Input from my OB/GYN friend, unedited:
I don’t know a lot about Soylent, but I read through the FAQs. I had a hard time finding the actual breakdown of the nutrients, vitamins, and minerals. While I do have some questions and concerns about the production of Soylent and what is used to make it (not all protein is created equal… what amino acids are there?), I don’t feel I know enough to comment on that. I will say though that the description of an item that “includes protein, carbohydrates… without undesirables such as sugars” is very confusing. What are the carbohydrates? Monosaccharides? Disaccharides? Oligosaccharides? Polysaccharides?
Anyhow, here are my biggest concerns based on what I know.
Consuming minerals and vitamins at the same time. If Soylent is always made of the same ingredients and it is meant to provide everything you need in your diet, this presents a major problem: our bodies were not made to process all the vitamins and minerals we need at the same time. Consuming calcium at the same time as iron decreases your iron absorption. So you might be consuming 100% of your recommended daily allowance as a pregnant woman, but you’ll only be absorbing 50% (that’s a random number). The same goes to zinc and copper, which also compete with each other, and which are also affected by iron and calcium absorption. It doesn’t make sense to consume all these things at the same time. Pregnant women who take iron supplements are always told to take it with orange juice since vitamin C helps absorption and to avoid milk, since calcium decreases absorption. While Soylent may theoretically provide you with everything you need, taking everything your body needs at the same time does not allow your body to actually process and absorb everything. Consider this article http://ajcn.nutrition.org/content/72/1/280s.full (scroll to Multinutrient interactions)
Toxicity of fat-soluble vitamins. Especially concerning since pregnancy is a hyperlipidemic state. Foods that claim to give you all the vitamins that you need often give you much more than you need. Your average person can deal with occasional excesses in vitamins, especially the water soluble vitamins. Fat soluble vitamins are more of a problem. Vitamin A specifically is a teratogen at high levels (it also causes other major problems like high blood pressure, liver toxicity, alopecia, vertigo) so excess consumption or supplementation is strongly discouraged in the first trimester of pregnancy. I’m not sure how much Vitamin A is in Soylent, but this is something to pay attention to. Example research article, although there are many many more on this topic http://www.nejm.org/doi/full/10.1056/NEJM199511233332101
Folate or folic acid. Pregnant women need more than normal people and this is the main reason we give pregnant women prenatal vitamins. The average pregnant women who has had no children with birth defects requires 0.4mg of folate, daily. If she’s had a child with a previous neural tube defect, this goes up to 4mg, daily. Does Soylent provide this?
Iron levels. Anemia in pregnancy is very common so pregnant women are often encouraged to increased their iron consumption. I’m not sure if there is sufficient iron in Soylent to accommodate for this increased need. Also, in reference to point #1, if there is calcium in Soylent, then whatever iron you’re getting isn’t being fully absorbed, since your body will preferentially absorb the calcium, so you may still be iron deficient even though you’re technically consuming all the iron you need (you’re just excreting a lot of what you consumed).
In general, I would hope I don’t need to say this but really, anyone who is pregnant should realize that their vitamin and mineral needs change. Caloric needs may only increase by 300 calories, but the RDA for calcium increases over 100% (just one example). Make sure that what you’re eating covers your body’s changing requirements and needs.