Protein Foods And Calculating Needs

LAB 3 PLANT BASED PROTEINS AND DIET QUALITY

LAB 5

Plant Based Diets and Calculating Protein Needs

 

What are Proteins?

Proteins are complex molecules that exhibit a four-stage structural hierarchy and three-dimensional folding. This complexity gives each molecule its unique shape and function. In the primary structure, different amino acids in each amino acid chain of a protein molecule interact laying the foundation for molecular folding and a unique three-dimensional shape. In the secondary structure hydrogen bonding between neighboring amine groups and carboxyl groups of a protein molecule creates folding. The tertiary structure is a stable secondary structure of an amino acid chain, or polypeptide, with its folds and conformations. A quaternary structure occurs in when there are multiple polypeptide chains that interact in a macromolecule. This all adds up to biologically active molecules that are structural (muscle, connective tissue, hair), catalysts of chemical reactions (enzymes), and regulator agents (hormones), blood components, cellular messengers, and antibodies.

 

Protein Composition

An amino acid is a carbon with four bonds: to an amino group, a carboxyl group, a hydrogen atom and a side chain [R])

A protein is one or more linked peptide molecule containing amino acids

A protein typically contains 100-600 linked amino acids (there are 51 amino acids in insulin)

 

Nomenclature

Dipeptide 2 linked amino acids

Oligopeptide 3-8 linked amino acids

Polypeptide 9 or more linked amino acids

 

Structure

Primary Order of the amino acids in the chain

Secondary Two-dimensional structure due to hydrogen bonding

Tertiary Three dimensional folding of a protein due to interaction of amino acids

Quaternary Association of polypeptides into a functioning protein

 

Denaturation

Loss of secondary, tertiary and/or quaternary structure

Loss of function rendering the molecule biologically inactive

Destruction of hydrogen bonds caused by temperature, pH, mechanical agitation, salts

 

Essential amino acids There are nine amino acids that humans are unable to manufacture or cannot do so in sufficient quantities to support protein synthesis. The nine essential or non-dispensable amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. There are four non-essential or dispensable amino acids that the human body can produce using carbohydrate and nitrogen if food does not provide them. The non-essential amino acids are alanine, asparagine, aspartic acid, and glutamic acid. There are seven conditionally essential amino acids that only are essential at specific stages of life, such as infancy, or when there is stress, illness, or injury. The conditionally essential amino acids are arginine, cysteine, glutamine, glycine, proline, serine, and tyrosine. Under normal circumstances body is able to manufacture non-essential amino acids from other available amino acids. As long as there is adequate protein in the diet acquiring non-essential amino acids is not an issue.

 

Table 1 Amino Acids Found in the Human Body

Essential (9)	Non-Essential (4)	Conditionally Essential (7)
Histidine	Alanine	Arginine
Isoleucine	Asparagine	Cysteine
Leucine	Aspartic acid	Glutamine
Lysine	Glutamic acid	Glycine
Methionine		Proline
Phenylalanine		Serine
Threonine		Tyrosine
Tryptophan
Valine
Source: MedlinePlus: A Service of the US Library of Medicine http://www.nlm.nih.gov/medlineplus/ency/article/002222.htm

 

Why Is Amino Acid Classification in Table 1 Different from that in the Textbook?

Table 1 replicates the amino acid classification of the National Institute of Medicine/National Institute of Health and is more sensitive to health states that affect the body’s ability to synthesize or manufacture, conditionally essential amino acids. The textbook simplifies the organization by providing only two groups: essential/non-essential. The authors classify cysteine, glutamine, glycine, proline, serine, and tyrosine as non-essential and arginine as essential. Arginine is recognized as essential during infancy and thought to benefit wound healing, thus its classification by the National Institute of Medicine as conditionally essential.

 

What Should You Conclude about the Discrepancy?

First and foremost you should realize that nutrition is a complex subject! Secondly, recognize that although most sources agree that protein in the human body is comprised of 20 amino acids, not all agree on how to classify those amino acids. Why is this relevant? Scientific knowledge continues to evolve as experiments are replicated and observations are refined to more clearly describe natural phenomenon. Protein supplements are a hotly advertised and prescribed group of substances. Understanding that our knowledge of protein function is incomplete gives you pause to decode market messages and make informed decisions. Track the science on conditionally essential amino acids and investigate their place in health messages and product sales.

 

 

Complete and Incomplete Proteins Not all protein foods are created equal and some provide more essential amino acids than others. Milk and eggs are sometimes called the protein gold standard in that their amino acid profile closely matches that needed for building body tissues. Most meat-food from seafood and animal sources provide complete proteins. Complete proteins contain all the essential amino acids in quantities that allow protein synthesis, or building, to take place. Soybean is the only plant food recognized as providing a complete protein. All other plant sources must be consumed in combinations that complement each other so that those that are low in a given amino acid, such as lysine, are combined with others that are high in that limited amino acid. Consuming complementary protein foods over the period of a day adequately supports protein synthesis.

 

Vegetarianism A vegetarian is someone living on a diet of grains, pulses, nuts, seeds, vegetables, and fruits with or without the use of dairy products and eggs. A vegetarian does not eat any meat, poultry, game, fish, shellfish or crustacean, or slaughter by products such as gelatin or animal fats. A vegetarian must obtain protein from plant foods, specifically, grains, legumes, nuts, seeds, and vegetables.

 

Rule of Thumb Generally speaking grains complement legumes as well as nuts and seeds. In a vegetarian diet, to have an adequate daily protein intake it’s advisable to include all types (grains, seeds, legumes and vegetables) of plant foods each day.

 

Grains Cereal grains include wheat, rice, corn, oats, barley, rye, millet, sorghum, buckwheat, and quinoa. In terms of worldwide utilization rates, wheat, rice and corn comprise over 85% of grains consumed by humans. Grains tend to be lacking in lysine while legumes are low in methionine. Combining grains and legumes provides a more complete protein than either does alone.

 

Legumes An important source of plant protein is found in the legume family. The term legume refers to either the plant itself or its edible portion such as the fruit or pod. The French word légume translates as vegetable, and most people place familiar legumes, such as pinto beans and black-eyed peas, in the vegetable food group. Legumes are chameleons though and when called upon can substitute for meats as their considerable protein content allows them to join the meats as meat-alternates. Legumes include beans, lentils, peas, peanuts, and soybeans that are sources of both foods and oils.

 

A legume is a simple dry fruit that opens along a seam on two sides. A common name for this type of fruit is a pod, although this term is sometimes applied to other fruits such as a pepper pod. Well-known plants that are legumes include clover, peas, beans, and peanuts. Peanuts are not nuts in the botanical sense. A peanut is a legume that does not spontaneously split open along a seam. Legume seed and foliage has comparatively higher protein content than non-legume plant foods. Due to an ability to fix atmospheric nitrogen legumes contain significant amounts that are important to protein synthesis.

 

Sources of Arginine a Conditionally Essential Amino Acid

Walnuts, filberts (hazelnuts), pecans, Brazil nuts, sesame and sunflower seeds, brown rice, raisins, coconut, gelatin, buckwheat, almonds, barley, cashews, cereals, chicken, chocolate, corn, dairy products, meats, oats, and peanuts are sources of arginine a conditionally essential amino acid.

 

 

Vegetarian Food Guide Pyramid

Source: National Center for Nutrition and Dietetics The American Dietetic Association; Based on the USDA Food Guide Pyramid

 

 

Investigating Protein Foods

 

Consider all the foods that you eat. Which ones are good sources of complete proteins? Which ones are poor sources? What criterion did you use to classify each as a good, fair or poor source? Did you assume that any food from the meat group is a good source while any from the grain group is a poor source?

 

Review the vegetarian food guide pyramid. Note that there is a box or group for dry beans (legumes), nuts, seeds, eggs and meat substitutes. This diverse group is a major source of protein in a vegetarian diet however, with the exception of soybean, the protein of each item is incomplete. Milk and dairy foods provide high quality protein yet in some vegetarian diets these animal sourced foods are not consumed. Some vegetables provide substantial amounts of incomplete proteins while most fruits have negligible amounts of protein. Surprisingly, a medium baked potato has 3 grams of protein, however, the quality is poor due to meager amounts of essential amino acids such as methionine and tryptophan. Grains such as rice, wheat, and corn provide incomplete proteins that must be complemented by the dry bean, nut, seed and egg or the dairy group. This complementation, or combining of incomplete protein sources to make a complete protein improves protein quality making it possible to meet daily needs for protein synthesis and body maintenance.

 

Calculating the Cost of a Gram of Protein

Complete Table 4 by determining the cost per gram of protein for some common foods. Why calculate cost per gram rather than per serving? A per gram value allows you to consistently compare data across all sources. Once you have the cost per gram you can rate the foods from highest to lowest cost and compare whole foods to protein supplements.

 

Table 2 Computing the Cost of Dietary Protein
Source	Serving size (g)	Protein (g)/serving	Cost/serving	Cost/gram protein
Milk (cow)	1 cup	8 g	$0.22	$0.03
Pinto beans	½ cup	10 g	$0.20	$0.02
Cod fillet	3 ounces	19 g	$3.00	$0.16
Soymilk	1 cup	8 g	$0.26	$0.03
Egg	1 large	6 g	$0.25	$0.04
Peanut butter	2 Tbsp.	8 g	$0.12	$0.02

 

 

Calculating cost per gram of protein in 1 cup of milk

1. Determine the price of one cup. To determine the cost of 1 cup of milk divide the cost of a gallon by 16 (there are 16 cups in a gallon).

If milk costs $1.85/gallon than the cost of 1 cup = $1.85/16 cups or $0.116 rounded to $0.12 per cup.

 

2. Determine the cost of a gram of protein. One cup of milk contains approximately 8 grams of protein. Divide the cost of one cup of milk by 8 to calculate the cost per gram

One cup costs $0.22 so 1 gram costs $0.22/8 grams or $0.0275 rounded to $0.03/gram of protein.

 

Calculating Protein Needs Based on Physical Measures

The online protein calculator linked below bases estimates protein needs on height, age, gender, body frame, and activity level. Why do you think that it does not include weight? What is the effect of age or gender on protein needs? How does activity level change needs?

 

University of Maryland Medical System Protein Calculator

http://www.healthcalculators.org/calculators/protein.asp

 

World Health Organization Recommendations

The World Health Organization recommends 0.75 (0.8) grams of protein per kilogram of body weight for non-obese adults of both genders when the biological value of the protein is similar to that of milk or egg. http://www.fao.org/docrep/003/aa040e/AA040E09.htm#ch8.

 

Table 3 Calculate Protein Needs Based on Weight

To calculate protein needs convert weight in pounds to kilograms and multiplying result by 0.8 grams.

Subject	Weight (Lb.)	÷ 2.2 lb./kg	X (factor) g/kg	Protein (g)
30 year- old man	185	84 kg	0.8	67 g
10 year-old boy	80	36 kg	0.8	29 g
50 year-old woman	145	66 kg	0.8	53 g
16 year-old girl	110	50 kg	0.8	40 g
You			0.8

 

 

Table 4 Calculate protein needs based on percent of daily calories

Calories in Diet	(20% of Calories)	Protein Calories	Calories/gram	Protein (g)
1500	X .20	300 calories	÷ 4	75 g
2000	X .20	400 calories	÷ 4	100 g
2500	X .20	500 calories	÷ 4	125 g
3000	X .20	600 calories	÷ 4	150 g

 

 

 

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