|The 9 Best Whole Food Sources of RS
MAKE THIS SPUD SO IT HAS FEWER CALORIES—MEANING, IS FULL OF RESISTANT STARCH.Want to know which foods give you the most RS bang for your buck? Sadly, there’s no universal guide that says how much RS is in whole foods—levels vary from plant to plant and with different cooling times. But there are a handful of studies to give us approximate amounts. Here, the best sources:
- Green bananas Peel a single small fruit for 38 g.
- Potatoes Roast one medium spud and then let it cool for 33 g.
- Rolled oats Put ½ cup uncooked oats in muesli or sprinkle over yogurt for 8.5 g.
- White beans Puree 1 cup for a tasty dip and you’ll get 10.5 g.
- White rice Just ⅔ cup of the cooked stuff gives you about 5 g—no cooling required.
- Pasta Let 1 cup cooked pasta cool and add it to a salad for 5 g.
- Lentils Only @frac12; cup cooked yields about 5 g.
- Frozen peas Steam or microwave ½ cup, let them cool, and toss in a salad for 5 g.
- Cashews Chomp on 1 oz (18 nuts) for 3.5 g.
The dawn of RS discovery came in the early 1980s, when British researchers identified a new type of starch that, oddly, wasn’t digested in the small intestine but headed straight to the colon. “At the time, this was regarded as just ridiculous,” says Topping. But RS’s unusual attributes would make sense years later, after researchers understood the purpose of RS in our colons—to feed trillions of gut bacteria that can improve our health in countless different ways.
Today, there are hundreds of published studies on RS, and researchers have learned that there are not one but four main types of the curious starch. The first two are found naturally in foods: RS 1 is in some grains, like oats, barley, and wheat, as well as legumes, like peas, lentils, and black beans, while RS 2 is in certain veggies and fruits, including raw potatoes of every kind and green bananas. But when you cook foods that have RS 2, their starches change and lose their resistant power. For example, while a raw potato is rich in RS 2, a hot, cooked potato has none, meaning all its starches will be digested and used for energy.
But you can still welcome mashed potatoes back into your dietary good graces if you take one more step: Let the spuds cool. Cooling hot, cooked carbs like potatoes, pasta, or rice produces RS 3, which acts just like RS 1 and RS 2 to lower calorie count. In fact, according to one groundbreaking study, allowing rice to cool before eating it can slash its calorie content by as much as 50%, turning a 200-calorie cup of rice into a 100-calorie cup, with the exact same taste and texture.
While the promise of RS 3 is incredible, there’s also reason to get excited by RS 4, created when food manufacturers take normal starches like wheat flour and treat them to be more resistant, thereby lowering calories in products considerably.
Regardless of whether you’re eating RS 1 or RS 4, the starch in general achieves its slimming benefits by helping the body burn more fat, better control its weight gain hormones, and curb appetite—in that order. The domino effect starts with melting fat, which RS does by affecting which nutrients the body burns and which ones it stores, says Janine Higgins, an RS researcher and an associate professor of pediatrics at the University of Colorado. In short, she says, RS nudges the body to burn fat, not carbs, for fuel, while shrinking the size of fat cells. One study discovered that people who got just 5% of their daily carbs from RS—about 11 to 16 g of RS per day, or the amount in half of a roasted-and-cooled potato—increased their fat burn by more than 20%. Other research has found that eating RS 4-enriched flour reduces body fat and waist size, and in mice, the starch increases fat burn by up to 45%, torching mostly dangerous belly fat that can surround the internal organs.
|The Best RS Products for Cooking and Snacking
Innovative food companies are churning out delicious packaged staples and snacks ridiculously high in RS. A few of our favorites:
1. Honeyville Hi-Maize Resistant Starch
This starch, developed 20 years ago from a non-GMO corn, is naturally high in RS—even when heated, it has 5 g per Tbsp. For optimal texture, swap for 1/3 of the regular flour in baked goods or add to smoothies. ($8 for 12 oz)
2. Bob’s Red Mill Unmodified Potato Starch
Raw spuds have more RS than cooked, cooled ones, but who chomps on raw taters? Instead, try mixing 1 Tbsp of this starch into smoothies(heating destroys its RS) and get 8 g. ($4 for 24 oz)
3. FiberGourmet Sharp Cheddar Thinables
Why eat regular cheese squares when these have the same taste and half the calories? Each 1 oz serving boasts only 60 calories and 14 g of RS. Eat a whole box for 360 calories. ($5 for 6 oz)
4. Organic Gemini TigerNuts
Tiger nuts are small root veggies, like potatoes, so it makes sense that they’re tiny RS powerhouses. Since they’re tough when raw, soak them before eating for a slightly chewy, nutty snack. ($6 for 5 oz)
How, exactly, RS burns fat is still a mystery, but researchers believe it has something to do with the starch’s ability to lower levels of insulin—a hormone that slows fat burn—by as much as 55%. You’ve probably heard that normal carbs low in RS, such as white bread, are packed with sugary starches that flood the bloodstream quickly, causing a commensurate spike in insulin. But because the RS in carbs that contain it can’t be digested and broken down into sugar, the insulin response is curbed. This insulin-suppressing power is, in fact, one of RS’s best-documented benefits. A new study in the British Journal of Nutrition found that insulin response was significantly lower in people who ate RS-rich bread for just 3 days, compared with those in the control group, who consumed normal wheat bread.
RS’s cascade of hormonal effects doesn’t end with insulin. After RS resists digestion in the small intestine, it moves south to the colon, where it appears to boost hormones that send signals of satiation to the brain. One study discovered that people ate up to 300 fewer calories per day after consuming RS-packed foods.
It’s also in the colon where RS wields its influence on our microbioms, the trillions-strong bacterial communities linked to better immunity, mental health, and metabolism. The bugs that live in our colons feed on RS and, in turn, create more “good” bacteria. The more good bacteria, the more potential for weight loss, according to suggestive research showing both that a healthy microbiome boosts metabolism and that lean people tend to have better-nourished gut bacteria than obese people do.
RS-gobbling bugs also help overall health by producing the fatty acid butyrate, which helps strengthen gut walls and prevents harmful bacteria and food particles from escaping the colon, bringing on inflammation and illness. Butyrate may even stall tumor growth, with one trial showing that people who consumed more RS for several weeks reversed risk factors for colon cancer caused by poor diet.
If RS has the potential to fight colon cancer, it makes sense that the starch could also temper other colorectal conditions like irritable bowel disease and colitis. In Australia, where the government has developed RS-enriched barley and added it to some packaged foods like cereal for the past 6 years, people have reported relief from the symptoms of irritable bowel, says Topping, whose work has influenced the country’s RS effort. Officials estimate that further investment in RS-enriched barley could save the country more than $300 million a year in health care costs.
|3 Ways to Boost RS in Your Favorite Carbs
PREP YOUR PASTA RIGHT AND DROP POUNDS.Here’s how to prep pasta, rice, potatoes, and grits to maximize the RS and slash calories, without changing taste or texture.
1. Cook, Cool, Repeat:
Cook a starchy food as usual, but before you eat, let it cool a few minutes on the countertop or stick it in the fridge or freezer. Repeatedly cooling and heating starchy foods can create even more RS, so embrace your leftovers.
2. Go Low and Slow:
Slow cooking methods like roasting increase RS more than fast ones like boiling do. (A roasted, cooled potato has 24 times the RS of a boiled, cooled potato.) Roast potatoes, cook grains over low heat, or opt for the slow cooker over the steamer basket or microwave.
Storing products like tortillas or bread in the freezer can more than double their RS content.
Though RS’s potential seems endless, it does face the same roadblock as almost every other dietary development—that “more research is needed” before doctors can recommend the starch wholeheartedly.
And it’s true. Most human studies on RS have lasted only a few weeks, not the several years researchers prefer. What’s more, the four types of RS seem to vary in effectiveness in ways we don’t understand. (A 2010 industry-funded study comparing the effects of RS 2 and RS 4 on bloodsugar levels found that RS 4—the type in packaged foods—was more effective.) Finally, researchers have found that different types of RS populate the gut with different bacteria—not a bad thing, necessarily, but another indication of nuances we haven’t mastered.
But while many areas of nutritional research produce two distinctly opposed camps (Paleo vs. non-Paleo, meat eaters vs. vegans, dairy lovers vs. dairy haters), that kind of battle isn’t happening with RS, and no expert we spoke with says that the starch is either a sham or bad for you. To date, the only documented unpleasant side effect of eating more RS is gas. Even experts who question whether RS could have adverse long-term effects are cautiously optimistic. Take Diane Birt, a professor emeritus of food science and human nutrition at Iowa State University: While she doesn’t believe we should necessarily add RS to our diets, she admits that “it is a wonderful area of research.”
Birt may be in the minority, too, as more experts argue it’s high time RS was intentionally included on our plates. “Even though it’s got 30 years’ worth of research supporting its health benefits, it often takes that many years for a functional ingredient to become an ‘overnight’ sensation,” says David Feder, author of The Skinny Carbs Diet, a cookbook of RS-rich recipes. “Olive oil is an example: From the 1960s to the 1990s, it went from being something used by Italian and Greek cooks to being in every single pantry in the United States.”
Could RS be the next olive oil?
One company on the RS forefront is FiberGourmet, which manufactures RS-rich crackers, flatbreads, and pastas with rock-bottom calorie counts but the tastes and textures of conventional versions. An entire box of its RS 4-infused cheese crackers has just 360 calories, while each 60-calorie handful has an incredible 14 g of RS.
The company’s 13-year journey to develop tasty RS products hasn’t been easy, though—which is why scores of other companies haven’t yet followed suit. Ingredients used to produce RS can cost up to six times more than standard ones like wheat flour. High concentrations of RS can make foods denser, harder, darker, and grainier, so retaining taste and texture is challenging. Companies like FiberGourmet also have to go through many recipe revisions to make palatable products with enough RS to lower calorie counts.
But when a company accomplishes all this, the effect is that of a magic trick. Executives at FiberGourmet say they’ve received testimonials from customers who’ve lost 15, 30, and even 50 pounds by swapping conventional high-calorie foods for its products. “The reason it works so well [as a weight loss strategy] is that it’s so easy,” says David Holzer, the company’s CEO. “Usually, you feel that you have to suffer in order to diet. But if you really have foods with half the calories and the same taste, that’s not a fad—it’s a no-brainer.”
Holzer, for one, believes RS’s trajectory could—and should—parallel that of olive oil. Topping does, too, arguing that as more people learn of RS’s benefits and add it to their diets, society will get healthier in profound ways. A rise in RS consumption could trigger declines in colorectalcancer, type 2 diabetes, depression (healthier guts have been tied to lower risk), and our collective waistlines. “In the long term, unequivocally, it can assist in preventing excessive weight gain,” he says.
And increasing RS consumption could be as easy as rethinking how we cook. While there’s no standardized cooking method for increasing RS agreed upon by all scientists, the process ultimately boils down to three steps: Cook rice, pasta, potato, polenta, or oatmeal; let it cool; and devour every bite. (Note: People with diabetes should be careful about consuming more starches, even those high in RS. Foods with RS still contain carbs and should be added cautiously in reasonable portions and combined with other nutrients like protein.) Whole-food RS sources like beans and barley are the best choices, Bazilian says: “I’d seek out RS in real foods that you want to put on your plate already for nutritional reasons like fiber, fullness, or vitamins.”
As for how much RS to eat, the answer’s not really known. Most Americans get only 5 g per day now, mostly from the small amounts in cooked grains, pastas, and starchy vegetables like potatoes and also from breads, which contain a small amount of RS (whole wheat has more than white). Topping suggests 20 g a day, with some studies seeing positive results from up to 50 g a day.
At some level, though, we probably shouldn’t overthink how much RS we consume as long as we start cooking, cooling, and eating more RS-rich foods. That’s what’s so revolutionary about RS: These are real carbs, whole and delicious, already in your pantry or on store shelves, part of your family’s recipes and favorite meals—and the opposite of the unpleasant pills, sweeteners, meals, shakes, and bars that we normally associate with weight loss plans. So think of this as your long-awaited license to stop eyeing starchy foods as fattening demons and start eating them again.
Welcome back, carbs. We missed you like crazy.
|Your Daily RS Diet
Experts say to aim for 20 g of RS per day, but how can you get it? Here, 3 easy meal plans to help you hit or exceed the daily target:
Add 2 Tbsp Hi-Maize flour to a smoothie: 10 g
Peel a ripe banana for a snack: 5 g
Mix 1 cup cooked and cooled whole wheat pasta and ½ cup chickpeas in pasta salad for dinner: 10 g
Total: 25 g
Make DIY muesli from ⅔ cup raw oats, nuts, and fruit: 11 g
Chomp on 2 oz cashews: 7 g
Serve a dinner that includes ½ roasted and cooled potato: 16.5 g
Total: 34.5 g
Top a salad with ½ cup lentils: 5 g
Stave off predinner pangs with 1 oz FiberGourmet Thinables crackers: 14 g
Cook and cool ½ cup green peas for a crunchy dinner side: 5 g
Total: 22 g