for those with estrogen dominance or sensitive body, soy can increase estrogenic effect by nature of its phytoestrogenic properties. for others, moderate amount of soy is acceptable.
soy comes in two forms, fermented and not fermented. Fermented form can be taken by all, and it included tempeh and miso and soy sauce. soy milk or tofu is non fermented and has be used with care ,especially in women.