Lecture 4A: Carbohydrates

FN 225: Nutrition
Tamberly Powell, M.S., R.D.
Health Professions Division
Lane Community College
Eugene, Oregon

LECTURE 4A: Carbohydrates (Sugar, Starch, Glycogen and Fiber)

I will email the average score for Exam 1 and update grades on Monday.

Policy about returning exams: To prevent exams from being in circulation (which would decrease their reliability as an assessment tool), you're not able to see graded exams online. Students in campus sections are also not allowed to keep their exams.

Those of you in this area are welcome to come see me during my office hours or schedule an appointment to see your exam results. Those who can not do this can call me during my office hours, 541-463-5525, or schedule a time to go over your results over the phone. If you missed 5 questions or less, I can email you the questions you got incorrect.

If you schedule a time to review your exam (either in person or over the phone) you will have the opportunity to earn up to 2 points back on your exam if you can support your incorrect answer(s).

I also will post your grade for the class the Monday after Exam 1 is due. It will show you your total points earned plus a percentage of total points, and a letter grade.

The second EXAM is Week 5 on carbohydrates. It will be available to take on Tuesday of Week 5, but is due THURSDAY of Week 5.

There is an online review quiz to be taken during week 4. This review quiz is the same format as your review quiz for Exam 1. You will see some similar/identical questions on the exam that are taken from the review quiz, so I highly recommend you participate in this activity.

FORUM (to be posted MONDAY of Week 4):

1. Do you have any questions or comments about Exam 1?

2. What did you learn in this chapter that made you think differently about carbohydrates? How will this impact your food choices?

As you're looking at this lecture, have in front of you your lecture outline for Ch. 4- Part 2 to fill in the blanks and to answer the questions.

The Lecture Outline begins by asking this question:

If someone told you "My carbohydrate intake is too high", what would you assume about what they're eating?

When I've asked this question in class, the two most common things people say are:

lots of bread
lots of sweets

BOTH of these kinds of foods are high in carbohydrates, but the kinds of carbohydrates are different. Bread is high in the carbohydrate starch and sweets are high in sugar. A third type of carbohydrate is fiber and it's the one that sometimes people don't think of as a carbohydrate. These are the three types of carbohydrates found in food: starch, sugar, and fiber.

Look how these lectures are organized.

Lecture 4A-

I Types of Carbohydrates,

which include A. SIMPLE and B. COMPLEX Carbohydrates.

Notice that sugar is a SIMPLE Carbohydrate and starch and fiber are both COMPLEX Carbohydrates.

Lecture 4B-

II Processing of Foods with Carbohydrate

III Digestion & Absorption of Carbohydrates

IV In the Body: Glucose As Fuel

I Types of Carbohydrates

A. SIMPLE CARBOHYDRATES

Notice that BOTH monosaccharides and disaccharides are SIMPLE CARBOHYRATES.

Glucose, fructose and galactose are MONOsaccharides and maltose, sucrose and lactose are DIsaccharides.

MONOSACCHARIDES

As you learned in Lecture 3B, when a plant is making glucose, the plant puts the sun's energy in the bonds between the carbon atoms. It makes that glucose to get energy in a form it can use for its own growth and later reproduction. That glucose the plant makes is critical for us because it is pretty much the only fuel for the brain and nervous system. Muscles, on the other hand, can get a lot of energy from fat, in addition to glucose.

In its purified form (shown below) glucose looks and tastes much like table sugar.

The plant makes fructose because it is the sweetest sugar and that sweetness helps to attract insects and animals and thereby plays a role with reproduction. One of the places a plant puts that fructose is in the nectar of its flowers.

A flower's parts are shown above. Different insects (like butterflies, ladybugs and bees) visit flowers to drink that sweet nectar. Sperm-containing pollen (notice it above) gets on the insect's legs. As the insect moves around the flower, some of the pollen gets on the stigma and travels down to the ovary, where it fertilizes it and starts the process of making a new seed-containing fruit.

Above and below are two examples of fruit forming after fertilization. Above is a tomato and below is squash. It's interesting that the squash begins forming even before the flower has dried up.

To make honey, a bee takes nectar from a blossom, then bee enzymes break down the slightly more complex sugars in the nectar into the sugars glucose and fructose. The bees then spread the nectar throughout the honeycombs where water evaporates from it, making it a thicker syrup that can be stored until the bees eat it.

Another place some plants put that sweet fructose is in their fruit. The sweetness attracts an animal, like this sheep. A sheep eats the apple, digests most of the apple, but the seeds resist digestion (since they are coated in fiber). So when the sheep defecates hours later, he deposits those seeds perhaps miles away from the original apple tree. Call him "Johnnie Applesheep".

When we eat foods that contain fructose, fructose gets absorbed into the blood stream from intestinal cells, and travels to the liver. The liver rearranges fructose to make glucose.

Galactose isn't in food alone. It is usually joined with glucose to make the disaccharide lactose and put into an animal's milk. Plants don't need to make galactose because they don't make milk to nurse their young.

Our body (more specifically the liver) takes the galactose it gets from drinking and digesting milk and rearranges it to make glucose, just as it does wish fructose.

Our digestive system doesn't do anything to the monosaccharides that are in food because they are already small enough to be absorbed. They are absorbed into the villi as is. In other words the monosaccharides do not need to be enzymatically digested in order to get absorbed into the villi or the cells lining the small intestine.

HIGH FRUCTOSE CORN SYRUP (HFCS):

I often get the question as to what sugar is best: high fructose corn syrup, honey, agave syrup, or sugar. As far as the body is concerned, sugar is sugar. They all are considered concentrated sweets. They all contain Calories with very few/no other nutrients.

Here is what an article, "Sugar is Back on Food Labels, This Time As A selling Point" has to say about the topic.

"Blamed for hyperactivity in children and studied as an addictive substance, sugar has had its share of image problems. But the widespread criticism of high-fructose corn syrup — the first lady, Michelle Obama, has said she will not give her children products made with it — has made sugar look good by comparison.

Most scientists do not share the perception. Though research is still under way, many nutrition and obesity experts say sugar and high-fructose corn syrup are equally bad in excess. But, as is often the case with competing food claims, the battle is as much about marketing as it is about science."

You can watch the following video for more information about HFCS and sugar, "Explained: The actual difference between sugar and high-fructose corn syrup".

Honey may have some nutritional properties, minerals, antioxidants, phytochemicals, and I have read about the possibility of honey acting as a prebiotic. However, we have many other nutrient dense choices to get phytochemicals, minerals, and prebiotics. Honey, should still be considered an empty Calorie food, and should be used in moderation. I think honey is a great choice as a sweetener because it taste good, and you can purchase it locally. But keep in mind it is a sweetener, not a nutrient dense food.

Sometimes the foods you find added sugars in are not nutrient dense. For example, high fructose corn syrup is the main sugar used to sweeten soft drinks, and research shows a clear link between soft drink consumption and body weight.

But sometimes foods that contain added sugars are nutrient dense. Like canned fruit packaged with high fructose corn syrup. And sometimes you can have "junk" food sweetened with organic cane sugar or rice syrup. In general, focus on naturally occurring sugars (fruits, veggies, dairy) and use added sugars to make nutritious foods more appealing (for example adding honey to plain yogurt).

Now let's review. According to the above information on sugars and food sources, does milk contain the monosaccharide galactose, not bound to other sugars?

Click here if your answer is "Yes".

Click here if your answer is "No".

Before we continue with Disaccharides, look at the table below:

Chemical Structure of GLUCOSE	Chemical Structure of GALACTOSE	Chemical Structure of FRUCTOSE

Glucose has: 6 carbon atoms 12 hydrogen atoms 6 oxygen atoms So the chemical formula of GLUCOSE is C₆H₁₂O₆	What would be the chemical formula of GALACTOSE? ____________________	What would be the chemical formula of FRUCTOSE? ____________________

B. SIMPLE CARBOHYDRATES: DISACCHARIDES

Disaccharides are double sugars which include maltose, sucrose and lactose. Maltose does not occur naturally in any appreciable extent in foods. Maltose is the sugar that is fermented during the production of beer and alcohol products. However, alcoholic beverages have very little maltose left after the fermentation process is complete.

The one food some people enjoy that has maltose is a type of bread, like the one pictured a little later in the lecture, that is made ENTIRELY from sprouted wheat. It looks much like other breads, but it is heavier and sweeter. More about sprouted wheat bread just a little later.

When we eat foods with maltose our digestive system needs to enzymatically digest maltose before anything can get absorbed, since our digestive system only absorbs monosaccharides. With enzymatic digestion of maltose, it is broken down into its building blocks, glucose, which can then be absorbed.

Sucrose is made by plants for the same reason fructose is made- to attract animals to eat it and thereby spread the seeds.

Sucrose is found naturally occurring in fruits and vegetables, but this sucrose can also be concentrated out to make refined table sugar. The sucrose in table sugar, and the sucrose in fruits and veggies is chemically identical, but fresh fruits and vegetables are the better choice to obtain sucrose since they come packaged with other nutrients.

When we eat foods with sucrose our digestive system needs to enzymatically digest sucrose before anything can get absorbed, since our digestive system only absorbs monosaccharides. With enzymatic digestion of sucrose, it is broken down into its building blocks, glucose and fructose, which can then be absorbed. Remember once fructose is absorbed it travels to the liver and is rearranged into glucose.

Lactose is found in dairy products like milk, yogurt, and cheese. These are the only animal foods that have significant amounts of carbohydrate. Most of our carbohydrates come from plant foods.

When we eat foods with lactose our digestive system needs to enzymatically digest lactose before anything can get absorbed, since our digestive system only absorbs monosaccharides. With enzymatic digestion of lactose, it is broken down into its building blocks, glucose and galactose, which can then be absorbed. Remember once galactose is absorbed it travels to the liver and is rearranged into glucose.

It is good for us to eat foods with sugar because they give us glucose for our brain and nervous system. Definitely the most nutritious foods for us to eat to get sugar are WHOLE fruits and vegetables and dairy because this sugar will come packaged with vitamins, minerals and phytochemicals.

You can use the table below to answer the part of the LECTURE OUTLINE referring to drawing what the disaccharides would look like and to answer the question about what all disaccharides have in common (what I mean by that is what does the structure of all disaccharides have in common).

Maltose (glucose-glucose) gets broken down into the monosaccharide glucose with the help of the enzyme, maltase.

Lactose (glucose-galactose) gets broken down into the monosaccharides glucose and galactose with the help of the enzyme, lactase.

Sucrose (glucose-fructose) bets broken down into the monosaccharides glucose and fructose with the help of the enzyme, sucrase.

Lets review where we find the different simple sugars in foods by looking at some different food labels.

Below is a sprouted wheat bread. The only ingredients are sprouted organic wheat kernels, and water. Can you recall what sugar is found in sprouted wheat?

If you guessed maltose you are correct. Remember a wheat kernel is a seed, and plants store starch in seeds for energy to sprout. When this wheat kernel begins to sprout the starch is broken down, and maltose is created.

Next we have a Toasted Oats Cereal. This cereal has 1gram of sugar per cup. What type of sugar is this? Well to determine this you need to look at the ingredient list. Look for added sugars, or ingredients that might have naturally containing sugars. What do you see?

The only sugar I see listed is actual sugar. This means the 1g of sugar in this product is sucrose.

Below is a label for milk. Notice that there are 11grams of sugar. There is no sugar listed in the ingredient list, so this is not added sugar, but naturally occurring sugar. What type of sugar is in the milk?

Lactose would be the naturally occurring sugar in this milk, 11grams per cup.

Okay last example. Lets think of the type of sugar that naturally occurs in fruits and vegetables. We will use a pear for this illustration. The label below shows that this pear has 21 grams of sugar (and 5 grams of fiber, wow!) and the only ingredient is Organic Pears. What type of sugar(s) are in this pear (and all whole fruits and veggies)?

Hopefully you came up with 3 sugars- fructose, glucose and sucrose.

C. COMPLEX CARBOHYDRATES: Polysaccharides

Which of the following are Polysaccharides?

Click here if your answer is only Starch.
Click here if your answer is only Glycogen.
Click here if your answer is only Fibers.
Click here if your answer is all 3.

The Video link below will help you fill in the part about Starch in your Chapter 4-2 Lecture Outline.

Polysacchrides- Starch (about 4 min.)

Here is link to the above video: https://video.lanecc.edu/media/Complex+Carbohydrates-Polysaccharides/0_cqu540kj/28810702

The above video mentions starch digestion. Here is an animation that was posted in last week's lectures about enzymatic digestion of starch in case you want a refresher.

http://www.wiley.com/college/grosvenor/0470197587/animations/dig3a/

The following experiment was done by Beth Naylor which demonstrates how beans (seeds) have all the nutrition they need packaged within them to sprout. All they need is water.

I was interested in seeing if there was a difference in the length of time depending on how big the bean was. I used two beans I order from an organization called Native Seeds/SEARCH. The small one is called Bolita Beans. The label says "Delicious roundish beans in shades of beige and tan, grown for centuries by the traditional Hispanic communities of northern New Mexico. Make wonderful refried beans." The bigger ones are Red Scarlet Runner Beans.	I poked a little hole in the top of a plastic film canister lid, put a cotton swab in each one, added some water so the swab was totally wet, put a bean in each one, put the lid on and put them in a sunny window.

ALL of this growth is due to the starch, protein, other nutrients and phytochemicals in the bean, along with the little bit of water I added. Notice a few leaves are also forming, but especially the bolita bean is showing signs of exhaustion. Its stem is weakening and beginning to decompose. It wants soil to help provide the other nutrients it needs in order to keep growing.	Potatoes are another starchy food but they can reproduce in another way. They have a number of "eyes" and as a potato ages, something in that "eye" begins to break that starch down to glucose. The glucose provides the energy to begin forming a sprout. (I won't tell you whose pantry had these potatoes.)

Click here for the second page of Lecture 4A.