Tip This smoothie is great for sustained energy throughout the day. The banana has high levels of potassium, helping you to quickly replenish electrolytes. ( the riper a banana, the higher sugar content), the peanut butter is high in protein and the raw oats is a Low GI filler. Flax seed is a great source of fibre and Omega 3 fatty acids, and yogurt contains protein, calcium, riboflavin, vitamin B6 and vitamin B12.