Hijiki adheres to a vegan diet, but it's not suggested for consumption, and in fact, it's prohibited in multiple nations because of high arsenic concentrations. Hijiki boasts calcium content that is 14 times higher than milk and is abundant in fiber, which may seem appealing, yet certain food safety organizations would strongly discourage its intake. In case you intend to consume hijiki, it's probable that you'll have to hydrate it due to its coarse texture.