College of Health Solutions, Arizona State University, Phoenix, AZ.
Adv Nutr. 2019 May 1;10(3):361-371. doi: 10.1093/advances/nmy104.
Refined grain intake is widely assumed to be associated with adverse health outcomes, including increased risk for cardiovascular disease (CVD), type 2 diabetes (T2D), and obesity. The 2015 Dietary Guidelines Advisory Committee recommended that to improve dietary quality, the US population should replace most refined grains with whole grains. This recommendation was based largely on results from studies that examined dietary patterns, not separate food groups. A Western dietary pattern typically includes red and processed meat, sugar-sweetened foods and beverages, French fries, and high-fat dairy products, as well as refined grains, and has been linked to increased risk of many chronic diseases. However, when evaluated as a distinct food category, 11 meta-analyses of prospective cohort studies, which included a total of 32 publications with data from 24 distinct cohorts, demonstrated that refined grain intake was not associated with all-cause mortality, T2D, CVD, coronary heart disease (CHD), stroke, hypertension, or cancer. By contrast, consumption of red and processed meat was consistently associated with increased risk of these same health outcomes. Refined grain consumption up to 6-7 servings/d (1 serving = 30 g) was not associated with higher risk of CHD, T2D, hypertension, or all-cause mortality. Moreover, total grain intake was not associated with risk of CVD, CHD, stroke, or cancer, but was associated with lower risk of all-cause mortality. Consequently, the recommendation to reduce refined grain intake based on results from studies linking a Western dietary pattern to numerous adverse health outcomes is contrary to a substantial body of published scientific evidence. Future research needs to better define refined grain intake to distinguish between staple grain foods and indulgent grain foods, and to better design randomized controlled trials to resolve discrepancies between results from observational studies and such trials with regard to determining the benefits of whole grains compared with refined grains.
精制谷物的摄入量被广泛认为与不良健康结果有关，包括增加心血管疾病（CVD）、2 型糖尿病（T2D）和肥胖的风险。2015 年膳食指南咨询委员会建议，为了提高饮食质量，美国人口应将大部分精制谷物替换为全谷物。这一建议主要基于研究饮食模式的结果，而不是单独的食物组。西方饮食模式通常包括红色和加工肉类、含糖的食物和饮料、炸薯条和高脂肪乳制品，以及精制谷物，并且与许多慢性疾病的风险增加有关。然而，当作为一个独特的食物类别进行评估时，11 项前瞻性队列研究的荟萃分析，其中包括来自 24 个不同队列的 32 份出版物的数据，表明精制谷物的摄入量与全因死亡率、T2D、CVD、冠心病（CHD）、中风、高血压或癌症无关。相比之下，食用红色和加工肉类与这些相同健康结果的风险增加始终相关。精制谷物的摄入量高达 6-7 份/天（1 份=30 克）与 CHD、T2D、高血压或全因死亡率的风险增加无关。此外，总谷物摄入量与 CVD、CHD、中风或癌症的风险无关，但与全因死亡率的风险降低有关。因此，基于将西方饮食模式与众多不良健康结果联系起来的研究结果来减少精制谷物摄入量的建议与大量已发表的科学证据相悖。未来的研究需要更好地定义精制谷物的摄入量，以区分主食谷物食品和放纵谷物食品，并更好地设计随机对照试验，以解决观察性研究和此类试验之间在确定全谷物与精制谷物相比的益处方面的差异。
