Food, Nutrition, and Health, Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada.
BC Children's Hospital Research Institute, Vancouver, British Columbia, Canada.
J Nutr. 2020 Dec 10;150(12):3208-3215. doi: 10.1093/jn/nxaa276.
Rice is one of the most commonly consumed cereal grains and is part of staple diets in the majority of the world. However, it is regarded as an incomplete protein, with lysine being a limiting amino acid.
Our objectives were to determine the bioavailability of lysine in school-age children consuming cooked white rice and to assess the effect of rice starch retrogradation.
Bioavailability or metabolic availability (MA) of lysine was determined using the indicator amino acid oxidation (IAAO) method in a repeated-measures design. Six healthy school-age children (3 boys, 3 girls) with a mean ± SD age of 6.8 ± 0.98 y randomly received 4 crystalline l-lysine intakes (2, 6, 10, 14 mg · kg-1 · d-1), and 5 rice intakes to provide lysine at 8, 11, or 14 mg · kg-1 · d-1. The 14 mg · kg-1 · d-1 intakes were measured twice as warm rice and once as cold rice (to assess the impact of starch retrogradation on MA). Diets provided protein at 1.5 g · kg-1 · d-1 and calories at 1.7 times the participant's measured resting energy requirement, and were isonitrogenous. Breath samples were collected at baseline and during an isotopic steady state for 13C enrichment measurement. The MA of lysine from rice was determined by comparing the IAAO response of rice with l-lysine using the slope-ratio and single intake methods. Starch retrogradation was characterized using differential scanning calorimetry.
MA of lysine in warm rice measured in school-age children was 97.5% and was similar to a repeated rice study (97.1%) within the same study population. MA of lysine was reduced significantly (P < 0.05) to 86.1% when the cooked rice was consumed cold, which corresponded to detectable starch retrogradation.
To our knowledge, this is the first study to measure the MA of lysine from rice in school-age children. Although the bioavailability of lysine from rice is high, it can be reduced by retrogradation of its starch component.This trial was registered at clinicaltrials.gov as NCT04135040.
大米是最常食用的谷物之一，也是世界上大多数国家主食的一部分。然而，它被认为是一种不完全蛋白质，赖氨酸是其限制氨基酸。
我们的目的是确定食用熟白米饭的学龄儿童中赖氨酸的生物利用度，并评估大米淀粉回生的影响。
采用指示剂氨基酸氧化法（IAAO），在重复测量设计中，测定赖氨酸的生物利用度或代谢利用率（MA）。6 名健康的学龄儿童（3 名男孩，3 名女孩），平均年龄（±标准差）为 6.8±0.98 岁，随机接受 4 次结晶 l-赖氨酸摄入（2、6、10、14mg·kg-1·d-1），以及 5 次摄入米饭以提供 8、11 或 14mg·kg-1·d-1 的赖氨酸。14mg·kg-1·d-1 的摄入量测量了两次，一次是热米饭，一次是冷米饭（以评估淀粉回生对 MA 的影响）。饮食提供的蛋白质为 1.5g·kg-1·d-1，热量为参与者测量的静息能量需求的 1.7 倍，并且等氮。在基线和 13C 丰度达到同位素稳定状态期间采集呼吸样本进行测量。通过斜率比和单次摄入法，将米饭的 IAAO 反应与 l-赖氨酸进行比较，确定赖氨酸在米饭中的 MA。利用差示扫描量热法来描述淀粉回生。
在学龄儿童中，热米饭中赖氨酸的 MA 为 97.5%，与同一研究人群中重复的米饭研究（97.1%）相似。当米饭冷却后食用时，赖氨酸的 MA 显著降低（P<0.05）至 86.1%，这与可检测到的淀粉回生相对应。
据我们所知，这是首次在学龄儿童中测量米饭中赖氨酸的 MA。尽管大米中赖氨酸的生物利用率很高，但它的淀粉成分回生会降低其生物利用率。本试验在 clinicaltrials.gov 注册为 NCT04135040。
