May reduce the risk of mortality in women
The calcium controversy continues to be a hot topic, with several new studies seemingly contradicting previous studies. The crucial question: Is there any benefit to taking calcium to prevent bone fractures? If so, which demographic benefits most, and how much should be consumed? From what sources should we get calcium: diet, supplement or both?
Recently, the U.S. Preventive Services Task Force took calcium supplementation to task. In February, the USPSTF said that the evidence for both calcium and vitamin D was inconclusive in preventing bone fracture risk in healthy men and in premenopausal and postmenopausal women. Therefore, they do not recommend that postmenopausal women without history of fracture take calcium or vitamin D supplements for bone health (Ann Intern Med. 2013;158:691-696).
In contrast, in 2011, the Institute of Medicine recommended calcium supplements of up to 800 to 1000 mg to reduce the risk of bone fracture in healthy adults (IOM.edu). Both the IOM and the USPSTF based their recommendations on two large systematic reviews that were not without their weaknesses. This implies that further evidence may be needed to determine the best approach.
Calcium supplementation has risks. There are potential increased risks of heart attacks, kidney stones and elevated cholesterol. In one of the most recent randomized controlled trials, postmenopausal women with already elevated cholesterol saw a significant further increase in cholesterol over two years when given 800 mg of supplemental calcium (Am J Clin Nutr. 2013 Nov.;98:1353-1359).
Regardless of the controversy, one thing is clear: postmenopausal women are at the greatest risk of having fractures and developing osteoporosis (clevelandclinic.org). In fact, one in two postmenopausal women will experience a fracture from osteoporosis. For those with hip fractures, there is a 400% increased risk of dying in the first three months, and one in five will lose her independence (Ann Intern Med. 2013;158:691-696, 701-702).
There have been several studies showing that calcium may increase heart attack risk. To read more about these studies, please read my Feb. 26 article entitled, “Calcium’s effect on heart disease and all-cause mortality.”
I will highlight one study I mentioned in that article, the European Prospective Investigation into Cancer and Nutrition study (Heart. 2012; 98:920-925). In this study, researchers found if patients were getting most of their calcium from supplements, they were at a twofold greater risk of a heart attack, compared to those who were not taking supplements.
However, patients who were getting a modest amount of calcium from both dietary sources and supplements actually saw a 30% decrease in heart attacks. The researchers believe that a large bolus (amount delivered at one time) of calcium from supplements may cause blood levels to surge, producing harmful effects on the heart and calcium deposits in the vasculature.
Even within this study, results vary depending on the source of calcium and the amount from each source. The authors suggest if calcium supplementation is needed, such as with postmenopausal women, then no more than 500 mg should be used, and splitting the dose between morning and night may be ideal.
Now let’s fast-forward to two of the most recent studies that question calcium’s relation to heart disease and death. There was a meta-analysis (a group of 19 randomized clinical trials) involving women over the age of 50 presented at the American Society for Bone and Mineral Research 2013 Annual Meeting. Results showed that there were no significant increased risks of heart disease, heart attacks or death from calcium supplementation in women (ASBMR 2013, abstract 1002). This does not necessarily allay fears, but it does call them into question.
At the same conference, a study called the Osteoporotic Fractures in Men study was presented. It implied that calcium supplements do not increase the risk of heart ailments for men (ASBMR 2013, abstract 1002).
If this were not confusing enough, in the Canadian Multicentre Osteoporosis Study, there was actually a 22% decrease in mortality in women who used calcium supplements, compared to those who did not (J Clin Endocrinol Metab. 2013;98:3010-3018). These results were seen in women who took 500 mg to 1000 mg per day of supplemental calcium, but not in men. Interestingly, women who had significant dietary calcium also saw a mortality reduction. Above 1000 mg calcium intake, the benefit was attenuated. This was an observational study with a 10-year duration.
However, the mortality story may not be the same for men. Results of an observational study showed that a large daily dose of calcium-only supplements (1000 mg per day or more) may actually increase the risk of mortality to 37% for heart disease death (JAMA Intern Med. 2013;173:639-646). The study found that half of men took calcium supplements.
When we think of bone health, we typically think of vitamin D supplements, with or without calcium. However, in a recent randomized controlled trial, the gold standard of studies, the opposite was true (J Clin Endocrinol Metab. online Sept. 24). Results showed that in postmenopausal women, calcium with or without vitamin D helped to improve bone health, whereas 4000 IU of vitamin D alone did not reduce osteoporosis risk. The study duration was six months with a population of 120 women.
Dietary sources of calcium are numerous. Dairy products, such as milk and yogurt, have calcium. Fortified nondairy products, such as soy milk, also do, but fortification is essentially supplementation. Natural forms of calcium include nuts, seeds, beans, dark green leafy vegetables and fish, such as salmon and sardines.
The bottom line is: use caution when considering calcium supplements. The appropriate dose may be 500 mg per day at the upper limit, since this is all we absorb at one time, and this should be reserved for postmenopausal women. It might be wise to divide this dose between the morning and evening to minimize a potential bolus effect.
Unfortunately, none of these studies are definitive. However, it is encouraging that postmenopausal women may benefit from calcium supplements and dietary intake rather than be harmed by them. Regardless, it’s best to get most of our intake from dietary sources rather than supplements, since dietary sources are much less likely to cause side effects, such as kidney stones.
Dr. Dunaief is a speaker, author and local lifestyle medicine physician focusing on the integration of medicine, nutrition, fitness and stress management. For further information, go to the website www.medicalcompassmd.com and/or consult your personal physician.