What Are Carbohydrates—And Are They Really That Bad?

Carbohydrates are key nutrients that your body converts into glucose to use for energy.

Have you been doing your best to steer clear of carbs? You're hardly alone: Many people believe carbohydrates are the enemy, nutritionist Rania Batayneh, author of "The One One One Diet," told Health.

Enthusiasts of low-carb eating plans say the macronutrient triggers weight gain and contributes to a host of health problems, including disease-causing inflammation and the fuzzy-headed, unfocused feeling known as brain fog. But healthcare providers warn that this type of all-or-nothing thinking can be risky.

Labeling an entire food group as "bad" is a vast over-simplification, David Katz, MD, founder and former director of the Yale-Griffin Prevention Research Center at Yale University and author of "The Truth About Food" told Health. "Carbs are everything from jelly beans to pinto beans," said Dr. Katz.

Indeed, one of the reasons carbohydrates cause so much confusion is that foods like cauliflower are lumped into the same category as hot dog buns. Research is clear, however, that choosing the most nutritious kinds of carbohydrates can improve your health.

The first step is reconsidering what you've always heard about your body's number one source of energy.

What Are Carbohydrates?

When you eat carbohydrates, they are broken down by your gut into glucose and released into your bloodstream. Your pancreas responds by releasing insulin to shuttle that glucose into cells.

The higher your blood sugar levels get, the more insulin circulates through your system. And that can be problematic because excess insulin damages cells, ups your risk of heart disease and diabetes, and triggers your body to store surplus glucose (the energy that your body doesn't currently need) as fat—especially in your midsection, Mark Hyman, MD, director of the Cleveland Clinic Center for Functional Wellness, told Health.

But here's the crucial caveat: Not all carbs cause a big spike in blood sugar.

There are two types of carbohydrates: simple and complex. Complex carbohydrates cause a more gradual rise in blood sugar that keeps it more steady whereas simple carbohydrates cause a rapid, high spike.

Simple and Refined Carbs

Simple carbohydrates are made of one or two sugar molecules and include sugars and refined carbs.

Refined carbs—the kind found in processed grains, like white rice, and anything baked with white flour—are stripped of nutrients and contain little to no fiber. They are broken down swiftly and send your blood glucose and insulin levels soaring.

Refined carbs include:

  • White bread
  • White rice
  • Cookies and cakes
  • Other pastries
  • Pizza

Complex Carbs

Complex carbs, on the other hand, are made up of longer chains of sugar molecules (a.k.a. starches), as well as fiber. They take more time to digest and provide a steadier stream of blood sugar, prompting a more gradual release of insulin, Kristin Kirkpatrick, RD, lead dietitian at Cleveland Clinic Wellness Institute, told Health.

These types of carbs are in a wide array of highly nutritious foods, including:

  • Legumes and pulses (beans, peas, lentils)
  • Nuts and seeds
  • Fruits
  • Vegetables

Complex carbs are found in whole grains, too. Whole grains contain the entire nut or seed kernel—including the endosperm (middle layer), bran (outer layer), and germ (inner part that contains nutrients)—from the plant. This includes brown rice and quinoa.

There are also foods that contain whole-grain ingredients. If you eat these foods as part of your diet, look for "100 percent whole grain" on labels (even on products like pasta and crackers).

Just don't be fooled by the so-called "whole-grain halo." A product that also contains added sugar or any ingredients that you may not recognize is not the healthiest option.

Are Carbs Bad for You?

If your diet consists mostly of packaged treats and soda, then yes, your carb intake may cause problems like chronic inflammation and brain fog, among other issues. But cutting back on all carbs comes at a real cost.

Despite their bad PR, carbohydrates boast many health benefits. For starters, "they help fuel your brain, kidneys, heart muscles, and central nervous system," said Batayneh. Research has suggested that carbs can also contribute to the production of the feel-good brain chemical serotonin.

Thanks to their fiber, complex carbs aid digestion, help you feel full, keep cholesterol levels in check, and ease bloating and constipation. And perhaps most important, complex carbs such as fruits and vegetables are rich sources of nutrients and powerful phytochemicals, which play a role in preventing and even fighting illness and cellular aging.

That may be why several studies show that people with the lowest carbohydrate intake have an increased risk of early death from all causes compared to those who eat moderate amounts.

How Many Carbs Should You Consume?

The answer differs for everyone, but aiming for a moderate-carb diet tends to be a healthy option overall.

A 2018 study found that those who ate a moderate-carb diet (50% to 55% of daily calorie intake) had lower mortality rates than those who typically ate low-carb meals (40% or less of daily calories) or high-carb meals (70% or more of their calories).

Moderate intakes of healthy complex carbs seem to have beneficial effects: "Research shows that the Mediterranean diet, which is higher in lean protein and healthy fat, and the Japanese Okinawa diet, which is low in fat and protein, are linked to a longer life span. These two diets are very different—except for the fact that they're both rich in whole, plant-based carbohydrates," said Dr. Katz.

As a general rule, you can eat as many carbs as you like when they come in the form of low-starch vegetables (like asparagus, broccoli, celery) and low-glycemic fruits (such as pears, kiwis, and oranges)—or in other words, produce that has a minimal effect on your blood sugar.

As for higher-starch complex carbs (hello, sweet potatoes and bananas), they're best eaten in moderation; aim for a serving or so per meal, though the ideal amount for you really depends on your age, weight, activity level, and personal biochemistry.

For example, an endurance athlete will need more than the average person since they're burning more energy and require more fuel.

Do Carbs Make You Gain Weight?

Too much of any food group can lead to weight gain, and there's no question it's easy to overdo it on "empty" refined carbs (potato chips, we're looking at you) and higher-starch carbs, like brown rice. "The reality is, most Americans are overconsuming carbs," said Dr. Hyman.

However, when you're eating mostly slowly digested complex carbs—think leafy greens and lentils—it's harder to go overboard. That's because those foods leave you feeling satisfied, so you're not craving a cookie 30 minutes later.

"Because high-fiber foods take longer to digest, they tend to even out blood sugar, leading to lower insulin levels—which keeps your body from creating excess belly fat," explained Dr. Katz.

Studies suggest that choosing complex carbs over the refined kind might even help lower body fat, particularly abdominal fat. Still, more research is needed.

That said, if you have a significant amount of weight to lose, a low-carb plan may be appropriate, said Dr. Hyman. But—and this is key—you need to work with a healthcare provider or nutritionist to make sure you're still getting the nutrients your body needs.

And beware of the risk of burnout, warned Dr. Katz: "If drastically limiting carbs was effective and sustainable, wouldn't fewer Americans be struggling with their weight?"

Dr. Katz suggested a simpler, more balanced approach. "A plant-based eating plan rich in complex carbs can help you stay healthy and lose weight—and it's a lot easier to stick with long-term," said Dr. Katz.

A Quick Review

Research suggests that diets that are high or low in carbs may not be as beneficial as a moderate-carb diet with about 50% of calories from carbohydrates.

When possible, opt for complex carbohydrates from fruits, vegetables, nuts, beans and legumes, and whole grains over refined carbohydrates, such as pastries and white bread. Complex carbs are more slowly digested, contain beneficial nutrients and phytochemicals, and help keep blood sugar steady.

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Health.com uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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