diet:
- Cornstarch is highly refined starchy carbohydrate without nutrients.
- Just 1-2 tablespoons can contain over 20g net carbs.
- It’s best avoided, especially when first adapting to keto.
- Low-carb thickeners like xanthan gum are excellent substitutes.
- Occasionally using 1-2 tbsp may work for some people, but it’s risky.
- Carefully measure portions and account for carbs if using.
- Completely avoid cornstarch on very low-carb keto versions.
While not toxic, cornstarch is a dense source of carbohydrates that can quickly raise blood sugar and insulin. For the carb-restricting keto diet, there are much better options.
Using keto-friendly thickeners provides the same results without disrupting ketosis. With all the amazing low-carb ingredients available today, cornstarch can generally be avoided on a well-formulated ketogenic diet.
