Nutrition Exam 2 Test Questions.txt
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1. What are the healthiest sources of carbohydrates?
- Grains that are intact and are unprocessed as much as possible such as:
- o Whole wheat bread
- o Brown rice
- o Whole grain pasta
- o Whole oats
- o Bulgur
- o Kasha
- o Quinoa
2. How do the effects of a high carbohydrate diet depend on the body weight and physical activity of the individual consuming that diet?
- ↑Carbohydrate diets have different effects on lean active people than they do on overweight sedentary people due to lack of exercise which ultimately leads to:
- o ↑Refined carbs => ↑weight gain, ↑fatigue, and ↓Energy from food
3. What are the effects of a diet high in refined carbohydrates on serum lipid values such as triglycerides and HDL cholesterol?
4. In contrast to the old system of classifying carbohydrates as either simple or complex, what is a better way of distinguishing healthy from unhealthy carbohydrates?
- High vs Low Glycemic Index/Load
- Whether they come from refined or whole grains
5. List the seven most common carbohydrate sources in the average American diet
- Cake, sweet rolls, doughnuts, pastries
- Potato chips, corn chips, popcorn
- French fries, frozen potatoes
6.· Explain how a meal rich in easily-digested carbohydrate can eventually result in low blood sugar levels and an early return of hunger.
- The resulting flood of insulin can drive glucose levels ↓↓. If there is not anymore digestible carbohydrates in the stomach or the intestines your gut and brain send out hunger signals to make you grab more food even though your liver is releasing stored glucose.
- ↑glucose => ↑insulin secretion => ↓↓↓blood glucose
7. Explain how insulin resistance affects pancreatic function.
- Resistance to insulin keeps blood glucose at high levels for longer periods of time and forces the pancreas to produce extra insulin in order to jam glucose into cells
- The insulin making cells in the pancreas may wear out from this abuse and eventually they may stop producing insulin all together ( THIS IS AN EARLY SIGN OF TYPE II DIABETES)
8. List the important contributors to the development of insulin resistance.
- Dietary fats
9. What health problems other than blood sugar disorders have been associated with insulin resistance?
- HTN (hypertension)
10. What do measurements of the glycemic index of different sources of carbohydrate tell us about the similarities and differences between sugars and complex carbohydrates?
- Simple sugars ↑Glycemic index
- Complex sugars ↑ & ↓ glycemic index
11. Which complex carbohydrate foods have a very high glycemic index?
- Total Cereal ®
- Grape Nuts®
- Raisin bran®
- Shredded wheat®
12. What is the difference between glycemic index and glycemic load, and which one appears to be a more accurate indicator of the effects of a food on blood sugar?
- GL = (GI x Carbs in grams)/100
- Glycemic load (GL) is more accurate
13. When calculating the glycemic index, a control or reference food is given the value of 100 for comparison. What are the two foods used in different tables as the reference food?
14. What characteristics of a carbohydrate-containing food determine its glycemic index or glycemic load?
- Amount of gelatin starch
- How processed it is
- Fiber content
- Fat content
15. Which micronutrients (vitamins or minerals) are depleted by more than 50% when whole wheat flour is refined into unenriched white flour?
- Vitamin E
16. Risk for which diseases can be lowered with a diet high in whole or intact grains?
- GI problems such as diverticulosis
- Speculated that is can lower the risk of some cancers ??????????????
17. List all of the possible mechanisms that may explain the role of whole grains in preventing disease.
- Delays absorption of glucose
- Eases the workload of the insulin producing cells in the pancreas
- ↓blood cholesterol levels
- ↑the bodies natural anticoagulants => ↓clot formation
- Antioxidants such as vitamin E prevent LDLs from reacting with oxygen
- Phytoestrogens => protection from some cancers
- Bran layer contains essential minerals => ↓risk of CVD & diabetes
18. What terms may be used in an ingredients label of a food product to indicate that refined flour was used in that product. What terms must be used only when a whole grain flour product is used?
- ↓ low carb, made with wheat flour
- whole wheat, whole oats, whole rye, whole grain
19. Why is the glycemic index an improvement over other ways of classifying carbohydrates?
Because blood glucose (glycemic) response to “complex” carbohydrates has been found to vary considerably. A more accurate indicator of the relative glycemic response to dietary carbohydrates is the glycemic index.
20. How does a high glycemic index food increase the likelihood of hypoglycemia after a meal?
- Rapid increases in blood glucose => ↑insulin released from the pancreas.
- Over the next few hours, the high insulin levels induced by consumption of high-glycemic index foods may cause a sharp decrease in blood glucose levels (hypoglycemia)
21. What measurement is used along with the glycemic index to arrive at the glycemic load of a food?
The amount of carbohydrates in grams
22. How does a high glycemic load diet influence the development of diabetes?
↑secretion of insulin overtime adds insult to the insulin producing cells in the pancreas and can lead to ↓pancreas function
23. In large prospective studies of nurses and male health professionals, which foods were most consistently associated with increased risk of diabetes?
- White rice
- White bread
- Carbonated sweet beverages
24. What are the benefits of low glycemic load diets in the treatment of existing diabetes?
↑ control of blood glucose => ↓episodes of hypoglycemia
25. What lipid abnormalities and other cardiovascular risk factors are associated with a high glycemic load diet?
- ↑ C-reactive protein (systemic inflammation marker)
26. What type of individual is likely to be most susceptible to the adverse cardiovascular effects of a high-glycemic load diet?
27. What are the probable mechanisms by which a low glycemic load diet improves the results of weight loss diets?
Feeling of feeling “full” for longer periods of time => ↓food consumption
28. What changes from a typical Western diet would still allow consumption of foods high in carbohydrates while lowering the overall glycemic load of the diet?
- Increasing the consumption of:
- o Whole grainsnuts,
- o Legumes,
- o Fruits
- o Nonstarchy vegetables
- Decreasing the consumption of:
- o starchy high-glycemic index foods like –
- ♣ potatoes
- ♣ white rice
- ♣ white bread
- ♣ sugary foods like cookies, cakes, candy and soft-drinks
29. Name the types of compounds that share many of the characteristics of dietary fiber, but have not typically been included in the definition of dietary fiber.
- Indigestible carbohydrates from animal sources
- Synthetic indigestible carbohydrates that are inaccessible to the human digestive enzymes
30. Contrast the way observational research has typically studied fiber from the way intervention research has typically studied fiber.
- Observational studies have looked at fiber rich foods
- Interventional studies have isolated pure fiber
31. What is meant by the term functional fiber?
Isolated or synthetic fibers that may be added to foods or used as supplements
32. What health-promoting properties are associated with viscous fiber?
- Ability to delay stomach emptying
- Delaying nutrient absorption
- ↓serum cholesterol
33. What health-promoting properties are associated with fermentable fiber?
- ↑the amount of bacteria in colon
- Formation of short chained fatty acids which are used for energy
34. What fiber-containing foods and fiber supplements lower LDL cholesterol?
- Oat products
- Supplements of:
- o Pectin
- o Guar gum
- o Psyllium
35. What is the effect of adding viscous fiber to a meal on subsequent blood glucose and insulin levels, compared to a meal lacking viscous fiber?
Shows a significant positive change in the glucose/insulin response which leads to smaller but more sustained increases in blood glucose and significantly lower insulin levels
36. What fiber-containing foods and fiber supplements consistently increase stool bulk, shorten transit time, and effectively treat constipation?
- Wheat bran
37. What is the clinical significance of diverticular disease, and what type of fiber appears to provide the strongest protection from this disease?
- Causes pockets/pouches in the colon which can become inflamed when food particles become trapped.
- Non viscous dietary fiber (cellulose)
38. Based on research on women consuming high fiber, low fat diets, how might these diets play a role in breast cancer prevention?
By decrease circulating estrogen levels by increasing the excretion of estrogens and promoting the metabolism of estrogens to less estrogenic forms NO SOLID EVIDENCE ON THIS THOUGH!!
39. By what mechanism might a high-fiber diet help prevent weight gain or promote weight loss?
- Provides less energy
- Extending the feeling of fullness after a meal
41. What are the best food sources of soluble/viscous fiber?
42. What are the best food sources of insoluble/nonviscous fiber?
43. What is meant by the term prebiotics and which fiber supplements are given this classification?
- Substances with the ability to stimulate the growth of bifidobactera in the colon
- Inulins and oligofructoses
44. What health claim about psyllium is approved by the FDA?
↓risk of CVD
45. What strategies may help people avoid gastrointestinal side effects of increasing their fiber intake?
↑water intake to 2litres/day
46. What strategy will help avoid interactions between fiber and medications?
- Add intake of kaolin-pectin
- Take medications 1 hour before or 2 hours after fiber intake
47. What component of cereal fiber is thought to be responsible for the effect of fiber on mineral absorption?
48. List the beneficial compounds present in abundance in whole grains.
49. What changes in fasting insulin levels and other measures of insulin resistance occur on a diet low in whole grains and high in refined grains?
50. In prospective studies of coronary heart disease risk, what whole grain foods were associated with reduced risk?
- Dark bread
- Whole grain cereal
- Brown rice
51. Fiber from which whole grains appears to improve total and LDL cholesterol levels?
52. How do Phytosterols in whole grains cause a decrease in serum cholesterol?
They interfere with intestinal absorption of cholesterol
53. By what mechanisms may constituents of whole grains reduce the risk of some types of cancer?
- Accelerate the passage of poop thru the colon
- ↓contact time of carcinogens
- Lignans in whole grain = Phytoestrogens => ↓hormone dependent cancer
- Phenolic compounds modify signal transduction pathway – alters metal
- 54. Other than cancer, what intestinal disorders may be prevented by diets rich in whole grains, and what biochemical or physiological mechanisms are involved?
- ↓constipation => softens and adds bulk to poop which speeds transit time out of the colon
- ↓diverticulosis risk
55. What strategies can be used to make sure whole grain foods are purchased when shopping?
- Items that list whole grain as 1st ingredient
- >>2grams fiber/serving
- Beneficial health claims such as : 51% or greater whole grain by weight
56. List some other strategies for increasing whole grain intake
- Whole grain:
- o Breakfast cereals
- o Bread/crackers
- o Pasta
- o Flour
- Brown rice
1. Which high protein foods are considered the healthiest choices?
2. What is meant by an "incomplete" protein?
- Lacking one or more essential amino acids
- Vegetable proteins are often incomplete
3. How does the typical protein intake on a Western diet compare with daily protein requirements?
Typically have more protein than what is needed
4. Which foods have the highest percentage of calories from protein?
- Water packed tuna fish
- Roasted chicken
- Low fat cottage cheese
- Broiled top sirloin
- Salmon filet
5. What are the important differences between animal and vegetable sources of protein in terms of their effects on health and disease?
Alone they are the same but the packaging of animal sources of protein often includes ↑saturated fat
6. What types of cooking may increase the risk of cancer from eating meat?
- Grilling to death can cause an ↑in carcinogens (heterocyclic amines)
7. List the possible mechanisms behind the cardio protective benefits of eating nuts.
- Unsaturated fats ↓LDL & ↑HDL
- Omega-3 ↓blood clotting
8. What are the environmental arguments for making certain choices among different protein foods?
- Vegetable proteins are more efficient
- ↑↑↑ requirements to feed beef/meat sources
9. What were the findings of the Nurses' Health Study regarding the effects of protein intake on the risk of heart disease?
An ↑in protein intake leads to a 25% decrease in the likelihood to have a MI vs. ↓protein intake
10. Why might increased protein intake contribute to successful weight control?
- Chicken, beef, and fish ↓ stomach emptying and therefore you have a longer satiety
- Protein has a low glycemic load
12. How does protein intake affect calcium balance in the body?
↑protein intake requires calcium to neutralize acids and this calcium is pulled from bone and this may have long term effects
14. Extensive tissue loss may increase protein requirements by how much in relation to the RDA?
Up to 2x of RDA
15. How do the protein requirements of athletes compare to non-athletes in terms of grams required per day?
↑ requirements in athletes can be met by ↑ caloric intake with normal proportions of protein (10-15% of total calories)
16. How do the protein requirements of athletes compare to non-athletes in terms of percentage of total calories that should come from protein?
- Endurance exercises : 1.2-1.4gProtein/kg body mass per day (150% RDA)
- Strength exercises: 1.7-1.8gProtein/kg body mass per day (220% RDA)
17. What are the pros and cons of a high-protein diet for normalizing glucose intolerance, weight-loss, and/or dyslipidemia?
- Normalizing glucose intolerance –
- o Substituting lean protein for carbohydrates with ↓glucose intolerance
- Weight loss –
- o Substituting lean protein for carbohydrates ↑HDL and ↓LDL
- Dyslipidemia –
- o Need to watch which proteins you use!!!! Favour plant protein over animal protein sources
18. What are the potential consequences of a very high meat protein diet?
- ↑risk of lung, colon, breast, nonhodgkin lymphoma (especially if over done)
- ↑risk of kidney stones
- Suggested upper limit of protein intake is no more than 2X RDA suggested intake (2.0g/kg/day)
19. List the common foods that belong to the legume family
20. Name the Phytoestrogens family found in soybeans
21. What are the mechanisms by which legume consumption decreases the risk of type 2 diabetes?
Legumes have a relatively low glycemic index
22. Which cardiovascular risk factors are affected by legume consumption?
It improves serum lipid and lipoprotein files
23. What health claim does the FDA allow on labels of foods containing soy?
Diets low in saturated fat and cholesterol with 25g soy protein/day may ↓CVD risk
24. Which cancer appears to be reduced in risk by consumption of both soy and other legumes?
- Prostate cancer
- Breast cancer
25. Is soy protein considered a complete protein?
Yes soy protein is considered a complete protein because it contains all of the essential amino acids
1. Which cardiovascular diseases and risk factors are affected by fruit and vegetable intake?
- ↓ incidence of MI
2. What nutritional components of fruits and vegetables are likely to contribute to their health effects?
- Vitamin C
3. Why are case-control studies of the relationship between fruit/vegetable intake and cancer less convincing than the results of prospective cohort studies?
The case control study showed positive results of ↑fruit/vegetable with ↓cancer however, the study leaves room for biased sampling
4. What are some explanations proposed to account for the disagreement between studies of cancer risk and fruit/vegetable consumption?
- Problems with population bias
- Showed reduction in individual cancers
5. Which specific vegetables have been associated with protection from which specific cancers?
- ↑fruit => ↓lung cancer
- ↑cruciferous vegetables =>↓bladder cancer
- ↑tomatoes =>↓prostate cancer
6. Explain the mechanism by which fruit and vegetable consumption may protect against bone loss.
Fruit and vegetables are high in bicarbonate which can be used as a buffer to keep calcium levels high
7. Increased fruit and vegetable consumption may prevent which diseases of the eye?
- Macular degeneration
8. Which foods are associated with protection against chronic obstructive lung disease (COPD)?
Higher fruit intakes, especially apple intakes, are associated with higher forced expiratory volume (FEV1) values, indicative of better lung function
9. What are the five categories of fruits and vegetables that are recommended for daily consumption in order to receive a wide variety of potentially beneficial phytochemicals?
Answer not found clearly at LPI website
10. Name the six principal dietary carotenoids. Which ones have vitamin A activity?
- Ones with vitamin A activity
- o α carotene
- o β carotene
- o β cryptoxanthin
11. List the potentially beneficial functions of carotenoids other than vitamin A activity
- Light filtering
- Intercellular communication
- Immune system activity
12. Which carotenoid is not typically associated with protection from lung cancer according to recent studies?
β carotene ???????????????
13. Which carotenoid is associated with tomato consumption?
14. Describe the conclusions of clinical trials of beta-carotene supplementation for reducing the risk of various diseases.
Experts feel that the risks of high-dose beta-carotene supplementation outweigh any potential benefits for cancer prevention, especially in smokers or other high-risk populations
15. Which carotenoids are concentrated in the retina and lens of the eye?
16. Which carotenoid is most abundant in the North American diet?
- α carotene
- β carotene
- β cryptoxanthin
17. Give examples of the major food sources of each of the principal dietary carotenoids.
- α and β carotene
- o Squash
- o Spinach
- o Carrots
- β cryptoxanthin
- o Pumpkin
- o Red peppers
- o Oranges
- o Tomatoes
- o Pink grapefruit
- o Watermelon
- Lutein and Zeaxanthin
- o Spinach
- o Kale
- o Turnip
- o Greens
18. What strategy for taking carotenoid supplements will allow for the best absorption?
They are best absorbed with a meal containing fat
19. What is the difference between synthetic beta-carotene and beta-carotene extracted from natural sources?
The supplemental form of β carotene has higher vitamin A activity
20. What methods of food preparation increase the bioavailability of carotenoids?
- Heating tomatoes in oil
21. What is the likelihood that high intake of beta-carotene could lead to vitamin A toxicity?
It is unlikely, it will NOT cause vitamin A toxicity
22. Describe the controversy around the effects of combining statin drugs with antioxidant supplements containing beta-carotene?
A 3-year randomized controlled trial in 160 patients with documented coronary heart disease and low serum high density lipoprotein (HDL) concentrations found that a combination of simvastatin (Zocor) and niacin increased HDL2 levels, inhibited the progression of coronary artery stenosis, and decreased the frequency of cardiovascular events, including MI and stroke (89). Surprisingly, when an antioxidant combination (1,000 mg of vitamin C, 800 IU of alpha-tocopherol, 100 mcg of selenium, and 25 mg of beta-carotene daily) was taken with the simvastatin-niacin combination, the protective effects were diminished. Since the antioxidants were taken together in this trial, the individual contribution of beta-carotene cannot be determined. In contrast, a much larger randomized controlled trial of simvastatin and an antioxidant combination (600 mg of vitamin E, 250 mg of vitamin C, and 20 mg of beta-carotene daily) in more than 20,000 men and women with coronary artery disease or diabetes found that the antioxidant combination did not diminish the cardioprotective effects of simvastatin therapy over a 5-year period (90), suggesting that the antioxidant combination may have interfered with the HDL-raising effect of niacin in the former trial. Further research is needed to determine potential interactions between antioxidant supplements and cholesterol-lowering agents, such as niacin and HMG-CoA reductase inhibitors (statins).
23. Give some examples of drugs or foods that might reduce the absorption of carotenoids.
- Foods made with olestra
- Plant sterol containing foods
24. Name the vitamin A molecules referred to as preformed vitamin A.
25. List the known functions of vitamin A in the human body
- Effects gene transcription
- Improves vision
- Maintains function of immune cells
- Differentiation of RBCs
- T lymphocyte activation
26. Name the visual pigment formed in part by a vitamin A metabolite
27. Which biological role of vitamin A results in most of the known physiological roles of this vitamin?
28. Which cells important for defense against infection do vitamin A compounds support?
Maintains functional integrity of skin and mucosal cells
29. What are the most serious consequences worldwide that result from vitamin A deficiency? Are deficiencies such as this common in developed countries?
Most preventable cause of blindness in developing countries
30. Why do men have a higher requirement for vitamin A than do women?
- Females need more vitamin A during pregnancy
- Males need more vitamin A during adolescence
31. Why is the standard measure known as retinol activity equivalency needed to appreciate the total vitamin A activity in foods and supplements?
- Represents vitamin A activity as retinol
- Different sources of vitamin A are absorbed differently
32. What molecular form of preformed vitamin A is found in both food and supplements?
33. Name the best vitamin A sources from a) fruit/vegetable products, b) animal products, and c) fortified foods
- Fruit/Vegetable products
- Animal products
- Cod liver oil
- Fortified foods
- Milk with vitamin A added
34. Why do the Daily Value levels recommended on supplement labels not agree with the most recent RDAs for those micronutrients?
Labels are based on older recommendations
35. What are the symptoms of vitamin A toxicity?
- Dry skin
36. How much higher than the RDA or Daily Value is the tolerable upper level (UL) set by the Institute of Medicine?
2X higher (5000IU vs 10,000IU)
37. Describe the special concerns about vitamin A excess during pregnancy.
Can cause birth defects if taken in excess
38. Describe the concerns about and the evidence for the effects on bone from high intake of preformed vitamin A.
Has shown an ↑in bone loss with prolonged ↑in vitamin A intake
39. What does the Linus Pauling Institute recommend for vitamin A content in multivitamins?
5000IU/day as retinol
40. List the known functions of vitamin C in the human body.
- Collagen synthesis
- Norepinephrine synthesis
- Carnitine synthesis
- Transports fats into mitochondria
- Metabolism of cholesterol
41. How do the functions of vitamin C explain some of the symptoms of vitamin C deficiency?
Scurvy – fatigue due to ↓carnitine
42. For what individuals is the RDA higher because of a personal habit?
43. What amounts of vitamin C intake is sufficient to saturate plasma and circulating cells with vitamin C?
44. Why may taking vitamin C supplements not confer the same health protection as a diet high in vitamin C?
5 servings/day is only about 200mg of Vitamin C
45. What is the mechanism by which vitamin C may reduce the risk of stomach cancer?
Vitamin C inhibits carcinogenic compounds from being made in the stomach
46. Is vitamin C more likely to help prevent the common cold, or to lessen the severity and duration of an existing cold?
- Can ↓the risk of the cold in marathoners
- ↑ dietary vitamin C did not ↓ the length of a cold once the symptoms were present
47. What is the justification for recommending mineral ascorbates over ascorbic acid to some people?
Mineral ascorbates are buffered and can be less irritating to the GI tract
48. What are bioflavonoids, and what is the likelihood that they improve the bioavailability or efficacy of vitamin C supplements?
They are water soluble plant pigments that make vitamin C more efficient
49. What is the most likely side effect that would result from ingesting large amounts of vitamin C?
50. Why are in vitro experiments showing the potential for vitamin C to produce free radicals probably irrelevant to conditions found in the human body?
Cannot be duplicated in the human body
51. Describe the controversy around the effects of combining statin drugs with antioxidant supplements containing vitamin C?
May block the activity of warafin
52. What is the justification for the Linus Pauling Institute's recommendation for a vitamin C intake of at least 400 mg per day?
For full saturation of plasma cells
53. List names of the eight vitamers belonging to the vitamin E family.
- 4 trocopherols (α,β,γ,Δ)
- 4 trocotrienols (α,β,γ,Δ)
54. Which vitamin E vitamer is actively maintained in the human body, and how is this accomplished?
α trocopherol blocks lipid destruction in cell membranes
55. List the known functions of alpha-tocopherol and gamma-tocopherol in the human body.
- α trocopherol
- antioxidant that blocks free radicals, inhibits protein kinase C, and ↓blood clotting
- γ trocopherol
56. What physiological problems can cause symptomatic vitamin E deficiency?
- Genetic defects
- Fat malabsorption
57. What tissues are primarily affected by severe vitamin E deficiency?
58. What is meant by suboptimal levels of vitamin E?
Blood level of α trocopherol less than 20µm/L (↑CVD below this)
59. What might explain the contrasting results of prospective observational studies and intervention studies of vitamin E as a means of preventing heart disease?
Prospective studies allow you to pick healthy subjects
60. For which cancer is there evidence that vitamin E supplements may have a risk-lowering effect?
- Lung cancer
- Breast cancer
61. What are the major food sources of vitamin E in the Western diet?
- Vegetable oils
- Whole grains
- Leafy green vegetables
62. Describe the nomenclature by which natural and synthetic vitamin E are distinguished from one another?
- RRR-alpha-tocopherol (natural or d-alpha-tocopherol)
- all-rac-alpha-tocopherol (synthetic or dl-alpha-tocopherol)
63. What is the justification for providing vitamin E in ester, rather than alcohol, forms?
Esters are more resistant to oxidation
64. What might be an advantage of using mixed tocopherol forms of vitamin E supplements?
You can get both α and γ together
65. According to the LPI are the conclusions of a recent meta-analysis evaluating the effect of vitamin E on all-cause mortality supported by further statistical analysis and by other meta-analyses on the same topic?
A recent meta-analysis that combined the results of 19 clinical trials of vitamin E supplementation for various diseases, including heart disease, end-stage renal failure and Alzheimer's disease, reported that adults who took supplements of 400 IU/day or more were 6% more likely to die from any cause than those who did not take vitamin E supplements (52). However, further breakdown of the risk by vitamin E dose and adjustment for other vitamin and mineral supplements revealed that the increased risk of death was statistically significant only at a dose of 2,000 IU/day, which is higher than the UL for adults. Furthermore, three other meta-analyses that combined the results of randomized controlled trials designed to evaluate the efficacy of vitamin E supplementation for the prevention or treatment of cardiovascular disease found no evidence that vitamin E supplementation up to 800 IU/day significantly increased or decreased cardiovascular disease mortality or all-cause mortality (53-55). At present, there is no convincing evidence that vitamin E supplementation up to 800 IU/day increases the risk of death from cardiovascular disease or other causes.
66. What is the most worrisome side effect that is possible from over ingestion of vitamin E?
Impaired blood clotting
67. When might it be advisable to temporarily discontinue vitamin E supplementation?
Individuals on anticoagulant therapy (blood thinners) or individuals who are vitamin K deficient should not take alpha-tocopherol supplements without close medical supervision because of the increased risk of hemorrhage
68. Describe the controversy around the effects of combining statin drugs with antioxidant supplements containing vitamin E?
A 3-year randomized controlled trial in 160 patients with documented coronary heart disease (CHD) and low HDL levels found that a combination of simvastatin (Zocor) and niacin increased HDL2 levels, inhibited the progression of coronary artery stenosis (narrowing), and decreased the frequency of cardiovascular events, such as myocardial infarction and stroke (56). Surprisingly, when an antioxidant combination (1000 mg vitamin C, 800 IU alpha-tocopherol, 100 mcg of selenium, and 25 mg beta-carotene daily) was taken with the simvastatin-niacin combination, the protective effects were diminished. However, in a much larger randomized controlled trial of simvastatin and an antioxidant combination (600 mg vitamin E, 250 mg vitamin C, and 20 mg beta-carotene daily) in more than 20,000 men and women with coronary artery disease or diabetes, the antioxidant combination did not adversely affect the cardioprotective effects of simvastatin therapy over a 5-year period (57). These contradictory findings indicate that further research is needed on potential interactions between antioxidant supplementation and cholesterol-lowering agents, such as HMG-CoA reductase inhibitors (statins).
69. When should vitamin E supplements be taken to ensure optimal absorption?
Should be taken with food
70. Selenium-dependent enzymes are also known as ______?
71. List the known functions of selenium in the human body.
- ESSENTIALLY THEY HELP FORM FUNCTIONAL PROTEINS
- Glutathione peroxidases
- o they are all antioxidant enzymes that reduce potentially damaging reactive oxygen species (ROS), such as hydrogen peroxide and lipid hydroperoxides, to harmless products like water and alcohols by coupling their reduction with the oxidation of glutathione
- Thioredoxin reductase
- o Maintenance of thioredoxin in a reduced form by thioredoxin reductase is important for regulating cell growth and viability
- Iodothyronine deiodinases (thyroid hormone deiodinases)
- o three different selenium-dependent iodothyronine deiodinases (types I, II, and III) can both activate and inactivate thyroid hormone, making selenium an essential element for normal development, growth, and metabolism through the regulation of thyroid hormones
- Selenoprotein P
- o Although the function of selenoprotein P has not been clearly delineated, it has been suggested to function as a transport protein, as well as an antioxidant capable of protecting endothelial cells from damage by a reactive nitrogen species (RNS) called peroxynitrite
- Selenoprotein W
- o Selenoprotein W is found in muscle. Although its function is presently unknown, it is thought to play a role in muscle metabolism
- Selenophosphate synthetase
- o Incorporation of selenocysteine into selenoproteins is directed by the genetic code and requires the enzyme selenophosphate synthetase. A selenoprotein itself, selenophosphate synthetase catalyzes the synthesis of monoselenium phosphate, a precursor of selenocysteine which is required for the synthesis of selenoproteins
- Antioxidant nutrients
- o selenium probably interacts with every nutrient that affects the pro-oxidant/antioxidant balance of the cell
- o Selenium deficiency may exacerbate the effects of iodine deficiency. Iodine is essential for the synthesis of thyroid hormone, but the selenoenzymes, iodothyronine deiodinases, are also required for the conversion of thyroxine (T4) to the biologically active thyroid hormone triiodothyronine (T3). Selenium supplementation in a small group of elderly individuals decreased plasma T4, indicating increased deiodinase activity with increased conversion to T3
72. Which family of selenium-dependent enzymes has a number of forms that are active as antioxidants in different tissues?
- Glutathione peroxidases
- Thioredoxin reductase
73. Which endocrine gland function involves selenium-dependent enzymes?
Thyroid hormone reactions
74. Maintenance of which vitamins may depend on adequate activity of selenium-dependent enzymes?
75. For which cancer is there evidence that selenium supplements may have a risk-lowering effect?
- Liver cancer
- Prostate cancer
76. What mechanisms may explain a protective effect of selenium against cancer?
- Improves antioxidant status
- Improves immune system function
- Metabolizes carcinogens
- Inhibits the growth of tumors
77. What are the major food sources of selenium in the Western diet?
- Organ meats
- Plant proteins especially nuts from selenium rich soil
78. What forms of selenium supplements, if any, may be the best choices?
- Selenomethionine, an organic form of selenium that occurs naturally in foods, is about 90% absorbed
- At present, it is not clear whether one form of selenium is preferable to another
79. What symptoms of selenium toxicity are the Upper Tolerable Limit intended to prevent?
- Hair loss
- Nail brittleness
80. Why does the LPI have different recommendations for selenium intake for men and women?
- Men can take up to 2X RDA recommendation to ↓prostate cancer risk
- Because there is no evidence that selenium supplementation decreases the risk of cancer in women who are not selenium deficient, there is no reason for women to take an extra selenium supplement.
81. Why are several types of antioxidant systems required to protect human tissues?
Different cell/tissue types??? DUNNO NO CLEAR INFO IN MATERIAL
82. What antioxidant enzymes are important for preventing cell damage, and what nutrients are required as cofactors for their function?
- Glutathione peroxidases
- o Converts peroxides to stable compounds
- ♣ Requires:
- • Selenium
- • Glutathione
- • Vitamin B2
- • Vitamin B3
- Superoxide dismutase
- o Converts superoxide to oxygen and hydrogen peroxide
- ♣ Requires:
- • Copper and zinc, or manganese, iron, or nickel as superoxide dismutase
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