Lecture 4A: Carbohydrates

FN 225: Nutrition
Rathakette Ph.D.
Health Professions Division
Lane Community College
Eugene, Oregon

LECTURE 4A: Carbohydrates

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 and you can see your exam then.

I also posted your grade as of Exam 1, it will show you your total points earned plus a percentage of total points. See syllabus for details on how this percentage translates into 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.

FORUM (to be posted MONDAY of Week 4):

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 in your packet 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.

Look through the sections of this Lecture Outline.

I Types of Carbohydrates,

which include SIMPLE and COMPLEX Carbohydrates.

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

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.

HIGH FRUCTOSE CORN SYRUP:

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/Calories with very few/no other nutrients. 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 recent research shows a clear link between soft drink consumption and body weight. The below study has more information on this topic:

Effects of Soft Drink Consumption on Nutrition and Health: A Systematic Review and Meta-Analysis.

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 brown 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 foods sources, does milk have galactose?

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 include maltose, sucrose and lactose. Maltose does not occur naturally in any appreciable extent in foods. Maltose is produced in the malting and fermentation of grains and may be present in beer.

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. I need to do more research on this, but I believe sucrose is also made by plants like sugar cane and sugar beets because it is an easy source of energy for the plant's growth especially when sunlight is limited.

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 they also give us 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.

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 Clip below will help you fill in some (but not all) of the Starch part of complex carbohydrates. The Video Clip will skip the "e" part.

The Video Clip will also help answer some of your Study Questions, that asks:

"Using information in the Lecture 4A Video Clip called “Starch”, calculate how many grams of starch are in a serving of the Ak Mak crackers. _________"

Video Clip: Starch
approximately 12 minutes

The Video Clip about starch says, in response to a question, that there's no advantage to calculating the starch in a food. There can be a reason to do it and we'll discuss it in Lecture 4B.

The Video Clip doesn't answer these questions in your lecture outline:

1e. What foods are the most nutritious foods to eat to get starch. AND

The answer to this question is the WHOLE foods that are a good source of fiber and other nutrients like corn, beans, oatmeal, brown rice, barley, and whole wheat products.

The following experiment was done by Beth Naylor:

Last summer I tried something that I saw described in a mailing I got. It described a little experiment to determine how long it took to sprout beans.

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 n 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 to find out some information about what early Oregonians ate to get starch. (If you're interested, not required).

Click here for the second page of Lecture 4A.

DISACCHARIDES

Click here if you think this represents Maltose Click here is you think this represents Sucrose Click here if you think this represents Lactose	Click here if you think this represents Maltose Click here is you think this represents Sucrose Click here if you think this represents Lactose	Click here if you think this represents Maltose Click here is you think this represents Sucrose Click here if you think this represents Lactose