Monday, August 02, 2010

Calcium: Prostate Cancer, Now Heart Disease

A new study is reporting that calcium supplements are associated with an increased risk for heart attack:

Effect Of Calcium Supplements On Risk Of Myocardial Infarction And Cardiovascular Events: Meta-Analysis, British Medical Journal, July 29, 2010

The study is a meta-analysis, not an original trial but a study of studies, in this case 15 prior studies (about 12,000 participants). Participants took supplements containing at least 500mg calcium/day.

Findings (Click to enlarge):

"Calcium supplements (without coadministered vitamin D) are associated with an increased risk of myocardial infarction. As calcium supplements are widely used these modest increases in risk of cardiovascular disease might translate into a large burden of disease in the population. A reassessment of the role of calcium supplements in the management of osteoporosis is warranted."
There was about a 30% increased risk for heart attack; the range went up to 70%.

Calcium And Prostate Cancer

Readers of this blog know that there is a strong association between calcium intake (both from supplements and from food, especially dairy products) and prostate cancer, that is, calcium increases cancer risk. For example:
"In summary, there is reasonable evidence that both vitamin D metabolites and calcium, and specifically calcium from dairy sources, play important roles in the development of prostate cancer."
- Dairy Products, Calcium, and Vitamin D and Risk of Prostate Cancer, Epidemiologic Reviews, 2001

Calcium Decreases Vitamin D

Various outlets are reporting that the increased risk for heart attacks is owing to calcium's possible role in increased vascular calcification, that is, hardening of the arteries. But again, readers of this blog know that calcium suppresses production of vitamin D in our body, and that might not be a good thing. (See also: Vitamin D: The Active Form, And The Role Of Calcium):
"When serum levels of calcium are low, 1, 25 D [this is active vitamin D] acts on the bones, kidneys, and intestines to increase retention and absorption of calcium until serum levels return to a normal range. Similarly, if serum levels of calcium are high, production of 1, 25 D is suppressed by reduced parathyroid hormone production."
- Dairy Products, Calcium, and Vitamin D and Risk of Prostate Cancer, Epidemiologic Reviews, 2001
Vitamin D is a hormone which is thought to play a role in, not just bone health, but heart disease, diabetes, hypertension, multiple sclerosis, arthritis, and cancer.

Note that in the study in the previous post about the diets of long-living Okinawans, they consumed only about 500 mg calcium/day, yet they have some of the highest number of centenarians in the world. This is a far cry from the 1000, 1200, 1500 mg/day recommended by various health organizations here.
Photo of calcium pills: Bix


Mike said...

Excellent post, Bix; concise and to-the-point. Thank you.

Bix said...

Nice of you, Mike. Thank you.

bee said...

does it mean a supplement that has both calcium and vitamin D is safe? or safer?

Bix said...

It's a good question, bee, whether adding vitamin D changes risk. It's not a question this study can answer.

Vitamin D you take in a pill is not the same as the active form in our body. The pill form has to be converted to what's known as calcitriol, that is, active vitamin D. The kidneys are thought to do that. High calcium intake or high blood calcium inhibits this conversion. To the degree that it does, taking vitamin D along with supplemental calcium may not mitigate the risk from the calcium.

The long-lived Okinawans in the previous post consumed a mere 0.4 micrograms of vitamin D a day (about 16 IU). That's just 2% of their RDA. They must have made enough from sun exposure to meet their needs.

bee said...

thank you for your response.

Family Nutritionist said...

What is the effect of calcium supplementation on osteoporosis and fractures?

Bix said...

" from the 5,500 women involved in trials of calcium monotherapy show consistent adverse trends in numbers of hip fractures (relative risk 1.50, 95% CI 1.06–2.12).

Observational data from the Study of Osteoporotic Fractures show a similar increase in risk of hip fracture associated with calcium use.

"Until there are further trial results to clarify this area, the present findings suggest that reliance on high calcium intakes to reduce the risk of hip fracture in older women is not appropriate."


Effect of Calcium Supplementation on Hip Fractures, Osteoporosis International, 2008