Background Global dietary magnesium insufficiency is widespread and seriously harmful to human health. There are few studies on dietary magnesium intake in China, and associated dietary intervention lacks scientific support.

Objective To explore the dietary magnesium intake level and food sources of Chinese adults aged 18-64 in 2018, and to identify the problems of dietary magnesium intake.

Methods A total of 9181 residents in the 2018 "China Health and Nutrition Survey" were selected as the study subjects. Types and intake of food collected from consecutive 3-day 24-hour dietary recalls and by household condiment weighing and counting method. The average daily dietary magnesium intake and the composition of main food sources were calculated using the food composition table. Multiple logistic regression was used to analyze the relationship between socioeconomic factors and insufficient dietary magnesium intake.

Results In 2018, the daily intake of magnesium in P₅₀ (P₂₅, P₇₅) of adults aged 18-64 in 15 provinces (autonomous regions and municipalities) of China was 252.28 (196.25, 326.27) mg. The proportion of residents with insufficient dietary magnesium intake was 60.9%. The proportions of women, adults aged 18-49, urban residents, southern region residents, and western regions residents with insufficient dietary magnesium intake were 66.4%, 63.4%, 62.4%, 65.2%, and 68.3%, respectively. The results of multiple logistic regression analysis showed that the risks of insufficient dietary magnesium intake were 64.6%, 24.6%, and 43.6% higher in women, urban residents, and southern region residents than those in men, rural residents, and northern region residents, respectively (OR=1.646, 95%CI: 1.509-1.794; OR=1.246, 95%CI: 1.126-1.379; OR=1.436, 95%CI: 1.311-1.573); the risk of insufficient dietary magnesium intake in residents aged 50-64 was 15.7% lower than that in residents aged 18-49 (OR=0.843, 95%CI: 0.771-0.921); the risks of insufficient magnesium intake in residents in middle and western areas were 1.202 times and 1.590 times of that in residents in eastern area (OR=1.202, 95%CI: 1.079-1.340; OR=1.590, 95%CI: 1.424-1.776). The effect of education level and income level on magnesium intake insufficiency was not observed (P>0.05). In addition, 41.4% of dietary magnesium of the subjects came from cereals and products (ranking first in food sources), and only 2.4% from dark vegetables with rich magnesium content (ranking sixth place). The top six dietary magnesium sources of men and women were the same. The proportion of dietary magnesium from cereals and products was 6.3% higher in rural residents than in urban residents, and 9.3% higher in residents living in northern regions than those in southern regions. The proportion of dietary magnesium from livestock meat and products was 1.3% higher in the 18-49 age group than in the 50-64 age group, 0.9% higher in urban residents than in rural residents, and 1.6% higher in western region residents than in eastern region residents.

Conclusion The dietary magnesium intake of Chinese residents is generally insufficient, and the source of dietary magnesium is irrational. Women, residents aged 18-49, residents in southern, middle, and western areas are high-risk populations of dietary magnesium insufficiency. Chinese residents are encouraged to eat more dark vegetables and whole grain food; women should improve their dietary quality and intake diverse magnesium-rich food; southern region residents and urban residents should increase the intake of whole grains and avoid over refining food; residents aged 18-49, urban residents, and those in western regions should adjust their dietary structure and reduce meat intake.