Improving the nutritional value and digestibility of rice to address double burden malnutrition in the Philippines and Thailand

水稻(Oryza sativa L.)大米是世界上一半以上人口的主食，大多数大米被作为精制的白米消费。然而，碾磨过程去除了许多基本的营养成分，包括基本的微量营养素，如铁和锌、维生素、脂肪酸、植物化学物质和膳食纤维。这可能导致以大米为主要卡路里来源的人群中出现微量营养素缺乏症。此外，白米往往有较高的血糖指数(GI)，淀粉在人体肠道中被迅速消化。高GI和高血糖负荷食物的消费，加上体力活动的减少和快速城市化，促进了非传染性疾病的扩大，如II型糖尿病，菲律宾的记录水平最高。因此，白米的高消费量是营养不良双重负担的一个主要例子。大米是许多民族文化的一部分，特别是在亚洲。因此，减少大米消费往往不是一个可接受的选择。当地的老品种，包括彩色大米(黑色或紫色，红色到棕色)已被证明具有更高的营养价值和许多健康益处，包括抗癌、抗糖尿病和抗高血脂特性。因此，消费者对促进健康的食品越来越感兴趣，尽管这主要是在较高收入的消费者中。2015年，泰国推出了一个成功的紫稻品种--米莓。然而，RiceBerry是低收益的，目前瞄准的是高收入市场。迫切需要提高低收入消费者对有色大米品种价值的认识，同时培育营养价值更高、GI低的高产大米品种，同时不影响消费者的接受程度。这将使数百万依赖大米的人受益，改善生计和经济。精白大米含有90%的淀粉，这是一种由直链淀粉和支链淀粉组成的复杂碳水化合物，具有高血糖指数。然而，降低淀粉在肠道中的分解率(低GI)可以导致淀粉到达大肠(结肠)，在那里它在类似于膳食纤维的庄园中经历细菌降解(发酵)，从而对肠道健康有利。IRRI的工作已经确定了大米淀粉分解和红米材料中发现的多酚之间的联系。作为α-淀粉酶抑制剂的山奈酚衍生物与低淀粉消化率有关，而红米单倍型与直链淀粉和支链淀粉比率的变化有关。虽然多酚一般被认为对人类健康有益，但有报道称，一些多酚可以抑制铁的生物利用度。有益的和拮抗的作用也与膳食纤维有关，例如促进钙，但限制铁的吸收。植酸盐是谷物中磷的主要储存物，也会干扰微量营养素的生物利用，与包括铁和锌在内的其他微量营养素结合。由于单胃动物缺乏足够数量的适当植酸降解酶，植酸盐被认为是一种抗营养物质，对必需膳食矿物质的生物利用率有负面影响。鉴于多酚、微量营养素和植酸盐、淀粉和膳食纤维之间对人类健康的复杂相互作用，该项目旨在确定每种比例都能优化大米的营养和健康益处的大米基因型，同时保持消费者的可接受性。通过我们在菲律宾和泰国的伙伴研究所的水稻育种计划，我们的目标是将这些有益健康的特征引入高产水稻品种。通过与政策制定者的接触，我们的目标是促进菲律宾和泰国的低收入家庭接受有色大米品种。

Rice (Oryza sativa L.) is a staple food for more than half of the world's population, with most rice being consumed as polished, white rice. However, the milling process removes many essential nutritional components, including essential micronutrients such as iron and zinc, vitamins, fatty-acids, phytochemicals and dietary fibre. This can lead to the development of micronutrient deficiencies among peoples for whom rice is the primary source of calories. Furthermore, white rice tends to have a high glycaemic index (GI), the starch being rapidly digested in the human intestine. The consumption of high GI and glycaemic load foods, alongside a decrease in physical activity and rapid urbanization, has contributed to the expansion of non-communicable diseases such as type-II diabetes, with the Philippines having the highest recorded levels. Thus, high consumption of white rice presents as a prime example of the double burden of malnutrition. Rice is very much part of the culture of many peoples, especially in Asia. Therefore a reduction in rice consumption is often not an acceptable option. Old local varieties, including coloured rice (black or purple, red to brown) have been shown to possess higher nutritional value and numerous health benefits, including anti-cancer, anti-diabetic and anti-hyperlipidaemic properties. Consequently there is growing interest among consumers for health-promoting food products, although this is primarily among higher-income consumers. In 2015 a successful purple rice variety was released in Thailand, RiceBerry. However, RiceBerry is low yielding and is currently directed at a high-income market. There is an urgent need to raise awareness of the value of coloured rice varieties among lower-income consumers, while breeding high-yielding rice varieties with improved nutritional value and low GI, without compromising consumer acceptance. This will benefit the millions of people who depend on rice, improving livelihoods and economies.Polished white rice is 90% starch, a complex carbohydrate made up of amylose and amylopectin that has a high GI. However, lowering the rate of starch breakdown in the gut (low GI) can lead to starch reaching the large intestine (colon) where it undergoes bacterial degradation (fermentation) in a manor analogous to dietary fibre, with consequential benefits to gut health. Work at IRRI has identified linkages between rice starch breakdown and the polyphenols found in red rice accessions. Kaempferol-derivatives, which act as alpha-amylase inhibitors, have been linked to low starch digestibility, while a red rice haplotype was found to be associated with altered amylose vs amylopectin ratios. While polyphenols are in general considered beneficial to human health, there have been reports that some polyphenols can inhibit iron bioavailability. Beneficial and antagonistic effects have also been associated with dietary fibre, e.g. promoting calcium, but limiting iron uptake. Phytates, which are the primary store of phosphorus in cereal grains, can also interfere with micronutrient bioavailability, binding other micronutrients, including iron and zinc. As monogastric animals lack sufficient amounts of appropriate phytate degrading enzymes, phytate is considered an anti-nutritional, having negative effects on the bioavailability of essential dietary minerals. Given this complex interplay between polyphenols, micronutrients and phytate, starch and dietary fibre on human health, this project aims to identify rice genotypes where the ratios of each optimise the nutritional and health benefits of rice, while maintaining consumer acceptability. Through the rice breeding programmes at our partner institutes in the Philippines and Thailand we aim to introduce these health benefit characteristics into high-yielding rice varieties. Through engagement with policy makers we aim to promote the uptake of coloured rice varieties by lower-income households in the Philippines and Thailand.