HW320 Unit 2 Macronutrient Analysis Example

Two Bars and a Latte: A Unit 2 Macronutrient Analysis of What Extra Protein Does in an Ordinary Day

[Student Name]

Purdue University Global

HW320: Contemporary Diet and Nutrition

Unit 2 Macronutrient Analysis

[Instructor Name]

[Date]

The subject, her meals and the products are composite; the reference intakes, the protein metabolism review and the supplementation meta-analysis cited are real.

What Protein Does

Protein is built from amino acids, nine of which the body cannot make and must get from food. It forms the structure of muscle, skin, hair and bone matrix. It makes up enzymes that run nearly every chemical reaction in the body and several hormones, including insulin. Proteins carry oxygen in the blood as hemoglobin and carry fats and some vitamins as lipoproteins and binding proteins. Antibodies are proteins. When carbohydrate and fat fall short, protein can also be broken down for energy, supplying about 4 calories per gram (Institute of Medicine, 2005).

The body does not store protein the way it stores fat. Amino acids beyond what is needed for building and repair are not saved for later use as protein; their nitrogen is removed and excreted, and the remaining carbon skeletons are used for energy or converted to glucose or fat (Wu, 2016).

How Much the Body Uses

Protein needs are set by the amount required to replace what the body breaks down each day and, in growing children or pregnant women, to build new tissue. Adults are in a constant cycle of building and breaking down body proteins, and the amino acids released are largely reused. The dietary requirement covers the portion that is lost, mainly as nitrogen in urine, plus a margin of safety. That is why the allowance is modest compared with the amounts printed on many products: the body is efficient at recycling the protein it already has.

The Subject

Jenna, a composite 35-year-old office worker, weighs 70 kilograms and walks for about thirty minutes most days. She does no resistance training. A typical day of her eating, before any additions, looks like this:

1. Breakfast: two eggs and a slice of whole-wheat toast, about 15 grams of protein.

2. Mid-morning: a cup of plain Greek yogurt, about 18 grams.

3. Lunch: a chicken wrap, about 30 grams.

4. Dinner: lentil soup with bread and a side salad, about 22 grams.

That comes to roughly 85 grams of protein, or about 1.2 grams per kilogram of body weight.

The Reference Standard

The Recommended Dietary Allowance for protein for adults is 0.8 grams per kilogram per day, which for Jenna is 56 grams (Institute of Medicine, 2005). The allowance is set to cover the needs of nearly all healthy adults. The Acceptable Macronutrient Distribution Range allows protein to supply 10 to 35 percent of energy. Jenna's usual 85 grams already exceeds her allowance by about half, and supplies roughly 17 percent of her energy, comfortably within the range.

The Additions

Jenna has started adding three products after seeing them advertised as ways to stay full and support "lean muscle":

1. A protein bar mid-morning, 20 grams of protein and 220 calories.

2. A second protein bar in the afternoon, 20 grams and 220 calories.

3. A bottled protein latte on the way home, 15 grams and 160 calories.

The additions bring her daily total to about 140 grams, or 2.0 grams per kilogram, and add about 600 calories.

What Happens to the Surplus

The central question is what her body does with roughly 55 extra grams of protein a day.

Without a training stimulus, extra protein is not built into muscle. Muscle grows in response to resistance exercise, and protein intake supports that growth only when the stimulus is present. A meta-analysis of 49 trials found that protein supplements increased gains in muscle size and strength during prolonged resistance training, and that intakes beyond about 1.6 grams per kilogram per day added no further gain even in people who were training (Morton et al., 2018). Jenna is not training and already exceeds that threshold with her additions.

The surplus amino acids are therefore broken down. Their nitrogen is converted to urea in the liver and excreted by the kidneys, which in healthy adults handle this load without difficulty (Wu, 2016). The carbon skeletons, carrying most of the energy, are oxidized for fuel or, when energy intake exceeds expenditure, contribute to fat stores. The 600 added calories matter more than the protein itself: if her intake was balanced before the additions, she is now eating more energy than she uses.

For Jenna, the extra protein does not become muscle, because nothing in her day asks her muscles to grow; it becomes fuel or fat, and the bars and latte are, in effect, 600 calories with a protein label.

Satiety

The claim that protein keeps people full has some support. Protein tends to be more satiating, calorie for calorie, than carbohydrate or fat. But satiety only reduces total intake if the protein replaces other food. Jenna added the products to her existing meals rather than substituting them, so whatever fullness they produce has not, by her own account, led her to eat less elsewhere.

Cost and Displacement

The three products cost Jenna about seven dollars a day, roughly 2,500 dollars a year. They also displace nothing; they sit on top of meals she already eats. If the bars replaced her afternoon snack of an apple, they would also remove fiber and potassium from her day. Whole foods that supply protein, such as yogurt, beans and eggs, also bring calcium, fiber, iron and potassium, and Jenna's usual meals already include several of them.

Is It Harmful?

For a healthy adult with normal kidney function, about 2 grams per kilogram per day is not known to be dangerous (Wu, 2016). People with kidney disease are a different case and should follow their clinician's advice. For Jenna, the concern is cost and energy, not toxicity: the three products cost about seven dollars a day and add calories she did not need.

What Would Change the Analysis

If Jenna began resistance training two or three times a week, a modest increase in protein toward 1.6 grams per kilogram could support muscle gain (Morton et al., 2018). Her usual diet, with one additional protein-rich food such as more yogurt or beans, would reach that figure without bars or lattes.

Conclusion

Protein performs essential functions, and Jenna's ordinary meals already supply more than she needs. The products she added raise her intake to a level that offers no benefit without training, and their main effect is to add energy. The analysis does not make protein a villain; it shows that more is not better once needs are met.

References

Institute of Medicine. (2005). Dietary reference intakes for energy, carbohydrate, fiber, fat, fatty acids, cholesterol, protein, and amino acids. National Academies Press. https://doi.org/10.17226/10490

Morton, R. W., Murphy, K. T., McKellar, S. R., Schoenfeld, B. J., Henselmans, M., Helms, E., Aragon, A. A., Devries, M. C., Banfield, L., Krieger, J. W., & Phillips, S. M. (2018). A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. British Journal of Sports Medicine, 52(6), 376-384. https://doi.org/10.1136/bjsports-2017-097608

Wu, G. (2016). Dietary protein intake and human health. Food & Function, 7(3), 1251-1265. https://doi.org/10.1039/C5FO01530H