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Low Carb Thickener

Dear Mark,

I try to be strictly primary / paleo, but I always have problems when thickening sauces or soups. I grew up dealing with flour / cornstarch like everyone else, but is there a good low carb / native alternative?

Many thanks,

I received this email a while ago, but it wasn’t the first. A number of readers have expressed their confusion about how to thicken sauces, sauces, or soups without traditional flour methods. The question of how to thicken sauces is one of the hurdles I face every time I post a recipe – it has become an internal battle (as you can see with the stir-fry recipe for beef and broccoli last week at which I hesitantly called for a teaspoon of flour as a thickening agent) because while adding some flour or cornstarch to a larger recipe doesn’t drastically affect carbohydrate counts, it complicates the consistently original message I’m trying to get across. I hope this post will solve that struggle.

There are many ways to thicken a sauce without resorting to refined starches. In fact, thickening a sauce using Primal methods can result in a richer, more satisfying meal.

Carbohydrates in corn starch

There are 7 grams of carbohydrates in 1 tablespoon of cornstarch. Since you’re only using a tablespoon or two in an entire recipe serving four or more people, cornstarch won’t send your carb count through the roof.

Many people who follow Paleo, Primal, or Keto will want to avoid corn and its derivatives because of its naturally occurring sugars and starch, and because it is not a nutrient-dense food.

Make a reduction

The most rewarding way to thicken a sauce is through reduction. In fact, learning how to reduce a sauce is important for any cook – at home or at work. It’s actually quite simple, but it’s an essential step in thickening sauce or soup (whether you’re primarily storing it or using starch). Reduce the moisture content of a potential sauce by simmering over low heat and taking over the evaporation. The water goes, but the flavors stay. If you cut down on too much, be prepared for incredibly strong flavors. Adding fats towards the end of the reduction process can complete the thickening process (more later).

Add fat

Ah, the epic battle between fats and carbohydrates continues. Fats can form effective thickeners, especially butter and especially with reductions. Suppose you just seared a steak with garlic and shallots in your cast iron pan. See those browned pieces and bubbles of delicious beef fat and leftover juices? Keep the heat low and add some red wine. Scrape the good stuff off the bottom and let the wine reduce towards the end, add a piece of cold butter and whisk everything together until it’s smooth and creamy and viscous. Drizzle over your finished steak and vegetables.

Heavy cream works well too, especially for white sauces and soups. Again the key is reduce, reduce, reduce.

Rendered duck, bacon, beef, or chicken fat can act like butter when you want to avoid dairy products altogether or add a different flavor profile. Just make sure you add the fat in its solid (cold) state towards the end.

Gluten-free roux

A roux is a sauce starter or thickener that involves whipping flour into a pan with heated fat. I’ve found arrowroot flour to be a great substitute for flour in most, if not all, uses that require a roux.

Here is my favorite recipe for arrowroot turkey sauce.

Can you make a roux with almond flour?

Almonds have no starch, and starch gives structure to the cooking liquid. So almond flour doesn’t make good roux.

Keto Roux

If you want a sauce-like consistency but not the carbohydrates of arrowroot or cassava, choose recipes that use a small amount of xanthan gum.

Pureed vegetables

Adding a few scoops of pureed vegetables is another option, especially for thickening soups. Almost any acceptable ancient vegetable will work: pumpkin, carrot, broccoli, cauliflower, zucchini, or mushrooms, to name a few. Simply steam or soften the vegetables, then toss in a food processor or other pulverize means. Canned tomato paste works well too. If you’ve been cooking a vegetable-filled stew or soup for hours, it can happen on its own as the vegetables crumble and add density to the broth.

Primeval meal

You already know how much we love almond flour here, and the other nut flours / flours can act as a sauce thickener. Unlike traditional flours, these don’t really clump together when added directly to a sauce. However, you can add flavors that you may not expect or really want in your sauce. So be careful. You can use nut butter too – a little goes a long way.

I’ve heard good things about defatted coconut flour. I’ve never used it myself, but it’s effectively low-carb (although high in fiber). Has anyone tried coconut flour?

Vegetable gum

Vegetable gums sound a bit unsavory, but are used in many Asian dishes. Essentially pure fiber that absorbs moisture to form a gel. The most popular vegetable gums are xanthan gum and guar. Sprinkle over sauces as you whisk to thicken, but be careful – a little goes a long way, and too much will make your sauce “gummy” and “sticky” rather than creamy.

Vegetable gums can be a little tricky to use, but there are products out there that make it easier. I’m curious to see what your favorites are once you’ve used them.

Is Xanthan Gum Keto?

There are 7 grams of carbohydrates per tablespoon of xanthan gum. A little goes a long way, and most recipes call for a tiny amount of xanthan gum – a pinch or fraction of a teaspoon or less. Hence, xanthan gum can be considered a keto and works well as a thickener.

Some people have gastrointestinal symptoms with gums like xanthan gum. Experiment yourself and see how you feel.


I’d say reduction is the purest way to thicken a sauce, but it’s not exactly the quickest or easiest way. It remains my favorite (besides the fact that I haven’t tried the gums, of course) because it produces the richest flavors and textures, especially with some type of animal fat as a thickener. The nut flours work well enough, but the resulting textures are never fully compared to traditional flour thickeners. Nuts are just too coarse and not absorbent. Vegetable purees are delicious, nutritious thickeners, but their uses are limited (mainly in soups and stews). I think the vegetable gums are technically PB-friendly – they’re natural-sourced and definitely low-carb – but I’m not sure I want to rely on them entirely and I’m skeptical of “low-carb” packaging . Of course, I plan to try them out at some point and I would love to hear your experiences with them.

Oh, and for the broccoli and beef recipe? I think a vegetable gum would be the best choice. I don’t know how well butter or cream would go with the flavors, and I doubt that nut flour will blend in seamlessly with the sauce. With this product, you’re just aiming for texture, and the gums would likely achieve that without sacrificing taste or cooking time.

further reading

Guide to fats and oils

8 Ur-friendly flours

Keto bread recipe

About the author

Mark Sisson is the founder of Marks Daily Apple, godfather of the Primal Food and Lifestyle movement, and the New York Times best-selling author of The Keto Reset Diet. His latest book is Keto for Life, which describes how he combines the keto diet with an original lifestyle for optimal health and longevity. Mark is also the author of numerous other books, including The Primal Blueprint, which is credited with the growth of the Primal / Paleo movement in 2009. After three decades of researching and educating people about why food is the key component to achieving optimal wellbeing, Mark launched Primal Kitchen, a real food company, the Primal / Paleo, Keto and Whole30-friendly kitchen staples manufactures.

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