"The key finding in this study is that magnesium intake from supplements has an impact on the likelihood of having elevated C-reactive protein, separate from and in addition to dietary magnesium intake," wrote lead author Dana King in the latest issue of the journal Nutrition Research (Vol. 26, pp. 193-196).
C-reactive protein (CRP) is a pro-inflammatory cytokine, meaning it is a signaling molecule associated with increased inflammation. Chronic inflammation, brought about by an over-expression or lack of control of the normal protective mechanism, can lead to a range of inflammatory related disease, particularly cardiovascular disease.
"Previous research has indicated that dietary magnesium may be a key component in the association between diet and inflammation; however, the role of intake from magnesium supplements has not been elucidated," explained King, a professor from the Medical University of South Carolina.
The researchers used data from the National Health and Nutrition Examination Survey 1999-2000 (NHANES 99-00), and focused on 10,024 people with valid measurements of both CRP levels and dietary and supplemental intake of magnesium.
Dietary intakes were quantified from 24-dietary recalls, which may not have adequately described the typical diet of the persons and also rely on personal reporting, which may be subject to under or over-estimation by the participants.
Among the participants it was found that 25.6 per cent were taking magnesium supplements of at least 50 mg per day, and generally tended to be older, female and non-smokers.
Of the people taking less that 50 mg/d of supplemental magnesium, only 21.9 per cent met or exceeded the US recommended daily allowance for the mineral: 420 mg for men over 30, and 320 mg for women over 30. In Europe the RDA for the mineral is 300 mg/d.
When the combined dietary and supplemental intakes of magnesium were compared with levels of CRP, King and co-workers calculated that people with dietary magnesium intake less than half the RDA, individuals taking at least 50 mg/d of magnesium supplements were 22 per cent less likely to have elevated levels of CRP.
People with a total (dietary plus supplements) magnesium intake below the RDA were found to be 40 per cent more probable to have elevated CRP levels.
"The implications of these findings are that magnesium supplementation intake may be a viable alternative for reducing inflammation in people who do not achieve the RDA for magnesium through dietary sources alone," said King.
"The findings also have some implications on whether magnesium plays a direct and important role in regulating inflammation."
The researchers did not perform a mechanistic investigation as part of the study, but suggest that the role of magnesium in many important metabolic pathways, and endothelial function, and therefore the apparent beneficial association between magnesium intake from both diet and supplements may be merely a reflection of improved/normal functioning of metabolic pathways.
It should be noted that the relationship between magnesium and CRP is "modest" and not an investigation of a causal effect.
Further prospective studies, and possible human intervention trials, are needed to extend the understanding of these relationships, and ultimately cardiovascular disease risk, said the researchers.
CVD causes almost 50 per cent of deaths in Europe, and is reported to cost the EU economy an estimated €169bn ($202bn) per year. According to the American Heart Association, 34.2 per cent of Americans (70.1m people) suffered from some form of cardiovascular disease (CVD) in 2002.