富碳水化合物食品血糖生成指数的体外回归模型

目的通过探讨富碳水化合物(CHO)食品营养组成及体外消化特性与体内血糖指数的关系,尝试建立体外回归模型。方法选择30种富CHO食品分析蛋白质、脂肪及CHO组成;在AOAC抗性淀粉测定的实验条件下,修改建立体外消化实验方法,测定淀粉在20min、120min、240min和16h的消化量以及不能消化的抗性淀粉含量;并采用国际标准方法完成食物血糖生成指数(GI)评估;通过逐步回归方法探讨各成分组成与GI关系。结果30种食品GI值分布为26～113,GI值高低与20min和120min内消化的淀粉量(S20、S120)呈明显正相关(P<0.05),而与抗性淀粉(RS)呈明显负相关(P<0.01)。将S120与葡萄糖含量相加定义为易利用糖(EAG),建立GI体外测试的回归方程为GI=39.65+1.008EAG-1.072RS。结论食品碳水化合物组成和体外消化实验有助于解释富碳水化合物食物体内血糖应答反应及预测GI值。     

抗性淀粉对大鼠锌营养状况的影响

目的 :　研究抗性淀粉 ( RS)对大鼠锌营养状况的影响。方法 :　 ( 1 )正常大鼠锌代谢 :3组 Wistar大鼠分别用基础饲料 (对照组 )、含有 1 3%或 2 6% RS的饲料喂养 1 8d,收集尿样、粪样 ,及血样 ,测定锌含量 ,计算锌表观吸收率。 ( 2 )高糖 ( 5 0 % )饮食大鼠锌营养状况 :3组 Wistar大鼠分别用基础饲料、高糖淀粉饲料 ( S- DS)及高糖抗性淀粉饲料 ( S- RS,含 1 4% RS)喂养 1 2 w。收集尿样 ,血样、肝脏、胰脏、肾脏等样品 ,测定锌含量。结果 :　 ( 1 )正常大鼠锌表观吸收率分别为 :对照组 5 6.5 9% ,1 3% RS组 5 0 .1 1 %及 2 6% RS组 5 4 .40 %。 ( 2 )高糖饲料使 S- DS组大鼠餐后血糖和糖化血红蛋白升高 ,空腹胰岛素水平降低 ;血锌和胰脏锌显著低于对照组 ( P<0 .0 5 )。 S- RS组血糖状态正常 ,尿锌排出低于 S- DS组 ,红细胞锌高于 S- DS组 ,且肾锌增高 ( P<0 .0 5 )。结论 :　 RS不影响正常大鼠锌表观吸收率 ,却可通过调节血糖维持高糖饮食大鼠锌营养状况。     

抗性淀粉的代谢及对血糖的调节作用

目的 :　利用天然稳定同位素技术 ,探讨抗性淀粉吸收代谢的特点及对血糖调节的影响。方法 :　 7名健康志愿者分别试食 40 g天然富1 3C的葡萄糖、可消化淀粉 ( DS)和抗性淀粉( RS) ,测定餐后 0～ 2 40 min血糖 ,1 3C-血糖、血胰岛素水平和餐后 3 0 h呼气中1 3CO2 转化率及累积转化率。结果 :　食用 RS后 ,血糖和 1 3C-血糖水平明显低于食用葡萄糖和 DS;以葡萄糖餐后 1 2 0min的血糖生成指数 ( GI)和 1 3C-GI为 1 0 0 % ,RS的 GI值和 1 3C-GI值分别为 2 3 .5 8%和 5 5 .5 6% ;RS餐后呼气中1 3CO2 转化率的峰值明显低于葡萄糖和 DS( P<0 .0 5 ) ,但是 3 0 h累积转化率可达94.0 % ,与葡萄糖 ( 96.9% )和 DS( 1 0 2 .0 % )接近 ( P>0 .0 5 ) ;RS使餐后胰岛素升高幅度、胰岛素 /葡萄糖比值明显低于葡萄糖和 DS( P<0 .0 5 )。结论 :　抗性淀粉吸收缓慢但较完全 ,与葡萄糖和DS相比 ,具有维持餐后血糖稳态 ,提高机体胰岛素敏感性的作用     

谷物淀粉的慢消化特性与餐后血糖应答

目的分析不同谷物淀粉的慢消化性能与餐后血糖应答。方法采用Englyst方法对淀粉进行体外营养学分类,同时10名空腹健康志愿者分别试食含碳水化合物50g的葡萄糖粉与不同淀粉,测餐后120min血浆中血糖水平并计算出血糖生成指数(GI)与增加血糖生成指数(EGI)值。结果在碳水化合物分类中谷物淀粉中主要含有SDS,约为50%。以葡萄糖GI为100%,不同谷物淀粉的GI均大于90%,属于高GI食品,但是其EGI均为正数。结论不同谷物的淀粉都有良好的慢消化性能与相似的餐后血糖应答,它们吸收缓慢而持久,可维持餐后血糖稳态,对健康有利。     

连续血糖监测评价水煮或油煎饺子对糖尿病患者餐后血糖的影响

目的　采用连续血糖监测（CGM)方法评价水煮或油煎饺子对糖尿病患者餐后血糖的影响。方法　纳入10例2011年2至5月在北京协和医院内分泌科住院的2型糖尿病患者,佩戴胰岛素泵平稳控制其空腹与餐前血糖,试验期内第2和第4天午餐分别给予油煎或水煮饺子,试验饮食的营养含量相同。利用抗性淀粉体外消化方法测定试餐的可消化淀粉中快消化淀粉与持续消化淀粉含量,以及抗性淀粉含量。试验阶段佩戴CGM记录全天血糖变化,观察试验餐对餐后各时点(0、15、30、60、90、120、150、180、240 min)血糖、峰值血糖、分时段（0~60 min、63~120 min、123~180 min、183~240 min）血糖曲线下面积(AUC)的影响。结果　体外消化法测定油煎方法的快消化淀粉含量低于水煮方法（30.8%和77.0%）;油煎方法持续消化淀粉含量高于水煮方法（67.3%和20.7%）,两种试餐中抗性淀粉含量均不高 (1.9%和2.3%)。而油煎方法餐后血糖峰值出现时间早于水煮方法 ［（93±53）min比（156±61）min, P=0.02］。各时点血糖均值差异无统计学意义,各时段血糖AUC差异无统计学意义（均P＞0.05）。结论　水煮方法淀粉消化速度快,但餐后血糖峰值却晚于油煎方法,油煎饺子对2型糖尿病患者升高血糖的作用比水煮方法更早。     

抗性淀粉对断奶仔猪血糖和激素水平的影响

目的:探讨抗性淀粉(RS)对动物血糖和激素水平的影响。方法:选择(28±2)d断奶的杜×长×大三元杂交仔猪(平均体重8.8kg±1.0kg)12头,随机分为4组,分别饲喂以玉米、早籼稻糙米、糯米和RS为淀粉来源配制的4种等能、等氮、等淀粉试验饲料,饲养25d后,测定不同饲料淀粉来源对断奶仔猪血糖、胰岛素、GH、T3和T4水平的影响。结果:与采食其他饲料组相比,RS组几乎所有时间点的胰岛素和血糖浓度均降低,并且维持在稳定水平,GH、T3和T4的浓度也降低;糯米饲料组采食后1h血糖和胰岛素浓度显著升高(P<0.05)。结论:RS可降低血液中血糖和胰岛素的浓度,减缓体内GH、T3和T4的分泌。     

抗性淀粉、脂肪和蛋白质对淀粉体外消化速度的影响

目的探讨抗性淀粉、脂肪和蛋白质对淀粉体外消化速度的影响。方法以抗性淀粉、脂肪和蛋白质为因素进行三因素三水平正交实验,参照Englyst建立的体外消化试验方法,测定240min内的10个时间点的还原糖释放率,绘制还原糖曲线图,比较各水平组合下还原糖释放率及释放指数的差异。结果正交实验各组合的还原糖水解速率有差异,方差分析显示随着抗性淀粉含量、脂肪含量的增加,各时间段的还原糖释放率显著下降(P<0.05),但蛋白质的影响不具有显著性。对2h还原糖释放指数影响最大的因素是脂肪,其次是抗性淀粉和蛋白质,使还原糖释放指数最高的组合是抗性淀粉占比例为0,脂肪占比例为0,蛋白质所占比例为20%。结论淀粉中添加抗性淀粉和脂肪可以显著降低淀粉的体外消化速度,蛋白质无此作用。     

有机锌在肉仔鸡小肠不同部位中的吸收特点

目的研究肉仔鸡小肠各段对无机锌和有机锌吸收特点的差异。方法采用原位结扎灌注肠段法,包括2个试验:试验1:以硫酸锌为锌源,根据锌的吸收率与肠段灌注时间(5个时间点)的曲线关系确定最佳灌注时间,试验2:在此灌注时间下比较不同形态锌(8种锌源)在肉仔鸡小肠中的吸收差异。结果(1)锌的吸收率在30min时即可达最大吸收的85%～90%;(2)不同锌源锌在回肠中的吸收均显著高于十二指肠和空肠;(3)十二指肠和空肠中锌的吸收率受到添加锌源的显著影响,其中,弱、中和强络合强度有机锌组及蛋氨酸锌组、赖氨酸锌组锌的吸收率明显高于硫酸锌、硫酸锌和蛋氨酸混合物组、硫酸锌和甘氨酸锌混合物组。结论30min为肠段的最适灌注时间;回肠是肉仔鸡小肠吸收锌的主要部位;有机锌吸收要好于无机锌。     

补钙对12～17岁青少年锌、铁吸收率的影响

目的通过代谢平衡实验探讨补钙对中国青春期少年锌、铁吸收率的影响。方法从320名参加1年补钙实验的4组12~17岁少年中,每组随机抽取男、女生各10人,共80人。采用代谢平衡的方法,收集研究对象10天内摄入的食品、排出的粪便和尿液样品,用电感耦合等离子体发射光谱法测定样品中的钙、铁、锌含量。结果不同补钙组之间钙摄入量有差异,但铁、锌摄入量差异无显著性。不同补钙组之间钙、铁、锌的表观吸收率差异无显著性。男生钙、铁、锌的表观吸收率平均为69.4%、12.5%和29.9%,女生的分别为46.4%、20.9%和35.3%。铁的表观吸收率与青春发育水平有关。男生钙摄入量为600~800mg/d时,钙、铁、锌的表观吸收率均处于相对较高水平(75.3%、23.2%和36.4%)。结论钙摄入量低于1400mg/d时,不影响12~17岁少年锌、铁的吸收率。当男生钙摄入量为600~800mg/d时,更有助于钙、铁、锌的吸收。     

火焰原子吸收分光光度法测定尿锰的方法研究

目的:探索尿锰检测的新方法。方法:采用原子吸收火焰法直接测定,同时在样品消化时采用了浓氨水沉淀,又用250 m l凯氏氮瓶消化法。结果:回收率:90.0%~99.5%;相对标准偏差为2.4%;方法检出限为0.0190 mg/L。结论:该法样品消化简单,回收率高,适宜大批量样品检测。     

Replacement of digestible wheat starch by resistant cornstarch alters splanchnic metabolism in rats.

Splanchnic metabolism was investigated in rats fed either a diet containing highly digestible wheat starch (DS diet) or amylase-resistant cornstarch (RS diet). In rats fed the latter diet, there was a considerable enlargement of the cecum and an increase in the production and absorption of volatile fatty acids (VFA), chiefly acetic and propionic acids. As a result, the major substrates absorbed from the digestive tract were glucose in rats fed the DS diet and both glucose and VFA in rats fed the RS diet. The liver removed about one-third of the absorbed glucose in rats fed the DS diet, whereas there was a slight release of glucose by the liver in rats fed the RS diet. Plasma insulin was higher in rats fed the DS diet, and there were smaller fluctuations of plasma insulin and liver glycogen between the fed and postabsorptive periods in rats adapted to the RS diet. In these animals, propionate was the major VFA taken up by the liver and approximately 50% of absorbed acetate was also removed by the liver. During the postabsorptive period, there was still a substantial contribution of VFA, especially propionate, to liver metabolism. A depressive effect of the RS diet on plasma triglycerides, cholesterol and free fatty acids was observed only during the postabsorptive period. Replacement of a large part of absorbed glucose by VFA apparently allows time for absorption of energy fuels to be extended and dampens the fluctuations of glucose metabolism during the light: dark cycle.     

The resistant starch level of heat moisture-treated high amylose cornstarch is much lower when measured in the human terminal ileum than when estimated in vitro

According to the definition of resistant starch (RS), the true value of foodstuff-derived RS can be assessed only from that found in the contents of the terminal ileum. To date, a few methods exist for in vivo measurement of RS in the terminal ileum, but their accuracy is questionable. The aim of this study was to quantify the level of RS in the terminal ileum to determine its true value as dietary fiber (DF). Volunteers (n = 7 men) were given a test meal containing 10 g of heat moisture-treated high amylose cornstarch (HMT-HAS) containing 8.8 g of RS as measured by Englyst's method. A double-lumen tube was positioned in the terminal ileum using the endoscopic retrograde bowel insertion method (ERBI). Intestinal contents were aspirated, and the amount of RS was measured as the glucose concentration (Englyst's method), and compared with the values for RS administrated orally using the same method. The mean amount of HMT-HAS-derived RS collected in the terminal ileum was 3.37 +/- 0.95 g (mean +/- SD), which was 34.5 +/- 9.7% of the in vitro RS value. Furthermore, there were large individual differences in recoveries, ranging from 22.2 to 47.5%. The measured amount of HMT-HAS-derived RS was much smaller in our in vivo study than that measured in vitro, suggesting that in vitro measurement may inaccurately estimate the RS and DF levels of foodstuffs. The problem is further compounded by the large individual in vivo variations in RS values from subjects consuming identical diets.     

Influence of sterilization, drying and oat bran enrichment of pasta on glucose and insulin responses in healthy subjects and on the rate and extent of in vitro starch digestion.

The effects of sterilization and oat bran enrichment of pasta on the glucose and insulin responses in healthy subjects were evaluated. Cooked and canned spaghetti and cooked fettucini without and with enrichment with oat bran (28%) were compared. Further, the effects of various low- and high-temperature drying conditions for spaghetti, cooking time and sterilization on the starch digestion rate and content of enzyme-resistant starch (RS) in vitro were also studied. Various cooking quality data were also determined to allow interpretation of results. The incremental glucose area (0-120 min) produced by canned spaghetti was twice the area of that produced by cooked spaghetti (69.03 vs 35.45 mmol/l x min, P less than 0.01). The incremental insulin area (0-120 min) was also significantly higher with canned spaghetti (17,500 vs 12,600 pmol/l x min, P less than 0.05). The rapid digestion was caused by excessive swelling of starch during sterilization that promoted a very soft texture of the spaghetti. Enrichment of fettucini with oat bran reduced slightly the incremental insulin area (15,600 vs 20,100 pmol/l x min, P less than 0.05, for 0-120 min), but did not significantly reduce the glucose area. Drying conditions and cooking times could be varied within broad limits without affecting the rate of starch digestion in vitro of cooked spaghetti. In sterilized spaghetti the content of resistant starch was higher than that found in cooked 'al dente' spaghetti (2.2-3.4 vs 0.5 mg/100 mg total starch). In conclusion, sterilization influences the nutritional properties of starch in pasta by substantially increasing the glucose and insulin responses and by formation of resistant starch. The effect of oatbran environment is restricted mainly to a slight decrease in the insulin response.     

Evaluation of gastric processing and duodenal digestion of starch in six cereal meals on the associated glycaemic response using an adult fasted dynamic gastric model

Purpose

To identify the key parameters involved in cereal starch digestion and associated glycaemic response by the utilisation of a dynamic gastro-duodenal digestion model.

Methods

Potential plasma glucose loading curves for each meal were calculated and fitted to an exponential function. The area under the curve (AUC) from 0 to 120 min and total digestible starch was used to calculate an in vitro glycaemic index (GI) value normalised against white bread. Microscopy was additionally used to examine cereal samples collected in vitro at different stages of gastric and duodenal digestion.

Results

Where in vivo GI data were available (4 out of 6 cereal meals) no significant difference was observed between these values and the corresponding calculated in vitro GI value.

Conclusion

It is possible to simulate an in vivo glycaemic response for cereals when the gastric emptying rate (duodenal loading) and kinetics of digestible starch hydrolysis in the duodenum are known.     

Amino acid absorption along the intestinal tract of chicks fed heated and raw soybean meal

Net absorption of individual amino acids along the intestinal tract was determined in chicks fed heated soybean meal (HS) and raw soybean meal (RS) using 91Y as a reference substance. In the duodenum of chicks fed either diet, the absorption of the amino acids varied. In chicks fed the RS diet, the differences were greater than in chicks fed the HS diet, and most of the values were negative. Methionine was the most rapidly absorbed amino acid. No cystine was found in the upper parts of the intestinal tract of chicks fed either diet. A linear relationship was obtained between the amino acid absorption values in the duodenum of chicks fed either diet. The differences recorded seem to be due to nitrogen secretion, which is enhanced in RS-fed chicks. The differences between individual amino acid absorption decreased gradually in the other segments and attained in the lower ileum an average cumulative value of 90% and 70% in chicks fed on HS and RS respectively. The 20% difference was probably a result of the inhibited digestion in the intestine (duodenum excluded) of chicks fed RS. The results indicate that the absorption process can proceed even when the digestion is inhibited.     

Rapid rehydration and moderate plasma glucose elevation by fluid containing enzymatically synthesized glycogen

Enzymatically synthesized glycogen (ESG) has high solubility and its solution has low osmotic pressure. Therefore ESG solution could be rapidly absorbed and could be adequate for water rehydration and carbohydrate supplementation during exercise. The object of this study was to evaluate the gastric emptying time and plasma glucose elevation after an administration of ESG solution in comparison with another carbohydrate solution by using a laboratory animal. Male BALB/c mice were administered 10% w/v solution of glucose, maltodextrin, starch, naturally synthesized glycogen (NSG) and ESG at a dose of 20 μL/g body weight for the measurement of gastric emptying rate (Experiment 1) and 10 μL/g body weight for the measurement of plasma glucose elevation (Experiment 2). The osmolarity of gastric content was lower in the ESG and maltodextrin group than the other carbohydrate group. Weight of gastric fluid was significantly lower in the ESG and water group than the glucose group (p<0.01). Plasma glucose level was significantly lower in the ESG group than the glucose group from 0 to 60 min after administration (p<0.01), whereas plasma glucose level was same from 60 to 120 min for the ESG and glucose group (p=0.948). In Experiment 3, BALB/c mice ran on a treadmill for 2 h and were administered 8% of ESG or glucose solution (1.75, 3.5 or 7.0 μL/g body weight) every 20 min during running. There was no difference in post-exercise muscle glycogen level. These data suggest that 1) ESG beverage does not disturb water absorption because of its short gastric emptying time and 2) ESG slowly elevates plasma glucose level and maintains it for a prolonged time compared to the glucose solution.