When it comes to adding millets to your diet, it may have some undesired effects on your body. The most common side effects are: if the millets are not cooked correctly, they can lead to kidney stones as they are high in oxalates. Another common side effect of too much millets in your diet are thyroid problems. And finally, as millets are incredibly high in fiber, they can lead to gut problems such as stomach pain and swelling. As long as you're consuming other gluten free grains (such as rice) and eating millets in moderation - they're a great addition to your diet.