From time to time, I get asked about meal replacers like Soylent, Joylent, Huel, and any number of similar competitors. Usually, the question is just “what do you think about them?”, and since it’s a fairly common question, I’d like to share my answer here.
First, I’d like to say that I don’t really believe most people use these as complete dietary replacements, as their inventors advertise can be done; I think most people use them as convenience meals. In this way, they’re not really much different from a protein shake (albeit a carb, fat, and micronutrient-fortified one), and I don’t see any problem with using them.
Where I see potential issues is when they’re used as a form of “total meal replacement”, where a person no longer consumes solid food (or very limited amounts, at any rate) in favor of shakes. Here, I wonder about long-term repercussions that would not be visible through the short-term lens we are currently limited to.
Of course, we don’t have evidence for long-term effects either positive or negative, nor are we likely to get any. What we do have, however, is a plethora of evidence that suggests that there’s something more to food than just the essential nutrients humans require to survive. I’m not talking about anything magical or any form or pseudoscientific alchemical syngergy—I just mean that evidence routinely shows that eating more fruits and vegetables improves health while routinely taking a multivitamin does not. If fruits and vegetables were just their macro- and micronutrients, I don’t think we would get this result.
In the end, food is tremendously complex. There are thousands of chemicals in any given fruit or vegetable. Most of them probably do nothing for human health. Some of them are certainly bad, or would be if we could consume enough of them. Some are also likely to be beneficial, though, even if they’re non-essential. In the coming decades, we’ll certainly see some of these non-essential nutrients gain clarity, much as happened with lycopene once upon a time. But we’ll still have an incomplete picture, and it’s unlikely that we’ll arrive at a “perfect food replacement” simply by adding every new non-essential-but-beneficial nutrient we come across.
As I mentioned, this is probably more of philosophical question than one based in clinical realities. Most people will neither want or be able to use a meal replacement shake every day for the rest of their lives, the same as most people wouldn’t be able to climb only a single route every day and never dream about climbing something else or wear the same clothes every day without ever wanting to change it up. Variety in food and flavor is, for most people, an enjoyable part of eating, and thus meal replacement shakes are a solution without a problem. If you incorporate these shakes into your life, they’ll probably be incorporated solely as a supplement, and there’s nothing wrong with that.
Long story short, I think meal-replacement shakes are unlikely to produce long-term health in the same way a healthy diet would but are perfectly healthy in the context of short-term diet choices. If you want to use them as a convenient way to get some calories at work or at the crag, go for it—but please eat some fruits and vegetables every now and again, too!