China: Consuming whole grains rather than refined grains can prevent cardiovascular disease (CVD), coronary heart disease (CHD), and all-cause mortality, findings from a meta-analysis have shown. The study appeared online in the January 2023 American Journal of Clinical Nutrition issue.
Worldwide, cardiovascular disease is the leading cause of mortality. CVD, globally, led to ∼17.9 million deaths in 2019, representing 32%. Dietary factors have a significant impact on human health. Eleven million deaths worldwide in 2017 were attributed to dietary risk factors, with CVD being the leading cause of diet-related deaths.
Grains are the most significant food source that, accounts for 50% of the daily calorie intake globally and as high as 54% in developing countries. Whole grains comprised germ, endosperm and bran with abundant beneficial phytochemicals and nutrients in the germ and bran. Refined grains are obtained by removing all or components of the outer bran layer or germ during pearling, grinding, or sterilizing.
Although relationships between refined and whole grains intake and the incidence of all-cause mortality and CVD events have been investigated, the conclusions have been inconclusive. Considering this, Huifang Hu from Zhengzhou University in Zhengzhou, Henan, People's Republic of China, and colleagues aimed to comprehensively summarize the evidence about the association between consumption of refined grains and whole grains and risks of all-cause mortality and CVD events and to assess the quality of meta-evidence.
For this purpose, the researchers searched online databases until 15 March 2022. The study included twenty-four articles comprising 68 studies (22 for refined grains and 46 for whole grains) with 1,624,407 participants.
The study led to the following findings:
Per 30-g increase in the consumption of daily whole grain, the RRs, coronary heart disease, heart failure, CVD, and all-cause mortality were 0.98, 0.94, 0.97, 0.92, and 0.94, respectively.
Whole grain consumption was linearly associated with coronary heart disease and nonlinearly with CVD and all-cause mortality.
Except for a positive correlation between the consumption of refined grain and all-cause mortality in the restricted cubic spline, the researchers did not detect any significant influence of refined grain intake on stroke, HF, CHD, and CVD.
The quality of the meta-evidence for the association of whole grain consumption with CHD, stroke, CVD, HF, and all-cause mortality was moderate, moderate, high, low and high, respectively. For refined grains, there was a low quality of all meta-evidence.
The meta-analysis showed that whole grains, rather than refined grains, prevent CVD, CHD and all-cause mortality.
"There is a need for further prospective cohort studies reporting different stroke types and look into the association between the intake of refined grains and whole grains and different stroke types separately," the researchers wrote. "Also, because of the low-quality meta-evidence for refined grains, the impact of refined grain consumption on all-cause mortality and CVD events requires further confirmation."
Reference:
Hu, H., Zhao, Y., Feng, Y., Yang, X., Li, Y., Wu, Y., Yuan, L., Zhang, J., Li, T., Huang, H., Li, X., Zhang, M., Sun, L., & Hu, D. (2023). Consumption of whole grains and refined grains and associated risk of cardiovascular disease events and all-cause mortality: A systematic review and dose-response meta-analysis of prospective cohort studies. The American Journal of Clinical Nutrition, 117(1), 149-159. https://doi.org/10.1016/j.ajcnut.2022.10.010