The glycemic index of a carbohydrate is a bad measure of its quality. A better measure is the degree to which it is fermented by bacteria in the intestines. Furthermore, there is research demonstrating that carbohydrates consumed without the phytonutrients that normally accompany them in whole food increase markers of oxidative stress and inflamation.

Soylent might be better than a frozen pizza or fast food, but in the big picture it's still shit compared to real food.