年輕素食及非素食者的營養素攝取與體內鐵狀況之研究

食物含鐵質的型式有血基鐵質（heme iron）和非血基鐵質（nonheme iron）。Heme iron主要存在於動物性食品，而non-heme iron 主要是存在於植物性食品。Heme iron與non-heme iron的吸收是經由不同的機制進行，non-heme iron可經由若干因子提高或抑制其吸收；如維生素Ｃ和一些動物性蛋白質可促進吸收，而磷酸鈣、植酸、穀類或存在茶與咖啡中的多酚類會減少吸收。報告指出素食者由於嚴格限制動物性食品，其食物主要來源是以蔬菜、水果、穀類、豆科植物、堅果等富含多酚類、黃豆蛋白的食物為主，而易干擾non-heme iron吸收，故素食者可能具有鐵缺乏的危險性。在臺灣由於並未於食物中強化鐵質，且佛教素食人口不斷增加，雖然鐵攝取量可能接近或高於每日營養素建議量（RDNA），但由於素食飲食中的某些因子會抑制non-heme iron 的吸收而損及鐵的營養狀況，故對素食者的鐵建議攝取量可能需要再考量。本研究之目的主要是在評估年輕素食者（vegetarian）及非素食者（nonvegetarian）之營養素攝取及比較體內鐵的營養狀況。35位素食者（男：15位；女：20位）及32位非素食者（男：13位；女：19位）參與本研究。每位受測者需完成12天的飲食記綠、體位測量及血液生化值的評估。其中血液生化值的評估包括測量血漿的血紅素（hemoglobin）、血鐵質（plasma iron）、鐵蛋白（ferritin ）、總鐵結合能力（total iron binding capacity）、轉鐵蛋白飽和度transferrin saturation） 。研究結果顯示素食者有較低的脂肪、蛋白質、纖維質、維生素Ａ、鐵、膽固醇及鈉的攝取。而在醣類、維生素Ｂ1、維生素Ｃ及鈣的攝取方面，素食及非素食者則無明顯的不同。雖然素食者比非素食者有較低的鐵攝取量，但素食男生及女生的鐵攝取仍分別高達275%及142% 的飲食建議量。1位素食女生的血漿鐵（32□g/dL）是處於貧血（anemia）的狀況；1位素食及1位非素食女生的鐵蛋白濃度小於10ng/mL；5位素食及1位非素食女生的總鐵結合能力大於 410□g/dL；而3位素食男生、6位素食及1位非素食女生的轉運鐵蛋白飽和度小於40□g/dL;總共有6位素食及1位非素食女生因有2種以上的鐵缺乏指標而被評估為貧血。雖然素食者有足夠的鐵攝取量，但其鐵在體內的生化利用率可能由於某些因子的影響（例如：飲食中的一些抑制鐵吸收因子或月經週期）而有所限制，特別是對素食女孩子而言。

Heme and non-heme iron are two types of iron in food. Heme iron exists mainly in animal products;while non-heme iron is in the plant foods. The absorption of heme and non-heme iron proceeds different mechanism pathway .The absorption of non-heme iron can be enhanced or inhibited by several factors. Vitamin C and animal protein can increase iron absorption; however, phytates, calcium phosphate, grains or polyphenols containing in tea and coffee have negative effects. Several studies indicated the vegetarians obtained most of their iron from vegetables, fruits, grains cereals, legumes and nuts, which supplied exclusively non-heme iron. These non-heme sources have lower bioavailability than heme iron in animal products which are an important iron source of nonvegetarians. Thus, the vegetarians may be at greater risk of iron deficiency. Food is not routinely fortified with iron in Taiwan, and the population of Chinese Buddhist vegetarians are continuately rising. Although Taiwanese vegetarians had an iron intake closer to or higher than the Taiwan RDNA, showed impaired iron status. The bicanailability of iron is probably the major determinant of the iron adequacy of a vegetarian diet. Therefore, particular attention must be given to vegetarians on their recommended iron intake.The purpose of this study was to investigate the nutrient intakes and examine the iron status of young vegetarian adults compared to nonvegetarians. Thirty -five vegetarians (15males, 20females) and 32 nonvegetarians (13males, 19females ) were participated in this study Each subject completed a 12-d diet record. Hemoglobin, plasma iron, ferritin, total iron binding capacity, and transferrin saturation were measured.Vegetarians had lower dietary fat, protein fiber, vitamin A, iron, cholesterol and sodium intakes than nonvegetarians. No significant differences were found in carbohydrate,thiamin, vitamin C, and calcium intakes between the 2 major groups. Although vegetarians had lower iron intake than nonvegetarians, their iron intakes was 275% and 142% above the RDNA for vegetarian males and females (p<0.05) , respectively. One vegetarian female was in an anemia stage with a plasma iron level of 32□g/dL;2 female subjects(1 vegetarian, 1 nonvegetarian) had anemic ferritin levels (<10ng/mL) ;5 vegetarian females and 1 nonvegetarian female subject had anemic total iron binding capacity levels>410□g/dL; and 3 vegetarian males,6 vegetarian females and 1nonvegetarian female showed anemia with transferrin saturation <15%. Six vegetarian females and1nonvegetarian female were anemic because they had two or more abnormal biochemical indices of iron status. Although vegetarian subjects had sufficient iron intake, the bioavailability of iron seemed limited to maintaining iron balance, especially in women.