Silvy Indriani wrote: > > Di milis ini ada yang ahli gizi ngga ??? Abis baca artikel tentang > vit-A, > saya jadi was-was juga nih... > Kalau ada yang bisa sharing, berapa sih batas maksimum pemberian / > kebutuhan > vit-A setiap harinya? Kalau Pepaya (yang udah masak tentunya), berapa > vit-A > yang terkandung dalam setiap gramnya? Mbak Silvy, saya bukan ahli gizi...:-) tadi saya dapat tentang vit. A, mungkin tidak menjawab semua, tapi lumayan lah. Tapi di situ malah disebutkan : asupan karoten yang tinggi tidak ada bahayanya (lihat : On the other hand, carotenoids as a source of vitamin A are not toxic, even with very high intakes.) Atau itu mungkin utk. orang dewasa...? Sumber : http://www.nutrition.org/nutinfo. -- O _/)(\_ |~ Salam, /~~\ o' |~ Rien. /_ _\ o' ^ ^ VITAMIN A The chemical name of vitamin A is retinol [3, 7-dimethyl-9-(2,6,6, trimethyl-1-cyclohexen-1-yl)-2,4,6,8-natetraen-1-ol]. Retinol is also found as retynyl (vitamin A) esters such as retinyl acetate and retinyl palmitate. The major storage site of vitamin A in the body is in the liver, primarily in the form of retinyl esters. The best known function of vitamin A is in vision, where it participates (as the metabolite retinal) in the visual cycle. However, in the chemical form retinoic acid, vitamin A plays an important role in control of gene expression. This function maintains differentiation of epithelial cells such as skin, lung, and intestinal tissue. Retinoic acid can be formed from retinol in the body, and shows strong biological activity in some functions but not in vision. Deficiencies: Night blindness is one of the early signs of vitamin A deficiency, because of the role of vitamin A in vision. Bacterial invasion and permanent scarring of the cornea of the eye (xerophthalmia) is a symptom of more profound deficiency, but this is due to a different mechanism, the lack of vitamin A for control of gene expression. Profound vitamin A deficiency also results in altered appearance and function of skin, lung, and intestinal tissues. Children are most at risk of vitamin A deficiency because they have not yet developed adequate vitamin A stores. It has been estimated that 0.5 million children in the world become blind each year, 70% of these due to vitamin A deficiency. Over half of these blind children die from malnutrition and associated illnesses. Diet recommendations: For adult human males, the Recommended Dietary Allowance (RDA) is 1000 ug Retinyl Equivalents (RE)/d; for adult females, 800 ug RE. Food sources: The RDA can be met by consuming dietary preformed vitamin A (retinyl esters) from liver, eggs and fortified foods, and provitamin A carotenoids such as beta-carotene, which are found in green leafy vegetables as well as in orange and red fruits and vegetables. Clinical uses: Synthetic retinoids such as 13-cis retinoic acid (trade name Accutane, also known as isotretinoin) are used to treat acne and skin wrinkling. Other derivatives, such as 4-hydroxyphenylretinamide (4-HPR, Fenretinide), are used to treat breast cancer. No one should consume vitamin A in quantities exceeding the RDA without a doctor's advice because of the dangers of toxicity. Toxicity: Acute intake of extremely high doses of vitamin A (>200 mg RE in adult humans) can cause nausea, vomiting, headache, and increased cerebrospinal pressure. Symptoms are generally transient. Chronic high intakes (e.g., >10x RDA) can cause hair loss, bone and muscle pain, headache, liver damage, and increased blood lipid concentrations. A particular danger in pregnant women is teratogenesis (birth defects). On the other hand, carotenoids as a source of vitamin A are not toxic, even with very high intakes. Recent research: Studies focusing on the role of retinoic acid isomers in the control of gene expression are explaining effects of vitamin A in hitherto unexpected metabolic pathways as well as in established functions. This role of vitamin A in gene expression undoubtedly explains the anti-cancer and anti-acne effects of vitamin A, for example. The presence of several nuclear binding proteins for retinoic acid as well as numerous controls on the metabolism and plasma transport of vitamin A provide an exquisite system for controlling the effects of vitamin A. >> www.jajak.com >> Pilih jawabannya dan rebut hadiahnya << >> Belanja Info & Keperluan Balita? Klik, http://www.balitanet.or.id >> Info balita, http://www.balita-anda.indoglobal.com Etika berinternet, email ke: [EMAIL PROTECTED] Stop berlangganan, e-mail ke: [EMAIL PROTECTED]
