(The Shambulance is an occasional series in which I try to find the truth about overhyped health products. My Shambulance co-captains this week are Steven Swoap and Daniel Lynch, both of Williams College.)
It could almost be a Zen question: What do you call a food with no food in it? In Japan they're called shirataki noodles, and are made from the root of the konjac plant. In the United States they're called "Miracle Noodles" or a "healthier alternative to pasta" and promise "NO calories...NO net carbs...NO GUILT!!!"
The konjac root's contribution to the noodle is straight dietary fiber, in a form called glucomannan. Since the noodles are made of nothing but fiber and water, the idea goes, they'll hurry right through you without leaving any calories behind. This is attractive to American dieters who would like to be able to eat a whole plate of food without actually eating any food. A dinner of pasta topped with marinara sauce becomes a dinner of marinara sauce topped with time on the toilet.
The Chicago-based brand "NoOodles" displays a set of nutrition facts with zeros nearly all the way down, like a perfect report card. However, "Don't be mistaken," says Williams College physiologist Steven Swoap. "These noodles have calories!"
Insoluble fiber, Swoap explains, does pass through our bodies untouched and make up the bulk of our feces. But glucomannan is a soluble fiber. This means it's dissolvable in water; it's also digestible by the bacteria living in our guts. The bacteria break down soluble fiber into products that we absorb as calories. (They also make methane, which, as Swoap points out, "we don't absorb but rather share with our surroundings.")
The key to the zero-calorie claim made by NoOodles might lie in that 1.6-ounce serving size at the top of the label. The FDA permits calories under 5 to be rounded to 0. If each of those dainty servings really has 4 calories, a whole package—which would fill a plate—has about 20. It's hardly a calorie count that will ruin anyone's diet. But zero, in this case, doesn't really mean zero.
Shirataki noodles have a distinctly non-zero amount of offensive odor, as I discovered when I tried some NoOodles for myself. (They're in the refrigerator aisle, which I only mention in case you want to buy your own and also want to avoid having this conversation with two different grocery store clerks: "I'm looking for a product called noodles?")
The product's website describes the smell, caused by the calcium hydroxide, as "a little odd." I would have used different words, like maybe "neglected fish." But the odor rinses away with water. The rectangular shape of the package is harder to dispel.
I followed directions and heated my NoOodles in a dry nonstick pan until all the water had evaporated, though they looked otherwise the same. At this point it's recommended that you cook the NoOodles with some sort of sauce (or eggs or ice cream), but I wanted to try them in their unadulterated form. As promised, they tasted like nothing at all. They had a texture, though, that I was deeply not okay with, like biting through rubber bands. I managed one mouthful followed by a lot of water.
The water is recommended too, because soluble fiber sucks up water in your body. In 2010, Health Canada issued an advisory about the importance of drinking a full glass of water when taking pills or powders containing glucomannan. It also urged consumers not to use glucomannan supplements right before bed, because the stuff can swell up and cause choking or blockages in the intestine while you sleep. The health advisory didn't address shirataki noodles.
The water that NoOodles absorb makes the material passing through your gut especially slippery, so your small intestine can't absorb nutrients (which is to say, calories) as easily. Their website claims this makes the rest of your meal less caloric too, as everything slides through you along with the NoOodles. But Swoap says that experiments have shown this simply isn't true. "The small intestine is still long enough to get all of the calories from your food."
Among several other promises, NoOodles makers also say their product makes you feel fuller, so that "one tends to eat less when NoOodle is part of the meal." It's certainly possible, though it's also possible that one tends to make up those calories at one's next meal, when one is starving because one only ate marinara sauce for dinner. "The key word that gets them off the hook is 'tends,'" Swoap says. "Otherwise the FDA would have a major problem with this."
Not all the claims made about glucomannan noodles are spurious. The product does let dieters eat more food for fewer calories. And some studies have found that glucomannan can lower cholesterol, both in healthy and diabetic subjects.
So is an all-fiber noodle really a "healthier alternative?"
"The 'benefits' are in comparison to refined wheat flour that is used to make breads, pastas, etc. Most everyone acknowledges that is not good in excess," says Daniel Lynch, a biochemist who's also at Williams College. "But moderation is the key." He adds, "You might as well just have a glass of Metamucil or Citracel as a pre-dinner cocktail and then enjoy real food in smaller portions!"
Swoap says, "I don’t think this is necessarily bad for you. I would just prefer to get my fiber with vegetables that also bring along a lot of micronutrients." In other words, if you want to bulk up your meal with a low-calorie fiber source, there are less rubbery and more vitamin-filled ways to do it.
If you're still tempted to try a food-free plate of pasta, go for it. Just remember to drink water.
Arvill A, & Bodin L (1995). Effect of short-term ingestion of konjac glucomannan on serum cholesterol in healthy men. The American journal of clinical nutrition, 61 (3), 585-9 PMID: 7872224
Chen HL, Sheu WH, Tai TS, Liaw YP, & Chen YC (2003). Konjac supplement alleviated hypercholesterolemia and hyperglycemia in type 2 diabetic subjects--a randomized double-blind trial. Journal of the American College of Nutrition, 22 (1), 36-42 PMID: 12569112
Thanks to Chris F. for the tip! If you want to summon the Shambulance to the site of an emergency, leave a comment or send me an email at the address above.