The associations between magnesium and the metabolic syndrome in overweight and obese women randomised to an energy-restricted high protein or high fibre diet

Abstract

Background: Dietary magnesium intake has reduced in developed countries over the last century, and consequently average magnesium intakes in New Zealand are well below the recommended dietary intake. Plausible biological mechanisms and a large body of cross sectional research have indicated a link between both dietary magnesium intake and magnesium status and cardiovascular risk factors and individual components of the metabolic syndrome. However, dietary interventions to modify magnesium intake and status and examine the effect on cardiovascular risk have not been previously carried out.

Methods: A randomised controlled weight-loss trial was carried out to examine the effect of a hypocaloric high carbohydrate, high fibre diet compared with a hypocaloric high protein diet on dietary magnesium intake and status, and to examine corresponding modifications in cardiovascular risk and individual components of the metabolic syndrome. Eighty-three overweight and obese women, who were free from medicated diabetes and dyslipidaeamia, took part. Fasting plasma magnesium was measured, and dietary magnesium intake was assessed using a three-day diet record at baseline and at the end of the study.

Results: Over eight weeks of follow-up, plasma magnesium and dietary magnesium intake did not change significantly in either diet group. In the high fibre diet group, an increase in 100mg of dietary magnesium daily was associated with a 1.3kg reduction in weight (p=0.005), an 8% reduction in fasting insulin concentration (p=0.043) and an 8% reduction in HOMA-IR (p=0.015). An increase in plasma magnesium concentration by 1mg/L in the high protein diet group was associated with a 600g weight loss (p=0.013), 350g reduction in trunkal fat (p=0.016) and an increase in McAuley IS (p=0.020).

Conclusions: Increases in both dietary magnesium and plasma magnesium were associated with a reduction in cardiovascular risk factors and individual components of the metabolic syndrome. This study suggests that weight loss in conjunction with an increase in magnesium intake and improvements in magnesium status, may work synergistically to reduce cardiovascular risk in an at risk population.