Calcium Supplementation May Lower Blood Pressure
Commentary by: Commentary by William F. Wulsin, ND, MPH, MA, LAc
Reference: Reid IR, Ames R, Mason B, et al. Effects of calcium supplementation on lipids, blood pressure, and body composition in healthy older men: a randomized controlled trial. Am J Clin Nutr. 2010;91(1):131-139.
Design: Randomized control
Key Findings: This study evaluated the effect of calcium supplementation HDL-to-LDL cholesterol ratios (primary endpoint) and on changes in cholesterol fractions, triglycerides, blood pressure, and body composition (secondary endpoints) for men over 40 years of age.
Placebo or 600 mg or 1200 mg daily supplementation of calcium was administered over 2 years to 3 cohorts among 323 healthy > 40 year old men in New Zealand. No statistically significant change was observed in HDL-to-LDL ratio levels (P=0.47), nor (P=0.28) on weight, body fat, lean body mass, total LDL cholesterol, or HDL cholesterol levels. Statistical significance is typically noted with P values ≤0.05. These findings are similar to earlier studies involving calcium supplementation.1,2,3 Similar studies of perimenopausal women have reported a moderate improvement of HDL-to-LDL ratios.4
Practice Implications: A slight statistically significant (P=0.05) yet mild decrease in blood pressure among those subjects entering the study with dietary calcium levels < 785 mg/d was noted and attributed to “the mineral’s impact on parathyroid hormone and 1,25-dihydroxyvitamin D levels, both of which have pressor effects on vascular smooth muscle cells.”5 Although this correlation was associated with those demonstrating subclinical calcium levels, it may be helpful to keep it mind when treating any age group of either gender who may be taking hypertension medicines or be prone to hypotension.
As naturopathic physicians, we are well schooled regarding the impacts that calcium supplementation may have on personal nutrition, bone density, muscle cramps, spasms, nerve transmission, parathyroid function, and hypertension. In particular, calcium supplementation is well accepted as effective in retarding bone loss in postmenopausal women.6
Although funding for the clinical trials cited was at least in part provided by a pharmaceutical company, the conclusions shed interesting light upon the differences observed for supplementation between older men and women. Most studies of calcium supplementation to date have focused on women, menopause, and bone integrity. This study’s findings of a different impact on lipid levels for men > 40 compared to perimenopausal woman justifies more careful studies of the impact of extra-dietary calcium on more diverse demographic populations.
Limitations: It is difficult to reach objective conclusions about the broad impacts of calcium supplementation from the evidence presented in this article. Questions of subjective and objective bias exist from the description of the study design. The reliability of results and the frequency of monitoring adherence to the test regime are not strong. These rates were reported for each cohort varying from 83% to 86% with P= 0.067 and thus did not fall within statistically significant parameters. Dietary intake of calcium was also made at the outset, after 12 months, and at the conclusion of the test period. Variations or specificity of any of these variables may have carried an impact on the results. Only one threshold (785 mg/d) describing baseline dietary calcium was described, but not how this threshold was measured.
References:
1. Bostick RM, Fosdick L, Grandits GA, Grambsch P, Gross M, Louis TA. Effect of calcium supplementation on serum cholesterol and blood pressure. A randomized, double-blind, placebo-controlled, clinical trial. Arch Fam Med. 2000;9(1):31-38.
2. Reid IR, Horne A, Mason B, Ames R, Bava U, Gamble GD. Effects of calcium supplementation on body weight and blood pressure in normal older women: a randomized controlled trial. J Clin Endocrinol Metab. 2005;90(7):3824-3829.
3. Yanovski JA, Parikh SJ, Yanoff LB, et al. Effects of calcium supplementation on body weight and adiposity in overweight and obese adults: a randomized trial. Ann Intern Med. 2009;150(12):821-829, W145-6.
4. Reid IR, Mason B, Horne A, et al. Effects of calcium supplementation on serum lipid concentrations in normal older women: a randomized controlled trial. Am J Med. 2002;112(5):343-347.
5. Reid IR, Ames R, Mason B, et al. Effects of calcium supplementation on lipids, blood pressure, and body composition in healthy older men: a randomized controlled trial. Am J Clin Nutr. 2010;91(1):131-139.
6. Nordin BE. The effect of calcium supplementation on bone loss in 32 controlled trials in postmenopausal women. Osteoporos Int. 2009 May 21.
About William F. Wulsin, ND, MPH, MA, LAc
William F. Wulsin, ND, MPH, MA, LAc, has been a physician, an acupuncturist and the director of Health Development Resources since 1991. In that capacity he consults for public health and research projects in the areas of project identification, design, implementation. His primary focus is with nutrition and food security and integration of traditional medicine. He is focused primarily with people in communities devastated by the impacts of chronic disease and poverty. He has worked with natural resource management and health development for over twenty years in many counties, and has also organized facilitated and presented at several workshops, symposia and conferences which involve health and personal development. He also maintains a private practice in Seattle.
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