Monday, June 4, 2012

Update on calcium

Recent reports of an increased risk of heart attack in people taking calcium supplements have been very confusing. For years we have been told to take calcium pills to supplement dietary sources of this mineral. Here’s the evidence so far. Calcium is critical for building and maintaining strong bones and teeth; it also plays a role in muscle contraction, nerve transmission, blood clotting and blood vessel flexibility.

A recent study in the Archives of Internal Medicine looked at 39,000 older women in the Iowa Women’s Health Study, and found a small decreased risk of death among women taking calcium supplements. This contrasts with two studies from the University of Auckland (British Medical Journal, 2010 and 2011) which looked at the U.S. Women’s Health Initiative and found that calcium supplements, with and without vitamin D, modestly increased the risk of a heart attack. The data are difficult to interpret, and more studies and further analysis is needed. A Canadian journal said “if 100 patients take calcium supplements, less than 1 will have a fracture prevented, and less than 1 will develop a heart attack
or stroke.” A small increased risk of kidney stones has also been shown in people taking supplemental calcium, but not with dietary calcium.

The Institute of Medicine concluded in 2010 that adults should get 1000 mg a day of calcium, and post-menopausal women should get 1200 mg. An adequate calcium intake is especially important in pregnancy and breast feeding. Girls ages 9 – 18 often do not get enough calcium in their diets due to a preference for sodas, fake foods and dieting. Supplements of calcium, magnesium and vitamin D as chewable tablets may be beneficial for them, as this is a critical time for bone building.

I conclude that it is vitally important to get enough calcium from our diets, and to use supplemental vitamin D if needed to raise levels of D to 30 ng/ml or higher. Good dietary sources of calcium include low fat milk products (think unsweetened yogurt and cottage cheese and nonfat or 1% milk), green vegetables (especially broccoli, collards, kale & bok choy), almonds, Brazil nuts, sunflower seeds, sesame seeds and dried beans. Calcium fortified soy milk and orange juice can help vegans get enough calcium. Some tofu is high in calcium; read labels to be sure. People with osteoporosis should talk to their doctor or nurse practitioner about the risks and benefits of supplemental calcium.

Studies of men have suggested that a high intake of calcium from dairy products may increase the risk of prostate cancer, but the evidence for this is inconsistent. Men can consider getting a maximum of dietary calcium from non-dairy sources of the mineral.

A 2006 study from the University of Pennsylvania showed that use of proton pump inhibitors (Nexium, Prilosec, Prevacid and others ) to reduce acid reflux is associated with an increased risk of hip fracture in people over 50, probably due to decreased calcium absorption and other mechanisms. Long-term use of these medicines increases the risk. Short term use is often indicated, but many people stay on these anti-reflux drugs for years. These medicines can also increase the risk of pneumonia, vitamin B12 deficiency and low magnesium levels. There are other ways of dealing with acid reflux, including weight loss, avoiding trigger foods and high fat meals, eating frequent small meals, and sleeping in a Lazy-Boy chair or with a wedge pillow if the problem comes on at night.

Here in West Marin are blessed to have local organic dairies that produce wonderful yogurt. Yea for farmers’ markets with their abundance of calcium rich vegetables

Sadja Greenwood, MD, MPH back issues on this blog

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