Written by Marcia J. Egles, MD. In this study of the Chinese population, it was determined that the calcium to magnesium ratio greater than 1.7 was associated with lower total death rates as compared to individuals whose diets had the calcium to magnesium ratio lower than 1.7.
Calcium, magnesium, phosphate, and Vitamin D are all recognized as essential to human health, especially to bone health. Several recent studies have voiced concerns that high calcium intakes may worsen the risk of cardiovascular disease (2,3,4). A new preliminary study from China, looking at large population data(1), has taken a somewhat new approach to unraveling the complexities of calcium’s role in disease prevention. This Chinese study found that overall, the ratio of the amount of calcium consumed relative to the amount of magnesium consumed, may be more important than the absolute amount of calcium in the diet. For example, they found that in the diets of Chinese men, a high ratio of calcium to magnesium, with the ratio greater than 1.7, was associated with lower total death rates, as well as lower death rates due to coronary heart disease, as compared to men whose diets had ratios lower than 1.7.
Both magnesium and calcium belong to the same family of elements. Within physiological activities, magnesium and calcium are often linked and can compete with each other. The same cell receptor that regulates calcium also senses magnesium. In the kidney, this calcium receptor can inhibit the re-absorption of magnesium such that excess magnesium can be passed into the urine (5 ). In the gut, calcium and magnesium may compete for intestinal absorption (6). If there is a small amount of calcium but an abundance of magnesium in the contents of the intestine, the magnesium gets more actively absorbed. However, a high intake of calcium can reduce the absorption of both calcium and magnesium. The amount of calcium or magnesium absorbed depends on the dietary ratio of calcium to magnesium.
The Chinese calcium/magnesium ratio study utilized data from the Shanghai Women’s Health Study and the Shanghai Men’s Health Study, which are two prospective, population –based cohort studies conducted in urban Shanghai, China ( 7,8). The two studies are similar 4 year studies enrolling 74,942 women aged 40 to 70 in the women’s study and 61,500 men ages 40 to 74 in the men’s study. Certified interviewers obtained information on various demographic characteristic, medical histories, dietary habits, and lifestyle factors. Calcium and magnesium intakes were assessed by validated food frequency questionnaires. Over the 4 years, statistics were collected on the participants including deaths and causes of death. The follow-up rate in both studies was more than 99.9% complete.
The study found that the calcium intake by itself was not consistently associated with any increase or decrease in overall death rates, or with any changes in death rate from cardiovascular disease or cancer. However, the calcium to magnesium ratio did have significance. Overall, the Chinese population has a low calcium to magnesium intake ratio (a median of 1.7 versus around 3.0 in United States populations). In the Chinese population, those with relatively high magnesium intakes (intakes greater than the Recommended Daily Allowance of320mg/day among women and 420 mg/day among men) had a trend of increased risks of total mortality for both men and women. Among men with a calcium to magnesium ratio greater than 1.7, increased intakes of calcium and magnesium were associated with reduced death rates overall, and with reduced death rates from coronary disease. In this same group, higher intakes of calcium were associated with reduced cancer mortality. With women with especially low calcium to magnesium intake ratios of less than 1.7, those who also had relatively higher magnesium intakes had increased risk of total mortality, and mortality due to cardiovascular disease and colorectal cancer.
This study should be considered preliminary and was conducted in a population with a low calcium to magnesium ratio. The authors cautioned against generalizing their findings to a population like that of the United States where the calcium to magnesium ratio is twice as high. Its findings do not address the use of calcium supplements. Consideration of the calcium to magnesium ratio may perhaps help rectify some of the seemingly disparate results of calcium research.
Source: Dai, Qi, et al. “Modifying effect of calcium/magnesium intake ratio and mortality: a population-based cohort study.” BMJ open 3.2 (2013): e002111.
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Posted June 25, 2013.
References:
- Dai,Qi Xiao-Ou Shu, Xinqing Deng et al , Modifying effect of calcium/magnesium intake ratio and mortality: a population-based cohort study, BMJ Open 2013: 3: e002111.doi: 10.1136/bmjopen-2012-002111.
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