Trapped between a rock (calcium carbonate) and a hard place (endovascular plaque)

Once again the issue of too much calcium intake rears its ugly head. This time it comes up in a prospective cohort study looking at all-cause, cardiovascular, ischemic heart disease, and stroke mortality. High intake of calcium in women was associated with higher death rates from all causes and cardiovascular disease but not stroke.1

We have already observed that low calcium intake is associated with higher fracture risk in the elderly and a higher risk of stroke and fatal ischemic heart disease. Also previously reported is a meta-analysis of some randomized studies that showed a higher risk of incident ischemic heart disease and stroke with calcium supplement use. To confuse the issue more, observational studies have suggested that calcium supplements are associated with both lower overall and CV mortality rate as well as a higher incidence of CV disease.

The most recent study on this perplexing subject is a Swedish prospective mammography cohort enrolled in 1987-90 with a large sample of 38,984. The birth dates were from 1914 to 1948 and the median follow up was 19 years. They prospectively followed the cohort for time to death (all cause, CV, ischemic heart disease, and stroke) with 11,944 deaths recorded. Diet was assessed by questionnaire at baseline and in 1997 and included total calcium intake (dietary and supplemental).

The results showed a non-linear risk of death for total calcium intake. Daily intake above 1,400 mg/day compared with 600 – 1,000 mg/day was associated with higher death rates from all causes (hazard ratio 1.4, 95% 1.17-1.67), cardiovascular disease (HR 1.49, 95% 1.09-2.02), and ischemic heart disease (HR 2.14, 95% 1.48-3.09). There was no difference in stroke mortality. 

The difference was more pronounced in those with high dietary calcium intake (>1,400 mg/day) who also consumed supplemental calcium. They had an increase in all-cause mortality (with a hazard ratio of 2.57) compared to those with a dietary intake of 600-999 mg/day who used supplemental calcium.

Just as a guideline about dietary sources of calcium is the table below. Even those with real lactase deficiency can get their dietary calcium up.

Food

Amount of Calcium in milligrams (mg)

                      1 cup of milk                                 300
                      6 oz of yogurt                                350
           1 oz hard cheese (cheddar)                                240
           2 slices processed cheese                                265
             1/4 cup cottage cheese                                120
       1/2 cup soft serve frozen yogurt                                100
                 1/2 cup ice cream                                 85
                    1/2 cup tofu                                258
      1/2 cup pinto beans or chick peas                                 40
                  1/4 cup almonds                                 95
               1 Tbsp almond butter                                 43

 Marshall Kubota, MD

  1.  Long term calcium intake and rates of all cause and cardiovascular mortality:  community based prospective longitudinal cohort study. Michaelsson, K et al, BMJ 2013:346:f228

One thought on “Trapped between a rock (calcium carbonate) and a hard place (endovascular plaque)

  1. Interesting post, Dr. Kubota. JAMA Internal Medicine just published a study showing that men who take supplemental calcium have a 20% increased risk of death from cardiovascular disease. Interestingly, this study found no increase risk of cardiac death among women taking calcium supplements. The study looked prospectively at 390,000 men and women, and found that half of men and 70% of women take calcium supplements. The evidence is mounting that we need to get our patients off calcium supplements. It is far better to eat more calcium-rich foods.

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