Protein power?
Imagine you are a registered dietitian and sports nutritionist for a university-
Jake’s 24-
BREAKFAST
2 slices whole grain bread
2 tablespoons peanut butter
1 orange
1 cup chocolate milk
LUNCH
Grilled chicken sandwich (3-
Sandwich bun
1 tablespoon mayonnaise
2 slices tomato, lettuce
1 cup French fries
12 ounces soda
SNACK
2 ounces pretzels
1 apple
1 ounce cheese stick
DINNER
2 cups pasta
1 cup marinara sauce
3 one-
2 cups tossed vegetable salad
2 tablespoons Ranch dressing
TOTAL: 3,226 calories, 158 grams protein
Consider
What is Jake’s RDA for protein? (Hint: To determine weight in kilograms, divide weight in pounds by 2.2.)
What is the AMDR for protein? Explain how the RDA for protein fits within the acceptable range for protein intake.
Do you feel the RDA meets Jake’s protein needs? From what you’ve learned in this chapter, discuss the rationale behind your answer.
Visit www.supertracker.usda.gov and set up a profile for Jake using his age, sex, height, weight, and activity level. Don’t register—
Click on “View your plan” under Welcome, Jake.
How many calories does Jake need each day?
Given his calorie requirements, what is the protein AMDR for Jake expressed in calories from protein and grams of protein? (Note: This will be a range, not an absolute number.)
After analyzing Jake’s intake using Supertracker, you determine that Jake’s typical intake is 3,226 calories with 158 grams of protein. Does this fall within his AMDR? (To calculate percent of calories from protein, multiply grams of protein by 4 and divide by total calories.)
Jake tells you that several of his teammates add protein powders to beverages to supplement their protein intake. He asks if he also needs to purchase protein supplements to make sure he is getting sufficient protein. What do you tell Jake?
If Jake’s intake remains the same, thus meeting his calorie needs, but he chooses to add 25 additional grams of protein through a protein supplement beverage, explain what will likely happen to the additional protein in his body.
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Protein has many critical roles in the body’s structure and processes, including catalyzing chemical reactions (enzymes), regulating body functions (hormones), and transporting substances in the blood. It also has central roles in immunity, fluid balance, and blood clotting.
Proteins are composed of carbon, hydrogen, and oxygen, but also contain nitrogen, which is supplied through amino acids, the building blocks of protein.
Protein needs are determined by sex, life stage, and other factors. The RDA for adults is 0.8 g/kg/d. The AMDR for protein is 10% to 35% of total calories.
Proteins are complex structures synthesized by linking up to 20 amino acids into chains of varying sequence and length. Nine of these amino acids are considered essential because they must be supplied through the diet. The remaining 11 nonessential amino acids can be manufactured by the body.
Sequences of DNA called genes provide the instructions for the synthesis of every protein in the body. This is a two-
The overall shape of a protein molecule determines its function, and how it interacts with other molecules.
The process of denaturation alters the shape and function of proteins.
The digestion of protein begins in the stomach, where proteins are denatured and fragmented, continues in the lumen of the small intestine, and is completed within the mucosal cells of the small intestine.
Proteins in the body are constantly being broken down into amino acids and reassembled in a process called protein turnover.
Nitrogen balance is a reflection of protein intake versus protein breakdown and is influenced by diet, hormones and growth factors, and muscle contractions.
Depending on the proportion of each of the essential amino acids present (protein quality), foods can be classified as complete or incomplete proteins.
Inadequate protein intake can have health and metabolic consequences.
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Review Questions
1. Like carbohydrates and fat, protein is composed of carbon, hydrogen, and oxygen. Protein differs in that it also contains:
calcium.
chloride.
nitrogen.
phosphorus.
sodium.
1. c
2. Functions of protein do NOT include:
serving as an energy source.
serving as a structural component of hair and fingernails.
serving as a store of excess amino acids.
serving as hormones.
catalyzing chemical reactions in the body.
2. c
3. There are 20 amino acids present in proteins; of these ______ are considered essential and are ______ considered nonessential amino acids.
7; 13
13; 7
15; 5
9; 11
11; 9
3. d
4. Nonessential amino acids:
are incomplete proteins.
are extra essential amino acids.
can be manufactured in the body.
enhance muscle development.
are found only in plant foods.
4. c
5. The Institute of Medicine has established that a safe range of protein intake is:
10% to 25% of total calories.
10% to 35% of total calories.
15% to 30% of total calories.
15% to 35% of total calories.
20% to 40% of total calories.
5. b
6. The second step of protein synthesis in which the order of amino acids added to the growing protein chain is read from (or dictated by) the information in the mRNA is termed:
phosphorylation.
gluconeogenesis.
transcription.
translation.
deamination.
6. d
7. The shape of a protein is a determinant of its _______ in the body.
storage form
energy potential
function
heat production
permanence
7. c
8. Protein denaturation refers to:
the lack of one or more essential amino acids in a food.
the process of adding an amino acid to a food that is not naturally present.
a change in shape of protein structure due to heat, light, motion, or change in pH.
breakdown of muscle mass during caloric restriction.
the conversion of protein to glucose or fatty acids.
8. c
9. Nick lifts weights and takes a daily protein supplement in addition to his 30% protein weight-
is an effective practice to add muscle weight without exercise.
is not necessary because his intake is already in excess of the RDA.
provides additional calories that can contribute to fat stores.
will increase his athletic performance.
Both b and c are true.
9. e
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10. Each of the following food choices is a source of complete proteins, EXCEPT:
beef.
black beans.
eggs.
quinoa.
yogurt.
10. b
11. Marasmus:
is characterized by deficiency in most nutrients, including protein.
is characterized by sufficient total caloric intake, but deficient intake in protein.
is associated with a swollen belly appearance.
only occurs in children.
may occur when consuming excess calories from carbohydrates.
11. a
Take It Further
Discuss the possible implications of consuming protein at levels near or above the upper end of the AMDR range. Include a discussion of how the dietary sources of protein might affect potential risk.
Protein: Intake and Implications
Using Supertracker, track your intake of dietary protein and compare it to the current dietary recommendations.
1. Log onto the United States Department of Agriculture (USDA) website at www.supertracker.usda.gov. If you have not done so already, you will need to create a profile to get a personalized diet plan. This profile will allow you to save your information and diet intake for future reference. Do not use the general plan.
2. Click the Track Food and Activity option. We will just focus on tracking food for this activity.
3. Record your food and beverage intake for one day that most reflects your typical eating patterns. Enter each food and beverage you consumed into the food tracker. Note that there may not always be an exact match to the food or beverage that you consumed, so select the best match available.
4. Once you have entered all of your food and beverage choices into the food tracker, on the right side of the page under the bar graph, you will see Related Links: View by Meal and Nutrient Intake Report. Print these reports and use them to answer the following questions:
Did your dietary intake of protein meet your target amount? If not, were you over the target or under the target?
If the target was not met, list two dietary changes you could make to meet the target amount.
Did you meet your target for the percent of total calories for protein? If not, were you over the target or under the target?
Next, look at your dietary sources of protein. Did the majority of them come from plant sources or animal sources?
Identify two potential health concerns associated with a diet high in animal protein.