No, magnesium glycinate does not cause cancer.
There is no evidence that magnesium glycinate or any form of magnesium supplementation increases cancer risk. In fact, the available evidence suggests that adequate magnesium intake may be protective against certain cancers, particularly colorectal cancer.
Evidence from Guidelines
The American Cancer Society guidelines on nutrition and cancer prevention do not identify magnesium as a cancer risk factor 1. These guidelines comprehensively address dietary factors and supplements in relation to cancer risk, and magnesium is notably absent from any list of concerning substances. The guidelines emphasize that men and women should try to get recommended levels of calcium primarily through food sources and that food is the best source of vitamins and minerals, not supplements 1, but this reflects general supplement guidance rather than specific cancer concerns about magnesium.
Clinical Use and Safety Profile
Recent gastroenterology guidelines 2 recommend magnesium oxide (MgO) as a first-line treatment for chronic constipation, noting that the combination of efficacy, tolerability, availability, and low cost make MgO an attractive option. While these guidelines specifically evaluated magnesium oxide, they note that the bioavailability and clinical efficacy of other formulations of magnesium (eg, citrate, glycinate, lactate, malate, sulfate) for chronic constipation are unknown 2. Importantly, no cancer risk was identified as a safety concern in these clinical practice guidelines.
Research Evidence on Magnesium and Cancer
The most recent and highest-quality evidence actually suggests a protective effect of magnesium against cancer:
A 2021 meta-analysis of prospective cohort studies involving over 1.1 million participants found that higher dietary magnesium intake was associated with reduced risk of all-cause mortality (13% reduction) and cancer mortality (20% reduction) 3. Each additional 100 mg/day of dietary magnesium was associated with 6% reduced all-cause mortality and 5% reduced cancer mortality.
A 2014 meta-analysis of 13 epidemiologic studies showed that the highest level of dietary magnesium intake was associated with a 20% reduction in overall cancer risk, with particularly strong protective effects for colorectal cancer 4.
A 2015 prospective cohort study found that magnesium intake below recommended levels was associated with increased pancreatic cancer risk, with every 100 mg/day decrement associated with 24% increased incidence 5.
Important Caveats
The relationship between magnesium and cancer is complex and U-shaped in some contexts. One 2020 nested case-control study in hypertensive adults found that both very low (<0.76 mmol/L) and very high (≥0.89 mmol/L) plasma magnesium concentrations were associated with increased cancer risk compared to reference levels of 0.83-0.89 mmol/L 6. However, this study examined plasma levels in a specific high-risk population (hypertensive adults), not supplementation in healthy individuals.
Clinical Context
In oncology practice, magnesium supplementation is commonly used to manage chemotherapy-induced hypomagnesemia, particularly with platinum-based agents like cisplatin and panitumumab 7, 8. Recent studies demonstrate that early magnesium supplementation effectively reduces severe hypomagnesemia in cancer patients receiving these treatments 7. This therapeutic use in cancer patients further supports the safety profile of magnesium supplementation.
Bottom Line
Magnesium glycinate is safe and does not cause cancer. The preponderance of evidence suggests adequate magnesium intake may actually reduce cancer risk, particularly for colorectal cancer. Standard supplementation doses are well within safe limits, though individuals with significant renal impairment (creatinine clearance <20 mg/dL) should avoid magnesium supplements due to risk of hypermagnesemia 2.