"Carbohydrates often get a bad rap, but all carbs are not created equal, and many carbs can be good for your health," Dr. Tania Elliott, allergist, internist, and Chief Medical Officer at EHE, tells Bustle. And one of the most helpful things they do is provide the body with energy.

Here's how it works: "Carbohydrates provide the body with glucose, which gets converted to energy to aid in physical activity," Dr. Elliott says. "Glucose helps your body do almost everything, from breathing to lifting a finger, to walking, and of course any kind of exercise."

That's why you often hear about runners eating a lot of pasta the night before a big race. "The more active you are, the more carbs you need, and the more effective that workout will be," Dr. Elliott says. It is, however, necessary for everyone to eat carbs — even if you aren't an elite athlete.

To boost your energy, go for complex carbs like sweet potatoes, beans, or whole grains and try to avoid simple carbs, which will cause your blood sugar to crash. "Complex carbs take longer to break down so they give you a steady state of energy," Dr. Elliott says. "And, carbs that are high in fiber give the best kind of long-lasting energy and have added [gastrointestinal] benefits, too."

If you've noticed that carb-rich bedtime snacks help you sleep better, there may be a reason for that. "[Carbs] not only help stabilize blood sugar and [prevent] you waking from hunger, but [carbs can also] potentially help you sleep better," Megan Ostler, MS, RDN, head of nutrition at iFit, tells Bustle. "Carbs increase the hormone insulin, which may play a role in promoting good sleep though increasing tryptophan to the brain, which makes serotonin." And it all adds up to increasing your chances of getting a great night's sleep.

"Carbs are the brain’s main energy source," Bracha Kopstick, RD, of BeeKay Nutrition, tells Bustle. "So if we want to stay focused throughout the day, and energized, carbs are prime!"

Again, it's all about that glucose. "Carbohydrates are broken down in digestion into monosaccharides, one of which is glucose," Kopstick says. "This is the main fuel for the brain, needed to create and send neurotransmitters and messages throughout the body."

If you aren't consuming an adequate amount of carbs, it may start to affect your cognitive abilities. "Because the brain can’t store much, it needs to be replenished often through food," Kopstick says. "If glucose levels fall too low, brain function can be impacted — ranging from irritability and inability to focus, to severe ... changes in brain function and disease."

We've all heard about insoluble fiber, which is the kind of fiber that keeps us regular. "But," as nutritionist Dr. Sonjan Kukuljan says, "there is another fiber that is also critical for health," known as soluble fiber. This is the type of fiber found in foods like oatmeal, nuts, beans, apples, and blueberries. And it has all sorts of heart-healthy benefits.

"Soluble fiber helps to blunt the rise in blood sugar levels after eating and is highly effective at lowering blood-cholesterol levels, especially LDL-cholesterol, the type that is associated with an increased risk of heart disease," Dr. Kukuljan says.

According to WebMD, soluble fiber works by attaching to cholesterol particles within your digestive tract and ushering them out of the body, which in turn helps reduce the body's "overall cholesterol levels and the risk of heart disease."

There are so many factors that can affect you mood. And what you eat is definitely one of them. "Eating carbs helps to boost serotonin levels in the body, [which is] the feel-good hormone," nutritionist Lauren Minchen, MPH, RDN, CDN, of Lauren Minchen Nutrition, tells Bustle. "This boost is made possible by L-tryptophan, an amino acid found in protein foods. However, carbs seem to increase the amount of L-tryptophan that can get to your brain (through the bloodstream), which can then boost serotonin."

Just make sure you're eating those healthy, fiber-rich carbs. "The important thing here though is to choose ... whole foods carbs like fruits, veggies, whole potatoes, beans, lentils and whole grains — all of which contain beneficial nutrients, like B vitamins (which also help to boost serotonin) and fiber," Minchen says. "Choosing processed carbs may work against the desired serotonin lift because they will cause your blood sugar to spike and then crash, leaving you lethargic and tired."

Since the word "carbs" is often associated with unhealthy foods, it's easy to make the mistake that they should be avoided at all costs, when in reality they're an excellent source of nutrition.

"Whole, unprocessed carbohydrates such as fruits and vegetables, as well as legumes and whole grains, provide a vast amount of nutrients such as vitamins, minerals and fiber, all of which are important in preventing diseases and keeping our bodies healthy," Opyt says.

The common belief that carbs are bad often stems from processed foods. "For the most part, processed foods, which have had their nutrients and fibers stripped away through a refining process, are carbohydrates that no longer offer a nutritional value and [can damage your health] when not consumed in moderation or in combination with other nutrient-dense foods," Opyt says. "Therefore, it is important to consume whole grains, such as brown rice and whole wheat products, as well as whole fruits and vegetables, and to avoid simple sugars that are added to foods such as 'junk' sweets (cookies, candy, cakes) as well as processed grains such as white pasta and white bread."

Eating carbs can also keep you feeling satiated or fuller, longer. That's because "whole grains such as brown rice and whole wheat bread include fiber in addition to the starch," Julia Werth, RD, tells Bustle. "The fiber makes the grain more difficult to digest and therefore whole grain foods take longer to leave your stomach and pass through your intestines — making you feel full longer."

This is why health experts often suggest we stay away from foods that have had the fiber removed — like white bread — and instead add more whole grains to our diet. It's all about that fiber.

The fiber found in carbohydrates is essential for digestion, too. For the whole process to work most efficiently, the goal is to eat the "right amount of the right carbs, which [includes] high fiber carbs," Tanya Zuckerbrot, MS, RD, NYC-based registered dietician and founder of F-Factor diet, tells Bustle.

Zuckerbrot suggests eating 25 to 30 grams of fiber per day, to aid in digestion. "Eating a high-fiber diet helps you have complete and regular bowel movements," she says. "Fiber increases stool bulk, which helps prevent constipation, bloating, and can offer relief from irritable bowel syndrome."

A well-rounded diet is where it's at when it comes to lowering your risk for certain health issues, like diabetes. "Carbohydrates that are complex, and likely therefore have fiber, can help us feel fuller longer and promote satiety," Monica Auslander Moreno, MS, RD, LD/N, nutrition consultant for RSP Nutrition, tells Bustle. "Robust fiber intake is associated with lower risk of diabetes, and complex carbohydrates are an excellent source."

Keep in mind, though, that simple carbs should be eaten in smaller quantities. "Refined carbohydrates (like sugar) can cause rapid apexes and troughs of certain neurotransmitters and hormones," Moreno says. "This erratic pattern is quite deleterious for your pancreas, which would secrete more insulin in response to refined carbohydrate ingestion and contribute to a cycle of requiring more and more insulin; which can be a risk factor for diabetes."

It's all about finding that middle ground, and — if you have or are at risk for diabetes — talking with your doctor to figure out the best diet plan for you.

In many ways, carbohydrates are an essential part of a healthy diet — regardless of what any diet fad says. By eating more complex carbs, such as whole grains, you can reap a world of health benefits.