The body eliminates some calcium in sweat, urine, and feces. Foods and activities that encourage these functions may reduce the levels of calcium in the body.
Taking supplements can increase daily calcium intake by about mg of calcium a day, on average. Many calcium supplements also contain vitamin D. Vitamin D encourages the synthesis of proteins in the body and helps the body absorb calcium. Magnesium also plays a role in strengthening bones, and calcium supplements may also contain magnesium. There are different types of supplements. A doctor can recommend the best option. Elemental calcium is the pure mineral, but calcium in its natural form exists with other compounds.
Supplements may contain different proportions of calcium compounds and elemental calcium. For example:. This type is commonly available, and it is relatively cheap and convenient. A person should take it with food, as stomach acid helps the body absorb it. A person can take it with or without food. It is useful for people with inflammatory bowel disease, achlorhydria, and some absorption disorders. Most experts agree that it is better to obtain nutrients from natural food sources, although sometimes it is not possible to get enough in this way.
Some people report gastrointestinal symptoms, such as bloating, constipation , gas, or a combination of all three when using calcium supplements. Calcium citrate usually has fewer and less pronounced side effects than calcium carbonate. Taking the supplements with food, or spreading their intake throughout the day may help reduce the occurrence or intensity of the side effects.
Although high calcium levels due to taking too many supplements might cause these severe side effects, they are more likely the result of cancer and thyroid problems, according to the ODS.
Past studies have raised concerns that taking calcium supplements may increase the risk of:. Calcium is essential for building and maintaining healthy bones and teeth. The RDAs are established with an understanding of calcium bioavailability in food. Also keep in mind that the exact amount of calcium absorbed in the body will vary among individuals based on their metabolism and what other foods are eaten at the same meal.
In general, eating a variety of calcium-rich foods can help to offset any small losses. Blood levels of calcium are tightly regulated. Bones will release calcium into the blood if the diet does not provide enough, and no symptoms usually occur. A more serious deficiency of calcium, called hypocalcemia, results from diseases such as kidney failure, surgeries of the digestive tract like gastric bypass, or medications like diuretics that interfere with absorption.
A gradual, progressive calcium deficiency can occur in people who do not get enough dietary calcium in the long-term or who lose the ability to absorb calcium. The first early stage of bone loss is called osteopenia and, if untreated, osteoporosis follows. Examples of people at risk include:. After a diagnosis of osteoporosis, your physician may prescribe over-the-counter calcium supplements. However, there are several points to consider when using calcium supplements. Too much calcium in the blood is called hypercalcemia.
The Upper Limit UL for calcium is 2, mg daily from food and supplements. People over the age of 50 should not take more than 2, mg daily, especially from supplements, as this can increase risk of some conditions like kidney stones, prostate cancer, and constipation. Some research has shown that in certain people, calcium can accumulate in blood vessels with long-term high doses and cause heart problems.
Calcium is also a large mineral that can block the absorption of other minerals like iron and zinc. Certain nutrients and medications may increase your need for calcium because they either lower the absorption of calcium in the gut or cause more calcium to be excreted in the urine.
These include: corticosteroids example: prednisone , excess sodium in the diet, phosphoric acid such as found in dark cola sodas, excess alcohol, and oxalates see Are anti-nutrients harmful? The contents of this website are for educational purposes and are not intended to offer personal medical advice. You should seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.
Never disregard professional medical advice or delay in seeking it because of something you have read on this website. The Nutrition Source does not recommend or endorse any products. Skip to content The Nutrition Source. Harvard T. The Nutrition Source Menu. Search for:. Blood pressure Several literature reviews on the topic of total calcium intake, from food and supplements, and blood pressure have suggested a possible link to lowering high blood pressure.
Cardiovascular disease Some research has raised concerns about calcium supplements and heart health. Bone health Calcium is one of the most important nutrients required for bone health. Possible reasons: The study only looked at calcium intakes from a supplement provided to the participants, and did not account for calcium from the diet or estimate the total amount of calcium from both food and supplements.
Back to Vitamins and minerals. A lack of calcium could lead to a condition called rickets in children, and osteomalacia or osteoporosis in later life.
Taking high doses of calcium more than 1,mg a day could lead to stomach pain and diarrhoea. Dual x-ray absorptiometry testing of bone mineral density can be used to assess cumulative calcium status over the lifetime because the skeleton stores almost all calcium in the body [ 3 ]. DRIs is the general term for a set of reference values used for planning and assessing nutrient intakes of healthy people.
These values, which vary by age and sex, include:. Table 1 lists the current RDAs for calcium [ 1 ]. For adults, the main criterion that the FNB used to establish the RDAs was the amount needed to promote bone maintenance and neutral calcium balance. For infants aged 0 to 12 months, the FNB established an AI that is equivalent to the mean intake of calcium in healthy, breastfed infants.
For children and adolescents, the RDAs are based on intakes associated with bone accumulation and positive calcium balance.
Food Milk, yogurt, and cheese are rich natural sources of calcium [ 1 ]. Nondairy sources include canned sardines and salmon with bones as well as certain vegetables, such as kale, broccoli, and Chinese cabbage bok choi.
Most grains do not have high amounts of calcium unless they are fortified. However, they contribute to calcium intakes, even though they contain small amounts of calcium, because people consume them frequently [ 1 ]. Foods fortified with calcium in the United States include many fruit juices and drinks, tofu, and ready-to-eat cereals [ 1 , 8 ].
Calcium citrate malate is a well-absorbed form of calcium used in some fortified juices [ 3 ]. Calcium absorption varies by type of food.
Certain compounds in plants e. In addition to spinach, foods with high levels of oxalic acid include collard greens, sweet potatoes, rhubarb, and beans [ 1 ]. The bioavailability of calcium from other plants that do not contain these compounds—including broccoli, kale, and cabbage—is similar to that of milk, although the amount of calcium per serving is much lower [ 3 ].
When people eat many different types of foods, these interactions with oxalic or phytic acid probably have little or no nutritional consequence. Net absorption of dietary calcium is also reduced to a small extent by intakes of caffeine and phosphorus and to a greater extent by low status of vitamin D [ ]. The U. The two most common forms of calcium in supplements are calcium carbonate and calcium citrate [ 1 ].
In people with low levels of stomach acid, the solubility rate of calcium carbonate is lower, which could reduce the absorption of calcium from calcium carbonate supplements unless they are taken with a meal [ 3 ]. Calcium citrate is less dependent on stomach acid for absorption than calcium carbonate, so it can be taken without food [ 1 ]. Other calcium forms in supplements include calcium sulfate, ascorbate, microcrystalline hydroxyapatite, gluconate, lactate, and phosphate [ 14 ].
The forms of calcium in supplements contain varying amounts of elemental calcium. Elemental calcium is listed in the Supplement Facts panel, so consumers do not need to calculate the amount of calcium supplied by various forms of calcium in supplements. The percentage of calcium absorbed from supplements, as with that from foods, depends not only on the source of calcium but also on the total amount of elemental calcium consumed at one time; as the amount increases, the percentage absorbed decreases.
Absorption from supplements is highest with doses of mg or less [ 15 ]. Some individuals who take calcium supplements might experience gastrointestinal side effects, including gas, bloating, constipation, or a combination of these symptoms.
Calcium carbonate appears to cause more of these side effects than calcium citrate, especially in older adults who have lower levels of stomach acid [ 1 ]. Symptoms can be alleviated by switching to a supplement containing a different form of calcium, taking smaller calcium doses more often during the day, or taking the supplement with meals.
Medicines Because of its ability to neutralize stomach acid, calcium carbonate is contained in some over-the-counter antacid products, such as Tums and Rolaids. Depending on its strength, each chewable pill or soft chew provides about to mg of calcium [ 14 ].
A substantial proportion of people in the United States consume less than recommended amounts of calcium. Average daily intakes of calcium from foods and beverages are 1, mg for men aged 20 and older and mg for women [ 18 ]. For children aged 2—19, mean daily intakes of calcium from foods and beverages range from to 1, mg [ 18 ]. Average daily calcium intakes from both foods and supplements are 1, mg for men, 1, mg for women, and to 1, mg for children [ 18 ].
Poverty is also associated with a higher risk of inadequacy. NHANES data from to show that the risk of inadequate calcium intakes less than to 1, mg is Calcium deficiency can reduce bone strength and lead to osteoporosis, which is characterized by fragile bones and an increased risk of falling [ 1 ]. Calcium deficiency can also cause rickets in children and other bone disorders in adults, although these disorders are more commonly caused by vitamin D deficiency.
In children with rickets, the growth cartilage does not mineralize normally, which can lead to irreversible changes in the skeletal structure [ 1 ]. Another effect of chronic calcium deficiency is osteomalacia, or defective bone mineralization and bone softening, which can occur in adults and children [ 1 ].
For rickets and osteomalacia, the requirements for calcium and vitamin D appear to be interrelated in that the lower the serum vitamin D level measured as hydroxyvitamin D [25 OH D] , the more calcium is needed to prevent these diseases [ 21 ].
Hypocalcemia serum calcium level less than 8. Hypocalcemia can be asymptomatic, especially when it is mild or chronic [ 23 ]. When signs and symptoms do occur, they can range widely because low serum calcium levels can affect most organs and symptoms [ 24 ]. The most common symptom is increased neuromuscular irritability, including perioral numbness, tingling in the hands and feet, and muscle spasms [ 23 ].
More severe signs and symptoms can include renal calcification or injury, brain calcification, neurologic symptoms e. Postmenopausal women Menopause leads to bone loss because decreases in estrogen production reduce calcium absorption and increase urinary calcium loss and calcium resorption from bone [ 1 ].
Over time, these changes lead to decreased bone mass and fragile bones [ 1 ]. The calcium RDA is 1, mg for women older than 50 years vs. Individuals who avoid dairy products People with lactose intolerance, those with an allergy to milk, and those who avoid eating dairy products including vegans have a higher risk of inadequate calcium intakes because dairy products are rich sources of calcium [ 1 , 27 ]. Options for increasing calcium intakes in individuals with lactose intolerance include consuming lactose-free or reduced-lactose dairy products, which contain the same amounts of calcium as regular dairy products [ 1 , 3 ].
Those who avoid dairy products because of allergies or for other reasons can obtain calcium from non-dairy sources, such as some vegetables e. However, these individuals typically need to eat foods fortified with calcium or take supplements to obtain recommended amounts [ 28 ].
This section focuses on six health conditions and diseases in which calcium might play a role: bone health in older adults, cancer, cardiovascular disease CVD , preeclampsia, weight management, and metabolic syndrome.
Bone health in older adults Bone is constantly being remodeled. Declining levels of estrogen in women during menopause and for approximately 5 years afterward lead to rates of bone resorption that are higher than rates of bone formation, resulting in a rapid decrease in bone mass [ 7 ]. Over time, postmenopausal women can develop osteoporosis, in which bone strength is compromised because of lower BMD and bone quality [ 1 ].
Age-related bone loss can also occur in men and lead to osteoporosis, but fracture risk tends to increase in older men about 5 to 10 years later than in older women [ 1 ]. Osteoporosis increases the risk of fractures, especially of the hip, vertebrae, and forearms [ 1 , 7 ].
FDA has approved a health claim for the use of supplements containing calcium and vitamin D to reduce the risk of osteoporosis [ 29 ]. However, not all research supports this claim. In spite of the importance of calcium in bone health, observational evidence is mixed on the link between calcium intakes and measures of bone strength in older adults. Support for such a link comes from an analysis of — NHANES cross-sectional data on 2, adults aged 60 and older Results were similar in of the women who were followed for 6 years, even though mean daily intakes of calcium dropped by an average of 40 mg during this period.
Some but not all clinical trials have found that calcium supplementation can improve bone health in older adults. On average, women lost 1.
Several recent systematic reviews and meta-analyses have found that supplementation with calcium alone or a combination of calcium and vitamin D increases BMD in older adults. For example, a systematic review and meta-analysis included 15 RCTs in postmenopausal women but did not include the two studies described in the previous paragraph in 78, women, of which 37, were in the intervention group and 40, were in the control group [ 34 ].
Supplementation with both calcium and vitamin D or consumption of dairy products fortified with both nutrients increased total BMD as well as BMD at the lumbar spine, arms, and femoral neck. However, in subgroup analyses, calcium had no effect on femoral neck BMD. Earlier systematic reviews and meta-analyses found a positive relationship between calcium and vitamin D supplementation and increased BMD in older males [ 35 ] and between higher calcium intakes from dietary sources or supplements in adults over 50 and higher BMD [ 25 ].
However, whether these BMD increases were clinically significant is not clear. As with the evidence on the link between increased calcium intakes and reductions in BMD loss, the findings of research on the use of calcium supplementation to prevent fractures in older adults are mixed.
For the most part, the observational evidence does not show that increasing calcium intakes reduces the risk of fractures and falls in older adults. For example, a longitudinal cohort study of 1, women aged 42 to 52 years at baseline who were followed for 10—12 years found that fracture risk was not significantly different in calcium supplement users some of whom also took vitamin D supplements and nonusers, even though supplement use was associated with less BMD loss throughout the study period [ 36 ].
Some clinical trial evidence shows that supplements containing a combination of calcium and vitamin D can reduce the risk of fractures in older adults. However, findings were negative in another systematic review and meta-analysis that included 14 RCTs of calcium supplementation and 13 trials comparing calcium and vitamin D supplements with hormone therapy, placebo, or no treatment in participants older than 50 years [ 38 ].
The results showed that calcium supplementation alone had no effect on risk of hip fracture, and supplementation with both calcium and vitamin D had no effect on risk of hip fracture, nonvertebral fracture, vertebral fracture, or total fracture.
Similarly, a systematic review of 11 RCTs in 51, adults aged 50 and older found that supplementation with vitamin D and calcium for 2 to 7 years had no impact on risk of total fractures or of hip fractures [ 39 ].
Preventive Services Task Force USPSTF concluded with moderate certainty that daily doses of less than 1, mg calcium and less than IU 10 mcg vitamin D do not prevent fractures in postmenopausal women and that the evidence on larger doses of this combination is inadequate to assess the benefits in this population [ 40 ]. The USPSTF also determined the evidence on the benefits of calcium supplementation alone or with vitamin D to be inadequate to assess its effect on preventing fractures in men and premenopausal women.
Additional research is needed before conclusions can be drawn about the use of calcium supplements to improve bone health and prevent fractures in older adults. Cancer Calcium might help reduce the risk of cancer, especially in the colon and rectum [ 1 ].
However, evidence on the relationship between calcium intakes from foods or supplements and different forms of cancer is inconsistent [ 4 ]. All-cancer incidence and mortality. Most clinical trial evidence does not support a beneficial effect of calcium supplements on cancer incidence. A 4-year study of 1, mg calcium and 2, IU 50 mcg vitamin D or placebo daily for 4 years in 2, healthy women aged 55 years and older showed that supplementation did not reduce the risk of all types of cancer [ 41 ].
The large WHI study described above also found no benefit of supplemental calcium and vitamin D on cancer incidence [ 42 ]. In addition, a meta-analysis of 10 RCTs that included 10, individuals who took supplements containing mg calcium or more without vitamin D for a mean of 3.
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