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Chapter 10 Nutrients and Phytochemicals That Function as Antioxidants Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Student Learning Outcomes 1 10.1 Understand oxidation and reduction, and how free radicals can alter normal cell function. 10.2 Describe how antioxidants function to neutralize free radicals. 10.3 Summarize the functions of vitamin E and describe its food sources and deficiency and toxicity symptoms. 10.4 Describe the functions of vitamin C as well as its dietary sources and deficiency symptoms. Student Learning Outcomes 2 10.5 Explain the functions and food sources of carotenoids. 10.6 Describe the role of antioxidant phytochemicals. 10.7 Summarize the functions of selenium and describe its food sources and deficiency and toxicity symptoms. 10.8 Describe how calorie and fat intakes contribute to cancer risk and the role other food constituents play in inhibiting cancer. Nutrients and Phytochemicals That Function as Antioxidants • Some vitamins, minerals, plant compounds function as antioxidants • Protect cells against free radicals • Nutrients that function as antioxidants: – Vitamin E (tocopherol) – Vitamin C (ascorbic acid) – Vitamin A (retinoids & carotenoids) – Phytochemicals – Selenium (Se) 10.1 Oxidation and Reduction 1. What happens to electrons during the processes of reduction and oxidation? 2. What is a free radical? 3. Why are free radicals thought to be harmful to cells? Protons and Electrons • Protons and neutrons are found in the nucleus • Electrons circle the nucleus in pairs • Nucleus is positively (+) charged • Electrons are negatively (-) charged • Positive and negative charges balance – atom has no overall charge Oxidative Stress • Atoms bond together in molecules • Oxidative stress – imbalance between production of reactive compounds and body’s ability to protect against their adverse effects • Reduction – gain of a negatively charged electron Oxidation and Reduction • Oxidation – loss of a negatively charged electron • We derive energy from food in the form of ATP and other high-energy compounds • Sharing electrons in outer shell makes bonds between atoms or molecules strong • Oxidation of these bonds produces stable compounds Free Radical Formation • A weak bond between atom or molecule produces possible molecule or atom left with an unpaired electron in its outer shell • Free radical – unstable atom with unpaired electron in its outermost shell • Overproduction of free radicals can be harmful to healthy cells Redox Reaction 10.2 Defense Against Free Radicals 1. Which micronutrients are known to have antioxidant roles? 2. How do antioxidant chemicals reduce cellular damage? Defense Against Free Radicals • Body has two defense mechanisms – Enzyme systems and antioxidant chemicals – Work together to limit free radical formation • Enzyme activity – requires presence of minerals selenium, manganese, zinc, iron, copper • Antioxidant – substance has ability to prevent or repair damage caused by oxidation – Derived from food nutrients Antioxidants Protect DNA More Fruits and Vegetables • 2010 Dietary Guidelines, MyPlate and Fruits & Veggies: More Matters© campaigns • Premise to increase consumption of fruits and vegetables – Increases fiber, vitamins, minerals, phytochemicals detoxifying reactive molecules including free radicals Dietary Antioxidants • Dietary antioxidant – substance in foods that significantly decreases adverse effects of reactive species such as reactive oxygen and nitrogen species on normal physiological function in humans (from DRI) Antioxidant Activity 10.3 Vitamin E (Tocopherols) 1. How does vitamin E work to prevent oxidative damage? 2. What are some rich food sources of vitamin E? 3. Why are preterm infants, smokers, and people with fat malabsorption particularly susceptible to oxidative damage to cell membranes? 4. What are the possible results of vitamin E toxicity? Functions of Vitamin E • Compound identified as essential for rat fertility, 1920s – No corresponding fertility effect in humans • Compound named tocopherol • Development of muscles • Development of central nervous system • Antioxidant • Maintains nervous tissue and immune function Vitamin E as an Antioxidant • Fat-soluble vitamin found in adipose tissue and cell membrane • Lipids in these membranes are polyunsaturated fatty acid (PUFA) – PUFAs susceptible to oxidative attack • Vitamin E donates electrons or hydrogens to free radicals to make cell more stable • Vitamin E important in areas exposed to ↑ levels of oxygen – RBCs and lungs Vitamin E Protects Cell Membranes • Vitamin E can insert itself into cell membranes • It helps stop freeradical chain reactions Vitamin E: Deficiency • Deficiency is rare because primary source of Vitamin E is plant oils and our diets are high in fat • Deficiency can be problem in preterm infants as transfer from mother occurs late in pregnancy Getting Enough Vitamin E • Plant products best sources, especially oils • RDA for adults: 15 mg/day of alpha-tocopherol (the most active form of vitamin E) • DV on labels is based on 30 mg Food Sources of Vitamin E • Only synthesized by plants, particularly their oils • Good sources include: – Salad oils – Margarines – Shortening – Fortified cereals – Nuts and seeds Bar Graph: Sources of Vitamin E MyPlate: Sources of Vitamin E Calculating Vitamin E Content of Dietary Supplements • Vitamin E content on Supplement Facts labels given in international units (IU) – measure of biological activity of a nutrient rather than its absolute quantity • Supplements contain variety of chemical forms – usually less bioactivity than natural or dietary vitamin E Avoiding Too Much Vitamin E • Megadosing does not provide significant health benefits or prevent against oxidative damage • Not stored in the liver – stored in fat tissue • UL is 1,000 mg/day • Excess can interfere with vitamin K and anticoagulant medications causing hemorrhage (Coumadin & aspirin) 10.4 Vitamin C (Ascorbic Acid) 1. How does vitamin C function as an antioxidant and regenerate vitamin E? 2. How do the signs of vitamin C deficiency relate to the many roles of the vitamin discussed in this chapter? 3. Why are fresh foods the best sources of vitamin C? Functions of Vitamin C • Collagen synthesis, most abundant protein in body • Carnitine synthesis, transports fatty acids • Serotonin and norepinephrine synthesis • Antioxidant • Increases iron absorption • Vital for immune function • May decrease formation of carcinogen nitrosamines in the stomach • Doesn’t prevent colds but may decrease severity Getting Enough Vitamin C • Adult RDA: – 75 mg/day for women – 90 mg/day for men • Smokers need an extra 35 mg because of increased oxidation by tobacco smoke in lungs • Average U.S. consumption: 70-100 mg/day Vitamin C Deficiency - Scurvy • Causes scurvy due to reduced collagen synthesis, causing bruising, bleeding gums • 1700s half of sailing crew on long voyages died • British physician discovered citrus fruits prevented and restored health of sailors • Future food rations included limes, resulting in nickname “limeys” Pinpoint Hemorrhages Early Scurvy Sign Food Sources of Vitamin C • Citrus fruits • Strawberries • Green peppers • Cauliflower & broccoli • Cabbage • Papaya • Romaine, darker color lettuce • Brighter fruits and vegetables = more vitamin C • Ready to eat breakfast cereals Avoiding Too Much Vitamin C • Increased iron absorption: problematic with hemochromatosis • Increased kidney function and urination above 100 mg per day • UL is 2,000 mg/day • Stomach inflammation and diarrhea • GI distress Bar Graph: Sources of Vitamin C MyPlate: Sources of Vitamin C 10.5 Carotenoids 1. What are the names of four carotenoids known to have antioxidant functions? 2. How are the carotenoids related to vitamin A? 3. What are some rich food sources of carotenoids? Carotenoids • Plants contain pigments called carotenoids • Carotenoids are phytochemicals with health promoting chemicals • Precursors of vitamin A, antioxidant properties Carotenoids • Three carotenoids are provitamins - can be turned into vitamin A: – Beta-carotene – Alpha-carotene – Beta-cryptoxanthin • Other carotenoids that may have health benefits: – Lycopene – Zeaxanthin – Lutein Functions of the Carotenoids • Vision, reduce macular degeneration – Leading cause of legal blindness in North America • Cardiovascular disease prevention – May inhibit oxidation of low-density lipoproteins • Cancer prevention, lung, oral, skin, prostate Age-Related Macular Degeneration (a)Age-related degeneration of the macular region as noted by the black arrow (b)The blurry center of the image simulates the vision of a person with macular degeneration Getting Enough Carotenoids • Dark green and yellow-orange vegetables and fruits • Green leafy vegetables, spinach, kale – lutein and zeaxanthin • Tomato products, juice, sauce – lycopene • Cooking frees carotenoids for better absorption Avoiding Too Much Carotenoids • Excess dietary consumption, no toxic effects • Hypercarotenemia, too many carrots or betacarotene supplements/pills – Skin may turn yelloworange 10.6 Other Phytochemicals 1. What categories of phytochemicals function as antioxidants? 2. Which food group has the richest supply of antioxidant phytochemicals? 3. What phytochemical group is responsible for the color of berries? 4. What is the ORAC assay, and what are the limitations to using its values to estimate antioxidant activity? 5. Diets rich in phytochemicals have been associated with a decreased risk of which diseases? Phytochemicals • Thousands of food substances in addition to 45 essential nutrients • Functional foods – have health benefits beyond basic nutrition • Zoochemicals – found in animal products that have health protective actions • Phytochemicals – health-promoting compounds found in plant food • Many foods contain hundreds of phytochemicals • Not essential nutrients, no deficiency disease when removed from diet Functions of Phytochemicals • Antioxidants • Inhibit cancer and cell death • Alter absorption, production, and metabolism of cholesterol • Mimic or inhibit hormones and enzymes • Decrease formation of blood clots • Decrease inflammation, affecting immunerelated disorders Antioxidant Activity of Food • 326 foods analyzed by USDA – oxygen radical absorption capacity (ORAC) – ORAC measures antioxidant capacity in test tube, not humans – USDA reports results may be abused by supplement manufacturers to promote products • Dietary Guidelines – eat variety of fruits, vegetables, and whole grains • 5-A-Day program results associated with lower oxidative stress, improved antioxidant status Antioxidant Activity of Foods 1 Antioxidant Activity of Foods 2 Antioxidant Activity of Foods 3 Getting Enough Phytochemicals • No specific recommendation for amount • Typical U.S. consumption is 3000-5000 ORAC units • Should be closer to 12,000 ORAC units – This would be 8-9 fruit, vegetable servings/day • Very little evidence supporting use of antioxidant supplements 10.7 Selenium (Se) 1. How does selenium play an antioxidant role? 2. What other functions does selenium play in the body? 3. What are the signs of a selenium deficiency? 4. What food groups are the best sources of selenium? 5. What are the signs of selenium toxicity? Selenium (Se) Functions • Trace mineral • Helps glutathione peroxidase: – Glutathione peroxidase chemically converts dangerous peroxides → water • Selenium spares vitamin E and helps maintain cell-membrane integrity • Activates thyroid hormone • Helps immune function Getting Enough Selenium • RDA: 55 mcg per day for adults • DV used on supplement and food labels is 70 mcg • Adults generally meet selenium needs Selenium Deficiency • Low blood levels linked to ↑ risk of some types of cancer (ex: prostate) • Muscle pain, wasting, heart damage • China’s Keshan province’s soil is known to be deficient in selenium Food Sources of Selenium • Selenium content of soil where plant or animal food comes from predicts selenium content in plant or animal food • Brazil nuts, fish, meat and organ meats, shellfish, eggs • Some grains and seeds grown in selenium rich soil Bar Graph: Sources of Selenium Avoiding Too Much Selenium • Selenium toxicity has not been reported from food sources • Supplementation for long periods of time is toxic • UL is 400 mcg • Toxicity signs: hair loss, weakness, cirrhosis Portion of 10 Brazil nuts contains 960 mcg of selenium, which exceeds the Upper Limit Nutrition and Your Health Nutrition and Cancer Detecting Cancer • Undetected, it can spread quickly – early detection • Use CAUTION acronym Change in bowel or bladder habits A sore that does not heal Unusual bleeding or discharge Thickening or lump in the breast or elsewhere Indigestion or difficulty in swallowing Obvious change in a wart or mole Nagging cough or hoarseness – unexplained weight loss an additional warning sign Detecting Cancer • Routine screenings important for early detection • Colonoscopy examinations – middle-aged and older adults • Prostate-specific antigen (PSA) tests – middle-aged, older men • Papanicolaou tests (Pap smears) and regular breast examinations – mammograms about age 40 for women (ACS) Cancer Statistics • Second leading cause of death, North America • Estimated 1600 die each day in U.S. • Four cancers, more than 50% of cancer deaths, lung, colorectal, breast, prostate cancers • Cancer is many diseases, by types of cells and contributing factors • Treatments vary Cancer Terminology • Tumor – mass of cells; cancerous or noncancerous • Benign – noncancerous; tumors that do not spread • Malignant – property of spreading locally and to distant sites • Metastasize – spreading of disease from one part of body to another, even parts of body that are remote from site of original tumor – cells spread via blood vessels, lymphatic system, or direct growth of tumor Factors That Influence Development of Cancer • Genetics, environment, lifestyle • Genetic role in colon, breast, and prostate cancer • Experts estimate that only 5% of most cancers can be explained by the inheritance • Diet likely to account for 30-40% of all cancers Contributions of Calorie and Fat Intakes to Cancer Risk • Food constituents may contribute to cancer development, some are protective • Excess calorie intake and obesity responsible for 14% of cancer death in men, 20% women – Increased estrogen and insulin output suspected • Nation Cancer Institute recommends reducing fat intake to 20% of total calories • Some researcher say to reduce calories to 70% of usual intake, increases longevity Cancer Deaths Cancer-Inhibiting Constituents of Foods • Include antioxidants and some phytochemicals • Some help prevent DNA mutations • Vitamin C and E help prevent formation of nitrosamines (carcinogen) in GI tract • Fruit and vegetable intake reduces risk of nearly all types of cancer • Use MyPlate guidelines to form diet Nutrition Concerns During Cancer Treatment • Overall goals of medical nutrition therapy to minimize weight loss, prevent nutrient deficiencies – Preserve muscle mass • Fatigue, mouth sores, dry mouth, taste abnormalities, nausea, diarrhea lead to poor food intake • Best food…any patient tolerates • Small, frequent, nutrient dense – Liquid nutritional supplements often needed American Institute for Cancer Research Recommendations for Cancer Prevention 1. Be as lean as possible without becoming underweight 2. Be physically active for at least 30 minutes every day 3. Avoid sugary drinks. Limit consumption of energydense foods 4. Eat more of a variety of vegetables, fruits, whole grains, and legumes 5. Limit consumption of red meats American Institute for Cancer Research Recommendations for Cancer Prevention 6. If consumed at all, limit alcoholic drinks to two per day (men) or one per day (women) 7. Limit consumption of salty foods, foods processed with salt 8. Don’t use supplements to protect against cancer 9. It is best for mothers to breastfeed exclusively for up to 6 months and then add other liquids and foods 10. After treatment, cancer survivors should follow the recommendations for cancer prevention – Don’t smoke or chew tobacco