A pair of posts from the author Rob Rhinehart outlining a meal replacement shake referred to as 'soylent' has been travelling around the internet the past few days. Soylent is a shake containing 200g carbohydrate (5g fiber), 50g protein, and 65g fatty acids (totalling around 1,585kcal). For the most part it includes the RDA value of all essential micronutrients. The carbohydrates are derived from starches, and the source of the protein and dietary fats are not stated in the article, though claimed to be from soya and lentil in a VICE interview. Beyond the above standard meal replacement shake, some other nutrients were added including Panax Ginseng (50mcg), Ginkgo Biloba (100mcg), Omega-3 fatty acds (750mg, source not stated), Lycopene (500mcg), lutein (500mcg), vanadium (100mcg), and alpha-carotene (similar to beta-carotene, a vitamin A precursor).

From what we can tell, the authors intentions are good hearted and prudent:

"I am reticent to provide exact brand names and instructions because I am not fully convinced of the diet's safety for a physiology different than mine"

"I was home for Christmas and saw an elderly family friend get admitted to the hospital after losing an unhealthy amount of weight. He was losing strength in one of his arms and found it very difficult to cook. I started wondering why something as simple and important as food was still so inefficient, given how streamlined and optimized other modern things are. I also had an incentive to live as cheaply as possible, and I yearned for the productivity benefit of being healthy. I'd been reading a lot of books on biology, and I started to think that it's probably all the same to our cells whether it gets nutrients from a powder or a carrot."

Yet too simplistic:

"The body is a complex machine. There are a lot of substances and chemicals required for it's optimal operation. However, it is also extremely robust. Many people aren't getting the recommended amount of any of these substances, but the body is able to compensate via complex regulatory systems. This hurts in the long run, though. In fact, turning food in to energy is the primary process that ages the body. By giving it only what it needs, and nothing it doesn't, I am optimistic about the long term effects. The short term effects are already clear."

The closing area of his article where he states:

So...I'll just ship you some of my batch. If you are willing to consume exclusively soylent, and get a CBC, chem panel, and lipid blood test before and after the week and share your results with me it's on the house. Bonus points for getting a psych evaluation before and after. The brain is an organ. I can ship it worldwide but it would be nice if you were in San Francisco so we can meet in person

Leads us to believe that this is more about self-experimentation than anything else. Thus, this seems to be more about good intentions than some kind of money-making scheme.

That being said, there are a few complications with the soylent formulation independent of the author's intentions:

It is indeed simplistic. Simplifying can be good, but not when you start losing critical nuances. The author notes himself that "Many people aren't getting the recommended amount of any of these substances, but the body is able to compensate via complex regulatory systems. This hurts in the long run, though" in regards to the basic vitamins and minerals, but doesn't appear to have included compounds that following vitamin-like motifs in the body (what we call pseudovitamin compounds) that are present in food but not soylent. Absolute exclusion of choline, creatine, or nitrates may have similar adverse health effects.

Fiber isn't digested, but that doesn't mean it is not needed. Especially with a liquid formulation, there needs to be some gel forming properties in the intestines to delay intestinal transit and allow maximal absorption. If the RDA of micronutrients is barely passable, at least do what you can to aid their absorption.

All added non-vitamin compounds are horrendously underdosed. Personally, I never knew you could dose ginseng or ginkgo in the microgram range (the dose of ginseng used is currently about 1800-fold less than the lowest recommended dose of 90mg). There does not appear to be any good rationale for adding these compounds to the shake and in these doses, and it seems merely the most popular compounds were added regardless of their benefit to soylent.

Cholesterol was omitted solely on the basis of not finding it necessary, an incorrect idea.

Protein set at 50g a day is sufficient for survival (according to the RDA values) although it may not be optimal for sedentary persons and definitely is not optimal for active persons. Given the benefit of physical exercise for the purpose of 'biohacking' the body, it can be expected that many active persons would want to try such a shake. Due to this, the protein content needs to be reevaluated. It should be noted that the 50g minimum was calculated for a 137.5 lb person. We've covered how much protein you need to consume every day.

Building on that, although the debate between having a 'complete' and 'incomplete' protein source does not matter too much at the higher range of intake (as you merely overconsume the insufficient amino acids) having plant based sources with low absorption percentages paired with a low dietary intake of protein is problematic. If protein intake is not increased, the source of protein should be switched to an animal based product like whey protein.

The intake of Vitamin D, and perhaps Vitamin K, need to be reevaluated.

Some trace elements, such as boron, are not present.

The fat source is exclusively from olive oil (mostly oleic acid) rather than being a mixed source. This needs to be revisited as no omega ratio appears to be investigated and the benefit of some other fatty acids (saturated ones in coconut oil or particularly gamma-linoleic acid or arachidonic acid) could be included rather than blindly using one fat source

The carbohydrate source appears to be maltodextrin (similar to starch in the sense it is a long chain of glucose), although it appears unclear if it is solely maltodextrin. This is not an ideal carbohydrate source for infrequent consumption due to its rapid absorption and high GI (although this bullet is more pedantic than the others). Switching to an alternate carbohydrate source that is absorbed slower or possible one that (with dietary fiber or other indigestible components such as cellulose) has some benefit to intestinal microflora, would be prudent

Soylent really needs a reformulation if this takes off and more people decide to 'experiment' with themselves. Bumping the fiber up to 30g and adding some pseudovitamins would be a good start, but honestly the exclusion of food is something not many people should even consider. Once that happens, then it would likely just become another standard meal replacement shake.

The inherent problem with micromanaging foods down to their molecules is that there is a remarkable amount of molecules that you need to keep track of - the essential vitamins and minerals are not enough. Meal replacement shakes have, up until now, thrived as they replace one or two meals in the day and then mention that the consumer should 'eat a healthy well balanced meal' otherwise; absolute exclusion of food has never been recommended traditionally.

Soylent is not a new concept, although the idea of a meal replacement shake may be getting a second wind due to soylent. It needs a reformulation as the current one is very loosely based on what the RDA of micronutrients. It's quite deficient in several areas, and needs a much more thorough evaluation on its contents.