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Carbohydrates: Sugar, Starch, and Fiber

This article will cover the basics of carbohydrates (“carbs”) — what they are, why we need them, and which types are better for our health.

What Are Carbohydrates?

Carbohydrates are organic compounds that contain single, double, or multiple sugar units. Simple sugars are only one or two sugar units long and are typically sweet tasting whereas complex carbohydrates are thousands of sugar units long and have a starchy taste. For more information about the chemistry of carbs, see Biology Online.

Simple sugars Complex carbohydrates
  • Milk
  • Fruit
  • Honey
  • Juice
  • Syrups – natural or commercial
  • Table sugar
  • Starchy vegetables (e.g. potatoes, peas, corn, dried beans/peas)
  • Grains and grain products (e.g. anything made with grain flour – bread, pasta, cereal, etc.)
  • Fiber (bran, gums, cellulose, etc)

All digestible simple sugars and starches eventually get converted to glucose in our body. Most types of cells use glucose as their main fuel source. After we eat sugars or starches, our blood glucose level rises. This signals our body to produce insulin, a hormone, so that cells can take the glucose out of the bloodstream and use it for energy. Excess glucose will be stored as glycogen in our liver and muscle. If there is still excess glucose after maxing out glycogen storage, it will be converted and stored as body fat. Eating too much sugar or starch of any type can cause you to gain weight.

Sometimes people get confused as to how simple sugars and starches affect blood glucose. Please read “Tips for Managing Diabetes” if you would like more information about carbohydrates and diabetes.


Fiber is a non-digestible complex carbohydrate. Our gut does not possess the enzymes needed to break apart the links between sugar units. Undigested fiber travels through our gut and while doing so, provides health benefits. Fiber also encourages growth of healthful bacteria in our lower gut. Benefits come from two different types of plant fibers that are classified based upon whether or not they dissolve in water (soluble) or not (insoluble). It is important to consume both types of fiber for maximum health benefits.

Fiber type Benefit Food sources
Insoluble Regularity (relieves constipation), lower risk of diverticulosis (gut pouches that get inflamed) Bran from grains/cereals, skins and seeds from fruits and vegetables, dried beans/peas, brown rice
Soluble Helps reduce straining with excretion, binds cholesterol in the gut, and helps blunt rise of blood glucose after a meal. Fleshy part of fruits and vegetables, oats, dried beans/peas

How Much Fiber Is Enough?

The Dietary Reference Intake (DRI) for total fiber intake for adults is 14 grams per 1000 calories intake. If you do not want to do the math, then the DRI for standard intakes is:

25 grams for women

38 grams for men

The DRI is for total fiber, there is no breakdown by type of fiber. However, to help reduce blood cholesterol levels, the National Institutes of Health (publication No. 06-5235) recommends 5 – 10 grams/day of soluble fiber.

One simple way to meet fiber goals is to eat three or more servings of whole grains and five or more servings of fruits and vegetables daily. Vegetables include both non-starchy and starchy types, as well as dried beans and peas. With this strategy, you consume a variety of healthful foods that provide both types of fiber.

MyNetDiary Tip

You can select fiber as one of your nutrients to track in the PLAN section on the web. Once you select it, you can enter your goal and it will show up on reports. As well, fiber will be displayed in the “Day Nutrition Summary” at the bottom of the meals screen within your iPhone app.

Current Sugar Guidelines

Last year, the American Heart Association published recommended limits for intake of added sugars as a means to help reduce risk for heart disease. The current recommended limits for added sugars are:

100 calories for women (25 grams or 6 teaspoons)

150 calories for men (38 grams or 9 teaspoons)

Added vs. Natural Sugar?

The guidelines specifically refer to added sugars: table sugar, honey, natural syrups (e.g. agave, maple, and molasses), commercial syrups (e.g. high fructose corn syrup), and concentrated fruit sugars added to foods to sweeten or preserve. The naturally occurring sugars in milk, fresh fruit, dried and frozen fruit without added sugar and 100% fruit juice are not considered added sugars. Artificial sweeteners and sugar alcohols are also not considered added sugars.

Sugar grams listed on the Nutrition Facts panel include both naturally occurring sugars and added sugars. This might change in the future with a new labeling law, but for now, you have to look at the ingredient list to find added sugars. Names for added sugars are numerous - MyPyramid has a list of commonly used names here.

MyNetDiary Tip

If you choose to select “Sugars” as a nutrient to track, just be aware that the value will include both naturally occurring and added sugars (total sugars). The added sugar limit of 25 – 38 grams should not be entered as a MyNetDiary goal as it will create a falsely low limit. Remember, there are naturally occurring sugars in almost all foods. A more appropriate goal for total sugars is 25% of total calories (e.g. 125 grams for a 2000 calories diet).

Hidden Sources of Added Sugars in “Healthy Foods”

It is easy to identify regular soda pop and energy drinks as examples of empty calories, but what about sugary foods and drinks that also have nutrients? Choose brands that have less added sugar than their rivals. Or, select unsweetened versions. See the list below for nutritious foods that often have too much added sugar:

Sweet Tooth Tip

One teaspoon of added sugar is about 4 grams. If you add your own sweetener to unsweetened foods and drinks, you can control added sugar more easily than buying presweetened foods.


Healthful carbohydrates are those that provide nutrients while limiting fat, sodium, and added sugar. The simplest way to consume healthier carbohydrates is to choose unprocessed whole grains, cereals, and starchy vegetables, fresh fruit, dried beans and peas, and skim milk or low sugar soy/rice milk. If you can choose these instead of refined versions, you should be able to meet your fiber goals while also limiting added sugars, sodium, and fat. Carbs are not a dieter’s are – but you do have to choose wisely.

If you have questions about this topic then ask them in MyNetDiary Community Forum!

Katherine Isacks, MPS, RD, CDE
Disclaimer: Please note that we cannot provide personalized advice and that the information provided does not constitute medical advice. If you are seeking medical advice, please visit a medical professional.


Medline Plus. “Carbohydrates.” Access online at:

MyNetDiary. “About Low Carb Diets.” Access online at:

National Heart Lung Blood Institute. “Food sources of soluble fiber. Access online at:

Harvard School of Public Health. “Fiber: start roughing it.” Access online at:

American Heart Association. “Whole grains and fiber.” Access online at:

Harvard School of Public Health. “Time to focus on healthier drinks.” Access online at:

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