Is Cornstarch Keto? 8 Low-Carb Cornstarch Substitutes
Keto Zone Kitchen • Low-Carb Swaps
By Don Colbert, MD • Board-certified in family practice and integrative medicine • Updated October 2026
Quick answer
No, cornstarch is not keto. One tablespoon has about 7 grams of net carbs and almost no fiber, which can use up a third of a strict keto day in a single spoonful of gravy.
The best keto swaps are xanthan gum (use about 1/4 teaspoon for every tablespoon of cornstarch), glucomannan, and guar gum, all with close to zero net carbs. For a whole-food option, try ground flaxseed, chia, almond flour, or puréed cauliflower.
~7 g
net carbs in 1 tablespoon of cornstarch
~0 g
net carbs in xanthan gum, glucomannan, or guar gum
1/4 tsp
of xanthan gum replaces 1 tablespoon of cornstarch
Why cornstarch is not keto
Cornstarch is the pure starch of the corn kernel. That is exactly what makes it such a good thickener, and exactly why it does not belong in a ketogenic kitchen. Starch is a chain of glucose molecules, and your body breaks it down into blood sugar quickly.
A single tablespoon carries about 7 grams of carbohydrate with almost no fiber to slow it down. If you are keeping net carbs around 20 grams a day to stay in ketosis, a beef stew or a holiday gravy thickened the traditional way can spend a big share of that budget before you take a bite of anything else.
The good news: cornstarch has only one job in most recipes, which is to thicken. Several low-carb ingredients do that job just as well, and some do it better.
Keto Zone tip
Hidden starches in sauces, soups, and gravies are one of the most common reasons people slip out of ketosis without realizing it. Learn a few simple swaps and you can keep enjoying the comfort foods you love.
Keto thickeners compared
Use this chart as your cheat sheet. Carb counts are approximate and vary by brand, so always check the label on the product you buy.
| Thickener | Net carbs (approx.) | Replaces 1 Tbsp cornstarch | Best for |
|---|---|---|---|
| Xanthan gum | ~0 g per tsp | 1/4 tsp | Gravy, pan sauces, dressings |
| Glucomannan | ~0 g per tsp | About 1/3 tsp | Soups, stews, puddings |
| Guar gum | ~0 g per tsp | About 1/2 tsp | Cold sauces, ice cream, baking |
| Psyllium husk powder | Under 1 g per tsp | Start with 1/2 tsp | Soups, breads, binding |
| Ground flaxseed | Under 1 g per Tbsp | 1/2 Tbsp + 2 Tbsp water | Hearty stews, chili, binding |
| Chia seeds (ground) | About 1 g per Tbsp | Add 1 tsp at a time | Puddings, jams, smoothies |
| Almond flour | About 1 g per Tbsp | About 2 Tbsp | Gravy roux, cream sauces |
| Puréed cauliflower | About 1 g per 1/4 cup | 1/4 to 1/2 cup, simmered | Creamy soups, chowders |
The 8 best low-carb cornstarch substitutes
The first three are the closest to cornstarch in how they behave. The rest bring extra fiber and nutrition along with the thickening.
1. Xanthan gum: the closest match
Xanthan gum is made by fermenting sugar with a beneficial bacterium, then drying the result into a fine powder. Almost all of its carbohydrate is fiber, so it adds virtually no net carbs. It is the most popular keto thickener because a tiny amount goes a long way and it holds up to heat, cold, and acid.
How to use it: Sprinkle 1/4 teaspoon over a simmering sauce while whisking constantly, wait a minute, then add more only if needed. Too much turns sauces slimy, so go slowly.
2. Glucomannan powder
Glucomannan is a soluble fiber from the root of the konjac plant (the same plant used to make shirataki noodles). It is tasteless, has close to zero net carbs, and acts as a prebiotic that feeds the good bacteria in your gut.
How to use it: It thickens more powerfully than cornstarch. Start with about 1/4 teaspoon for every 2 teaspoons of cornstarch. Mix it into a little cold water first to prevent clumps, then stir it into the hot liquid.
3. Guar gum
Guar gum comes from the guar bean. Like xanthan, its carbohydrate is almost entirely fiber, which brings the net carb count to about zero. It works especially well in cold or frozen recipes such as dressings and keto ice cream.
How to use it: Start with about 1/2 teaspoon per tablespoon of cornstarch. Some people with sensitive digestion notice bloating with gums, so use small amounts and see how you feel.
4. Psyllium husk powder
Psyllium is a plant-based soluble fiber with under 1 gram of net carbs per teaspoon. It is a great way to add gut-friendly fiber to a low-carb diet while thickening at the same time.
How to use it: Begin with 1/2 teaspoon, stir well, and give it a few minutes to gel before adding more. Use the fine powder, not whole husks, for a smooth texture.
5. Ground flaxseed
Flaxseed brings soluble fiber and plant omega-3 fats along with its thickening power. The texture is a little grainier than cornstarch, which makes it perfect for chili, stews, and meatballs rather than silky sauces.
How to use it: Mix 1 tablespoon of ground flaxseed with 4 tablespoons of water. That gel replaces about 2 tablespoons of cornstarch.
6. Chia seeds
Chia seeds swell and gel when they meet liquid, and they are rich in fiber, omega-3s, magnesium, and calcium. One tablespoon has about 1 gram of net carbs.
How to use it: Grind them for a smoother result, then add 1 teaspoon at a time until you reach the thickness you want. Chia is ideal for puddings, quick jams, and smoothies.
7. Almond flour
Almond flour is one of the best low-carb flour alternatives, with about 3 grams of net carbs in a quarter cup. It thickens gently and adds vitamin E, magnesium, and healthy fats.
How to use it: Whisk about 2 tablespoons into melted butter to make a keto roux for gravy, or stir directly into a cream sauce and simmer for a few minutes.
8. Puréed cauliflower
If you would rather skip powders altogether, cauliflower is your friend. Puréed until smooth, it thickens soups much like potatoes do, for a fraction of the carbs.
How to use it: Blend steamed cauliflower with a little grass-fed butter or cream cheese, then stir 1/4 to 1/2 cup into your soup and simmer 20 to 25 minutes.
Put these swaps to work
These Keto Zone recipes use low-carb thickeners in place of cornstarch or flour:
Thickeners to avoid on keto
These are often sold as “healthier” or “gluten-free” alternatives, but they are still starches and will raise your blood sugar much like cornstarch does.
About 7 g net carbs per Tbsp
About 8 to 9 g net carbs per Tbsp
About 10 g net carbs per Tbsp
About 6 g net carbs per Tbsp
Other ways to thicken without a thickener
Sometimes the simplest fix is a technique, not an ingredient:
- Reduce it. Simmer uncovered on low so extra liquid evaporates and flavors concentrate.
- Add healthy fat. Heavy cream, cream cheese, sour cream, or full-fat Greek yogurt stirred in at the end adds body.
- Use egg yolks. Temper a yolk with a little hot liquid, then whisk it back in over gentle heat for a rich, custard-like sauce.
- Bloom a little gelatin. About 1 teaspoon of unflavored gelatin, softened in cold water, gives pan sauces a glossy, restaurant-style finish.
- Blend in vegetables. Purée part of the soup itself, or add blended zucchini or cauliflower.
Want to convert a family favorite? See Dr. Colbert’s steps to turn any recipe into a Keto Zone dinner, and pair it with these low-carb sugar substitutes.
“So whether you eat or drink or whatever you do, do it all for the glory of God.”
1 CORINTHIANS 10:31 (NIV)
From Dr. Colbert’s kitchen
Quick and Healthy Keto Zone Cookbook
Fast, family-friendly keto recipes from Dr. Colbert, including sauces, soups, and comfort foods made without starchy thickeners. A simple way to keep your favorite meals on the table while staying in the Keto Zone.
Frequently asked questions
Is cornstarch keto friendly?
No. Cornstarch is a refined starch with about 7 grams of net carbs per tablespoon and almost no fiber. Xanthan gum, glucomannan, and guar gum thicken the same way with close to zero net carbs.
Can I use a little cornstarch on keto?
A teaspoon spread across a large pot of soup adds well under 1 gram of carbs per serving, so it will not ruin your day. Still, the low-carb swaps above work just as well, so there is rarely a reason to reach for it.
What is the best keto substitute for cornstarch in gravy?
Xanthan gum is the easiest: whisk 1/4 teaspoon into simmering pan drippings and broth. For a more traditional texture, make a roux with butter and almond flour.
Is arrowroot keto?
No. Arrowroot is a starch with roughly the same carbs as cornstarch. It is a good gluten-free choice, but not a low-carb one.
Is xanthan gum healthy?
In the small amounts used for cooking, xanthan gum is considered safe for most people and acts as a soluble fiber. If gums upset your stomach, choose psyllium, flax, or chia instead.
Written and medically reviewed by Don Colbert, MD
Dr. Colbert has been board-certified in family practice and in anti-aging and integrative medicine for more than 25 years. He is the New York Times bestselling author of Keto Zone Diet and Beyond Keto. More about Dr. Colbert
This article is for educational purposes only and is not medical advice. Consult your healthcare provider before making significant dietary changes, especially if you have diabetes or take medication that affects blood sugar. These statements have not been evaluated by the Food and Drug Administration. Products mentioned are not intended to diagnose, treat, cure, or prevent any disease. Nutrition values are approximate and vary by brand.
Was this helpful?
Get Dr. Colbert's weekly health tips
Simple, faith-filled health tips in your inbox once a week. Plus a free gift: the 21-Day Keto Zone Challenge.
Unsubscribe anytime. We never share your email.
What stood out to you most, and have you tried any of this yourself?
Tell us on Facebook
Comments are closed.