Understanding Simple and Complex Carbohydrates

Complex carbohydrates come from whole grains and vegetables like sweet potatoes. Simple carbohydrates are found in everything from table sugar to fruit.

Both types of carbs give your body energy, but because simple carbs are easier to break down, they give you a short burst of energy while complex carbs, which take longer to digest, provide a lasting source of energy.

This article explains how simple and complex carbs work, the benefits and drawbacks of each, and examples of foods that fall into each category.

What Are Carbohydrates?

Carbs are nutrients present in the food you eat. During digestion, they are broken down into sugars that, after making a quick stop in the liver, go into the bloodstream and become an immediate source of energy for the body's cells to use.

There are two types of carbohydrates: simple and complex. Simple carbs are short molecule chains. Complex carbs are longer chains. Because they're short molecule chains, simple carbs are easy for your body to break down. Complex carbs take longer.

Complex Carbohydrates

Complex carbs are made of long, complex chains of sugar molecules. These are called oligosaccharides and polysaccharides. Complex carbs take longer to digest than simple carbs do. This means they have a less immediate impact on blood sugar, causing it to rise more slowly.

Examples

Some complex carbs are better choices than others. The healthiest complex carbs have not been processed or refined and include whole grains, starchy vegetables and non-starchy vegetables, and beans and legumes.

Some examples of nutritious complex carbs include:

1. Brown rice
2. Wild rice
3. Steel-cut oats
4. Whole-grain (rather than pearled) barley
5. Quinoa (a seed)
6. Buckwheat (a grass)
7. Starchy veggies like potatoes, sweet potatoes, and corn
8. Non-starchy veggies like asparagus and zucchini
9. Lentils
10. Kidney beans
11. Chickpeas

All of these foods are excellent sources of fiber. Fiber helps keep blood sugar levels from spiking too high, helps control cholesterol levels, and is essential for digestive health.

Refined Grains and Processed Foods

Avoid or limit refined grains and processed foods, even if they are made with ingredients like wheat or oats. "Refined" means two of the three elements of each kernel of grain—the bran and the germ—have been removed, along with the fiber, healthy fats, and nutrients found in them.

The part of the kernel that's left is the starchy endosperm. It has less fiber and nutrients, even though vitamins and minerals are sometimes added to refined grains. Products made with them are sold as "enriched," but there really is no substitute for the natural grains.

Processed foods made with refined grains include:

• Bagels
• Baked goods like cakes and cookies
• Cereals made from refined grains
• Crackers
• Hamburger or hot dog buns
• Pancakes and waffles
• Pizza dough
• Rice snacks
• Soft sandwich bread 
• White rice and pasta

Many of these foods are also sources of added sugar, making them even less ideal for managing blood glucose. But that doesn't mean you must eliminate everything on the list above. Many of these foods also come in whole grain options, which can be a nutritious way to continue enjoying them.

What Are Simple Carbohydrates?

As the name suggests, simple carbs have a very basic chemical structure. They may be monosaccharides comprising a single sugar molecule, like glucose. Or they may be disaccharides, which have two simple sugars linked together, as with lactose (milk sugars).

Simple carbs are fairly easy for the body to digest. Enzymes in the small intestine break them down before they enter the bloodstream. Any sugar that isn't used right away is stored as fat, and that's why eating foods with lots of added sugar can add to weight gain.

Examples

Many foods contain simple carbs and are also rich sources of vitamins, minerals, and other nutrients. These foods include things like fruit, dairy, and some vegetables.

Not all simple carbs are nutritious, however. Many simple carbs are found in refined sugars, which add calories but lack vitamins, minerals, and fiber. Examples of simple carbs to limit or avoid include:

• Candy
• Soda
• Syrups
• Sugar

The added sugars in cookies, pastries, and many other processed foods are also simple carbs.

When to Limit Simple Carbohydrates

Because simple carbs are digested quickly, they can cause a spike in blood sugar that is higher and happens faster than when you eat complex carbs. This is why it's best to limit simple carbohydrates, especially those with low nutritional value.

The simple carbs present in foods like candy, cookies, and pastries tend to be "empty calories," so they more easily lead to weight gain and health problems like heart disease.

The Centers for Disease Control and Prevention (CDC) recommends limiting added sugars to less than 10% of total daily calories. For most adults, that comes out to about 12 teaspoons. Kids under 2 shouldn't have any added sugars at all.

Summary

Carbs are necessary for a healthy diet. Simple carbs have a basic chemical structure and are easy for the body to digest. Some simple carbs, like fruit and dairy, are good for you, while others, like candy, soda, and sugar, are unhealthy and should be limited.

Complex carbs have longer, more complex chains of sugar molecules and take longer to digest. The healthiest complex carbs include whole grains, most vegetables, beans, and legumes.