• Department of Hepatobiliary Surgery, the Second Affiliated Hospital of Chongqing Medical University, Chongqing, China.
• Department of Geriatrics, the Fifth People's Hospital of Chengdu, Chengdu, China.
• Department of Endocrine and Breast Surgery, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China.
• Department of Hepatobiliary Surgery, The People's Hospital of Dazu District, Chongqing, China.
• Department of Nutrition and Food Hygiene, School of Public Health and Management, Chongqing Medical University, Chongqing, China.
• Pediatric Surgery Center, Qingdao Women and Children's Hospital, Qingdao University, Qingdao, Shandong, China.
• Department of Gastrointestinal Surgery, the Second Affiliated Hospital of Chongqing Medical University, Chongqing, China.

Epidemiological studies on magnesium intake and primary liver cancer (PLC) are scarce, and no prospective studies have examined the associations of magnesium intake with PLC incidence and mortality. We sought to clarify whether higher magnesium intake from diet and supplements was associated with lower risks of PLC incidence and mortality in the US population. Magnesium intake from diet and supplements was evaluated through a food frequency questionnaire in a cohort of 104,025 participants. Cox regression was employed to calculate hazard ratios for PLC incidence and competing risk regression was employed to calculate subdistribution hazard ratios for PLC mortality. Restricted cubic spline regression was employed to test nonlinearity. We documented 116 PLC cases during 1,193,513.5 person-years of follow-up and 100 PLC deaths during 1,198,021.3 person-years of follow-up. Total (diet + supplements) magnesium intake was found to be inversely associated with risks of PLC incidence (hazard ratio_{tertile 3 vs. 1} : 0.44; 95% confidence interval: 0.24, 0.80; p_trend = 0.0065) and mortality (subdistribution hazard ratio_{tertile 3 vs. 1} : 0.37; 95% confidence interval: 0.19, 0.71; p_trend = 0.0008). Similar results were obtained for dietary magnesium intake. Nonlinear inverse dose-response associations with PLC incidence and mortality were observed for both total and dietary magnesium intakes (all p_nonlinearity  < 0.05). In summary, in the US population, a high magnesium intake is associated with decreased risks of PLC incidence and mortality in a nonlinear dose-response manner. These findings support that increasing the consumption of foods rich in magnesium may be beneficial in reducing PLC incidence and mortality.