The Function of Disaccharides

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Watermelon contains sucrose.
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Disaccharides may not come up in your day-to-day conversation, but the two-molecule sugar is probably present in some of the foods you eat. Now before you go and clear out your kitchen of this sugar, you need to understand the biological importance of disaccharides.

Why You Need Carbohydrates

While the human body is an amazing machine, it can't perform all the necessary functions of life without a little outside help. Nutrition, which refers to the energy and nutrients provided by the food you eat, plays a major role in supporting normal body function and overall health. Many of the nutrients found in the food you eat are essential, meaning your body can't make them on their own, and they must come from outside sources.

Essential nutrients are divided into two camps:

  • Macronutrients: nutrients needed in large quantities, including fat, protein and carbohydrates
  • Micronutrients: nutrients needed in tiny amounts, including vitamins and minerals

While carbohydrates currently seem to be your nutritional enemy and the reason for your growing waistline, they're the macronutrient your body needs in the largest amount. According to the Dietary Guidelines for Americans, 45 to 65 percent of your calories should come from carbohydrates. By comparison, the Dietary Guidelines recommend that 10 to 30 percent of your calories come from protein and 25 to 35 percent of your calories from fat.

Your body needs carbohydrates because this macronutrient provides your cells with its preferred source of energy: glucose, according to the Royal Society of Chemistry. Glucose is a monosaccharide, which is the simplest form of carbohydrate, and serves as a building block for other carbohydrates, including disaccharides.

Glucose and other monosaccharides, which include fructose and galactose, are rarely found by themselves in nature. The glucose your body needs for energy comes from more complex carbohydrates like disaccharides and polysaccharides.

Read more: A Complete Guide to Complex Carbohydrates

What Is a Disaccharide?

A disaccharide is a carbohydrate composed of two monosaccharides, which are more often referred to as simple carbohydrates. In your body, a disaccharide function is to provide your body with a quick source of energy. Because they're only made up of two sugar molecules, they're easily broken down by enzymes in your digestive system into their respective monosaccharides and then absorbed into your bloodstream.

Disaccharide examples include:

  • Sucrose: glucose + fructose
  • Maltose: glucose + glucose
  • Lactose: glucose + galactose

By comparison, polysaccharides, also known as complex carbohydrates, are made up of a long string of monosaccharides that can be twisted, branched and even folded, which requires more time to break apart and supply energy.

While it's impossible for your cells to absorb a disaccharide, your cells have the capability of making disaccharides. If your cell gets more glucose than it needs, it strings the monosaccharides together to create disaccharides and polysaccharides, which serve as a stored source of energy.

Read more: The Best Healthy Carbs You Should Be Eating More Of

Sources of Disaccharides

Disaccharides are found in a wide variety of foods, including healthy and not-so-healthy foods, and may be a regular part of your daily diet.

Disaccharide examples of foods that contain sucrose:

  • Fruits: apples, watermelon, mango and banana
  • Vegetables: carrots, corn, beets and tomatoes
  • Table sugar
  • Candy
  • Soft drinks

Disaccharide examples of foods that have maltose:

  • Sweet potatoes
  • Edamame
  • Bread
  • Pizza
  • Pies
  • Cakes
  • Cookies

Disaccharide examples of foods that contain lactose:

  • Milk
  • Yogurt
  • Ice cream
  • Cheese

On the food label, disaccharides are classified as a sugar, which can be confusing if you're trying to limit your sugar intake. However, when it comes to eating and nutrition, it's important to note the total package and not the one nutrient. Natural food sources of these disaccharides, including fruits, vegetables and milk products, come with other essential nutrients your body needs such as protein, fiber, vitamins and minerals.

It's the foods with added sugar, such as candy, soft drinks, cakes, cookies and ice cream, that you need to be concerned about. These foods are calorie dense and nutrient deficient and don't add much overall value to your health. The American Heart Association recommends limiting your intake of added sugar to 36 grams for men (9 teaspoons) and 25 grams for women (6 teaspoons).

Read more: How Much Sugar You Should Really Be Eating Each Day

Biological Importance of Disaccharides

From a biological standpoint, disaccharides serve a very important role for health and energy. As previously noted, carbohydrates, including disaccharides, provide your body with glucose, which gives you energy to run all your organ systems, get through your day at work and fuel your workout.

While you may think that your muscles are responsible for burning through all the glucose, it's actually your brain that consumes the largest percentage. According to an October 2014 article published in Trends in Neurosciences, your brain uses 20 percent of the glucose you consume. Much of that glucose is used to make neurotransmitters, which are the chemicals in your brain that relay messages pertaining to mood, muscle control and cognitive function.

If you're an endurance athlete, such as a marathoner or triathlete, you rely on carbohydrates to help you get through your long workout or race. According to a January 2018 expert report panel published in Nutrition Today, fast-absorbing carbs like disaccharides are the best choices immediately before and during your workout. The quick source of energy provided by disaccharide-rich foods improves muscle performance and endurance.

What About Ketones?

If you're following a ketogenic or very-low-carb diet, your goal is to get into what's referred to as a state of ketosis, which is when your body is burning fat to make ketones.

Your brain can also use ketones as a source of energy. While the ketogenic diet has been shown to be effective at promoting weight loss, the long-term effects of cutting out a major essential nutrient is not known, according to the Academy of Nutrition and Dietetics. If you're considering cutting carbs to help you lose weight, consult with your doctor first.

The Problem With Lactose

Disaccharides have their place in a healthy diet, but not all disaccharides are well-received. Lactose is a disaccharide found in milk. This particular disaccharide requires a digestive enzyme called lactase to break it down into its monosaccharides, glucose and galactose.

Whether due to genetics or aging, your body may not produce enough lactase or any at all, which means your body can't break down lactose. If left intact, the disaccharide causes digestive issues such as abdominal pain, bloating and diarrhea. If you're lactose intolerant, you want to avoid foods that contain lactose, drink lactose-free milk or use digestive enzymes to prevent the side effects.

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