Higher intakes of magnesium were also associated with benefits, with a 22% reduction in the risk of ischemic heart disease (IHD) reported by the Boston-based researchers.
The study, which combined data from 313,041 people, provides the “most robust evidence to date of the associations between circulating and dietary magnesium across their usual physiologic ranges and CVD risk”, wrote Dr Dariush Mozaffarian and his co-authors in the American Journal of Clinical Nutrition.
The researchers noted that the data related to dietary magnesium and their findings support an increase in consumption of magnesium-rich foods, such as whole grains, nuts/seeds, and vegetables, rather than supplements.
With between 70 and 80% of the US population not meeting their recommended intakes of magnesium, consumers – and the health care professionals who advise them - are waking up to the importance 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 (with potential for sports nutrition) 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.
The European Food Safety Authority (EFSA) has issued positive opinions on magnesium and the maintenance of normal bone, teeth, and protein synthesis; the reduction of tiredness and fatigue; electrolyte balance; normal energy-yielding metabolism; neurotransmission, and muscle contraction.
The agency was not convinced by claims about magnesium and blood glucose, blood pressure, stress relief, protection of DNA, proteins and lipids from oxidative damage, the immune system and fat metabolism.
Despite negative opinions from EFSA, a number of meta-analysis and high-profile studies have been published in recent years supporting the mineral's benefits for metabolic pathways, blood pressure, reducing the risk of stroke, and reducing the risk of colon cancer.
The new meta-analysis supports the potential heart health benefits of the mineral. Dr Mozaffarian and his co-workers identified 16 studies with data for 313,041 people.
After crunching the numbers, the researchers found that every 0.2 mmol/L increment increase in circulating magnesium was associated with a 30% lower risk of cardiovascular disease, but no significant association with IHD.
On the other hand, increasing dietary magnesium intakes were linked to a 22% lower risk of IHD.
The researchers noted that these observational studies cannot establish causality, and called for “additional experimental studies and randomized trials […] to elucidate the roles of circulating and dietary magnesium, at usual physiologic concentrations and intakes, on CVD risk.”
Source: American Journal of Clinical Nutrition
Published online ahead of print, doi:10.3945/ajcn.112.053132
“Circulating and dietary magnesium and risk of cardiovascular disease: a systematic review and meta-analysis of prospective studies”
Authors: L.C. Del Gobbo, F. Imamura, J.H.Y. Wu, M.C. de Oliveira Otto, S.E. Chiuve, D. Mozaffarian