When it comes to vegetables the better question is, which vegetables are best on Keto. Unlike sugar, wheat or other grains, kidney beans are low on the glycemic index. Which means when eaten in low moderation, they are not going to cause a significant spike in your blood sugar. But they are complex carbohydrate. So, if you are tracking your macros for Keto, there are better choices you can make to save on daily carb amounts.