Product Review: Calcium Supplements (Including Vitamin D, Vitamin K, and Magnesium)
Initial Posting: 5/17/17 Last update: 11/7/17
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Summary: What You Need to Know About Calcium Supplements
What It Is:
- It is important that you get an adequate amount of calcium, as it is essential to maintaining your bones and plays critical roles in nerve transmission, muscle contraction, and your cardiovascular system. In fact, getting sufficient calcium each day (1,000 to 1,200 mg for adults) may decrease your risk of dying from cardiovascular disease. For details, see What It Does >>
- You may already get enough calcium in your diet from dairy, beans, green-leafy vegetables, and other foods. In fact, with the exception of girls ages 9 to 18, most individuals take in enough calcium from what they eat. For the recommended intakes of calcium and to learn how much you may already get from food, see What to Consider When Using >>
- If you're not getting enough calcium from your diet, supplements can help. Calcium supplements have shown some modest benefits for postmenopausal women, particularly those on hormonal therapy after hysterectomy (see What It Does >>). But be careful! Calcium from supplements may increase the risk of heart attack and stroke if you get too much from supplements (generally over 1,000 mg per day) or if you already get at least 805 mg of calcium from your diet. Calcium supplements also increase the risk of kidney stones in postmenopausal women. See Concerns and Cautions for more information. >>
- How much calcium to take? Since you can't absorb more than about 500 mg of calcium at a time, consider limiting intake from supplements to 500 mg or less at a time and, certainly, no more than 1,000 mg total per day. Also, be sure you are getting enough vitamin D, as it is necessary for your body to absorb and utilize calcium from both foods and supplements and may reduce some of the risks associated with calcium supplements. Vitamin D is in many of the supplements tested in this Review. For extensive information about vitamin D, see the Vitamin D Supplements Review >>
- Which supplement is best? This depends, first, on your particular needs. Use the Results table below to narrow in on products which provide the right amount of calcium and other ingredients to meet your needs. Be sure focus on products which have been approved by ConsumerLab.com because not all supplements are properly made and live up to their ingredient claims. Then compare prices in the last column of the table -- you can get some good products for just pennies a day. See What CL Found -- Cost >>. Taking these factors into consideration, ConsumerLab.com has come up with several Top Picks for calcium supplements.
- When to take calcium? If your calcium supplement includes vitamin D and/or vitamin K, take it with the meal that contains most fats and oils, as this may increase absorption of those vitamins. Otherwise, you can take calcium with any meal, but don't take it at the same time that you take other mineral supplements as the calcium may reduce their absorption. If you are taking calcium citrate, you may be able to take it with or without food. Follow the directions on the supplement.
Calcium is an essential mineral for the body and is one of the most popular dietary supplements in the U.S. Calcium can be obtained exclusively from food. Many types of calcium supplements are available and in an increasing variety of delivery forms including tablets, caplets, softgels, syrups, chewable tablets, softchews, gummies, antacids, and calcium-fortified foods and juices. The most common and generally least expensive form of calcium is calcium carbonate. Other types include calcium malate, calcium citrate malate, calcium lactate and calcium gluconate. The forms vary somewhat in how they are best used (see ConsumerTips™ for discussion of different forms).
(See separate reviews of Vitamin D and Vitamin K, which are also important to bone health).
What It Does:
Adequate calcium is critical for building and maintaining strong bones, where 99% of the mineral is found in the body. The rest is present in the blood, extracellular fluid, muscle and other tissues, where it plays a necessary role in vasodilation, muscle contraction, nerve transmission and glandular secretions.
In girls ages 9 to 13, regular supplementation with calcium and vitamin D has been shown to significantly increase bone density and bone strength (measured in arms and legs) compared to placebo (Greene, Osteoporosis Int 2011).
Calcium supplements, taken with vitamin D, appear to at least modestly protect against osteoporosis in postmenopausal women. However, a review of studies in which calcium (500 to 1,500 mg/day) and vitamin D (100 to 1,000 IU/day ) were given to women being treated for breast cancer found no benefit in preventing bone mineral density loss (Datta, Crit Rev Onc Heme 2013). This is unfortunate, as women receiving breast cancer therapy are at increased risk of osteoporosis.
Studies have not been consistent as to whether calcium and vitamin D reduce the risk of fractures. For example, a long-term study in postmenopausal women found that those receiving 500 mg of calcium (from calcium carbonate) and 200 IU of vitamin D3 twice daily slightly reduced their risk of hip fracture compared to those receiving placebo, but the reduction was not statistically significant (Jackson, NEJM 2006). However, the same study found that when the calcium/vitamin D supplement was given to women receiving hormonal therapy (after hysterectomy), the risk of hip fracture was reduced by half compared to women who did not receive the supplementation (Robbins, Menopause 2013.)
A large 4-year placebo-controlled study of post-menopausal women in rural Nebraska found that 1,500 mg of calcium (500 mg from calcium carbonate taken three times daily) and 2,000 IU of vitamin D3 daily did not significantly lower the risk of cancer overall or specific cancers, including colon, ovarian, breast, lung or skin (Lappe, JAMA 2017). It should be noted that most women in the study were not lacking calcium intake, with average daily calcium intake from foods of 676 mg and many averaging another 500 mg daily from their own supplements, which they were allowed to continue. Another, a large, multi-year study in the U.S. found that daily supplementation with calcium (1,200 mg) and/or vitamin D3 (1,000 IU) did not reduce the risk of developing new precancerous colorectal polyps (adenomas) among people who had adenomas removed in the past. There was no statistically significant difference in the occurrence of adenomas between those who were or were not given the supplements. On average, without the study supplements, dietary intake of calcium in the study was somewhat inadequate (about 600 to 700 mg daily (Baron, NEJM 2015). (Note: These findings may not apply to people with vitamin D levels which are inadequate, i.e., under 20 ng/mL).
A study of white postmenopausal women found that calcium supplementation was associated with a 3.8% reduced risk of death over a 22 year period (Mursu, Arch Int Med 2011). However, the benefit did not exist when more than 900 mg of calcium per day was taken from supplements (see Concerns and Cautions for potential risks of calcium supplementation). Similarly, a study in Canadian adults found that taking daily supplements containing up to 1,000 mg of calcium was associated with a 22% reduced risk of death in women (but not men) over the 10-year study period compared to those not taking a calcium supplement. At doses of 1,000 mg or more, no reduction in death was found for women or men (Langsetmo, J Clin Endocrinol Metab 2013).
Looking specifically at the risk of death from cardiovascular disease, a large, 12-year study of men and women found that deaths from cardiovascular disease decreased with increasing total calcium intakes (from all sources combined) up to approximately 1,200 mg per day (which is the RDA for women and all older adults) (Xiao, JAMA Intern Med 2013).
While early studies seemed promising, hopes that increased calcium intake could aid weight loss have largely been dashed by subsequent studies. Exceptional health claims made in recent years about coral calcium, such as the ability to cure cancer, are unsubstantiated. In fact, some evidence suggests that calcium intake may be associated with an increased risk of prostate cancer (Schwartz, Canc Epidemiol Biomarkers 2012)(See Cautions and Concerns).
Other possible benefits of calcium supplementation include reducing PMS symptoms, and slightly lowering blood pressure.
For more information about the uses, see the excellent article about calcium in the Natural Products Encyclopedia on this Web site.