The Calcium Conundrum

Doctor of Osteopathic Medicine

Many people take calcium supplements to benefit bone health. There is, however, a dose ceiling where taking too much can increase perhaps cardiovascular risk. The recommendation for osteopenia and osteoporosis prevention and treatment is often about 1200 mg per day of calcium. Many people struggle with getting this in through the diet either due to dietary restrictions or preferences, particularly with the exclusion of the calcium heavy hitter- dairy.

Calcium and the Cardiovascular System

There are multiple studies showing that calcium supplementation over prolonged periods of time at doses exceeding 600 mg may increase the risk of cardiovascular mortality. There seems to be a dose relationship in that higher doses infer greater risk.

In a 2021 meta-analysis in the journal Nutrients of randomized controlled trials, it was found that calcium supplementation in doses of 700 -1200 mg (which is often the dose for bone health) was found to be associated with a 15% higher cardiovascular mortality. Another in the British Medical Journal 2011 stratifies risk based on dosages utilized as well as gender. In this study, there was a dose-dependency of cardiovascular mortality in that the greater the dose utilized in the study the higher the risk. This study also showed the effect was statistically significant in men but not women. The dose-dependent risk was still present in women, but the magnitude was less.

The Dose is the Poison

It seems that doses of 600 mg or less in supplemental calcium were not associated with cardiovascular mortality. It is important to think about getting calcium from the diet – it is possible to consume foods with calcium. It is easier with the inclusion of dairy but even if dairy is off the table there are foods that have a good amount of calcium to boost the intake of food. This is particularly important if there is a risk of cardiovascular disease at the individual level. There have not been studies showing increased risk with dietary sources of calcium.

Vascular Calcifications

Serum calcium levels increase significantly with calcium supplementation. This elevated circulating calcium is thought to increase vascular calcifications which is part of the pathophysiology of cardiovascular disease. Another potential mechanism is an increase in coagulability – or the tendency toward forming blood clots in the body.

Renal Calcifications

With the elevated circulating levels of calcium, there also is increased urinary calcium as our body has mechanisms to maintain balance. In people susceptible to kidney stones, calcium supplementation may also increase the risk of renal calcifications. Studies do not show an increased risk of kidney stones with food sources of calcium.

Keeping it Real

There seems to be some protective effect of getting your calcium from real food. Maybe it is the dose in food, maybe it is the combination of other vitamins and nutrients from the food that is helpful. This may not be possible in many circumstances with dietary limitations and preferences to get the amount needed for bone health. In those cases, supplementation is important but keeping it to 600 mg or less seems to be the risk-benefit ceiling. You can use tables of food sources of calcium such as one found in the Dietary Guidelines For Americans which can be helpful in calculating how many mg of calcium you are getting from food.

Better Together

There is some evidence that perhaps nutrient combinations are better together when it comes to calcium supplementation. For example, we know that vitamin D assists in the absorption of calcium from the gastrointestinal tract. We also know that certain vitamins are protective against cardiovascular calcifications. Vitamin K2 is involved in regulating the calcium in the body and is important for bone health. It is very common in western diet patterns for insufficiency of vitamin K2. This nutrient is made and metabolized in the gastrointestinal tract and disruptions of the microbiota can lead to decreased levels of this vitamin in the body. When taking calcium supplements, it is important to be getting sources of vitamin D and K2 either through food or supplementation for better processing and utilization of the calcium.

References

•Katarzyna Maresz. Integr Med (Encinitas) 2015 Feb; 14 (1) 34-39 Proper Calcium Use: Vitamin K2 as a Promoter of Bone and Cardiovascular Health

•Mark Bolland. BMJ. 2011 April 19; 342 Calcium supplements with or without vitamin D and Risk Of Cardiovascular Events: Re-analysis of the Women’s Health Initiative and MetaAnalysis

•Seung KwonMyung. Nutrients. 2021 Feb; 13(2)368 Calcium Supplements and Risk of Cardiovascular Disease MetaAnalysis of Clinical Trials

The Calcium Conundrum

Calcium and the Cardiovascular System

The Dose is the Poison

Vascular Calcifications

Renal Calcifications

Keeping it Real

Better Together

References

Elisa Mercuro

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