Is brown rice really healthier than white rice?

糙米真的比白米健康吗？

英文部分选自经济学人20261107期科技版块

Science & technology | Well Informed

Is brown rice really healthier than white rice?

糙米真的比白米健康吗？

The scientific evidence goes against the grain

科学证据却与常识背道而驰

RICE SUPPLIES nearly a fifth of the world’s calories. Which sort, though, is healthiest? Brown rice becomes white when milling removes its fibrous outer layer (known as the bran), and nutrient-rich seed embryo (the germ), so nutritional lore naturally favours the former. Indeed, some striking findings seem to support that preference. Look closer, though, and the colour of rice may not be what matters most.

人类所需的能量约五分之一由大米提供。但是哪一种大米最健康呢？糙米经过碾磨，去掉富含膳食纤维的表层麸皮和营养丰富的胚芽后，就成为了白米。因此，营养学界一直以来更加推崇前者。确实，一些有影响力的研究结果似乎也印证了这种偏好。但仔细研究就能发现，米的颜色未必是最关键的因素。

Rice is rich in starch, which digestion turns into glucose, or blood sugar. If the body struggles to regulate it, type-2 diabetes can eventually develop. Consider a review of eight observational studies that tracked the diets and health of 577,426 people. Writing in BMJ Open in 2022, the researchers calculated that once daily consumption exceeded about two 158-gram servings of cooked white rice, each additional serving was linked to a 13% higher risk of the disease.

大米淀粉含量很高，淀粉消化后成为葡萄糖，也就是我们说的血糖。如果身体血糖控制出问题，久而久之就可能引发Ⅱ型糖尿病。一篇综述对八项观察性研究进行了汇总。这些研究共追踪了577,426人的饮食和健康状况，结论发表于2022年《英国医学杂志·开放版》，即：每天食用两份158克的熟白米后，每再多吃一份， Ⅱ型糖尿病的风险就增加13％。

 Brown rice, meanwhile, appears to offer some protection. Fibre in the bran slows the breakdown of starch, so glucose enters the bloodstream more gradually. The bran and germ also contain magnesium, B vitamins and other nutrients that may help the body regulate blood sugar. A paper in Archives of Internal Medicine in 2010, included in the 2022 review, analysed three studies that followed 197,228 Americans for 14 to 22 years. Modelling suggested that replacing 50 grams of cooked white rice a day with brown rice was linked to a 16% lower risk of type-2 diabetes.

相比之下,糙米似乎对血糖有一定的防护效果。麸皮里的膳食纤维可以放慢淀粉的分解速度，从而放缓葡萄糖进入血液的速度。另外米糠和胚芽中含有镁、B族维生素和其他营养物质，或有助于身体调控血糖。2022年的这篇综述还纳入了2010年发表于《内科学文献》的一篇论文。该论文分析了三项研究，对197,228名美国人追踪了14至22年。模型推算显示，每天以糙米替代50克熟白米，则患Ⅱ型糖尿病的风险降低16%.

Correlation, though, is not causation. People who prefer brown rice tend to smoke less, exercise more and eat healthier food overall. Although the authors of the papers from 2022 and 2010 attempted to account for such confounding lifestyle differences, they acknowledged that their findings could still be skewed. So what happens when researchers actually instruct people to eat brown rather than white rice?

但相关不等于因果。偏好糙米的人往往吸烟更少、运动更多，整体饮食也更健康.尽管两篇论文的作者都试图对生活方式差异带来的影响加以修正，但也承认他们结论仍可能存在偏差。那如果研究人员要求人们去吃糙米而非白米，情况会怎样呢？

Not much. The 2022 review also examined 11 randomised controlled trials involving 1,034 participants. Those assigned to eat brown rice showed no statistically significant improvements in their short- or longer-term control of blood sugar. There was also no clear evidence of improved sensitivity to insulin, which helps cells absorb glucose. Nor did the trials consistently find improved blood pressure.

收效甚微。2022年的一项研究综述中，还考察了11项随机对照试验，共涉及1034名参与者。被分配吃糙米的受试者，无论短期还是较长期，血糖控制均未出现统计学意义上的显著改善也没有明确证据表明他们体内胰岛素敏感性有所改善，胰岛素的作用是帮助细胞吸收葡萄糖。该试验也没能一致发现糙米对血压的改善。

What matters more for blood sugar than rice’s colour, it turns out, is how much of a starch called amylose it contains. Amylose resists rapid digestion, so it limits spikes in blood sugar. A review of 32 randomised controlled trials published in 2015 identified amylose content—which is largely a function of a rice’s variety—as “the most consistently important” determinant of how sharply rice raises blood sugar.

相较于米的颜色、研究人员发现影响血糖更关键的因素是一种叫直链淀粉的淀粉含量。直链淀粉不易被快速消化，因此能抑制血糖飙升.2015年发表的一篇综述分析了32项随机对照试验，认为直链淀粉含量（很大程度上取决于稻米品种）是决定米饭升糖幅度的因素，且在各项试验中表现最为一致。

Processing matters, too. Parboiling—soaking and steaming rice before milling—moves B vitamins from the bran into the grain while making its starch more resistant to digestion. An experiment reported in Nutrition in 2018 found that, among people without diabetes, eating parboiled rather than ordinary white rice reduced the cumulative rise in blood sugar over the following two hours by 38%. It also appeared to have an edge over ordinary brown rice.

大米的加工方式同样会产生影响。蒸谷工艺，即在碾磨前将稻谷浸泡、蒸煮，可使B族维生素从米糠转入米粒，同时让其中的淀粉更不易被消化。2018年发表在《营养学》（Nutrition）期刊上的一项实验发现，食用蒸谷米而非普通白米，可使非糖尿病人群随后两小时内的血糖累积升幅降低38%.研究结果还显示，蒸谷米的表现似乎优于普通糙米。

A similar trick can be performed at home. Refrigerating cooked rice, whether brown or white, alters some of its starch so that it is digested more slowly. Care, though, is needed: to limit bacterial growth, rice should be cooled within an hour and reheated only once, until steaming hot, within a day.

我们在家也能如法炮制。无论是糙米还是白米，将煮熟的大米放入冰箱冷冻，都能改变其中一部分淀粉的结构，使其消化速度变慢。不过，在操作时需要注意食品安全：为抑制滋生细菌，煮熟的大米应在一小时内冷却，并且在一天内只重新加热一次，且须加热至热气腾腾。

翻译组：

Cece，消防人+经济学人粉丝

Lee，爱骑行的妇女之友+Timberland粉

Crystal ，SISU小菜鸡，扎根生长也自然流淌

审校组：

Xia Jiehai，创作者

Rachel，学理工科，爱跳芭蕾，热爱文艺的非典型翻译

---END---