This root vegetable has garnered attention for its low-carb qualities. Here we reveal konjac's potential benefits and side effects and how you can use it.
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If you follow a keto lifestyle or you just try to keep your carb count low, you'll probably run across konjac in your quest for low-carb products. Konjac is a starchy root vegetable used in low-carb food products. Here, we'll explain more about what it is, what its potential benefits and downsides are and how to cook with it.

What Is Konjac?

Konjac, also known as elephant yam, is a plant commonly grown in Asia. The starchy bulb root, known as a corm, is used to make food like noodles and "rice" (similar to how you rice cauliflower). It contains glucomannan, a water-soluble dietary fiber, and is sometimes used as a weight-loss supplement, according to a 2020 review in Obesity Medicine. Whether or not weight-loss supplements that contain konjac work is still up for debate, however, and more research needs to be done.

It's important to beware of weight loss supplements, including ones that contain konjac. For example, according to a 2021 Food and Drug Administration (FDA) warning letter sent to Genesis Nutrition Ultra Slim, their weight loss supplement contained konjac, but it also contained undeclared and unauthorized pharmaceutical ingredients that were known to increase the risk of heart attack and stroke—and had cancer-causing properties. While the FDA regulates dietary supplements, it does not approve them like it does pharmaceuticals. Because of this, it's important to look for supplements that have been certified by credible organizations, such as NSF International, ConsumerLab, or the US Pharmacopeial Convention.

How Do You Cook with Konjac?

In powder form, konjac is used to thicken soups and sauces the way you might use cornstarch. Several brands use it to make shirataki noodles or shirataki rice, both of which are considered low-carb and keto-friendly.

Shirataki noodles have a gelatinous texture and are commonly used in Japanese cooking. You can buy shirataki noodles online or find them in the Asian food section of your supermarket. The noodles and rice are marketed as low-carb (or no-carb). This is because their carb content is so low the net carbs for a serving are zero. The theory is that those few carbs are fiber-rich and pass through your body without being absorbed.

You might also find konjac in your gluten-free baked goods. According to 2021 research in Foods, konjac flour is being used as an ingredient in gluten-free bread. Researchers state that the bread that had about 37.5% of its flour in the form of konjac had the best formulation (as opposed to others with more or less of the flour), including color, texture and volume.

But what about the taste? In a 2022 study done by many of the same researchers and also published in Foods, researchers included taste to see how different percentages of konjac flour ranked. In this case, the breads with over 25% konjac flour were less palatable due to a fishy taste. The study authors explained that konjac can have a seafood-like flavor due to a compound called trimethylamine.

Is Konjac Good for You?

While its nutritional worth is still being evaluated, in January 2020, the FDA announced its intention to propose glucomannan be added to the definition of dietary fiber that was established in 2016.

According to the FDA's 2020 statement, they made the decision based on scientific evidence that shows konjac may help lower blood cholesterol levels. A 2021 review in Biomolecules backs this claim up and adds that konjac has also been shown to alleviate constipation, improve the gut microbiome and reduce blood sugar levels. Study authors of a 2022 review in Food Science and Technology were so impressed by konjac's blood sugar-reducing abilities that they feel it may be a promising new way to prevent and treat diabetes.

What Are the Side Effects of Konjac Root?

We mentioned that konjac is used as a thickener in cooking—which means it swells when it's mixed with water. This can be potentially dangerous when eaten in certain forms. In the early 2000s, for example, the FDA issued several recalls for fruit jelly candies made from konjac because of choking hazards. The problem was that the candies didn't dissolve in your mouth and could get caught in your throat.

While konjac can affect the digestive system positively by relieving constipation, it might also have some negative effects on it, like bloating, gas, and abdominal discomfort, according to a 2021 review in Trends in Food Science & Technology.

What Does Konjac Taste Like?

As previously mentioned in the Foods study, konjac can have a fishy flavor. Companies that sell shirataki noodles and rice, however, say that they have very little taste on their own and will take up whatever flavors you're cooking with them.

If you're curious about shirataki noodles but are hesitant to try them, EatingWell's Shrimp Tofu Noodles recipe is a good place to start. The noodles in this recipe are a blend of konjac and tofu, which can mellow the flavor. And the noodles will soak up the zesty homemade sauce, so the only thing you'll be tasting is the punch of flavor from the ginger, garlic, hoisin and Sriracha.