Rice is a staple food that provides about 30% of the dietary energy consumed by over 65% of the human population in China [1]. As living standards improve, the consumption of high eating quality rice—mainly soft-textured rice with low amylose content—has substantially increased in China [2]. However, it is well documented that rice with a lower amylose content is generally less resistant to digestion and has a higher glycemic index [3]. Diets with a high glycemic index are associated with increased incidence of non-communicable diseases such as type 2 diabetes and cardiovascular [4, 5]. Thus, the development of low amylose content rice varieties may counter efforts to promote a healthy population in China, highlighting the urgent need to evaluate the change in the glycemic index of rice in China [6].

The middle reach of the Yangtze River (including Hunan, Jiangxi, and Hubei provinces) is a major rice-producing region in China that contributes to over 30% of the total national rice production [7]. As a result of targeted breeding efforts, the amylose content of new rice varieties has experienced a steady decreasing trend in the middle reach of the Yangtze River since 2006 (Fig. 1A). Amylose content significantly decreased from 20.0% in rice varieties released during 2006–2009 to 17.7% in those released during 2013–2015, to 16.6% in those released during 2016–2018, and to 15.9% in those released during 2019–2021.

Fig. 1
figure 1

Amylose content (A) and estimated glycemic index (B) of rice varieties released during 2006–2021 in the middle reach of the Yangtze River. Values on error bars are the number of varieties released per year. Data points are means, and error bars show 95% confidence intervals. Means are significantly different if their confidence intervals do not overlap, and dashed red lines are used to indicate significant differences. ** denotes significant trend at the 0.01 probability level. The data of amylose content was obtained from the China Rice Data Center (http://www.ricedata.cn/variety)

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Based on the linear relationship between the glycemic index and amylose content of rice plotted by Fitzgerald et al. [3], we estimated the glycemic index of rice varieties released from 2006–2021 in the middle reach of the Yangtze River (Fig. 1B). The results showed that the estimated glycemic index significantly increased from 68.3 in rice varieties released during 2006–2009 to 70.4 in those released during 2013–2015, to 71.4 in those released during 2016–2018, and to 72.0 in those released during 2019–2021. Moreover, trend analysis indicated that the estimated glycemic index of rice varieties increased in accordance with their year of release; the estimated glycemic index of rice increased by approximately 0.3 per year in newly released varieties.

In summary, the estimated glycemic index of newly released rice varieties used in the middle reach of the Yangtze River in recent years has significantly increased as a result of the development of soft-textured rice with low amylose content in response to consumer preference. This finding can also be supported by an in vitro starch digestion assay using seven rice varieties grown in the middle reach of the Yangtze River, which showed that starch digestion rate significantly increased with decreasing amylose content (Fig. 2).

Fig. 2
figure 2

The relationship between starch digestion rate (i.e., the rate of digestion of starch into glucose) and amylose content across seven rice varieties grown in the middle reach of the Yangtze River. ** denotes significant relationship at the 0.01 probability level. The rice varieties were selected based on the amylose content representing the range of mean amylose content of rice varieties released during 2006–2021 in the middle reach of the Yangtze River. The starch digestion rate was determined by an in vitro method using a NutriScan GI20 Glycemic Index Analyser (Next Instruments, Condell Park, New South Wales, Australia) [2]

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We hope the finding of this study will attract societal attention and help raise awareness of the health risks associated with the consumption of this type of rice in China and other major rice-consuming countries. We also appeal to the government to immediately initiate an interdisciplinary collaboration between crop and food scientists and the public health sector to (1) comprehensively assess the potential health risks associated with the consumption of soft-textured rice with low amylose content and (2) find feasible approaches to resolve the contradiction between rice-eating quality and unintended health risks to rice consumers.