Yes, you can make natto with a wide range of beans and legumes beyond soybeans. The fermenting bacteria that produce natto grow just as well on chickpeas, lentils, green peas, and lupins as they do on soy. In fact, a 2024 study published in Heliyon found that red lentils, green peas, chickpeas, and lupins all outperformed soybeans as a fermentation substrate in several important measures, including vitamin K2 content and amino acid levels.
Which Beans Work Best
Researchers tested five European-grown legumes head-to-head against soybeans: red lentils, chickpeas, green peas, lupins, and brown beans (a type of kidney bean). The fermenting bacteria, Bacillus subtilis, grew equally well on all of them with no significant difference in bacterial counts at the end of fermentation. The key differences showed up in flavor, nutrition, and texture of the finished product.
Red lentils came out on top overall as the most optimal fermentation substrate. Green peas, chickpeas, and lupins also scored well. The one legume that didn’t work was brown beans, which produced a final product with lower vitamin content, fewer aroma compounds, and less of the sticky mucilage that defines natto. So while common kidney beans and similar varieties might not be your best bet, most other legumes are fair game.
Chickpea natto produced the highest amount of sticky strands when stirred, which is the hallmark spider-web texture natto lovers expect. Red lentils, interestingly, scored lower on strand formation despite excelling in other areas. If that sticky, stringy quality matters to you, chickpeas are the strongest alternative to soy.
Vitamin K2 Levels Vary Widely
One of the main reasons people eat natto is for its vitamin K2 (specifically the MK-7 form), which plays a role in bone and cardiovascular health. Soybeans still lead the pack here, producing the highest K2 levels at around 1,527 micrograms per 100 grams at peak fermentation. But several alternatives produce meaningful amounts.
Mung beans reached about 806 micrograms per 100 grams, roughly half the soy level but still substantial. Peas hit around 637 micrograms. Lentils, lupins, and field beans clustered in a lower range of 247 to 289 micrograms per 100 grams. Chickpeas peaked at about 258 micrograms on the third day of fermentation.
Timing matters too. The vitamin K2 content rises and falls over the course of fermentation, and different legumes peak on different days. Mung beans and peas showed their strongest K2 levels around day five, while chickpeas peaked earlier on day three. Fermenting too long can actually reduce K2 content in some legumes. For soybeans, mung beans, and lupins, the concentration kept climbing almost until the sixth day.
Safety With Non-Soy Beans
Some legumes, particularly kidney beans and lentils, contain compounds called lectins that can cause digestive distress if the beans aren’t properly cooked. The good news is that natto fermentation provides a double layer of protection. First, the beans are thoroughly cooked (pressure steamed) before fermentation begins. Second, the 72-hour fermentation process itself has been shown to destroy almost all lectins in lentils. Between cooking and fermenting, these compounds are effectively eliminated.
If you’re switching to non-soy natto specifically because of a soy allergy or intolerance, chickpea and lentil versions give you a genuinely soy-free fermented food with many of the same nutritional benefits.
How to Adjust Your Process
The basic natto-making method stays the same regardless of which legume you use: soak, cook until very soft, inoculate with Bacillus subtilis starter, and ferment at around 100 to 115°F (38 to 46°C) for roughly 22 to 36 hours. The details shift depending on bean size and density.
For soybeans, the standard approach is soaking for about 12 hours, then pressure steaming at 250°F (121°C) for around 33 to 35 minutes. Smaller legumes like red lentils and split peas need less soaking and cooking time. Whole chickpeas, being larger and denser, may need soaking times similar to soybeans but should be steamed until they’re soft enough to crush easily between your fingers. The beans need to be very tender before fermentation starts, softer than you’d want for a salad or soup.
Split or dehulled legumes like red lentils and split lupins ferment differently than whole beans. They break down more during cooking, so the final texture will be mushier and more paste-like rather than individual sticky beans. This isn’t a failure. It’s just a different product. Some people actually prefer this for stirring into rice or spreading on toast.
How to Tell It Worked
Successful natto, regardless of the bean, has a few telltale signs. The surface should look slightly glossy and sticky. When you touch the beans and pull your finger away, thin strands should stretch between them, resembling spider webs. The aroma will be sour and somewhat pungent, driven by compounds like isovaleric acid. A nutty undertone is also normal.
If your alternative-bean natto has less stringiness than you’re used to with soy, that doesn’t necessarily mean something went wrong. Some legumes simply produce less of the sticky polymer (called gamma-PGA) that creates those strands. Brown beans and red lentils naturally produce fewer strands, while chickpeas tend to get very stringy. As long as you see some stickiness and smell that characteristic sour, fermented aroma, the bacteria did their job.
A completely dry surface, off-color mold (pink, black, or green), or a rotten rather than sour smell are signs of failed fermentation. These same indicators apply whether you’re using soy or any other legume.
The Bottom Line on Taste
Each legume brings its own flavor profile to natto. Chickpea natto tends to be milder and slightly nuttier than soy, making it a good entry point for people who find traditional natto’s flavor too intense. Green pea natto carries a vegetal sweetness. Red lentil natto is earthy and soft. The fermentation process generates the same types of aroma compounds across all legumes, so you’ll still get that distinctive natto smell, but the base flavor of each bean comes through underneath.
For anyone avoiding soy, wanting to experiment, or simply working with what’s available locally, alternative-bean natto is not a compromise. Several legumes match or exceed soybeans in key nutritional markers while supporting the same bacterial fermentation. The process is forgiving, and the results are genuinely worth eating.