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53 Cards in this Set
- Front
- Back
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what is the only animal-derived food with a significant amount of carbohydrates?
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milk
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the three important monosaccharides:
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-glucose (most common.. "blood sugar")
-fructose (fruit sugar, sweetest) -galactose (found in milk) *all forms of single sugars are converted to glucose in the liver |
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the three important disaccharides:
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-lactose (glucose and galactose)
-maltose (2 glucose.. breakdown of starch) -sucrose (glucose and fructose.. table sugar |
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Starch
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-polysaccharide
-plant's storage system of glucose |
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Glycogen
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-polysaccharide
-animal's storage system of glucose -resembles starch except its branches are longer and more branched -glycogen is nearly undetectable in meats because glycogen breaks down rapidly when the animal is slaughtered |
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Fiber
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the indigestible parts of plant foods, largely nonstarch polysaccharides that are not digested by human digestive enzymes, although some are digested by resident bacteria of the colon. Fibers include cellulose, hemicelluloses, pectins, gums, mucilages, and the nonpolysaccharide lignin
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Soluble Fiber
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Food components that readily dissolve in water and often impart gummy or gel-like characteristics to foods. an example is pectin from fruit, which is used to thicken jellies. soluble fibers are indigestible by human enzymes but may be broken down to absorbable products by bacteria in the digestive tract
*associated with lower risks of chronic diseases (slows glucose absorption, lowers cholesterol) |
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Insoluble Fiber
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the tough, fibrous structures of fruit, vegetables, and grains; indigestible food components that do not dissolve in water
*they aid the digestive system by easing elimination (increases fecal bulk, decreases intestinal transit time) |
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Ogliosaccharides
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-short carbohydrate chains of 3-10 monomers
-found in dried beans, peas, lentils, human milk -examples: 1. raffinose 2. stachyose ^^ neither of these can be digested by human enzymes, however can be broken down by bacteria in colon |
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alpha and beta bonds in polysaccharides
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-alpha bonds are easily broken by human enzymes
-beta bonds are indigestible by human enzymes but can be broken down by bacteria in the intestine |
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amylose vs amylopectin
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both are starches.
-amylose is a straight chain whereas amylopectin is a branched chain |
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Cellulose
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-long straight chains of glucose
-provides strength and rigidity to cell walls in plants -ex. stringy threads in celery |
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Hemicelluloses
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-diverse, vary from plant to plant
-found in the outer bran layer of cereals |
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Pectins
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-form gels
-abundant in fruit (ex. apples) |
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Gums and mucilages:
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-form gels
-abundant in psyllium seeds |
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Beta glucans
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-branched chains of glucose
-abundant in barley and oats -beneficial for lowering blood cholesterol |
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Chitin and Chitosan
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-found in exoskeletons of crabs, lobsters, fungi
-usually sold as supplements targeting weight control |
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Lignins
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not actually carbohydrates but formed from multi-ringed alcohol units
-found in flax seeds, carrots, broccoli, seeds of strawberries (they form the woody part of these vegetables) |
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Carbohydrate digestion in the mouth:
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-chewing initiates mechanical digestion
-salivary amylase begins breaking down starches |
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Carbohydrate digestion in the stomach:
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-low pH inactivates salivary amylase (carbohydrate digestion stops)
-fibers remain in the stomach longer, delaying gastric emptying |
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Carbohydrate digestion Pancreas:
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-pancreas secretes the enzyme pancreatic amylase
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carbohydrate digestion in the small intestine
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-enzymes located on the cell membranes of the intestinal epithelial cells complete digestion
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Absorption of monosaccharides in small intestine:
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-glucose: active transport
-galactose: active transport -fructose: facilitated diffusion (occurs more slowly, so fructose produces a smaller rise in blood sugar compared to glucose and galactose) |
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Portal vein:
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delivers monosaccharides from small intestine to the liver (the liver converts galactose and fructose to glucose)
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Carbohydrate digestion and absorption in the large intestine:
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-a small fraction of starches remain undigested (especially from whole legumes, raw potatoes, and unripe bananas)
-some fibers and resistant starches may be digested by bacteria -this produces short chain fatty acids (provides about 2kcal/g) -also lowers blood cholesterol |
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Main functions of carbohydrates:
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-carbs are the primary energy source for the body
-very important for nerve cells, esp. in the brain -sugars can also change the shape of a protein, thereby altering its function |
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Fiber's 4 health benefits:
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1. promotion of normal blood cholesterol concentrations (reduced risk of heart disease)
-viscous fibers binding with cholesterol-containing bile in the intestine and carrying it out with the feces. The liver responds to the loss of bile by calling on the body's cholesterol to synthesize more. Also in the bacterial fermentation of fiber, a small fatty acid is released and travels to the liver where it helps to reduce cholesterol synthesis 2. modulation of blood glucose concentrations (reduced risk of diabetes) -when viscous fiber from foods trap nutrients and delay their transit through the digestive tract, glucose absorption is slowed, and this helps prevent the roller-coaster surges in blood glucose and the hormone insulin thought to be associated with the onset of the most common form of diabetes 3. maintenance of healthy bowel function (reduced risk of bowel disease) -cellulose enlarges and softens the stool (alleviates/prevents constipation) -reduces pressure making hemorrhoids less likely to occur -prevents appendicitis -resists diverticula -protects against colon cancer 4. promotion of a healthy body weight -fibers create feelings of fullness and delay hunger because they swell as they absorb water from the digestive juices. |
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diverticula
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sacs or pouches that balloon out of the intestinal wall, caused by weakening of the muscle layers that encase the intestine. The painful inflammation of one or more of these diverticula is know as diverticulitis.
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butyrate
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a small fat fragment produced by the fermenting action of bacteria on viscous, soluble fibers; the preferred energy source for the colon cells
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DRI recommendations for fiber:
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men, 19-50: 38g/day
men, 51+: 30g/day women, 19-50: 25g/day women, 51+ 21g/day |
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Chelating agents:
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molecules that attract or bind with other molecules and are therefore useful in either preventing or promoting movement of substances from place to place.
ex. fibers may link with iron (which is usually absorbed at the beginning of the intestinal tract) and it may not be absorbed since it is expedited through the upper part of the digestive tract |
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Digestion of starch:
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-begins in mouth, salivary amylase begins to break down (also there is mechanical digestion)
-goes to stomach, acidity of gastric juices deactivates the salivary amylase. -the digestion resumes in the small intestine where the pancreas provides another starch-splitting enzyme -epithelial cells of small intestine finish splitting disaccharides so they can be absorbed into the bloodstream -glucose is ready for use, but fructose and galactose need to be transported to the liver to be converted into glucose |
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Lactose Intolerance
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-occurs as a result of insufficient lactase activity
-lactose molecules remain in the intestine, undigested -undigested lactose is digested by bacteria in the colon which produces irritating acid and gas (bloating, abdominal discomfort, and diarrhea) -often people overestimate the severity of their 'lactose intolerance' -Not to be confused with milk allergy, which is an immune response to milk protein |
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Splitting Glucose for energy:
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-glucose (6 Carbon compound) is split into 2 3-C chains and releases energy
-at this point it can either reform glucose molecule or split again -if it splits again it releases more energy and can no longer be turned back into glucose -can be split again for another release of energy -also yields CO2 and H2O as byproducts ^Krebs Cycle or the smallest units can be linked together to form units of body fat (if we have too many carbs) |
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What happens if we have a carbohydrate deficit?
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-although we can convert glucose to fat, we can't convert fat to glucose.
-if carb consumption is < 50-100g two problems arise: 1. body must use protein to make glucose, diverting protein from critical functions of its own (such as maintaining immune defenses) *PROTEIN-SPARING PRINCIPLE: the action of carbohydrate and fat in providing energy that allows protein to be used for purposes it alone can serve 2. The second problem arises because fat fragments normally combine with a compound derived from glucose before being used by the cells to supply energy. W/o the help of this compound, fat fragments combine with each other instead, producing increased amounts of the normally scarce acidic products, ketone bodies. KB can accumulate in the blood and affect the acid-base balance. Adults consuming a diet that produces ketosis may also face deficiencies in minerals and vitamins, loss of bone minerals, altered blood lipids, increased risk of kidney stones, an impaired mood and sense of well-being, and glycogen stores that are too scanty to meet a metabolic emergency or to support maximal high-intensity muscular work. |
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Ketosis
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-incompletely metabolized fats will result in the production of ketones
-accumulation of ketones is referred to as ketosis -ketones are acidic, so as they accumulate they will disrupt the acid-base balance, leading to acidosis -this will affect heart, nerve, enzyme activity, and various other body functions *you must consume >50-100g of carbs a day to prevent ketosis |
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Negative Effects of fiber:
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-can lead to dehydration
-abdominal discomfort -interference with absorption of other nutrients examples: -phytates bind to calcium, iron, and other minerals and prevent them from being absorbed -increased transit time through digestive tract reduces time for digestion and absorption *buying pure fiber compounds is neither necessary nor advisable |
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Body's response to hyperglycemia:
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-too much glucose in blood, pancreas releases insulin which:
1. stimulates glucose uptake into cells 2. stimulates glycogen synthesis 3. decreases blood glucose |
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Body's response to hypoglycemia:
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-not enough glucose in the blood, pancreas releases glucagon which:
1. mobilizes energy stores 2. stimulates glycogen breakdown and gluconeogenesis 3. increases blood glucose |
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Effects of epinephrine and cortisol on blood glucose:
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Epinephrine (adrenaline):
-produced in adrenal glands -released during stress (short term) -part of body's "fight or flight" response -helps mobilize energy from storage Cortisol: -produced in adrenal glands -released during stress (long term) -helps mobilize energy from storage |
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Type I Diabetes:
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-about 10% of all diabetes patients
-occurs from the destruction of beta cells in pancreas (cells that produce insulin) -blood glucose levels rise, unable to be taken up by cells -have to be injected with insulin (can't take orally because it is a protein and body would digest it) |
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Type II Diabetes:
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-90% of all diabetes patients
-"insulin resistance" or "insulin insensitivity" -leads to increased insulin in blood called hyperinsulinemia |
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Hypoglycemia:
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-decreased levels of blood glucose
-very rare (can occur in people with poorly managed diabetes) -symptoms are similar to an anxiety attack - |
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Postprandial hypoglycemia:
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an unusual drop in blood glucose that follows a meal and is accompanied by symptoms such as anxiety, rapid heartbeat, and sweating (also called reactive hypoglycemia)
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Fasting hypoglycemia:
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hypoglycemia that occurs 8 to 14 hours after fasting
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The glycemic index
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-a measure to the extent to which a particular food can raise the blood glucose concentration and elicit an insulin response when compared to pure glucose (100)
-The theory is that consuming foods with a low GI will minimize dramatic fluctuations in blood glucose -this reduces the need for insulin secretion and may help manage Type II diabetes -diets with a low glycemic load are associated with an increased level of HDL cholesterol (not many foods actually have their GI calculated, and even still foods can have a different GI for different people, GI can change when combined with different foods, etc... it is not the most practical measurement) |
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Glycemic Load:
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(Glycemic Index x Carbohydrates Consumed) / 100
-probably a better indicator of blood glucose than glycemic index. -useful for those with diabetes to know how much insulin they need |
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Does sugar cause diabetes?
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MYTH
-Premise: Since sugar stimulates insulin secretion it exhausts our ability to produce insulin causing Diabetes -Facts:Although studies have shown a correlation between an increased risk of developing diabetes and excess dietary sugar intake IF caloric intake is in excess of needs: 1.Other risk factors are more strongly associated (e.g. obesity, physical inactivity, genetics) 2. Mechanism has not been demonstrated |
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Does sugar cause hyperactivity in kids?
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MYTH
-Premises: Since sugar provides energy, refined sugar causes children to have difficulty sleeping, act impulsively, and be unable to pay attention -Facts: exact causes of hyperactivity is unknown (likely multiple factors) -Affects 5% of school-aged children -sugar has a sedative effect (increases drowsiness) though increased production of serotonin -no scientific evidence supports the premise |
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Artificial Sweeteners and Weight Control:
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-Several studies have reported that potent sweeteners may stimulate appetite and in the process lead to weight gain
-While other studies show no correlation between consumption of sweeteners, hunger, food intake, or body weight -yet more studies found that artificial sweeteners were associated with weight loss and lower energy intake |
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How much carbohydrate do you need?
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-AMDR: 45-65%
-RDA: 130g -DV (2000calorie): 300g |
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DRI for sugars
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<10%
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dialysis
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in kidney disease, treatment of the blood to remove toxic substances or metabolic wastes; more properly "hemodialysis" = dialysis of the blood
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