What Are Simple Sugars?

There are three major macronutrients that you can get from the food you eat: carbohydrates, protein and fat. Carbohydrates, which your body likes to burn first for energy (because they are the most easily accessed), include starches, cellulose and sugar, which can be either ​simple or complex.​

Simple sugars are carbohydrate molecules that contain only one or two sugar molecules, also called saccharides. Eating a lot of simple sugars can contribute to health problems like obesity, diabetes and chronic inflammation, so it's best to stick to complex carbs whenever possible.

Saccharides are sugar molecules that join together to form different types of carbohydrates. You can further divide both simple and complex sugars (carbs) into four more specific categories:

• ​Monosaccharides​: contain one sugar molecule ("mono" means one).
  
• ​Disaccharides​: contain two sugar molecules ("di" means two).
  
• ​Oligosaccharides:​ usually contain between three to nine sugar molecules ("oligo" means a few).
  
• ​Polysaccharides​: contain long chains of monosaccharides ("poly" means many).
  

A simple sugar has one or two sugar molecules or saccharides; complex carbs have three or more. Monosaccharides and disaccharides are classified as simple sugars, while oligosaccharides and polysaccharides are complex carbs.

Simple sugars (or simple carbs) occur naturally in foods like milk and fruit. They're also added to processed foods to enhance the flavor, texture and shelf-life. You can easily identify simple sugars because they often end in the suffix "ose," like glucose, fructose, sucrose and lactose.

​Read more:​ Uses of Glucose

Monosaccharides are the simplest of sugars, which means that your body cannot break them down any further. Because of this, your body digests monosaccharides quickly and easily, which results in a significant spike in glucose levels. Galactose, glucose and fructose are examples of the types of sugar on the monosaccharide list:

• ​Glucose​, which is found naturally in vegetables, fruit and honey and in processed foods, is the most basic energy source for all life forms. All other carbohydrates are converted into glucose as your body digests them.

• ​Fructose​, also known as "fruit sugar," is found primarily in fruit and root vegetables, like sweet potatoes, carrots and honey. When fructose is used as a commercial sweetener, it's usually derived from sugar cane, sugar beets and corn. Fructose bonds with glucose to make sucrose, the type of table sugar that you'll find in your sugar bowl.

• ​Galactose​ occurs naturally in milk and a few other foods like avocados and sugar beets. When galactose bonds with glucose, it forms lactose, or "milk sugar."

Simple sugars occur naturally in ​healthy whole foods​, including all vegetables, fruits and milk. When you eat fresh veggies, fruit and unsweetened dairy products, you're taking in simple sugars in their natural form. In this case, as long as you don't overdo it, it's unlikely that the simple sugars will have a significant negative effect on your health.

The problem is when simple sugars are added to foods. That means the sugar added to your coffee or the candy and desserts made with sugar or that fructose in your soda or the hidden sugar in foods like ketchup and dressing. It's easy to overload your body with added simple sugars, and this can lead to a number of health issues.

There are several serious health issues associated with eating (or drinking) too many simple sugars. Most of these health issues occur when the simple sugars you're eating come from ​processed foods,​ rather than whole foods.

​Read more:​ 10 Easy Drink Swaps to Cut Down on Sugar

According to the Centers for Disease Control and Prevention, nearly 40 percent of U.S. adults have obesity. Health conditions related to obesity, including heart disease, diabetes and cancer, are some of the leading causes of death in the United States, and they can be largely prevented by eating healthier foods and maintaining a healthy weight.

Recent research shows that obesity is caused not only by excess calories, but even more so by ​excess carbohydrates​ in the diet, especially carbs with a high-glycemic index. Among common sugars in the diet, glucose and dextrose (a type of glucose derived from corn) have the highest glycemic index, sucrose (table sugar) and lactose are in the mid-range, and fructose is quite low on the index.

However, that doesn't mean fructose doesn't have negative effects. As long as you restrict your fructose consumption to two or three daily servings of fresh or frozen fruit, you're probably going to be okay. Fructose becomes dangerous when it's consumed in excess through processed foods and sugar-sweetened drinks.

Over the years, there's been a significant increase in the consumption of ​processed fructose​, which is directly related to obesity and other related health issues. Fructose actually stimulates the appetite and changes the way you metabolize fats and carbs, leading to fat accumulation.

According to a study published in Diabetes Care in 2014, drinking sugar-sweetened beverages can contribute to fatty liver disease and metabolic syndrome, which increases your risk of diabetes.

Because simple sugars are easily digested, your body quickly absorbs them, and they ​raise your blood sugar​ much faster than complex carbohydrates. When you eat a lot of processed foods or drink beverages sweetened with fructose and other simple sugars, you're consuming more simple sugar than is healthy, and this can lead to insulin resistance and, eventually, type 2 diabetes.

A diet high in simple sugars is directly related to low-grade inflammation. Drinking just one can of regular soda a day causes an increase in uric acid (especially in people with overweight), which triggers inflammation. Common inflammatory diseases include inflammatory bowel disease, allergies, auto-immune disease and asthma.

According to research published in the journal JAMA Internal Medicine in 2014, Americans whose daily calories included 25 percent or more of added sugar had a much higher chance of dying from heart disease than those who kept their consumption of added sugar to less than 10 percent of their daily calories.

Too much sugar can suppress your immune system, leaving you more susceptible to cancer. Cancer cells also tend to generate and grow in areas of inflammation, and too many simple sugars can lead to inflammation.

Recent studies also show that severely limiting simple sugars (as with the ketogenic diet) may be an effective adjunct treatment for slowing the growth of some cancers, especially some brain cancers, colon cancer and breast cancer. When the body switches from glucose to ketones as the major source of energy, it ​starves the cancer cells​ while your normal cells can adapt to using ketones for energy.

Natural simple sugars, like those in fruit and milk, probably won't cause any major health issues, as long as most of your diet is based on whole foods (foods that haven't been processed); however, it's best to eliminate sugar-sweetened drinks completely and strictly limit other added sugars in your diet in the form of processed foods and sweets.