A study recently published in the American Journal of Clinical Nutrition found that, in overweight adults, increasing intake of oral magnesium lowers cardiovascular disease risk
Heart disease is one of the leading causes of death in Canada; because of this, it is important to find strategies that can decrease individuals’ risk of developing cardiovascular illnesses. Previously, studies have found evidence that increasing dietary magnesium may lower risk of cardiovascular disease. These studies have been mostly epidemiological in nature and examined data that was collected by observing how likely individuals were to have developed heart disease based on how much magnesium they consumed. However, these studies could not confirm that increased magnesium caused the decrease in heart disease risk. Unfortunately, few intervention studies have been done to assess whether purposefully increasing a patient’s magnesium intake actually leads to a decreased risk of cardiovascular disease. Recently, an article published in the American Journal of Clinical Nutrition set out to determine just that.
To assess whether increasing magnesium intake decreases the risk of cardiovascular disease, the researchers looked at participants’ arterial stiffness, or the elasticity of their arteries. Stiffer arteries are an indicator of a higher risk of cardiovascular disease. To measure arterial stiffness, carotid-to-femoral pulse wave velocity (PWVc-f) was used. An arterial pulse is created when the left side of the heart contracts and pumps blood to the body. PWVc-f measures how long this pulse takes to travel from the carotid artery in the neck to the femoral artery in the leg. Stiffer arteries result in a slower speed and therefore a higher PWVc-f. It has been shown that this measurement is the most accurate way to directly and non-invasively measure arterial stiffness and predict a person’s risk of cardiovascular disease.
Fifty-two individuals were recruited to the study through posters and newspaper advertisements. In order to be eligible for the study, these individuals had to be healthy 45 to 70 year olds that were either overweight or slightly obese (BMI between 25 and 35 kg/m2). This requirement was instated due to the fact that overweight middle-aged and elderly individuals are more likely to have pre-existing arterial stiffness that has the potential to show improvement in response to intervention with magnesium supplements.
The study was a randomized, double-blind, placebo controlled intervention trial. This means that participants were randomly assigned to one of two groups; receiving either 350mg magnesium per day (the treatment) or a placebo pill containing only starch. The double-blind aspect of the trial refers to the fact that neither the participants nor the investigators knew which group individuals had been assigned to; this trial design acts to reduce as much bias as possible.
The investigators carried out their study for 24 weeks. Measurements of blood pressure, blood and urine magnesium levels, and PWVc-f were taken prior to the beginning of the study and were repeated at 12 and 24 weeks. At 12 weeks there was no significant change observed in the PWVc-f between the placebo and magnesium-receiving group indicating no improvement in arterial stiffness. However, at the end of the 24 weeks, PWVc-f had significantly decreased by 1.0m/s in the group receiving magnesium supplements. This indicates a decrease in arterial stiffness as well as risk of cardiovascular disease. The significance of this finding is highlighted by the fact that other studies have shown that a decrease of this magnitude in PWVc-f corresponds to a 14% decrease in risk of heart disease. Additionally, it is important to note that no serious adverse effects were observed from increasing magnesium intake in this population.
The study presented here indicates that long-term increased magnesium intake in overweight or slightly obese middle-aged and elderly adults decreases their arterial stiffness and therefore their risk of cardiovascular disease. This is a valuable finding as these individuals are, by nature, at an increased risk of developing heart disease and as such, could greatly benefit from risk reduction. The results of this study are promising but, as always, it is important to talk to a doctor before consuming any new dietary supplement.
Written By: Katrina Cristall, BSc (Hons)