Hypertension is a leading risk factor for cardiovascular disease and yet divisions and controversy still surround its causes. The role of sodium intake in the development of hypertension has been supported by the mainstream medical authorities in Western nations for decades. However, the epidemiological and clinical evidence does not fully support this viewpoint. While in a small number individuals dietary sodium intake appears to play a role in the development of hypertension, in a large percentage of the population sodium has no significant effect on blood pressure whatsoever. While resources have been spent attempting to educated individuals on the benefits of lower sodium diets, evidence has been accumulating that it is dietary calcium, and not sodium, that is the macromineral most heavily involved with the maintenance of correct blood pressure. As was pointed out in a review article on the subject ‘It’s very simple: adequate dietary calcium intake is critical to optimal blood pressure regulation’ 1 .
Many nutritional papers have been published showing and association between calcium and hypertension. The association between calcium and blood pressure was first identified in the 1984 NHANES study. The authors of this study concluded that dietary deficiency was the typical nutritional situation that characterised high blood pressure as opposed to dietary excess. In addition, they also reported that it was primarily calcium and potassium that were the two minerals most associated with hypertension. The patterns seen in epidemiological papers showing an inverse association between calcium and blood pressure are supported by evidence from clinical trials. In a meta-analysis of 33 studies involving 2412 individuals2 researchers reported that sufficient intake of dietary calcium was able to lower systolic and diastolic blood pressure by 1.3mmHg and 0.2mmHg, respectively. In hypertensive subjects these figures increased to 4.3 mmHg and 1.5 mmHg reductions in systolic and diastolic blood pressure, respectively.
Another meta analysis3 used 23 studies to show that calcium had a statistically significant but small inverses association with blood pressure. However, when this paper was analysed by other researchers it was found to have serious methodological errors. During a reworking of the statistical analysis, researchers showed that the small inverse effect was actually 30-fold greater than had originally been reported. This changed the drop in systolic blood pressure for men per 100 mg of calcium from 0.01 to 0.34mmHg and for diastolic pressure from 0.01 to 0.22mmHg. This raised suspicions of scientific bias in the literature at the time and subsequent comments to leading peer reviewed journals highlighted that in addition to the methodological flaws, there was also a misuse of references such that a bias was placed on the anti-calcium view point. Treatment of blood pressure with simple calcium supplements would reduce the need for expensive hypertensive drugs.
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