Not sure how that applies here, even if we disregard the processed foods that many people live on also being quite unnatural.
We are adapted to obtain nutrients from food. Since we currently lack a good understanding of exactly what properties of food are nutritionally relevant, it seems unwise to replace natural food with artificial food.
Yes, processed foods are quite unnatural. But Soylent is even less natural than processed foods, so this is irrelevant in the present context.
Rob Rhinehart's food replacement Soylent now has a crowdfunding campaign.
If you're interested in one or more of these benefits, send in some money! There is also a new blog post.