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Summary: What You Need to Know About Calcium Supplements
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. Taking these factors into consideration, ConsumerLab selected 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.
Watch LIVE Q&A with CL Founder, Dr. Tod Cooperman
What It Is:
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: Bone Health and Fractures
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.) Overall, studies have not shown supplementation with calcium, vitamin D, or the combination to significantly reduce the risk of hip fractures in older, community-dwelling (i.e., not in nursing or hospital facility) adults, according to an analysis of 33 clinical trials. A potential weakness of this analysis is that some of the studies did not assess baseline levels of vitamin D, i.e., whether or not patients were deficient to start (Zhao, JAMA 2017).Consistent with these earlier findings, the use of calcium supplements was not associated with a reduced incidence of bone fracture in women who were pre-menopause or early peri-menopause even though it was associated with a slower rate of decline in bone mineral density (measured at the lumbar spine and neck of the femur, i.e., the thigh bone) -- particularly in pre-menopausal women. The study involved women aged 42 to 52 years at enrollment who were followed for 10 years (Bailey, JBMRPLUS 2019).
For bone health, everyone should try to get the recommended daily intake of calcium from their diets. If your diet is not adequate, it would seem prudent and safe -- particularly for girls ages 9 to 13 and women from the time of pre-menopause and after -- to supplement with moderate amounts of calcium (no more than 300 mg to 500 mg per serving).
Cancer and Mortality 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, study in the U.S. found that daily supplementation with calcium (1,200 mg) and/or vitamin D3 (1,000 IU) for 3 to 5 years did not reduce the risk of developing new precancerous colorectal polyps (adenomas) among men and women 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, but the vast majority of women had adequate levels of vitamin D (Baron, NEJM 2015). (Note: These findings may not apply to people with vitamin D levels which are inadequate, i.e., under 20 ng/mL). Disturbingly, over six to ten years after this study, the risk of precancerous polyps was 165% and 281% higher, respectively, among those who had taken the calcium or calcium plus vitamin D supplements compared to those who had taken no supplement. Supplementation with vitamin D alone did not increase the risk of developing polyps. The increase in risk was greatest among women and current smokers. Bear in mind that calcium from the diet (such as from dairy products) is not associated with an increased risk of polyps (Crockett, Gut 2018).
Very preliminary studies indicate that calcium levels fall in patients with COVID-19, the disease caused by the coronavirus SARS-CoV-2. For example, 75% of hospitalized patients in a study in Wuhan China had low blood levels of calcium (hypocalcemia) on admission (i.e., below, 2.20 mmol/L or 8.8 mg/dL) and this correlated with worse values on other biologic markers of disease. Those with levels at or below 2.0 mmol/L were more likely to have organ injury and to die over the 28-day study period (Sun, Research Square 2020 — preprint, not peer-reviewed). A review of the records of 15 patients hospitalized for COVID-19 at the Mayo Clinic in Arizona from late March to early April showed that those with severe cases also experienced progressive declines in calcium, as well as albumin, while those with mild cases did not. Patients with severe cases also had high levels of unbound fatty acids, which other research suggests may cause injury to organs. Calcium and, to a lesser extent, albumin, are effective at binding up these fatty acids and the researchers hypothesized that supplementing with calcium and albumin during COVID-19 hospitalization may, consequently, reduce organ failure and the need for intensive care. However, clinical studies are necessary to prove this (El-Kurdi, Gastroenterol 2020).
Mortality and Cardiovascular Disease 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).
Age-Related Macular Degeneration (AMD)
Higher consumption of calcium from foods has been associated with lower risk of AMD, while there is mixed evidence regarding the effects of calcium from supplements. A study in Australia that followed over 2,000 men and women (age 50 and older) for 15 years found that those who reported the lowest calcium intake from foods (< 565 mg per day) had a modestly higher risk of developing late (i.e., advanced) age-related macular degeneration (AMD) after 10 to 15 years than those who reported consuming the highest amount of calcium from foods (> 1,247 mg per day) (Gopinath Br J Nutr 2014). With regard to calcium intake from supplements, a study among over 3,000 men and women found that, after age 67, those who reported consuming more than 800 mg of calcium per day from supplements and/or antacids were 164% more likely to be diagnosed with AMD than those who did not take calcium supplements (Kakigi, JAMA Ophthalmol 2015). On the other hand, analysis of data from the Age-Related Eye Disease Study (AREDS) found that women over 65 with high intakes of calcium (averaging about 1,400 mg/day) from supplements had, over the following 10 years, a statistically significant 30% lower risk of developing neovascular ("wet") AMD than those who did not take supplements. They also had a 22% lower risk of late AMD, although this was not deemed statistically significant, and there was no risk reduction with regard to atrophic ("dry") AMD. High intake of calcium from food (about 1,200 mg or more per day) by men and women was associated with a 27% lower risk of late AMD and 20% lower risk of atrophic AMD compared to low intake (about 600 mg or less per day) (Tisdale, JAMA Opthal 2019). Note that none of these studies prove a cause-and-effect relationship, as they were not clinical trials.
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.