Is Cornstarch Keto-Friendly?

Imge of Is Cornstarch Keto-Friendly?



In this article we will explore the popular and versatile ingredient known as cornstarch. Since the mid-1800s people all over the world have been using this product as a thickener in their cooking as well as in many other household applications. 

It is, however, a derivative of corn, a grain. So is cornstarch keto-friendly, or do you need to use a substitute? Keep reading to gain some knowledge so you can make an informed choice.


What is cornstarch?

Like other grains, the corn plant has a few distinct components, one of them being the endosperm. The endosperm is full of starch molecules, which are long polymers of glucose molecules. Cornstarch is an extract made exclusively from the starch in the endosperm.

As such, of all the macronutrients, it contains only carbohydrates with negligible amounts of proteins or fats. 

The world’s biggest producers and users of this food are the US and Brazil.  

Cornstarch nutrition facts

It is hard to determine an average serving size for this product. As it is used as an ingredient and not as a food, the amount you use will vary from recipe to recipe. Here’s the data for 1 tablespoon.

Serving size: 1 tablespoon (8 g)

  • Calories: 31 kcal
  • Fat: 0 g 
  • Net carbs (total carbs - fiber): 7.2 g
  • Total carbs: 7.3 g
  • Fiber: 0.1 g
  • Protein: 0 g

As expected, this scratchy endosperm extract is very full of carbohydrates. It contains negligible protein and fat and little fiber per serving. The starchy granules in this product consist of large, branched amylopectin and the smaller linear amylose molecules.

How about micronutrients? Does this product contain any?

Even a whole cup (16 tablespoons), an amount you would never eat in one sitting, contains very low amounts of micronutrients.  


Can you eat cornstarch on a keto diet?

No, this product is best avoided on a keto diet due to its very high carb count and negligible amount of nutrients. 

The powder is usually only used as an ingredient, most frequently as a thickener in sauces, gravies, and soups. This means you will add one tablespoon and then, if still too runny, add another and another until desired consistency is reached.

Using it like this is an easy way to quickly go past your daily carb limit and get knocked out of ketosis. 


How much cornstarch on the keto diet can you eat?

Just 1 tablespoon (about 8 g) has 7.2 grams of net carbs.

Although it would technically be possible to include that amount of cornstarch in a keto diet, those carbs would be better spent on nutrient-rich foods like vegetables, fruits, or even small amounts of lentils, beans, oats, or quinoa.

So, it is better to use an alternative thickener that contains less carbohydrates.


What kind of cornstarch can you have on keto?

It is best to avoid all types of this product because they are all high in carbohydrates and low in micronutrients.

There are some genetic variations between the different kinds. Some corn varieties have an endosperm which is almost only amylopectin, while others have a composition that contains a large percentage of amylose. These differences can sometimes make a difference in terms of digestion and absorption of the carbohydrates.

One of the well known uses for this corn-based powder is as a thickener. But how does this work?

In a nutshell, when exposing the starch granules to moisture and heat simultaneously, the granules swell in size and form a gel-like substance.

Once removed from heat, another process known as retrogradation begins. This process expels the absorbed moisture and seeks to rebond the starch molecules to each other.

Generally speaking, the gelatinised product is digested very rapidly, whereas the non-gelatinised one does not. So when you mix the powder in your hot gravy to thicken, if you consume it right away, the starch content is actually digested even quicker and hence the blood sugar response will be more acute. If however, you allow the mixture to cool or retrograde, then the results can be different.

In amylose based starch, about 20% of the starch is reformed as resistant starch; this behaves like fiber and is not digested. This would be better for keto. However, unfortunately there is no indication on standard commercial packaging of the composition of the starch, so practically speaking it’s difficult to put this knowledge to use.  




What can you use cornstarch with?

Cornstarch is mainly used as a thickener in the following liquid-based dishes:

  • Soups
  • Sauces
  • Gravies
  • Stews
  • Custard

It also has anti-caking properties and is often used in packaged grated cheese to prevent clumping and adherence to the packaging.


Keto-friendly cornstarch alternatives 

  • Xanthan gum -  this thickening agent is well known to those who indulge in gluten-free cooking. It has a net carb score of 0 g as all the carbs present are fiber, making it an excellent choice in keto.
  • Glucomannan powder - this is a powder produced from the root of the konjac plant. It is purported to have thickening properties. 
  • Guar gum - similar to xanthan gum, this is an ingredient with very few calories and its carbs are all fiber. This high fiber content is what allows water absorption and retention and hence its thickening properties. Definitely recommended as a low-carb substitute for cornstarch. 


FAQs about cornstarch on a keto diet

Want to learn more? Click to see the answers to commonly asked questions about this corn-based powder.

It was discovered in the 1840’s by a man named Thomas Kingsford of New Jersey, USA. He worked at a wheat starch factory and stumbled upon the discovery of isolating corn endosperms from the rest of the kernel. This is how the product was born.

Nope, it is made entirely from the starchy endosperm and hence contains very few nutrients and very little fiber at all.

The available data ranges between 55 and 62 for a modified cornstarch of a specific brand. Other sources put the score at 77, a high GI score. So on average, this food would fall under the medium GI food group. There possibly is a greater variety between brands and the manner in which it is used may also have a strong effect to bring this score up or down. 

Keeping this ingredient in the freezer is not beneficial. It is better kept in a cool, dry place such as a cabinet and in an airtight container. Refrigeration and freezing can introduce moisture, which in turn can promote spoilage.

It does not seem to be too good for your health. For starters, as it’s medium GI it may be harmful for diabetics and exacerbate the risk for getting diabetes in those who are prediabetic.

It is also a highly refined product stripped for a meaningful amount of nutrients. Such foods that are highly refined and nutrient sparse are not conducive for optimal health.

Yes, just 1 tablespoon has 7.2 grams of net carbohydrates. It’s also relatively high in calories, 31 kcal per tablespoon.


Other types of grains to consider for keto