Antioxidants and Diseases 4.ppsx

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DR.SAEED BAHRMEDICAL NUTRITIONAL CONSLUTANT

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Free Radicals and Diseases

ANTIOXIDANTS

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Vitamin A&B-Carotene Vitamin E

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Manganese

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THE MOST PUBLICIZED ANTIOXIDANTS HAVE BEEN:

fat-soluble antioxidants: vitamin A and carotenoids, vitamin E, Coenzyme Q10water-soluble antioxidants: vitamin C, minerals zinc, selenium, manganese

Some

antioxidants are made in the body and are poorly absorbed from the intestine. One example is glutathione, which is made from amino acids. Glutathion as a supplemet in the gut is broken down and have little effect on the concentration of glutathione in the body. Ubiquinol (coenzyme Q) is also poorly absorbed from the gut and is made in humans body.

The body has a limited ability to excrete vitamins and minerals, so excessive consumption may cause a number of health problems, even in relatively small dosages. Vitamin supplements may be necessary for individuals whose diets don't provide the recommended amounts of specific vitamins and especially important for pregnant and nursing women and people with specific illnesses. However, the benefits of vitamin supplements for the general population remain uncertain.

. E,C .ASCORBIC ACID

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VITAMIN C Sources:

fruits and vegetables vary in their vitamin C content Vitamin C, also known as ascorbic acid, is a water-soluble vitamin. Unlike most mammals, humans do not have the ability to make their own vitamin C. Therefore, we must obtain vitamin C through our diet. Vitamin C is known as a highly effective antioxidant in living organisms.

Supplements: Vitamin C (ascorbic acid) is available in many forms, but there is little scientific evidence that any one form is better absorbed or more effective than another. Natural vs. synthetic vitamin C: Natural and synthetic ascorbic acid are chemically identical and there are no known differences in their biological activities or bioavailability Toxicity: A number of possible problems with very large doses of vitamin C have been suggested, mainly based on in vitro experiments or isolated case reports, including: genetic mutations, birth defects, cancer, atherosclerosis, kidney stones, increased oxidative stress, excess iron absorption, vitamin B-12 deficiency, and erosion of dental enamel. However, none of these adverse health effects have been confirmed, and there is no reliable scientific evidence that large amounts of vitamin C (up to 10 grams/day in adults) are toxic.

TOCOPHEROLS E

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VITAMIN E Major

sources of alpha-tocopherol in the diet include vegetable oils (olive, sunflower, safflower oils), nuts, whole grains, and green leafy vegetables. The main function of alpha-tocopherol in humans appears to be that of an antioxidant. The term vitamin E describes a family of eight antioxidants:

four tocopherols, alpha-, beta-, gamma- and delta-, and four tocotrienols (also alpha-, beta-, gamma- and delta-).

Alpha-tocopherol

is the only form of vitamin E that is actively maintained in the human body.

Toxicity: High-dose vitamin E supplementation increases the risk of hemorrhage. Supplementation with 400 IU/day of vitamin E has been found to accelerate the progression of retinitis pigmentosa.

GOOD SOURCES (THE RDA FOR VITAMIN E WAS PREVIOUSLY AND 10 MG/DAY FOR MEN)

8 MG/DAY FOR WOMEN

Food Olive oil Soybean oil Corn oil Canola oil Safflower oil Almonds Hazelnuts Peanuts Spinach Carrots Avocado

Serving 1 tablespoon 1 tablespoon 1 tablespoon 1 tablespoon 1 tablespoon 1 ounce (30 g) 1 ounce (30 g) 1 ounce (30 g) cup, raw chopped cup, raw chopped 1 medium

Alpha-tocopherol (mg) 1.9 1.2 1.9 2.4 4.6 5.6 7.3 4.3 2.4 1.8 0.4 3.4

Sunflower oil 1 tablespoon

Vit A ,BETA_ CAROTENE

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VITAMIN A

Vitamin A is a generic term for a large number of related compounds: Retinol (an alcohol) and retinal (an aldehyde) are often referred to as preformed vitamin A. Retinol, retinal, retinoic acid, and related compounds are known as retinoids. Beta-carotene and other carotenoids that can be converted by the body into retinol are referred to as provitamin A. Hundreds of different carotenoids are synthesized by plants, but only about 10% of them are provitamin A. The main function of vitamin A in humans appears to be that of an antioxidant, beta-carotene has stronger antioxidant activity than retinol.

The

combination of vitamin A and iron seems to reduce anemia more effectively than either iron or vitamin A alone. Toxicity: Vitamin A toxicity is relatively rare. Symptoms include nausea, headache, fatigue, loss of appetite, dizziness, and dry skin. Consumption of excess vitamin A during pregnancy is known to cause birth defects.

GOOD SOURCES, (RDA = 1000 MCG, OR 5000 IU, FOR ADULT MALES AND 800 MCG, OR 4,000 IU, FOR ADULT FEMALES)

Food Cod liver oil Fortified breakfast cereals Egg Butter Whole milk Carrot (raw) Spinach Squash, butternut

Serving 1 teaspoon 1 serving 1 large 1 tablespoon 1 cup (8 fl ounces) 1/2 cup, chopped

Vitamin A, 1,350 mcg 150-230 mcg 91 mcg 97 mcg 68 mcg 385 mcg 472 mcg 572 mcg

Vitamin A, IU 4,500 IU 500-767 IU 303 IU 323 IU 227 IU 1,283 IU 1,572 IU 1,906 IU

1/2 cup, cooked1/2 cup, cooked

CAROTENOIDS

The main carotenoids: Alpha-Carotene, Beta-Carotene, BetaCryptoxanthin, Lycopene, Lutein and Zeaxanthin Carotenoids are yellow, orange, and red pigments synthesized by plants. Fruits and vegetables provide most of the carotenoids in the human diet. Orange and yellow vegetables like carrots and winter squash are rich sources of alpha- and beta-carotene. Spinach is also a rich source of beta-carotene, although the chlorophyll in spinach leaves hides the yellow-orange pigment. Alpha-carotene, beta-carotene, and beta-cryptoxanthin are provitamin A, meaning they can be converted by the body to retinol (vitamin A). Lutein, zeaxanthin, and lycopene have no vitamin A activity.

Beta-carotene is less easily absorbed than retinol and must be converted to active form. Two micrograms (mcg) of beta-carotene in oil provided as a supplement can be converted by the body to 1 mcg of retinol. However, 6 mcg of beta-carotene from foods are required to provide the body with 1 mcg of retinol. Retinol is found in foods from animals. Plants contain carotenoids.

Supplementation: Although diets rich in beta-carotene have generally been associated with reduced cardiovascular disease risk in observational studies, there is no evidence that beta-carotene supplementation reduces cardiovascular disease risk. Toxicity: Two randomized controlled trials found that high-dose beta-carotene supplements increased the risk of lung cancer in smokers.*

* Michaud DS, Feskanich D, Rimm EB, et al. Intake of specific carotenoids and risk of lung cancer in 2 prospective US cohorts. Am J Clin Nutr. 2000;72(4):990-997. Holick CN, Michaud DS, Stolzenberg-Solomon R, et al. Dietary carotenoids, serum beta-carotene, and retinol and risk of lung cancer in the alpha-tocopherol, beta-carotene cohort study. Am J Epidemiol. 2002;156(6):536-547.

THE VITAMIN A ACTIVITY OF BETA-CAROTENE IN FOODS IS 1/6 THAT OF RETINOL (PREFORMED VITAMIN A). THUS, IT WOULD TAKE 6 MCG OF BETA-CAROTENE FROM FOODS TO PROVIDE THE EQUIVALENT OF 1 MCG OF RETINOL.

Beta-Carotene Content of Selected Foods Food Serving Beta-Carotene (mcg)

Carrot juice Pumpkin, cannedSweet potato, baked Spinach, frozen, cooked Carrots, cooked

1 cup (8 fl oz) 1 cup1 medium 1 cup 1 cup

21,955 17,00316,803 13,750 12,998

Collards, frozen, cookedKale, frozen, cooked Pumpkin pie Dandelion greens, cooked

1 cup1 cup 1 piece 1 cup

11,59111,470 7,366 6,248

Winter squash, cookedCantaloupe, raw

1 cup1 cup

5,7263,232

MANGANESE

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Manganese Rich sources of manganese include whole grains, nuts, leafy vegetables, and teas. Foods high in phytic acid, such as beans, seeds, nuts, whole grains, and soy products, or foods high in oxalic acid, such as cabbage, spinach, and sweet potatoes, may slightly inhibit manganese absorption. Although teas are rich sources of manganese, the tannins present in tea may moderately reduce the absorption of manganese Manganese is a mineral element that is both nutritionally essential and potentially toxic.

Supplements:

Several forms of manganese are found in supplements, including manganese gluconate, manganese sulfate, manganese ascorbate, and amino acid chelates of manganese. Relatively high levels of manganese ascorbate may be found in a bone/joint health product containing chondroitin sulfate and glucosamine hydrochloride Toxicity:

A single case of manganese toxicity was reported in a person who took large amounts of mineral supplements for years, while another case was reported as a result of taking a Chinese herbal supplement.

GOOD SOURCES (RDA: 2-5 MG)FoodPineapple, raw Pineapple juice Pecans Almonds Peanuts Whole wheat bread Beans, cooked Spinach, cooked Tea (green)

Serving1/2 cup, diced 1/2 cup (4 ounces) 1 ounce 1 ounce 1 ounce 1 slice 1/2 cup 1/2 cup 1 cup (8 ounces)

Manganese (mg)1.28 1.24 1.12 0.74 0.59 0.88 0.65 0.48 0.84 0.41-1.58

Brown rice, cooked 1/2 cup

Tea (black)

1 cup (8 ounces)

0.18-0.77

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SELENIUM

SELENIUMThe richest food sources of selenium are organ meats and seafood, followed by muscle meats. In general, there is wide variation in the selenium content of plants and grains because plants do not appear to require selenium. Thus, the incorporation of selenium into plant proteins is dependent only on soil selenium content. Brazil nuts grown in areas of Brazil with selenium-rich soil may provide more than 100 mcg of selenium in one nut, while those grown in selenium-poor soil may provide 10 times less. Selenium is a trace element that is essential in small amounts, but can be toxic in larger amounts. Humans and animals require selenium for the function of a number of selenium-dependent enzymes, also known as selenoproteins (e.g. coating of sperm is made from selenoproteins).

Supplementation:

Selenium supplements are available in several forms. Sodium selenite and sodium selenate are inorganic forms of selenium. Selenate is almost completely absorbed, but a significant amount is excreted in the urine before it can be incorporated into proteins. Selenite is only about 50% absorbed, but is better retained than selenate, once absorbed. Selenomethionine, an organic form of selenium that occurs naturally in foods, is about 90% absorbed (enriched are yeast, which are also available as supplements). It is not clear whether one form of selenium is preferable to another.

Toxicity: Although selenium is required for health, high doses can be toxic.

GOOD SOURCES

(RDA: 70 MCG FOR MEN, 55 MCG FOR WOMEN)Food Brazil nuts (from selenium-rich soil) Shrimp Crab m...