Heart attack risks & calcium

Mothers have been telling us for decades to drink our milk to have strong bones. They are not necessarily wrong; calcium from diet is essential. However, what about calcium from supplements?
Many people, especially women after menopause, take calcium supplements as a preventive measure to reduce the chances of osteoporosis. Patients who have osteoporosis are instructed to take calcium to prevent fracture.
In a meta-analysis, 1200 mg of calcium plus 800 mg of vitamin D resulted in preservation of bone mineral density at the hip and spine. In fact, there was a 12 percent reduction in the risk of fracture in patients taking this combination.
The demographics included people over the age of 50. So, you can understand why patients would readily use calcium supplements.

Is it possible that calcium supplementation is dangerous?
A meta-analysis that looked at five randomized control trials in 2007, showed that calcium taken without vitamin D may increase the risk of a heart attack. Patients who had a heart attack had calcification (hardening) of the coronary arteries. The average dose of calcium supplementation was approximately 1000 mg.
In the treatment group, there was a 31 percent increase in incidence of heart attack, compared to the placebo group. The authors recommended at the time that most of your calcium come from diet.
I agree that it is important to take calcium and vitamin D together; vitamin D helps with the absorption of calcium. However, high levels of calcium may interfere with vitamin D’s functioning.
Still, a study published in the British Medical Journal in 2011 illustrated that calcium with vitamin D increased the risk of a heart attack by about 20 percent. The authors analyzed data from the Women’s Health Initiative, with over 20,000 participants.
The most damaging impact to calcium supplementation is the authors’ conclusion that for every 1000 people taking calcium for five years, regardless of vitamin D intake, there would be an increase of six heart attacks or strokes, but prevention of only three fractures.
This may mean that the risks outweigh the benefits with calcium supplementation. The study used 1000 mg of calcium and 400 IUs of vitamin D. The conclusion of the authors is that patients should get most of their calcium from diet.

What are the different types of calcium supplementation?
The two common types are calcium carbonate and calcium citrate. Calcium carbonate is less expensive, found in products like Tums, and it has a higher propensity to cause the most common type of kidney stone, calcium oxalate stones.
Calcium citrate is better absorbed. Therefore, I recommend to my patients, if they take calcium, it should be calcium citrate.

What is the optimal dose of calcium?
We see all varying doses of calcium on pharmacy shelves. The body absorbs <500 mg of calcium most effectively at one time, according to the Institute of Medicine. Therefore, it is best to target this amount. Also, the studies above showed an increase in heart attack with 1000 mg of calcium supplementation. Where should we get most of our calcium?
Even though it is not completely clear what to do about calcium supplementation, there is a recurrent theme of recommending dietary calcium. Interestingly, there was a study that showed that a diet rich in calcium, but not in vitamin D or dairy, lowered risk of death due to ischemic heart disease.
Foods that are naturally high in calcium include soybeans and vegetables, such as kale and bok choy. High levels of sodium and protein cause decreased levels of calcium.
There is definitely value in supplementing vitamin D in patients who are insufficient or deficient, but most people, including those with osteoporosis or osteopenia, may not have low levels of calcium. So, if patients have normal levels, there is no need for them to take calcium supplements.