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 Kickstarter 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 Kickstarter, 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."
Soylent is not entirely unlike a milkshake. Without added flavoring, the version I had tasted yeasty and chemically, like a vanilla milkshake that traveled through a wormhole and came out wrong. Its taste has also been described as "unsweetened custard," "slightly sweet and earthy with a strong yeasty aftertaste," and "chalky." Rhinehart says it's "more sweet than anything."
Humans, generally, don't like bland, monotonous food. "The mouth really does get bored," Roach said. "I can't think of anything more depressing than living on a milkshake texture."
In a 2000 study on food cravings, Pelchat examined the effects of a "nutritionally adequate, liquid, sweet, monotonous diet" (hm, what does that sound like?) on young and elderly adults' cravings. She found that while people's liking for the diet didn't change significantly over five days, the young adults did start to crave more savory foods, or entrees. Their cravings for sweet foods were the same both on and off the diet. Elderly adults seemed more okay with the monotony, and didn't have significant changes in cravings.
"Older participants didn't complain as much as the younger people did about a chemical or vitamin taste," Pechat adds. One danger of older adults' willingness to go along with boring diets is that they might not get adequate nutrition—Soylent, in these cases, could be a boon.
"Society has been going in the direction of convenience foods and healthy meal substitutes, protein bars and things like that," Pelchat says. "So I guess it's not totally surprising that somebody would want to go one step further." She notes that while she's found in her studies that monotonous diets tend to induce cravings, it may be different if someone chooses to live on Soylent, as opposed to being told to drink the same beverage for five days for a study.
The monotony effect extends beyond just liquids—solid meal replacements tend to meet with similarly lukewarm responses. Pelchat says that servicemen eating the U.S. military's "Meals Ready to Eat" (MRE) rations sometimes had trouble taking in enough calories because, even though there were different options, there wasn't a large variety. Early this year, the Department of Defense awarded $16 million to Louisiana State University to support research to improve soldier health and make the MREs more palatable. A boring, non-military diet could have bring similar problems—a 2011 study published in The American Journal of Clinical Nutrition found that daily exposure to the same food caused women to eat fewer calories.
Taking this to an extreme, some prisons serve a bland "nutraloaf" as punishment for unruly inmates. While prison officials claim it provides all necessary nutrients, NPR reports that the boredom of having it for every meal causes some prisoners to stop eating altogether, which is why some human rights advocates say it's an unethical form of punishment. Chicago Magazine dining critic Jeff Ruby once tried the loaf at Cook County Jail, and described the taste as "blank, as though someone physically removed all hints of flavor."
Pelchat says she and her team have done some experimenting with creating a loaf of their own—a "slightly sweet, slightly savory cheese bread" that also included vegetables, protein powder, and milk powder. It was intended not as a punishment though, just an attempt to create a nutritionally-complete food source.
"It wasn't actually horrible," she says. "If we put the freshly baked loaf out at work, people did eat all of it."
Obviously, Rhinehart's gotten a lot of interest in his idea, mostly from "younger, educated males," he says. Men like himself, who don't want to spend time on food. Maybe they don't get that much pleasure from it to begin with, and don't mind the monotony as much. Pelchat says in another study she did, she asked people if a pill were invented that contained all the nutrients they needed, would they take it? Though most people, even picky eaters, said they'd stick with food, "some people said, 'Yes, it's a big pain to make food, and I just eat to maintain myself. I don't enjoy it that much, so sure,'" Pelchat says.
It's not hard to imagine situations in which Soylent would be very convenient. Perhaps for some people, Soylent could serve as a healthier fast food—something to grab when you're running late instead of going through the McDonald's drive through. Or backpackers could bring the powder and oil with them to mix quickly while hiking. "Another interesting piece of food trivia we've come across is that people are more likely to eat the same breakfast every day than to [do that] for lunch or dinner," Pelchat adds.
It's the thought of replacing most meals with Soylent that seems unlikely to catch on.
"Based on everything that I know about variety and crunch and the human mouth and the human psyche, I wouldn't think it would be a tremendously wide-reaching or long-lasting fad," Roach said. "But who knows?"
"I'd rather get takeout," Pelchat says.
