FEB 2

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6. FEB 2

Assigned Work

  • Nix, Stacy. Chapter 3: Fats Williams' Basic Nutrition and Diet Therapy (pp. 31-46)
  • Fill out Fats Worksheet Due Tonight by midnight

In-class

  • Giving Peer Criticism
  • Norming Rubric Scores
  • The Lancet, Carcinogenicity of consumption of red and processed meats
  • American Academy of Nutrition and Dietetics, "Vegetarian Diets"

Nix, Chapter 3, "Fats"

  • Nature of lipids:
  • C, H, O -- note that Carbs are different arrangements of these.
  • fatty acids are chains of C-H bonds with a methyl group on one end (so-called the "omega") and an acid on the other (which bonds to a glycerol)
  • Saturated (so called because no spaces in the C-H string), mono-unsaturated (space at the 9th H), polyunsaturated (spaces after 6) (linoleic acid) and, if after 3, Omega-3 or (alpha-linolenic acid)
  • Visible fats: saturated fats are dense, form solids at room temp.
  • Trans-fatty acid: natural unsaturated fats are “cis” - Carbon on the same side. Hydrogenation of fats in industrial foods are sometimes “trans” to produce more shelf-stable fat. Heath concerns of trans-fats.
  • Functions of Fats
  • Essential fatty acids: linoleic acid (omega 6) and alpha-linolenic acid (omega-3). We can produced saturated fats and cholesterol, but we cannot produce these two fatty acids.
  • 34: diet of less than 10% calories from fat not consistent with health.
  • Lipoproteins: the body's way of moving fat through the blood stream. Wrapped in protein these bundles of fat can be relatively high density (lots of protein) or low density. High density lipoproteins are important because the help with the process for removing carry cholesterol out of the body.
  • Some interesting detailed functions in phospholipids such as lecithin (for cell membranes), and eicosanoids (signaling hormones that relate inflammatory and immune response, and cholesterol, which we need for cell membrane health. Phospholipids also transport fats. (Lesson: Food is not just fuel. It plays many metabolic roles.)
  • Fats essential for tissue strength, cholesterol metabolism, muscle tone, blood clotting, and heart action. As with carbs, you can think of fats as energy sources, but don't forget other metabolic functions.
  • Storage of energy.
  • Source of fat soluble vitamins.
  • Saiety! Don’t underestimate the importance of fats in producing satisfaction. Digression here on “trade ups” in fats. Animal to plant. Plant fats with better profiles of O6/O3.
  • Food Sources
  • Fat from meat is compatible with a healthy diet, but better when taken with fiber and balanced with high ratio of polyunsaturated fats. Trade up to lean meats, without skin.
  • Fish have mostly unsaturated fat [1] compared to red meat [2] or chicken [3] or a Starbuck's caramel brownie [4]! Think about your saturated fat budget goal.
  • Visible and invisible fats - similar point as the Dutch study in Moss.
  • Note pull out box on fat metabolism by ethnicity -- still very open research areas as far as mechanisms. Interesting to look into further. Hypotheses....
  • Digestion
  • In the mouth: Ebner's glands secrete lingual lipase, mostly designed for non-chewing infants.
  • Enzymes in small intestine (from pancreas), bile from gallblader, bile emulsifies fat, increasing surface area for enzymes to act. Pancreatic enzymes also enter the small intestine.
  • Frying foods at high temperatures makes digestion harder and compounds can break down into carcinogens. (Recall Lancet article.)
  • Recommendations
  • US overconsumption of sat. fats. should have less than 7% of calories from sat&trans fat combined. Some progress: US eaters went from 13 to 11%.
  • Very low fat and fat free diets are dangerous to health (p. 43). Essential fatty acid deficiency.
  • DRIs: 20-30% of calories from fat. DRI for linoleic acids at 17 g. alpha linolenic acid 1.1 g/day. Not something a person on a plant based diet needs to track. (notion of "can't miss" diet).
  • Note recommendations on p. 44.
  • Some more "Fat" Details
  • Your fat budget: 2000 calories, 20-35% from fat, 9 grams/calorie, 44-72 grams per day. Going Below 22 grams, or less than 10% incompatible with health. Recommended less than 7% from saturated fat (15 grams).
  • Tracking O6 / O3: The two essential fatty acids (ones we need and can't make).
  • Looking at foods and food products in terms of fat profiles:
  • Compare various Trader Joe's packaged and prepared foods with your fat budget. TJ's trades on its healthy image, but some of its product are very high in saturated fat.
  • Example: Trader Joe's Orange Chicken
  • Individual and Small Group moment: Take a few minutes to look up fat values for some of your favorite foods. Compare notes with each other.

Giving Peer Criticism

  • Some thoughts on helpful peer commenting:
  • You are only asked to write two or three sentences of comments, so choose wisely!
  • Giving criticism someone would want to consider.
  • Give gentle criticisms that focus on your experience as a reader:
  • "I'm having trouble understanding this sentence" vs. "This sentence makes no sense!"
  • "I think more attention could have been paid to X vs. "You totally ignored the prompt!
  • Wrap a criticism with an affirmation or positive comment
  • "You cover the prompt pretty well, but you might have said more about x (or, I found y a bit of a digression)"
  • "Some interesting discussion here, esp about x, but you didn't address the prompt very completely ...."
  • General and specific -- Ok to identify general problem with the writing, but giving examples of the problem or potential solutions.
  • I found some of your sentences hard to follow. E.g. "I think that the main ...." was a bit redundant.
  • I thought the flow was generally good, but in paragraph 2 the second and third sentence seem to go in different directions.

Norming Rubric Scores

  • We'll take a look at the Assignment Rubric scores in order to clarify their meanings. This should help you with your peer review.

The Lancet on Meat, and Am Acad of Nutrition on Vegetarian diets

  • The Lancet -- "Carcinogenicity of Consumption of Red and Processed Meat"
  • Major conclusions, evidence, authoritativeness
  • curing, frying, grilling and barbequing produce carcinogenic chemical
  • 17% increase risk of colon cancer at 100/grams of red meat and 18% for 50 grams of processed meats.
  • Note mechanistic evidence for red meat strong, for processed meat moderate.
  • What are the specific thresholds and risk factors by consumption?
  • Many hundreds of studies across many countries. less certainty about the red meat conclusion from epidemiological data, though mechanistic evidence seemed stronger for red meat. Note studies on second page. More on HAA and PHA, which are chemicals formed at high heats that we often cook meat.
  • American Academy of Nutrition and Dietetics: Position on Vegetarian Diets
  • What is the overall assessment of the Academy of the healthiness vegetarian and vegan diets?
  • bio availablity of iron lower for vegs, but not all bad. No longer higher DRI for iron due to new evidence
  • What are the major recommendations for dietary supplementation or monitoring?
  • Vit D, B12, maybe calcium, (but these are common supplements for non-vegs as well)
  • To what degree do low and no-meat diets reduce your risk of Western Dietary Diseases? 12ff: long list of health benefits. Please read through this part especially.
  • Note: effect of both the Lancet and Academy articles: most of benefits from veg diet available to low-meat diet, most of hazards of high meat diet concentrated on red & processed meat.