Adequate magnesium intakes may support heart health for heart attack survivors, say researchers

By Nicola Gordon-Seymour

- Last updated on GMT

© piotr_malczyk / Getty Images
© piotr_malczyk / Getty Images

Related tags: Magnesium, Heart health, Cardiovascular disease, cardiovascular health

Older patients with a history of myocardial infarction (MI) could reduce their chances of premature cardiovascular disease (CVD) and all-cause mortality by consuming sufficient dietary magnesium, according to a Dutch study.

Researchers investigated magnesium intake of 4,365 patients over 12 years (including follow-up) and found an inverse association between mineral levels and CVD mortality.

High magnesium intake of 322 mg daily was linked to lower risk of CVD and all-cause mortality, and particularly among participants taking diuretics.

Based on current results and previous evidence, the authors suggest that magnesium intake could be more strongly related to mortality risk in CVD patients than in the general population.

“Our findings emphasize the importance of an adequate magnesium intake in CVD patients, on top of cardiovascular drug treatment,” ​wrote the researchers in Frontiers in Cardiovascular Medicine.

“Highest CVD mortality risks were observed for magnesium intakes below the median intake. Protective risk estimates for CVD mortality were shown for magnesium intakes above the adequate intake.”

Different requirements

The results add to an ever-growing body of science supporting the potential health benefits of the mineral. The National Institutes of Health (NIH) lists magnesium as being necessary for more than 300 biochemical reactions in the body, from helping maintain normal muscle and nerve function, to keeping heart rhythm steady, supporting a healthy immune system, and keeping bones strong. The mineral is also needed for blood sugar management and healthy blood pressure. 

European experts recommend daily magnesium intake of 350 mg for men and 300mg for women as adequate levels can help control blood glucose levels, blood pressure, and myocardial metabolism.

Hypomagnesemia may also lead to insulin resistance, altered lipid metabolism, and impaired endothelial and kidney function.

Requirements can be different for patients with CVD who have experienced physiological changes to their cardiovascular system, are more prone to comorbidities, and who take medication that can interfere with absorption. In addition, the effects of magnesium intake on long-term mortality risks are unclear.

The current research therefore examined the relationship between dietary magnesium and CVD, all-cause, and CHD mortality in patients with prior MI and who were taking medication.

Study protocol

Male and female participants with an average age of 69 years were selected from the cohort involved in the Alpha Omega Trial, where MI patients had been monitored to assess the effects of low doses of omega-3 fatty acids or a placebo for 40 months.

Dietary intake was established with a FFQ that verified food and drink frequency, quantity, food type, and preparation methods. Supplement use was determined with a self-reported Lifestyle and Health questionnaire.

Questionnaire results determined that magnesium supplements were used by 235 (5.4%) of patients and average overall magnesium intake was around 300 mg/d.

Researchers adopted Cox proportional hazard models to assess the association of energy adjusted magnesium intake and mortality risk factors, and restricted cubic splines (RSC) to determine continuous and threshold associations.

Influence of diuretics

Results showed a direct link between magnesium status and lower CVD risk in both male and female participants. There was no significant associated link with magnesium intake and death from coronary heart disease (CHD).

The authors write that a difference of 100mg/d in magnesium intake related to a 30-40% lower risk of CVD and all-cause mortality in several subgroups.

They note that protective associations were more apparent in the presence of diuretics and speculate that they may impact magnesium status by inhibiting sodium in the kidney and indirectly affect magnesium absorption.

“Based on sensitivity analyses by type of diuretics, we conclude that both thiazide diuretics and potassium-sparing diuretics could be involved in the relationship between magnesium intake and CVD mortality,” ​they wrote.

Effect of dietary fibre

The presence of dietary fibre rather than magnesium may also explain the inverse relationship with CVD mortality, the authors assert, as both are derived from similar food sources and were highly correlated in the study.

Population-based studies have identified an association between dietary fibre and CVD morality risks, however most of these did not correct for magnesium so protective elements could be linked to either compound, they maintain.

In addition, researchers conducted subgroup and sensitivity analyses, which revealed inverse associations for magnesium in patients with low and high fibre intake and in magnesium depleted diuretic users.

“Based on the totality of findings, we think that magnesium intake independently of fibre could have contributed to the lower risk of CVD mortality in the Alpha Omega Cohort,” ​they wrote.

Finally, they suggested that study limitations should be considered in the context of findings, given the observational nature of the study and the shortcomings of self-reporting - and despite adjustments for confounding elements, such as dietary and lifestyle factors.

Source: Frontiers in Cardiovascular Medicine
Published online, August 12, 2022: doi: 10.3389/fcvm.2022.936772
‘Dietary magnesium and risk of cardiovascular and all-cause mortality after myocardial infarction: A prospective analysis in the Alpha Omega Cohort’
Author: I. Evers, et al.

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