Vitamins: Their Functions, Sources and deficiency

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Vitamins are organic (carbon-containing) substances required in small amounts to regulate various processes within living cells. Humans need 13 vitamins; of these, four are fat-soluble (A, D, E, and K), and nine are watersoluble (C and the B vitamins; thiamin, riboflavin, niacin, vitamin B-6, folate, vitamin B-12, biotin, and pantothenic acid). Solubility affects how a vitamin is absorbed, transported, and stored in the body. The water-soluble vitamins are absorbed directly into the bloodstream, where they travel freely. Excess amounts of water-soluble vitamins are generally removed by the kidneys and excreted in urine. Fat soluble vitamins require a more complex absorptive process. They are usually carried in the blood by special proteins and are stored in the liver and in fat tissues rather than excreted.

Functions of Vitamins

Many vitamins help chemical reactions take place. They provide no energy to the body directly but help release the energy stored in carbohydrates, proteins, and fats. Other vitamins are critical in the production of red blood cells and the maintenance of the nervous, skeletal, and immune systems. Some vitamins act as antioxidants, which help preserve the health of cells. Key vitamin antioxidants include vitamin E, vitamin C, and the vitamin A precursor beta-carotene.

Sources of Vitamins

The human body does not manufacture most of the vitamins it requires and must obtain them from foods. Vitamins are abundant in fruits, vegetables, and grains. In addition, many processed foods, such as flour and breakfast cereals, contain added vitamins. A few vitamins are made in certain parts of the body: The skin makes vitamin D when it is exposed to sunlight, and intestinal bacteria make vitamin K. Nonetheless, you still need to get vitamin D and vitamin K from foods.

Vitamin Deficiencies and Excesses

If your diet lacks a particular vitamin, characteristic symptoms of deficiency can develop. For example, vitamin A deficiency can cause blindness, and anemia can develop in people whose diets lack vitamin B-12. Vitamin deficiency diseases are most often seen in developing countries; they are relatively rare in the United States because vitamins are readily available from our food supply. However, many Americans consume lower than-recommended amounts of several vitamins. Nutrient intake that is consistently below recommended levels can have adverse effects on health even if it is not low enough to cause a deficiency disease. For example, low intake of folate increases a woman’s chance of giving birth to a baby with a neural tube defect (a congenital malformation of the central nervous system). Low intake of folate and vitamins B-6 and B-12 has been linked to increased heart disease risk. A great deal of recent research has focused on vitamin D, suggesting that vitamin D supplementation can reduce the risk of cardiovascular disease and linking low vitamin D levels to an increased risk of several cancers. As important as vitamins are, however, many Americans consume less-than-recommended amounts of some vitamins.

Extra vitamins in the diet can be harmful, especially when taken as supplements. Mega doses of fat-soluble vitamins are particularly dangerous because the excess is stored in the body rather than excreted, increasing the risk of toxicity. Even when supplements are not taken in excess, relying on them for an adequate intake of vitamins can be problematic. There are many substances in foods other than vitamins and minerals that have important health effects. Later, it discusses specific recommendations for vitamin intake and when a supplement is advisable. For now, keep in mind that it’s best to get most of your vitamins from foods rather than supplements.

The vitamins and minerals in foods can be easily lost or destroyed during storage or cooking. To retain their value, eat or process vegetables immediately after buying them. If you can’t do this, store them in a cool place, covered to retain moisture—either in the refrigerator (for a few days) or in the freezer (for a longer term). To reduce nutrient losses during food preparation, minimize the amount of water used and the total cooking time. Develop a taste for a crunchier texture in cooked vegetables. Baking, steaming, broiling, grilling, and microwaving are all good methods of preparing vegetables.

Vitamins: Their Functions, Sources and deficiency

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Chinese Dishes that are steamed, poached (jum), boiled (chu), roasted (kow), barbeceued (shu) or lightly stir fried Hoisin sauce, oyster sauce, wine sauce, plum  sauce, velvet sauce or hot mustard

Fresh fish seafood, skinless chicken, tofu

Mixed vegetables, Chinese greens

Steamed rice, steamed spring rolls, soft noodles

Fried wontons or egg rolls

Crab rangoon

Crispy (Peking) duck or chicken

Sweet and sour dishes made with breaded and deep fried meat, poultry, or fish

Fried or crispy noodles

Fried rice

Greek Dishes that are stewed, broiled, or grilled, including shish

kabobs (souvlaki)

Dolmas (grape leaves) stuffed with rice

Tzatziki (yogurt, cucumbers, and garlic)

Tabouli (bulgur-based salad)

Pita bread, especially whole wheat

Moussaka, saganaki (fried cheese)

Vegetable pies such as spanakopita and tyropita

Baba ghanoush (eggplant and olive oil)

Deep-fried falafel (patties)

Gyros stuffed with ground meat

Baklava

Indian Dishes prepared masala (curry), tandoori (roasted in a clay oven), or tikke (pan roasted); kabobs

Raita (yogurt and cucumber salad) and other yogurt-based dishes and sauces

Dal (lentils), pullao or pilau (basmati rice)

Chapati (baked bread)

Ghee (clarifed butter)

Korma (meat in cream sauce)

Samosas, pakoras (fried dishes)

Molee and other coconut milk-based dishes

Poori, bhatura, or paratha (fried breads)

Italian Pasta primavera or pasta, polenta, risotto, or gnocchi with marinara, red or white wine, white or red clam, or light mushroom sauce

Dishes that are grilled or prepared cacciatore (tomato-based sauce), marsala (broth and wine sauce), or piccata (lemon sauce)

Cioppino (seafood stew)

Vegetable soup, minestrone or fagioli (beans)

Antipasto (cheese, smoked meats)

Dishes that are prepared alfredo, frito (fried), crema (creamed), alla panna (with cream), or carbonara

Veal scaloppini

Chicken, veal, or eggplant parmigiana

Italian sausage, salami, and prosciutto

Buttered garlic bread

Cannoli

Japanese Dishes prepared nabemono (boiled), shabu-shabu (in boiling

broth), mushimono (steamed), nimono (simmered), yaki (broiled), or yakimono (grilled)

Sushi or domburi (mixed rice dish)

Steamed rice or soba (buckwheat), udon (wheat), or rice noodles

Tempura (battered and fried)

Agemono (deep fried)

Katsu (fried pork cutlet)

Sukiyaki

Fried tofu

Mexican Soft corn or wheat tortillas

Burritos, fajitas, enchiladas, soft tacos, and tamales filled

with beans, vegetables, or lean meats

Refried beans, nonfat or low-fat; rice and beans

Ceviche (fish marinated in lime juice)

Salsa, enchilada sauce, and picante sauce

Gazpacho, menudo, or black bean soup

Fruit or flan for dessert

Crispy, fried tortillas

Dishes that are fried, such as chile rellenos, chimichangas, flautas, and tostadas

Nachos and cheese, chili con queso, and other dishes made with cheese or cheese sauce

Guacamole, sour cream, and extra cheese

Refried beans made with lard

Fried ice cream

Thai Dishes that are barbecued, sautéed, broiled, boiled, steamed, braised, or marinated

Sáte (skewered and grilled meats)

Fish sauce, basil sauce, chili or hot sauces

Bean thread noodles, Thai salad

Coconut milk soup

Peanut sauce or dishes topped with nuts

Mee-krob (crispy noodles)

Red, green, and yellow curries, which typically contain coconut milk

 

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