飲食攝取鈣質低於平均值者(785 mg/天)之中，研究者指出在血壓有些微改變(接受每天1200鈣質者和安慰劑組在兩年時的改變P值分別是P = .05和 P = .06；收縮壓 –4.2 mm Hg；舒張壓 –3.3 mm Hg)。他們將這個改變歸因於鈣質的排鈉利尿效果，以及對副甲狀腺素和1,25-dihydroxyvitamin D的礦物質影響，這兩者都對血管平滑肌細胞有加壓效果。
紐西蘭健康研究委員會以及Osteoporosis New Zealand公司資助本研究。由德州的Mission Pharmacal of San Antonio公司提供研究藥物。Reid醫師接受Mission Pharmacal提供對本研究的支持，他也擔任該公司的顧問。其他研究作者皆宣告沒有相關財務關係。
Am J Clin Nutr.線上發表於2009年11月11日。
Calcium Supplements Do Not Affect Men's Serum Lipids, Body Weight
By Nancy Fowler
Medscape Medical News
November 30, 2009 — Calcium supplements do not alter serum lipids or result in weight loss (or gain) in older men as they seem to do in women, but they can improve blood pressure in those whose diets are lacking in the mineral, according to a New Zealand study published online November 11 in the American Journal of Clinical Nutrition.
"The suggestion that calcium intake might have an effect on serum lipid concentrations has arisen from clinical studies, predominantly in women, and from human and animal studies showing that calcium binds to fatty acids and bile acids in the gut, which leads to reduced absorption of fat," write Ian R. Reid, MD, and colleagues in the Department of Medicine, Faculty of Medical and Health Sciences, at the University of Auckland in Auckland, New Zealand.
"Other mechanisms may also be involved, because there is evidence that both parathyroid hormone and 1,25-dihydroxyvitamin D regulate adipocyte activity, the former reducing lipolysis when present in high concentrations in vitro. These effects could also contribute to the weight loss that has been reported with the use of calcium and to the inverse association between calcium intake and body weight found in several observational studies."
The randomized controlled trial, begun in 2004, involved 323 healthy 40-year-old men who took a placebo, 600 mg of calcium daily, or 1200 mg of calcium daily. The study's primary endpoint was a ratio change of high-density lipoprotein (HDL) to low-density lipoprotein (LDL) cholesterol levels. Alterations in cholesterol fractions and triglycerides, blood pressure, and body composition were secondary endpoints.
After 2 years, the subjects showed no significant change in their ratio of HDL to LDL (P = .47). Researchers also found no modification of weight, fat or lean mass, triglycerides, or total LDL or HDL levels (P = .28 for all). The findings regarding HDL-to-LDL ratios and triglycerides contrast with the results of previous studies that suggest supplemental calcium has a positive impact on the serum lipids and body mass in postmenopausal women.
"This suggests that calcium supplements have a smaller effect on lipid metabolism in men than in women. The reason for a sex difference in response is not clear. Whereas testosterone clearly has effects on cholesterol metabolism, an interaction between these and the use of calcium supplementation is unexpected," the study authors write.
In subjects with dietary calcium intakes below the median value (785 mg/day), researchers did note slight changes in blood pressure (P = .05 and P = .06 for changes at 2 years in those who received 1200 mg of calcium per day vs placebo: systolic, –4.2 mm Hg; diastolic, –3.3 mm Hg). They attributed this alteration to the natriuretic effect of calcium and the mineral's impact on parathyroid hormone and 1,25-dihydroxyvitamin D levels, both of which have pressor effects on vascular smooth muscle cells.
The study authors have reported no limitations of the study. They noted that their study was the largest randomized trial of the effect of calcium on men's weight and that its results support previous findings regarding lack of effect on body mass. Furthermore, they stated that this 2-year study was longer than previous trials, which allowed it to show sustained results.
The slight decrease in blood pressure found in the study, though important, is not significant enough to warrant the widespread use of calcium as a treatment of hypertension.
"Thus, we conclude that the therapeutic value of calcium in managing hypertension is likely to be small and insufficient to justify its routine use in hypertensive subjects on average calcium intakes," the study authors write. "However, selective supplementation in those with low dietary intakes could be considered."
The study was supported by the Health Research Council of New Zealand and by Osteoporosis New Zealand. The study medication was provided by Mission Pharmacal of San Antonio, Texas. Dr. Reid has received research support for this study from Mission Pharmacal, for whom he has also acted as a consultant. The other study authors have disclosed no relevant financial relationships.
Am J Clin Nutr. Published online November 11, 2009.
