TL;DR
Cornstarch is not keto-friendly. It is 100% carbohydrates, with no fiber, fat or protein. Even a small amount of cornstarch can kick you out of ketosis. There are some low-carb substitutes that may work in some recipes, like glucomannan powder, psyllium husk powder, xanthan gum or almond flour. But in general, on a keto diet you’ll want to avoid dishes that rely on cornstarch for thickening.
What is Cornstarch?
Cornstarch is a white, powdery starch that is extracted from corn kernels. It is used as a thickening agent and can be found in a variety of products including:
- Sauces, gravies, soups
- Pie fillings and puddings
- Cakes, cookies, muffins, breads
- Meat marinades
- Fried foods
- Soups and stews as a thickener
Some common brands of cornstarch include Argo, Clabber Girl, and Maizena. It can be purchased as a fine powder or larger granules.
Nutrition Facts of Cornstarch
One tablespoon (8 grams) of cornstarch contains (1):
- Calories: 31
- Fat: 0g
- Carbs: 8g
- Fiber: 0g
- Sugars: 0g
- Protein: 0g
As you can see, cornstarch is 100% carbohydrate with no other macronutrients.
It contains 25 grams of net carbs per 100 grams. The carbs are in the form of starch, which is a polysaccharide made up of long chains of glucose molecules (2).
Humans don’t have the enzymes needed to digest raw starch. However, when cornstarch is cooked, the starch granules swell and burst, allowing the starch to be digested.
So cornstarch spikes blood sugar and insulin rapidly once cooked. It has a very high glycemic index of 85, which is even higher than pure glucose (3).
Is Cornstarch Keto-Friendly?
No, cornstarch is not considered keto-friendly.
A ketogenic diet typically limits net carbs to 20-50 grams per day. Even small amounts of cornstarch can put you over this limit or kick you out of ketosis.
Just two tablespoons of cornstarch contains 16 grams of net carbs. That’s already 66-80% of the daily allotment on keto.
Using cornstarch can also stimulate hunger and cravings. The blood sugar spike causes a surge in the hormone insulin, leading to unstable blood sugar levels and more carb cravings.
So recipes that rely on cornstarch for thickening or binding are best avoided on a keto diet.
There are some exceptions where you may be able to fit in 1-2 tablespoons in a day. But it’s generally recommended to avoid cornstarch when following a keto diet.
Health Concerns with Cornstarch
There are some potential health concerns with over-consuming cornstarch and highly processed grains in general:
Blood Sugar Spikes
As mentioned earlier, cornstarch has a very high glycemic index. It can spike blood sugar and insulin rapidly (3).
High blood sugar can worsen insulin resistance over time and increase the risk of type 2 diabetes and related issues like nerve damage and vision loss (4).
Inflammation
Refined grains like cornstarch promote inflammation in the body (5).
Chronic inflammation is linked to diseases like heart disease, diabetes, cancer, osteoporosis and Alzheimer’s (6, 7, 8).
Nutrient Poor
Since cornstarch is highly refined, all of the vitamins, minerals and antioxidants have been removed. It provides empty calories and no beneficial nutrients.
A diet overly reliant on refined grains has been linked to nutrient deficiencies (9).
Gut Health
The resistant starch and fiber in whole grains can act as prebiotics and feed the friendly bacteria in your gut microbiome (10).
However, cornstarch contains no fiber or resistant starch. Eating it may shift the bacteria in your gut to be less favorable.
An unhealthy gut microbiome is linked to inflammation, weight gain, obesity, diabetes, heart disease and even neurological conditions like Parkinson’s (11, 12, 13).
Low-Carb Substitutes for Cornstarch
If you’re following a keto diet, there are several substitutes that can be used instead of cornstarch for thickening:
Xanthan Gum
Xanthan gum is a popular keto-friendly cornstarch substitute. It’s a polysaccharide that’s commonly used as a thickening agent.
Xanthan gum contains 5 grams of net carbs per tablespoon, which is much less than cornstarch (14).
It works well for thickening sauces, gravies, baked goods, dressings and drinks. Start with a small amount like 1/4 teaspoon. It thickens more as it sits, so it’s easy to over-thicken.
Glucomannan Powder
Glucomannan, also known as konjac root, is a water-soluble polysaccharide that comes from the konjac plant.
It’s an excellent source of soluble fiber. In fact, it absorbs up to 50 times its weight in water (15).
Glucomannan powder can be used to replace cornstarch as a thickener for stew, chili, curries or gravy. It also gels up nicely when added to pudding.
It has 0 grams of carbs per serving since it’s a fiber. It may cause digestive issues if too much is consumed at once.
Psyllium Husk Powder
Psyllium is a soluble fiber derived from the Plantago ovata plant. When mixed with water, it forms a thick gel-like substance.
Psyllium husk powder contains 2 grams of carbs and 1 gram of fiber per tablespoon, so it’s a low-carb option (16).
It works well for thickening smoothies or to add thickness to keto baked goods. Make sure to drink plenty of fluids.
Too much psyllium without adequate hydration can cause choking or an intestinal blockage.
Chia Seeds
Chia seeds are tiny black seeds that gel up when mixed with liquid.
They can be used as an egg substitute in keto baking recipes to help bind ingredients together. Chia seeds contain 5 grams of carbs and 4 grams of fiber per tablespoon (17).
Flaxseeds
Like chia seeds, flaxseeds also form a thick, viscous gel when mixed with water.
You can use ground flax as a substitute for cornstarch to thicken sauces or bind ingredients in baking. There are 2 grams of net carbs in flaxseed per tablespoon (18).
Almond Flour
Almond flour is made from blanched, ground almonds. It can be used in small amounts to thicken sauces or soups.
There are 3 grams of net carbs in almond flour per tablespoon, along with protein and healthy fats (19).
However, almond flour clumps more than cornstarch and can slightly alter the texture and flavor.
Gelatin
Unflavored gelatin powder works as a binder in recipes. It gels up when combined with liquid.
It’s useful for making keto puddings, mousses, smoothies or gummy snacks. Gelatin has no carbs (20).
Guar Gum
Guar gum comes from the guar bean. It’s commonly used as a thickener or emulsifier.
It contains 5 grams of carbs per tablespoon, with 4 grams being fiber (21). Guar gum can be used like xanthan gum in sauces, gravies and dressings.
However, guar gum doesn’t dissolve as well and can clump if not properly hydrated first. It’s best used in cold foods.
Fresh Egg Yolks
Using fresh egg yolks is a simple way to naturally thicken and enrich sauces, gravies or custards without cornstarch.
Egg yolks contain emulsifiers like lecithin that help bind ingredients. There are 0.6 grams of carbs in an egg yolk (22).
Coconut Flour
Coconut flour is high in fiber and soaks up liquid well, which makes it useful for thickening.
It contains 5 grams of carbs per tablespoon, but 4 grams come from fiber (23).
Keep in mind that coconut flour has a strong flavor that may overpower some recipes. It’s best used in small amounts.
Heavy Cream
Adding heavy whipping cream is an easy way to thicken sauces and gravies. The high fat content also helps bind ingredients.
Heavy cream contains 0.4 grams of carbs per tablespoon (24). It works especially well in cream-based sauces.
Cream Cheese
Cream cheese can be whipped into sauces, soups or omelets to add thickness and richness.
It contains 1 gram of carbs per tablespoon (25). Just a tablespoon or two is enough to thicken most sauces.
Nut Butters
Nut butters like almond butter, cashew butter or peanut butter can help thicken sauces, shakes or desserts naturally.
Just 1-2 tablespoons will add body. Most nut butters contain 3-5 grams of carbs per 2 tablespoon serving (26, 27, 28).
Cornstarch Substitutes for Frying
Cornstarch is often used to coat meat or fish before frying to help create a crispy crust.
Some low-carb alternatives include:
- Almond flour – Finely ground blanched almond flour can mimic cornstarch for frying. There are 3 grams of net carbs per tablespoon (19).
- Coconut flour – Very absorbent like cornstarch. Contains 5 grams of carbs per tablespoon (23).
- Pork rinds – Crushed pork rinds make an excellent keto breading with 0 grams of carbs (29).
- Parmesan cheese – Grated parmesan can be mixed with almond flour or pork rinds to coat meats before frying while adding flavor.
You can also skip any coating and fry foods directly in hot oil. The key is getting the oil hot enough (around 350°F or 175°C) so the food fries up quickly and becomes crispy.
Is Cornstarch Bad for Keto?
Yes, cornstarch is considered unsuitable for the keto diet. Here’s a recap why:
- It’s 100% carbohydrates, containing 25g of net carbs per 100g.
- Even small servings of 1-2 tablespoons can surpass your daily carb limit on keto.
- It causes rapid spikes in blood sugar and insulin.
- It’s highly processed and provides no beneficial nutrients.
- Health concerns like inflammation, gut dysbiosis, and nutrient deficiencies.
Occasionally fitting in a small amount may be fine, but it’s best limited or avoided altogether on keto.
There are many low-carb thickeners that can be used instead with little impact on ketosis.
The Bottom Line
Cornstarch is not keto-friendly. It provides nothing but quick-spiking carbs, without any beneficial nutrients.
Even a tablespoon or two may be enough to kick you out of ketosis or stall weight loss. It’s best avoided when following a ketogenic diet.
If you need a thickener, there are many better options like xanthan gum, psyllium husk powder, chia seeds, almond flour, gelatin or guar gum.
While cornstarch won’t directly harm your health in moderation, it’s unnecessary empty calories that can increase cravings and inflammation.
There are easy substitutes that will keep you in ketosis without sacrificing texture or taste.
