Is more magnesium linked to lower cancer risk?

The claim checked: In one 18-year study of men, those with the highest magnesium levels had 50% lower cancer mortality Hear it at 6:10

What do the studies say?

Conflicting

Two studies linked higher magnesium intake to lower cancer mortality or less liver cancer; three others found no link for colorectal, lung or prostate cancer.

Computed from 5 studies that test this point, each judged by two readers, in full. Sources land on both sides. 10 more studies are waiting for a full read and do not count yet.

What was said on the podcast?

“a study involving 47,000 men that were followed for 18 years found that those men with the highest magnesium levels had the had 40% decreased in all cause mortality and a 50% decrease in cancer mortality compared to men with the lowest magnesium levels”

Rhonda Patrick, FoundMyFitness · DEBUNKED: 2/3rds of Cancer "Just Bad Luck" · 6:10 on YouTube
The quote says 47,000 men. The study it describes, PMID 16570028, followed 4,035.
Comes up in 5 episodes of the show.

The point checked Conflicting

Higher magnesium is linked to lower cancer (her framing: incidence; her data: cancer mortality)

Agree 2

pooled analysis · 2021

“The summary effect size for cancer mortality comparing the highest with the lowest categories of dietary magnesium intake was 0.80 (95% CI: 0.67, 0.97; P = 0.023), indicating a significant inverse association between dietary magnesium intake and risk of cancer mortality.”

Total, Dietary, and Supplemental Magnesium Intakes and Risk of All-Cause, Cardiovascular, and Cancer Mortality: A Systematic Review and Dose-Response Meta-Analysis of Prospective Cohort Studies. Adv Nutr
Who: Adults aged 20-89 in prospective cohort studies from the US, Europe and Asia
PMID 33684200

other primary study · 2021

“Higher magnesium intake was associated with a lower risk of incident liver cancer (P-trend = 0.005), with magnesium intakes in the highest compared with lowest quartile associated with an overall 35% lower risk of incident liver cancer (HR: 0.65; 95% CI: 0.48, 0.87) (Table 2).”

Magnesium intake is associated with a reduced risk of incident liver cancer, based on an analysis of the NIH-American Association of Retired Persons (NIH-AARP) Diet and Health Study prospective cohort. Am J Clin Nutr
Who: 536,359 NIH-AARP participants aged 50-71 y in 6 US states and 2 metro areas
PMID 33330925

Partly agree 0

None.

Disagree 3

other primary study · 2012

“These prospective results do not support an independent association of magnesium intake with either colorectal cancer risk or plasma C-peptide levels in women.”

Magnesium intake, plasma C-peptide, and colorectal cancer incidence in US women: a 28-year follow-up study. Br J Cancer
Who: 85,924 US female nurses free of cancer in 1980 (Nurses' Health Study)
PMID 22415230

pooled analysis · 2018

“Pooled results suggested that magnesium levels in patients with lung cancer was not significantly lower than healthy controls [summary SMD = 0.193, 95%CI = − 1.504 to 1.890, I 2 = 99.6%, P for heterogeneity < 0.001] (Fig. 2 ).”

Serum magnesium levels and lung cancer risk: a meta-analysis. World J Surg Oncol
Who: 11 case-control studies (9 China, 1 Spain, 1 Turkey) comparing serum magnesium in lung cancer patients vs healthy controls
PMID 30001198

trial or observed group · 2019

“However, we found no evidence of a protective association between magnesium and prostate cancer in either black or white men.”

Blood and dietary magnesium levels are not linked with lower prostate cancer risk in black or white men. Cancer Lett
Who: Men over 40 undergoing diagnostic prostate biopsy in Nashville, TN and Durham, NC (about 50% black)
PMID 30776477