King William I, or William the Conqueror, was, by all accounts, a very fat man. Some say that in 1087, he decided he was too fat to ride his horse. So he went on a liquid diet, eating nothing and drinking only alcohol for days. I guess technically it was a liquor diet. No word on how well it worked, but he did ride his horse again the following year.
The phrase “liquid diet” typically connotes weight loss, an abstention from food to atone for eating too much of it earlier. Juice cleanses, Slimfast come to mind. Above all, something temporary. Once you’ve cleansed or slimmed or atoned, you’ll be back on the solid stuff. Plus, those diets aren’t usually very successful, as Robin Kanarek, interim dean of the Friedman School of Nutrition at Tufts University, points out. “Once you go off the diet, you tend to gain all the weight back,” she says. And it’s more difficult to stick to them, because it’s boring to have nothing but the same taste, the same texture, every meal.
There are some liquid diets with intentions other than dropping pounds, of course. Hospitals put people on liquid diets before surgeries, to keep them hydrated, but those diets are really just a stopgap—they don’t provide all the nutrition a person really needs. Then there are meal-replacement beverages, like Carnation Instant Breakfasts. Carnation’s website promises the shakes will deliver “balanced breakfast nutrition,” but I doubt anyone lives entirely off of them.
The most recent and extreme entry into the canon of liquid diets is Rob Rhinehart’s Soylent—a beverage made of nutrients (protein, carbohydrates, vitamins, etc.) in their raw form. He found himself exhausted by his constant need to prepare and consume food the traditional way, so he invented the drink and tested it on himself, to see if he could totally replace food. He wrote about the experience on his blog, and the Internet lost its collective mind. When Rhinehart put together a crowdfunding campaign on Crowdtilt last year with the goal of manufacturing Soylent, it was completely funded within two hours. Now, after working with RFI Ingredients to tweak the recipe and get it ready for production, it’s ready to ship. The first batch, for people who contributed to the funding campaign, started shipping last week.
Its healthiness is up for debate. In the FAQ section of the Soylent website, the creators answer the “Is it safe?” question with: “Everything in Soylent is GRAS (generally recognized as safe) by the FDA. The founders and scores of DIYers have been living on Soylent for months and there is much evidence that is considerably healthier than a typical diet.”
Kanarek says that some studies have found that absorption of nutrients such as omega-3 fatty acids is better when participants get them from food than from supplements. “There are other things in those foods besides pure vitamins and minerals,” she says. “I think the problem [with Soylent] is we won’t know the answer until people have done it for some period of time.”
Marcia Pelchat, an associate member at the Monell Chemical Sense Center, also reserves judgment. “I would want to run a clinical trial before saying whether it’s good one way or the other,” she says. “It’ll be interesting to see.”
If Soylent is all it claims to be, it could be a big deal. More than just serving as a quick fix for people too busy to make dinner, it could have implications for world hunger and nutrition, especially if it’s cheap and easy to manufacture. (Rhinehart says that now, Soylent provides “three calories per penny,” and they hope to lower the price from here.) But this is all if—and it’s a big if—people actually want to drink it.
My own Soylent experience was less than ideal. I lived on a homemade DIY version for a week last year, and while I lost three pounds and never felt hungry, I found the drink distasteful and occasionally gastrointestinally challenging. (To be fair, this was a homemade version, so the fault’s not totally with Rhinehart et al. on that. The manufactured version is certainly different, and Rhinehart has long claimed the drink to be “delicious,” and that he feels great while living on it). It kept me nourished, and didn’t cause any lasting harm.
During my Soylent adventure, I spoke with science writer Mary Roach, author of Gulp: Adventures on the Alimentary Canal, who seemed skeptical that the beverage would find a wide audience.
“We, as humans, seem to have this need to chew,” Roach told me then. “Animals and humans like to chew; they like to destroy things with their mouths. It's kind of a basic pleasure.”
NASA discovered as much when it tested a milkshake-esque liquid diet at Wright-Patterson Air Force Base in 1964 (astronauts, presumably, being even more inconvenienced by food than Rhinehart). “The milkshake diet was unbelievably unpopular,” Roach said. “The subjects were emptying it under the floorboards of the space cabin simulator. It was that unappealing.”