by Sudha Bhat on  April 15, 2015 at 7:42 PM Health In Focus
What is the Link Between Dietary Magnesium and Hypertension in Mexicans?
Hypertension, or what is most often called a silent killer, is uncontrolled high blood pressure, which more often than not, displays no obvious symptoms. High blood pressure is defined as a reading above 140/90 mm Hg (millimeters of mercury) and basically, refers to blood pushing against the walls of the arteries with chronically elevated force. If blood pressure continues to remain above normal levels, it could lead to increased risk of heart disease, heart failure, stroke and kidney failure, amongst others.

Magnesium, which is the fourth most abundant mineral in your body, has heart healthy actions and is responsible for dilatation of blood vessels of the heart, prevent spasms in heart muscle, counteract action of calcium which increases spasm and also helps dissolve blood clots. Magnesium is mainly found in many unprocessed foods, such as whole grains, green leafy vegetables, legumes, and nuts.

In 2008, nearly 40% of adults greater than 25 years of age had been diagnosed with hypertension. According to the 2012 National Health and Nutrition Survey, in Mexico, 32.4% of men and 32.3% of women had hypertension.

The increasing incidence of hypertension has been linked to insufficient intake of dietary magnesium. Numerous studies have been conducted in the past to study the relationship between dietary magnesium and various health outcomes such as blood pressure, but epidemiological evidence supporting this relationship is inconsistent.

The Health Workers Cohort Study (HWCS) was a longitudinal study, which was conducted to investigate the effect of magnesium intake on blood pressure in apparently healthy Mexican adults. The study had a total of 1,378 participants (77.4% women and 22.6% men), aged 20 to 87 years. These participants were free of hypertension at baseline (systolic blood pressure <140 mmHg or/and diastolic blood pressure <90 mmHg).

A self-administered questionnaire was used to collect information on participants' socio-demographic factors (age, sex, and education), medical history, and lifestyle, including alcohol and tobacco consumption. A semi-quantitative food frequency questionnaire was used to try and understand and evaluate the magnesium intake of the participants. The longitudinal relationship between the dietary intake of magnesium and the occurrence of hypertension were analyzed with generalized estimation equations.

During a median follow-up of 7 years, scientists observed that 16.4% of women and 31.9% of men became hypertensive. They also found a trend of decreasing diastolic blood pressure with rising magnesium intake, by tertiles (the coefficients were −0.75 mmHg [95% confidence interval (CI): −1.77, 0.27], −1.27 mmHg (95% CI: −2.73, −0.02; P for trend = 0.01). This inverse relationship was attenuated after further adjustment for known risk factors. In the fully adjusted model, magnesium intake was inversely associated with the risk of developing hypertension, however it was not significant. The subjects in the highest tertile of magnesium intake had a decreased risk for hypertension (odds ratio 0.83, 95% CI: 0.49-1.39, P for trend = 0.48).

Magnesium intake was inversely associated with intake of fat and cholesterol and positively associated with the consumption of fiber and glycemic load. The study revealed a modestly decreasing trend of diastolic blood pressure with higher amount of magnesium intake. However, there was insufficient evidence to conclusively prove a significant association between dietary magnesium intake and the subsequent development of hypertension in this adult Mexican population.

The study had certain limitations: firstly, they did not separately compare the effects of dietary magnesium and supplementary magnesium; secondly, the participants in this cohort study were adults from a specific segment of the Mexican population that cannot be considered representative of the Mexican adult population as a whole.

Even though results of the study do not support the hypothesis that magnesium intake reduces the development of hypertension, a modest inverse association with blood pressure, however, cannot be ruled out.

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