Minecraft wiki entry for Hunger_management, associated text: Disadvantages:
Like all other stews, suspicious stew doesn't stack (though the ingredients do).
Suspicious stew can have negative effects too (Blindness, Poison, Weakness, or even Wither).
Remembering the correct flower for the recipe is important.
Once a suspicious stew is crafted, there is no indication to the nature of its effect. This also applies to stew purchased from villagers.
The above points make it risky to eat any suspicious stew that you didn't craft yourself, thus its name.