维生素B_(12)和叶酸对辐射损伤的效应——三、氮代谢

按照维生素B_(12)与叶酸的不同供给量。将大鼠60只,分为3组。第1组供给不足,第2组接近正常,第3组较为充裕。饲养四周后,第1组氮摄入量,尿中总氮与脲氮低于第2组与第3组。口服50mgL—组氨酸的负荷试验可使各组尿氮增加量超过负荷量,并使第1组尿中氨基氮与氨氮增加。照射700拉德后氮摄入量减少系食欲不振所致。摄食量减少或辐射损伤可使维生素B_(12)与叶酸营养不足时尿中氨基氮与氨氮排出量增加。增高维生素B_(12)与叶酸供给量不仅可消除组氨酸负荷、摄食量减少或辐射损伤对氮代谢的影响,而且还可有所改善。     

维生素B_(12)与叶酸对辐射损伤的效应研究——四.大鼠的体重、白细胞数和死亡率

雄性大鼠分别全身一次照射800、850与875rad。分组在照射后不同时期注射或不注射抗菌素的条件下给与治疗剂量的维生素B_(12)和叶酸,其中有的组还给与大量的维生素C。主要结果为:(1)使用相当正常需要量200倍的维生素B_(12)和叶酸对于800rad照射后大鼠的死亡率、死亡动物活存日数和体重的影响与10倍量的维生素相比较并无明显差别,但是前者的第1～30天死亡率显著地较对照为低。(2)使用大量维生素C并未增加维生素B_(12)和叶酸对850rad所致急性辐射损伤的疗效。(3)850rad照射后使用抗菌素并在第7～25日使用大量的维生素B_(12)与叶酸对大鼠体重恢复的效应比单用抗菌素或维生素为佳。(4)在800,850与875rad照射后不同时期使用大量的维生素B_(12)和叶酸不能显著降低第1～40天的死亡率,但是在体重、白细胞数与死亡动物活存日数的方面,照射后不同时期使用大量维生素B_(12)和叶酸的效果是不同的,如800与850rad照射后第7～25日给与维生素B_(12)和叶酸的大鼠体重恢复程度较第1～25日给与维生素的大鼠为高;875rad照射后第1～25日给与维生素B_(12)和叶酸,其死亡动物的活存日数较第7～25日或第15～25日给与维生素的大鼠为少,而且第15～25日给与维生素B_(12)和叶酸的大鼠白细胞恢复程度较第1～25日或第7～25日给与维生素的     

不同剂量叶酸联合维生素B_(12)治疗老年高血压合并高同型半胱氨酸血症的临床疗效分析

目的探讨不同剂量叶酸联合维生素B_(12)治疗老年高血压合并高同型半胱氨酸(Hcy)血症(简称"H型高血压")对患者Hcy、叶酸和血压水平的影响。方法本研究选取2015年1-5月于重庆市九龙坡区西彭镇体检的140例H型高血压患者为研究对象。将患者分为3组:对照组(n=36)、叶酸A组(n=60)和叶酸B组(n=44)。对照组患者治疗方案:常规降压治疗;叶酸A组患者治疗方案:常规降压治疗+叶酸(0.4mg/次)+维生素B_(12)(500μg/次);叶酸B组患者治疗方案:常规降压治疗+叶酸(0.8mg/次)+维生素B_(12)(500μg/次)。结果治疗12周时,对照组、叶酸A组和叶酸B组患者Hcy水平分别为(26.73±8.99)μmol/L,(16.26±5.71)μmol/L,(16.59±6.12)μmol/L。3组患者Hcy水平比较,差异有统计学意义(P0.05)。叶酸A组、叶酸B组患者Hcy水平均低于治疗前,差异有统计学意义(P0.05)。同时,叶酸A组、叶酸B组患者Hcy水平均低于对照组,差异均有统计学意义(P 0.05)。治疗12周时,对照组、叶酸A组和叶酸B组患者叶酸水平分别为(3.88±1.37)μg/L,(10.72±3.39)μg/L,(12.78±4.73)μg/L。3组患者叶酸水平比较,差异有统计学意义(P0.05)。叶酸A组、叶酸B组患者叶酸水平均高于治疗前,差异有统计学意义(P0.05)。同时,叶酸A组、叶酸B组患者叶酸水平均高于对照组,差异均有统计学意义(P0.05)。叶酸B组患者叶酸水平高于叶酸A组,差异有统计学意义(P0.05)。治疗12周时,对照组、叶酸A组和叶酸B组患者收缩压(SBP)水平分别为(141.2±10.9)mmHg(1mmHg=0.133kPa),(133.8±10.6)mmHg,(129.3±7.8)mmHg。3组患者SBP水平比较,差异有统计学意义(P0.05)。叶酸A组和叶酸B组患者SBP水平均低于对照组,差异均有统计学意义(P0.05)。此外,治疗过程中,3组患者均未出现药物过敏、肝肾损伤等药品不良反应。结论适当补充叶酸和维生素B_(12)可显著降低Hcy水平,提高叶酸水平,改善血压水平,同时每天服用0.8mg叶酸在改善Hcy水平及SBP水平方面的效果优于每天服用0.4mg叶酸,值得在基层医疗机构中推广应用。     

母亲维生素B_(12)缺乏与婴儿继发性甲基丙二酸尿症

目的探讨母亲维生素B_(12)缺乏导致的婴儿继发性甲基丙二酸尿症(MMA)的临床特点,以及该病的诊断、治疗及转归。方法选择2014年11月12日,因"吐奶、贫血、疑为遗传性MMA",于北京大学第一医院被确诊为因母亲维生素B_(12)缺乏导致的继发性MMA、日龄为27d的男性双胎新生儿为研究对象。对双胎患儿及其母亲进行血常规、血清维生素B_(12)与叶酸检测,以及血清与尿液总同型半胱氨酸检测,尿液有机酸谱及血液氨基酸、肉碱谱检测,同时检测患儿及其父母的MMA相关基因突变情况。本研究与2例受试者监护人签署临床研究知情同意书,本研究遵循的程序通过北京大学第一医院医学伦理委员会的审核批准。结果 12例患儿生后4d于当地医院就诊时,尿液甲基丙二酸浓度分别为479.21 mmol/mol肌酐和65.90 mmol/mol肌酐(正常参考值为0.20~3.60mmol/mol肌酐);血液丙酰肉碱浓度分别为12.01μmol/L和10.55μmol/L(正常参考值为1.00~5.00μmol/L)。生后27d于北京大学第一医院就诊时发现,2例患儿均存在中度贫血,长子血清总同型半胱氨酸浓度轻度增高,为17.6μmol/L(正常参考值为0~15.0μmol/L),次子正常,为14.3μmol/L;血清维生素B_(12)浓度均降低,分别为121.0pmol/L与105.0pmol/L(正常参考值为133.0~675.0pmol/L);血清叶酸浓度均正常,分别为26.50nmol/L与18.60nmol/L(正常参考值为6.80nmol/L);尿液中均未检出甲基丙二酸,血液丙酰肉碱均增高,分别为9.26μmol/L与15.90μmol/L。给予维生素B_(12)肌内注射,口服亚叶酸钙及左卡尼汀治疗后,2例患儿尿液中均未检出甲基丙二酸,血液丙酰肉碱浓度恢复正常,智力、运动发育正常,贫血好转。22例患儿母亲于早孕期出现厌食、呕吐等早孕期妊娠反应,中孕期出现糖尿病、甲状腺功能减低、大细胞性贫血及同型半胱氨酸血症,曾口服补血中药及铁剂治疗,未曾补充维生素B_(12)治疗。产后2个月时,母亲血清维生素B_(12)浓度降低,血清总同型半胱氨酸浓度升高。经左卡尼汀、甲钴胺、叶酸等营养干预治疗2个月后,母亲血清维生素B_(12)及总同型半胱氨酸浓度均恢复正常。3对于与遗传性MMA相关基因的检测结果显示,2例患儿及其父母均未见MUT、MMAA、MMAB、MMACHC等基因突变。结论母亲孕期营养不良及健康状况不佳,可导致维生素B_(12)缺乏,继而引起婴儿继发性MMA。临床注意对继发性MMA患者与遗传性MMA的早期鉴别诊断,并于确诊后及时给予维生素B_(12)治疗,是救治继发性MMA,改善其预后的关键。对于妊娠期贫血的母亲,更应注意维生素B_(12)缺乏的可能性,以免导致婴儿罹患继发性MMA。     

维生素B_(12)与叶酸水平检测在二甲双胍治疗妊娠期糖尿病中的临床意义

目的探讨维生素B_(12)与叶酸水平检测在二甲双胍治疗妊娠期糖尿病中的临床意义。方法选取2017年2月-2018年2月深圳市龙华区人民医院收治的120例妊娠期糖尿病患者为研究组,另选取同期在该院产检的50例正常妊娠孕妇为对照组。入组后次日及二甲双胍治疗8周后采集空腹静脉血3 ml检测血清维生素B_(12)与叶酸水平。统计不良妊娠结局的发生率。结果研究组治疗前后血清维生素B_(12)与叶酸水平均显著低于对照组,差异均有统计学意义(均P0. 05)。研究组治疗后血清维生素B_(12)与叶酸水平均显著低于治疗前,差异均有统计学意义(均P0. 05)。B_(12)高水平组、B_(12)中水平组,叶酸高水平组、叶酸中水平组剖宫产、蛋白尿症、体质量增加、子痫前期发生率明显低于B_(12)低水平组和叶酸低水平组,差异均有统计学意义(均P0. 05)。叶酸低水平及B_(12)低水平与不良妊娠结局密切相关(P0. 05)。结论二甲双胍长期治疗可导致血清维生素B_(12)和叶酸水平下降,血清维生素B_(12)及叶酸水平越低产妇不良事件发生率越高,值得临床重视。     

叶酸在高同型半胱氨酸血症中的治疗作用

<正>同型半胱氨酸(Hcy)是人体摄入蛋白质中的蛋氨酸,在体内叶酸、维生素B_2、维生素B_6、维生素B_(12)、锌、锰、三甲基甘氨酸等营养素的催化下,经过一系列代谢转化为谷胱甘肽(体内重要的抗氧化酶之一)和S腺苷蛋氨酸(体内甲基的供体,有助于生化反应的正常进行)的中间产物。一旦体内缺乏这些营养素,尤其是缺乏叶酸、维生素B_6、B_(12),不能将高Hcy分解为无毒     

妊娠期妇女贫血状况调查分析

本文对259名正常初孕妇女的营养性贫血状况进行了调查分析。于不同孕期取血测定血清铁蛋白,红细胞原卟啉,血红蛋白,血清叶酸及血清维生素B_(12)含量。结果发现,孕妇体内铁缺乏、叶酸及维生素B_(12)不足随孕周增加日趋明显,至孕后期血清铁蛋白<12μg/L者达72.0％;红细胞原卟啉>500μg/L(全血)者占25.9％;血清叶酸<3μg/L者占32.1％;血清维生素B_(12)<150μg/L者为25.6％。259名孕妇中89名患有贫血,总患病率为34.4％。对89名贫血孕妇按缺铁性、叶酸缺乏,及铁和叶酸双缺进行分类,以缺铁性贫血为主,为61例(68.5％),叶酸缺乏贫血22例(28.1％),双缺者3例(3.4％)。不同孕期贫血的分类结果表明,缺铁性贫血随孕周增加所占比例逐渐下降;而叶酸缺乏贫血所占比例随孕周增加逐渐增高。     

脐血中同型半胱氨酸、叶酸、维生素B_(12)水平变化与宫内胎儿生长发育的相关性分析

目的探讨脐血中维生素B_(12)、叶酸、同型半胱氨酸(Hcy)水平变化与宫内胎儿生长发育的关联性。方法选取2017年1-12月于该院进行分娩的孕妇69例,分娩后依据胎龄和出生体质量百分位数间关系分为胎儿生长受限(FGR)组(24例)、适于胎龄儿(AGA)组(25例)及大于胎龄儿(LGA)组(20例)。分别抽取孕妇静脉血及分娩后脐静脉血4 ml,离心处理后检测血清维生素B_(12)、叶酸及Hcy水平,并统计对比3组新生儿生长参数[体质量指数(BMI)、胎盘质量、腹围、头围、身长、出生体质量],分析新生儿脐血血清维生素B_(12)、叶酸、Hcy水平与生长参数的相关性。结果新生儿生长参数:3组新生儿BMI、胎盘质量、腹围、头围、身长、出生体质量比较,差异均有统计学意义(均P0.05),且FGR组BMI、胎盘质量、腹围、头围、身长、出生体质量均小于AGA组与LGA组,差异均有统计学意义(均P0.05)。脐血血清维生素B_(12)、叶酸、Hcy水平:3组新生儿脐血血清维生素B_(12)、叶酸、Hcy水平比较,差异均有统计学意义(均P0.05),且FGR组血清Hcy水平高于AGA组与LGA组,血清维生素B_(12)、叶酸水平低于AGA组与LGA组(P0.05)。脐血血清指标水平与生长参数相关性:新生儿脐血血清维生素B_(12)、叶酸水平与新生儿生长参数无明显相关性(P0.05),血清Hcy水平与新生儿BMI、胎盘质量、腹围、头围、身长、出生体质量呈明显负相关(P0.05)。结论生长发育受限胎儿生长参数及脐血血清维生素B_(12)、叶酸、Hcy水平均与正常胎儿存在明显差异,妊娠期缺乏维生素B_(12)及叶酸可能会引发高同型半胱氨酸血症(HHcy),而胎儿宫内生长发育受限可能与血清Hcy水平增高具有一定相关性。     

检测血清同型半胱氨酸、叶酸及维生素B12在妊娠期高血压疾病的临床意义

目的:探讨检测血清同型半胱氨酸(Hcy)、叶酸和维生素B_(12)在妊娠期高血压疾病的临床价值。方法:回顾性收集2017年4月—2019年10月本院收治并确诊的143例妊娠期高血压疾病患者,按照疾病类型分为妊娠期高血压组50例、轻度先兆子痫组48例、重度先兆子痫组45例。另选健康孕妇40例为健康孕妇组和非妊娠健康女性35例为对照组。检测并比较所有组别的血清同型半胱氨酸、叶酸及维生素B_(12)水平,并采用受试者工作特征曲线(ROC)分析3个指标诊断妊娠期高血压疾病效能,logistic回归分析影响妊娠期高血压疾病孕妇妊娠结局的危险因素。结果:与对照组和健康孕妇组比较,妊娠期高血压、轻度子痫和重度子痫组的同型半胱氨酸依次增高,叶酸及维生素B_(12)依次降低(P0.05),同型半胱氨酸与叶酸及维生素B_(12)呈负相关关系(P0.05),叶酸与维生素B_(12)呈正相关关系(P0.05)。血清同型半胱氨酸、叶酸、维生素B_(12)均可用于诊断妊娠期高血压疾病,且联合诊断效能最高(P0.05)。与不良妊娠结局比较,妊娠结局良好组孕妇血清同型半胱氨酸增高,叶酸及维生素B_(12)降低(P0.05)。同型半胱氨酸、叶酸及维生素B_(12)是妊娠期高血压疾病孕妇不良妊娠结局的独立影响因素(P0.05)。结论:血清同型半胱氨酸、叶酸和维生素B_(12)联合诊断妊娠期高血压疾病效能高于单独指标检测,高水平的同型半胱氨酸、低水平的叶酸和维生素B_(12)预示着妊娠期高血压疾病孕妇不良妊娠结局。     

叶酸、维生素B_(12)及同型半胱氨酸与阿尔茨海默病的相关性研究

目的研究阿尔茨海默病(Alzheimer’s disease,AD)和外周血中叶酸、维生素B_(12)以及同型半胱氨酸(homocysteine,Hcy)之间的关系,为开展叶酸等膳食维生素防治AD提供依据。方法于2012年11月至2017年11月选取来自天津脑系科专科医院认知障碍门诊的231例AD患者作为研究对象,选取天津市塘沽区某社区医院认知正常的230例老年人作为正常参照人群。收集基本信息,采集空腹静脉血测定血中叶酸、维生素B_(12)以及Hcy浓度。采用SPSS 17.0软件进行t检验、χ~2检验和多因素非条件logistic回归分析。结果 AD患者血中的叶酸、维生素B_(12)和Hcy浓度中位数(P_(25)~P_(75))分别为11.00 nmol/L(P_(25)~P_(75):7.16~16.10 nmol/L)、292.17 pmol/L(P_(25)~P_(75):202.82~406.53 pmol/L)和15.56μmol/L(P_(25)~P_(75):11.10~20.64μmol/L),叶酸和维生素B_(12)浓度均低于正常人群[14.74 nmol/L(P_(25)~P_(75):10.19~20.67 nmol/L)和381.81 pmol/L(P_(25)~P_(75):275.04~519.60 pmol/L)],Hcy浓度高于正常人群[11.75μmol/L(P_(25)~P_(75):8.66~15.63μmol/L)],差异均有统计学意义(P0.01)。AD患者血清叶酸过低、维生素B_(12)过低及Hcy过高的比例(分别为73.16%、8.66%和54.11%)均高于正常人群(分别为54.78%、3.91%和28.70%),差异均有统计学意义(P0.05,P0.01)。多因素logistic回归分析结果显示,调整混杂因素后,正常叶酸水平(OR=0.586)和正常维生素B_(12)水平(OR=0.079)者患AD的风险较低;高Hcy者患AD风险较高(OR=2.405),均有统计学意义(P0.05,P0.01)。结论叶酸、维生素B_(12)过低以及Hcy过高均与AD发病相关,针对老年人开展食品叶酸、维生素B_(12)强化可以在一定程度上防治或延缓AD的发生发展。     

The administration of a multivitamin/mineral fortified dairy product improves folate status and reduces plasma homocysteine concentration in women of reproductive age

BACKGROUND AND OBJECTIVES: Folate deficiency during the periconceptional period is related to the occurrence and recurrence of neural tube defects. The aim of the study was to assess whether the administration of folic acid and other vitamins and minerals as a fortified dairy product (400 microg per day of folic acid) improves the folate status in women of reproductive age. DESIGN AND METHODS: Plasma and red blood cell folate, plasma vitamin E, B12, total plasma homocysteine, plasma lipid profile, and serum ferritin and transferrin levels were investigated in 31 healthy nonpregnant women receiving 500 mL/day of the fortified dairy product for eight weeks. RESULTS: The women showed a significant increase in plasma levels of folate and vitamin B12 concentrations after four and eight weeks of supplementation. Moreover, we observed an increase in red blood cell folate concentration during the period of the study. Simultaneously, total plasma homocysteine levels decreased significantly during the intervention period. CONCLUSIONS: The regular consumption of a folic acid and other vitamins (mainly vitamins B6 and B12) and minerals in a fortified dairy product improves folate status and reduces total plasma homocysteine concentration in healthy women of childbearing age.     

Effects of folate, vitamin B-12 and vitamin B-6 supplementation on methionine-induced hyperhomocysteinemia in rats

An excessive intake of dietary methionine increases plasma total homocysteine (tHcy, an independent risk factor for premature cardiovascular disease) by enhancing the synthesis of homocysteine. Information on the influence of excess dietary vitamins involved in homocysteine metabolism on the methionine-induced hyperhomocysteinemia is, however, limited. Thus, a six-week study was conducted to determine the influence of excess folic acid, vitamin B-12 and vitamin B-6 on the methionine-induced hyperhomocysteinemia in rats. Supplementation of the casein control diet with 10 and 20 g/kg L-Met increased plasma tHcy to 2.0 and 8.0 times control, respectively. The hyperhomocysteinemia caused by the addition of 10 g/kg L-Met to the control diet, was completely counteracted by extra folic acid or three vitamins combined (folic acid, 2 mg/kg; vitamin B-12, 25 μg/kg; plus vitamin B-6, 6 mg/kg) but the addition of extra vitamin B-12 or vitamin B-6 alone had no effect on plasma tHcy. Similarly, extra dietary folic acid or the three vitamins combined caused substantial reduction in plasma tHcy of rats fed the control diet supplemented with 20 g/kg L-Met but addition of vitamin B-12 or vitamin B-6 alone exacerbated plasma tHcy.     

Dietary intake of seven B vitamins based on a total diet study in Japan

The present study estimated the dietary intake of seven B vitamins using a total diet study (TDS) in Japan. The daily intake of vitamins estimated by TDS was calculated based on the mean contents of vitamins in 18 food groups, and the amount of food intake in the Nation Health and Nutrition Survey in Japan, 2006. The estimated daily intake of these vitamins for all ages was 22.8 mg NE/d for niacin, 7.4 μg/d for vitamin B(12), 146 μg/d for folic acid, 4.52 mg/d for pantothenic acid, 1.06 mg/d for riboflavin, and 1.44 mg/d for pyridoxine. The estimated daily intake of the vitamins of niacin, vitamin B(12) and pyridoxine exceeded the dietary reference values for adults aged 18-29 y. The estimated daily intake of these vitamins by TDS was higher than the daily intake reported in the National Health and Nutrition Survey in Japan, 2006. There was a strongly positive correlation between the intake levels estimated by TDS and those reported in the National Health and Nutrition Survey. This suggests that TDS is an effective dietary survey for estimating the dietary intake of water-soluble vitamins. Therefore, when being determined by TDS, the estimated daily intake of biotin was 51.0 μg/d for all ages.     

Assessment of vitamin and trace element supplementation in severely burned patients undergoing long-term parenteral and enteral nutrition

The efficacy of an oral supplement of vitamins and trace elements during a longterm artificial parenteral and enteral nutrition was investigated for 3 months in patients with extensive burns. Thirty severely burned patients (22 male, 8 female, age 41 +/- 18 years, range 23-59 years, 33 +/- 12% total body surface area burn, 22% +/- 8 full thickness burn surface area) were included. Every 10 days, from day 10 until day 90, we determined serum levels of: *vitamins B1, B12, A, E, *folic acid, *copper, zinc, iron, *transferrin, albumin, prealbumin, total proteins, *fibronectin, retinol binding protein (RBP), *calcium, *phosphorus, *triglycerides, *total cholesterol, *C reactive protein (CRP), *erythrocyte folic acid. The mean daily nutritional support was 60 Kcals and 0.4 g N per kg of body weight, 70% enterally and 30% parenterally administered, with enteral vitamin and trace element supplementation. On day 10, there was a decrease of the serum level of 19/20 parameters. For 8 parameters (vitamin A, total cholesterol, iron, transferrin, fibronectin, phosphorus, RBP, total proteins), the level was lower than usual. Between day 10 and day 20, a significant normalization of 6 of them was noted, the average levels of transferrin and iron remaining below normal values until day 50. There was a significant decrease in C-reactive protein levels, however above normal limits. No deficiency in vitamins or trace elements was found. Cyclic variations of serum levels occurred which may be more related to volemic, hydroelectrolytic, endocrine and inflammatory disorders than to nutritional problems.     

Folacin deficiency and requirement in the squirrel monkey (Saimiri sciuresus).

Acute folacin deficiency was studied in eight young squirrel monkeys (Saimiri sciureus). Half of the animals were fed a semipurified deficient diet (no added folic acid) and half were fed a control diet (0.84 mg of added folic acid per kilogram of dry diet). Monkeys fed the deficient diet lost weight and suffered from diarrhea and dehydration leading to the death of one of the animals after 6 weeks. Folacin deficiency also was studied in six older animals fed diets containing varying levels of added folic acid. Monkeys fed diets containing 0.14 or 0.27 mg of added folic acid per kilogram of dry diet slowly developed alopecia, a scaly dermatitis, and a mild macrocytic anemia. When these animals were fed the deficient diet, they lost weight rapidly, the alopecia and dermatitis worsened, excretion of formiminoglutamic acid in the urine increased, and a severe megaloblastic anemia with profound intramedullary hemolysis developed. Deficient monkeys had low plasma and red blood cell folacin values but maintained normal plasma vitamin B12 values. Repletion of the animals fed the deficient diet with injections of folic acid reversed both the hematological and physical deterioration. The folacin requirement for maintenance of body weight in these animals was 28 micrograms of total folacin per kilogram of body weight per day. More than 75 micrograms of total folacin per kilogram of body weight/day may be needed to assure growth and normal hematological parameters and bone marrow cytology.     

If high folic acid aggravates vitamin B12 deficiency what should be done about it?

The most common cause of vitamin B12 deficiency in older people is malabsorption of food-bound vitamin B12. Thus, it is suggested that the recommended daily allowance of 2.4 microg/d be met primarily with crystalline vitamin B12, which is believed to be well absorbed in individuals who have food-bound malabsorption. There is concern that high intakes of folic acid from fortified food and dietary supplements might mask the macrocytic anemia of vitamin B12 deficiency, thereby eliminating an important diagnostic sign. One recent study indicates that high serum folate levels during vitamin B12 deficiency exacerbate (rather than mask) anemia and worsen cognitive symptoms. Another study suggests that once vitamin B12 deficiency is established in subjects with food-bound malabsorption, 40 microg/d to 80 microg/d of oral crystalline vitamin B12 for 30 d does not reverse the biochemical signs of deficiency. Together, these studies provide further evidence that public health strategies are needed to improve vitamin B12 status in order to decrease the risk of deficiency and any potentially adverse interactions with folic acid.     

Effects of vitamin B12-deficiency on testes tissue in rats.

The state of vitamin B12-deficiency in rats was evaluated by determination of hepatic vitamin B12-dependent enzyme activities after the animals had fed on a vitamin B12-deficient soybean protein diet for 150 days. The effect of vitamin B12-deficiency on testicular tissue was also studied by morphological observations. Growth of vitamin B12-deficient rats was retarded and marked increase in urinary methylmalonic acid was observed. Vitamin B12 contents in the organs were depressed distinctly by the deficiency, especially in testes, vitamin B12 content decreased to 2.5 ng/g. Hepatic methionine synthase and methylmalonyl-CoA mutase activities showed striking depression to 5% of the control rats and extreme vitamin B12-deficiency was confirmed. Testes weight also showed marked decrease together with their relative weight per 100 g body weight. Morphological observations of testes of vitamin B12-deficient rats revealed atrophy of the seminiferous tubules and aplasia of sperms and spermatids. The above results proved that vitamin B12-deficiency affected rat testes, and suggested that the rat could be the animal model for elucidation of the mechanism of B12 action on testicular functions.     

Effect of fortified spread on homocysteine concentration in apparently healthy volunteers

OBJECTIVE: To determine the effect of folic acid, vitamin B(6) and B(12) fortified spreads on the blood concentrations of these vitamins and homocysteine. DESIGN AND SETTING: A 6-week randomized, double-blinded, placebo-controlled, parallel trial carried out in a clinical research center. SUBJECTS: One hundred and fifty healthy volunteers (50% males). INTERVENTIONS: For 6 weeks, the subjects consumed the test spreads (20 g/day): containing per 20 g (1) 200 microg folic acid, 2 microg vitamin B(12) and 1 mg vitamin B(6), or (2) 400 microg folic acid, 2 microg vitamin B(12) and 1 mg vitamin B(6) or (3) no B-vitamins (control spread). RESULTS: The B-vitamin status increased on using the test spreads, with the largest effect on the serum folate concentration: 48% in men and 58% in women on spread 1 and 92 and 146%, respectively, on spread 2 (P-values all <0.05). The plasma homocysteine decreased in the groups treated with the fortified spreads as compared to the control group. Average decreases were for males: 0.7+/-1.5 micromol/l (6.8%) on spread 1 and 1.7+/-1.7 micromol/l (17.6%) on spread 2 and for females: 1.4+/-1.2 micromol/l (14.2%) and 2.4+/-2.0 micromol/l (23.3%), respectively (P-values all <0.05). CONCLUSIONS: Consumption of a spread fortified with folic acid, vitamin B(6) and vitamin B(12) for 6 weeks significantly increases the blood concentrations of these vitamins and significantly decreases the plasma concentration of homocysteine. Fortified staple foods like spreads can contribute to the lowering of homocysteine concentrations.