I have a bit of a love/hate relationship with natto. I thoroughly enjoy eating it, but I always get sick from it afterwards. I've made natto many different ways and each time I get sick in exactly the same way. I first feel a sort of pressure in my stomach and later my intestines constrict. I grow irritable, fatigued, and constipated for days.
I am always very careful to ensure that no contamination occurs during the fermentation process. I've used natto spores as a starter for some batches and frozen professionally made natto I bought for other batches. Some batches were made with normal sized soybeans, others with small type natto soybeans, and even garbanzo beans. The fermentation seems to go well, with slimy threads and all.
No matter which method I use to make natto, sickness is always the result. I can only conclude that I am intolerant to the bacteria used to make natto. Has anyone else experienced something similar? I am at my wits' end and about to completely give up on natto.