FEB 7

7. FEB 7

Assigned Work

• Nix, Stacy. Chapter 4: "Proteins" Williams' Basic Nutrition and Diet Therapy (pp. 47-63).
• Shepard, Gordon, C7 "Images of Smell: An "Aha" Moment" (66-76; 10)
• Fill out Proteins Worksheet (Points)

In-class

• Energy density v. Nutrient density.

Nix, "Proteins"

• Nature of

• 20 amino acids, 9 essential; proteins are polypeptides -- chains of amino acids 100s of links long. Proteins exist in specific forms in foods (ex. casein is milk protein) and are broken down by us into amino acids and resembled as protein in metabolism.
• Classes of amino acids: indispensable (9), dispensable (5), and conditionally indispensable (6).
• Conditionally dispensable: Example: If low on Mthionine(essential), then you need cysteine (cond. indis.) from diet.
• About 16% nitrogen; protein is a primary source of nitrogen in diet.
• Catabolism and Anabolism: Metabolic process of breaking down tissue and building it up.
• Nitrogen Balance is shown when excretion of urinary nitrogen occurs as by product of protein metabolism (ratio of 1 g of urinary nitrogen to 6.25 g of protein). Negative nitrogen balance can be a symptom of protein deficiency. Kwashiorkor.
• Tissue proteins, plasma proteins, and dietary protein. You dietary protein is contributing to a much larger and complex protein manufacture and delivery service.

• Functions of Protein Metabolism

• Tissue growth/repair: largest component of tissue by dry weight. 75% of dry body weight.
• Water and pH balance; plasma proteins can exert osmotic pressure to help circulation of tissue fluids (I think this is the "interstitium", but I'm not completely sure).[1]
• Proteins can take up acids to contribute to blood Ph management.
• Metabolism, transport, immune system, energy system. Wide range of functions here. We have already met "lipproteins" that help carry fats around. Here you learn that enzymes, transport agents, and hormones also have protein structures.
• Proteins also help make white blood cells, so support your immune system.

• Food Sources

• Complete proteins mostly from animal sources, including dairy, cheese.
• Soy is the only complete plant protein.
• Completing proteins, or, more current “protein scores”: p. 52. also compare links ceci beans [[2]], lentils [3], peanut butter [[4]]. Sirloin steak [5]. Note how you can use the site to find complementary foods for foods with relatively low amino acid scores.
• Advice on vegetarian diets - Mix grains and legumes, eat soy based foods like tofu if possible. Note reference to the Academy of Nutrition and Dietetics document (in your links collection)
• Old Advice for plant proteins: Balance for "complete proteins". New Advice: Choose a variety of plant proteins over days. Consider "protein score", which is typically a combination of a PDCAAS (Protein digestivility Correted Amino Acid Score) [6] and an Amino acid score [7]
• Note health benefits of vegetarian diet on p. 54.

• Digestion of Proteins

• Occurs in stomach and small intestines - unlike Carbs and Fats, which are not digested in stomach.
• Proteing enzymes have to be stored in inactive form (proenzymes or “precursors”) or they would break down body tisssue!

• Overconsumption of protein by Americans, p. 59 Men at 181% of DRI, Women at 152%.

• Recommendations

• 10-35% of calories from diet
• .8g / Kg of body weight.
• To meet essential amino acids, choose a variety of protein sources over days, not within a single meal. Do a ("personal protein tally" on your typical diet.)
• If necessary, check your "protein diet" with a blood test once in a while. [Prealbumin test [8]

• Reasons not to consume excess amounts of proteins:

• Often associated with high fat dietary sources
• Crowds out other food sources
• Kidneys work harder to get rid of nitrogen.
• Further reading: Risks of too much protein

• Debates about protein quality and quantity for athletes. [9]

Gordon Shepherd, Neurogastronomy C7 "Images of Smell"

C7: Images of Smell

• The Olfactory Bulb: molecular and neural pathways at the bulb. Glomerulus (glom) - convergence site of receptor cells. Interneurons: often specialized processors. Periglomeral cells, Mitral cells, tufted cells. Granule cells.

• How does olfactory bulb represent smell? Story of discovery: 1930s Edgar Adrian, hedgehogs, noticed how patterns of excitation could create an “image” of the smell, using electrophysiology techniques.
• Sokoloff method for tracking energy used by the brain with a marker for glucose uptake. Important work that led to PET and fMRI. Follows his own research from 70s in using this method to track energy use in the olfactory bulb as it is exposed to odors.
• Confirms idea of a “smell image” or pattern of activation in the glomeruli. Started to fill in a “map” of the receptor sites on the bulb. 1990s.
• Some “odor images” from the work of Michael Leon and Brett Johnson. [10]
• Final point: The olfactory pathways are heavily modulated - sensitive to behavioral state: appetite, aversion, openness to experience, all affect flavor perception.

Personal Protein Tally

• We've used a "profile" metaphor to talk about carbs and fats (profiles of complexity in carbs and fat saturation for fats), but with proteins, it makes sense to "tally" or add up your intake, while watching for protein quality.

• Calculate your protein goal in grams. 150 lbs. = 68kg x .8 = 54grams RDI /day
• Go through your diet and look at the amounts of good protein in your day. How hard is it to meet your goal?

Food	Protein Value
Breakfast
Egg/toast/butter	11
Midmorning
Muffin	6
Lunch
Ceci/fruit/yogurt	14
Appetizers - cheese/crackers	11
Dinner Options
Lentils & Rice	12
Lentil Soup	15
Black Beans & Rice	23
Tuscan Bean Soup	10
Pasta (125g)	18
Tuna	19
Salmon (8oz)	45
Tofu (1/2 cup)	10