This smoothie contains a lot of vitamin C due to the grapefruits. One grapefruit already contains 200% of the recommended amount of vitamin C, so with the juice of two grapefruits you are in the right place. Also in the kale there is still a lot of vitamin C and other minerals, such as iron, calcium and magnesium.
Fun fact about smoothie glasses
The well-known mason jars that are often used as smoothie glasses were originally not intended for drinks at all, but for preserving vegetables and fruit. Only much later did they become glassware for smoothies and healthy drinks!