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  • Office of Dietary Supplements
  • NIH Clinical Center
  • National Institutes of Health


Calcium absorption refers to the amount of calcium that is absorbed from the digestive tract into our body's circulation. Calcium absorption can be affected by the calcium status of the body, vitamin D status, age, pregnancy and plant substances in the diet. The amount of calcium consumed at one time such as in a meal can also affect absorption. For example, the efficiency of calcium absorption decreases as the amount of calcium consumed at a meal increases.


Net calcium absorption can be as high as 60% in infants and young children, when the body needs calcium to build strong bones {2,11}. Absorption slowly decreases to 15-20% in adulthood and even more as one ages {2,11,12}. Because calcium absorption declines with age, recommendations for dietary intake of calcium are higher for adults ages 51 and over.

Vitamin D:

Vitamin D helps improve calcium absorption. Your body can obtain vitamin D from food and it can also make vitamin D when your skin is exposed to sunlight. thus, adequate vitamin D intake is essential.: http://ods.od.nih.gov/factsheets/VitaminD-Consumer/


Current calcium recommendations for nonpregnant women are also sufficient for pregnant women because intestinal calcium absorption increases during pregnancy {2}. For this reason, the calcium recommendations established for pregnant women are not different than the recommendations for women who are not pregnant.

Plant substances:

Phytic acid and oxalic acid, which are found naturally in some plants, may bind to calcium and prevent it from being absorbed optimally. These substances affect the absorption of calcium from the plant itself not the calcium found in other calcium-containing foods eaten at the same time {6}. Examples of foods high in oxalic acid are spinach, collard greens, sweet potatoes, rhubarb, and beans. Foods high in phytic acid include whole grain bread, beans, seeds, nuts, grains, and soy isolates {2}. Although soybeans are high in phytic acid, the calcium present in soybeans is still partially absorbed {2,13}. Fiber, particularly from wheat bran, could also prevent calcium absorption because of its content of phytate. However, the effect of fiber on calcium absorption is more of a concern for individuals with low calcium intakes. The average American tends to consume much less fiber per day than the level that would be needed to affect calcium absorption.
Calcium excretion refers to the amount of calcium eliminated from the body in urine, feces and sweat. Calcium excretion can be affected by many factors including dietary sodium, protein, caffeine and potassium.

Sodium and protein:

Typically, dietary sodium and protein increase calcium excretion as the amount of their intake is increased {5,14}. However, if a high protein, high sodium food also contains calcium, this may help counteract the loss of calcium.


Increasing dietary potassium intake (such as from 7-8 servings of fruits and vegetables per day) in the presence of a high sodium diet (>5100 mg/day, which is more than twice the Tolerable Upper Intake Level of 2,300 mg for sodium per day) may help decrease calcium excretion particularly in postmenopausal women {15,16}.


Caffeine has a small effect on calcium absorption. It can temporarily increase calcium excretion and may modestly decrease calcium absorption, an effect easily offset by increasing calcium consumption in the diet {17}. One cup of regular brewed coffee causes a loss of only 2-3 mg of calcium easily offset by adding a tablespoon of milk {14}. Moderate caffeine consumption, (1 cup of coffee or 2 cups of tea per day), in young women who have adequate calcium intakes has little to no negative effects on their bones {18}.

Other factors:

Phosphorus: The effect of dietary phosphorus on calcium is minimal. Some researchers speculate that the detrimental effects of consuming foods high in phosphate such as carbonated soft drinks is due to the replacement of milk with soda rather than the phosphate level itself {19,20}.


Alcohol can affect calcium status by reducing the intestinal absorption of calcium {21}. It can also inhibit enzymes in the liver that help convert vitamin D to its active form which in turn reduces calcium absorption {3}. However, the amount of alcohol required to affect calcium absorption is unknown. Evidence is currently conflicting whether moderate alcohol consumption is helpful or harmful to bone.
In summary, a variety of factors that may cause a decrease in calcium absorption and/or increase in calcium excretion may negatively affect bone health


Calcium and bone health:

Your bones are living tissues and continue to change throughout life. During childhood and adolescence, bones increase in size and mass. Bones continue to add more mass until around age 30, when peak bone mass is reached. Peak bone mass is the point when the maximum amount of bone is achieved. Because bone loss, like bone growth, is a gradual process, the stronger your bones are at age 30, the more your bone loss will be delayed as you age. Therefore, it is particularly important to consume adequate calcium and vitamin D throughout infancy, childhood, and adolescence. It is also important to engage in weight-bearing exercise to maximize bone strength and bone density (amount of bone tissue in a certain volume of bone) to help prevent osteoporosis later in life. Weight bearing exercise is the type of exercise that causes your bones and muscles to work against gravity while they bear your weight. Resistance exercises such as weight training are also important because they help to improve muscle mass and bone strength.

Examples of weight bearing exercise:

  • walking
  • running
  • dancing
  • aerobics
  • skating

Examples of NON-weight bearing exercise:

  • swimming
  • bicycling
  • water aerobics

Osteoporosis is a disorder characterized by porous, fragile bones:

It is a serious public health problem for more than 10 million Americans, 80% of whom are women. Another 34 million Americans have osteopenia, or low bone mass, which precedes osteoporosis. Osteoporosis is a concern because of its association with fractures of the hip, vertebrae, wrist, pelvis, ribs, and other bones {22}. Each year, Americans suffer from 1.5 million fractures because of osteoporosis {23}.

Osteoporosis and osteopenia can result from dietary factors such as: {11,24,25}

  • chronically low calcium intake
  • low vitamin D intake
  • poor calcium absorption
  • excess calcium excretion

When calcium intake is low or calcium is poorly absorbed, bone breakdown occurs because the body must use the calcium stored in bones to maintain normal biological functions such as nerve and muscle function. Bone loss also occurs as a part of the aging process. A prime example is the loss of bone mass observed in post-menopausal women because of decreased amounts of the hormone estrogen. Researchers have identified many factors that increase the risk for developing osteoporosis. These factors include being female, thin, inactive, of advanced age, cigarette smoking, excessive intake of alcohol, and having a family history of osteoporosis {26}.

In 1993 the FDA authorized a health claim for food labels on calcium and osteoporosis in response to scientific evidence that an inadequate calcium intake is one factor that can lead to low peak bone mass and is considered a risk factor for osteoporosis {27}. The claim states that "adequate calcium intake throughout life is linked to reduced risk of osteoporosis through the mechanism of optimizing peak bone mass during adolescence and early adulthood and decreasing bone loss later in life".




Although osteoporosis affects people of different races, genders and ethnicities, women are at highest risk because their skeletons are smaller to start with and because of the accelerated bone loss that accompanies menopause. Adequate calcium and vitamin D intakes, as well as weight bearing exercise are critical to the development and maintenance of healthy bone throughout the lifecycle. Older adults should strive to maintain recommended daily calcium intakes as well as an adequate vitamin D intake.

Calcium and high blood pressure:

Some observational studies (type of research study in which the treatment/intervention is observed and not controlled by the researchers) and experimental studies (type of research study in which the researchers control the treatments/interventions and that are assigned to participants) indicate that individuals who eat a vegetarian diet high in minerals (including calcium, magnesium and potassium) and fiber, and low in fat, tend to have reduced blood pressure {29-31}.

Findings from some clinical trials (a specific type of experimental study) used to evaluate the effects of one or more treatments/interventions in humans) indicate that an increased calcium intake lowers blood pressure and the risk of hypertension (high blood pressure) {32,33}. However, the results of some studies produced small and inconsistent reductions in blood pressure. One reason for these results is because these research studies tended to test the effect of single nutrients rather than foods on blood pressure.

Calcium and kidney stones:

Kidney stones are crystallized deposits of calcium and other minerals in the urinary tract. Calcium oxalate stones are the most common form of kidney stones in the US. High calcium intakes or high calcium absorption were previously thought to contribute to the development of kidney stones. However, more recent studies show that high dietary calcium intakes actually decrease the risk for kidney stones {55-57}. Other factors such as high oxalate intake and reduced fluid consumption appear to be more of a risk factor in the formation of kidney stones than calcium in most individuals {58}.

Calcium and weight managemen:

Several studies, primarily observational in nature, have linked higher calcium intakes to lower body weights or less weight gain over time {59-62}. Two explanations have been proposed for how calcium may help to regulate body weight. First, high-calcium intakes may reduce calcium concentrations in fat cells by lowering the production of two hormones (parathyroid hormone and an active form of vitamin D), which in turn increases fat breakdown in these cells and discourages its accumulation {61}. In addition, calcium from food or supplements may bind to small amounts of dietary fat in the digestive tract and prevent its absorption, carrying the fat (and the calories it would otherwise provide) out in the feces {61,63}.

When can a calcium deficiency occur?:

Inadequate calcium intake, decreased calcium absorption, and increased calcium loss in urine can decrease total calcium in the body, with the potential of producing osteoporosis and the other consequences of chronically low calcium intake. If an individual does not consume enough dietary calcium or experiences rapid losses of calcium from the body, calcium is withdrawn from their bones in order to maintain calcium levels in the blood.

Signs of calcium deficiency:

Because circulating blood calcium levels are tightly regulated in the bloodstream, hypocalcemia (low blood calcium) does not usually occur due to low calcium intake, but rather results from a medical problem or treatment such as renal failure, surgical removal of the stomach (which significantly decreases calcium absorption), and use of certain types of diuretics (which result in increased loss of calcium and fluid through urine). Simple dietary calcium deficiency produces no signs at all. Hypocalcemia can cause numbness and tingling in fingers, muscle cramps, convulsions, lethargy, poor appetite, and mental confusion {1}. It can also result in abnormal heart rhythms and even death. Individuals with medical problems that result in hypocalcemia should be under a medical doctor's care and receive specific treatment aimed at normalizing calcium levels in the blood. {Please note that the symptoms described here may be due to a medical condition other than hypocalcemia.} It is important to consult a health professional if you experience any of these symptoms.


Post-Menopausal Women:

Menopause often leads to increases in bone loss with the most rapid rates of bone loss occurring during the first five years after menopause {75}. Drops in estrogen production after menopause result in increased bone resorption, and decreased calcium absorption {12,76,77}. Annual decreases in bone mass of 3-5% per year are often seen during the years immediately following menopause, with decreases less than 1% per year seen after age 65 {78}. Two studies are in agreement that increased calcium intakes during menopause will not completely offset menopause bone loss {79,80}.

Is there a health risk of too much calcium?:

The Tolerable Upper Limit (UL) is the highest level of daily intake of calcium from food, water and supplements that is likely to pose no risks of adverse health effects to almost all individuals in the general population {2}. The UL for children and adults ages 1 year and older (including pregnant and lactating women) is 2500 mg/day. It was not possible to establish a UL for infants under the age of 1 year.

While low intakes of calcium can result in deficiency and undesirable health conditions, excessively high intakes of calcium can also have adverse effects. Adverse conditions associated with high calcium intakes are hypercalcemia (elevated levels of calcium in the blood), impaired kidney function and decreased absorption of other minerals {2}. Hypercalcemia can also result from excess intake of vitamin D, such as from supplement overuse at levels of 50,000 IU or higher {1}. However, hypercalcemia from diet and supplements is very rare. Most cases of hypercalcemia occur as a result of malignancy - especially in the advanced stages.

Another concern with high calcium intakes is the potential for calcium to interfere with the absorption of other minerals, iron, zinc, magnesium, and phosphorus {108-111}.

Most Americans should consider their intake of calcium from all foods including fortified ones before adding supplements to their diet to help avoid the risk of reaching levels at or near the UL for calcium (2500 mg). If you need additional assistance regarding your calcium needs, consider checking with a physician or registered dietitian.

Calcium and Medication Interactions:

Calcium supplements have the potential to interact with several prescription and over the counter medications. Further information about these interactions is described below. Some examples of medications that may interact with calcium include:

  • digoxin
  • fluroquinolones
  • levothyroxine
  • antibiotics in tetracycline family
  • tiludronate disodium
  • anticonvulsants such as phenytoin
  • thiazide, type of diuretic
  • glucocorticoids
  • mineral oil or stimulant laxatives
  • aluminum or magnesium containing antacids

Calcium supplements may decrease levels of the drug digoxin, a medication given to heart patients {112}. The interaction between calcium and vitamin D supplements and digoxin may also increase the risk of hypercalcemia. Calcium supplements also interact with fluoroquinolones (a class of antibiotics including ciprofloxacin), levothyroxine (thyroid hormone) used to treat thyroid deficiency, antibiotics in the tetracycline family, tiludronate disodium (a drug used to treat Paget's disease), and phenytoin (an anti-convulsant drug). In all of these cases, calcium supplements decrease the absorption of these drugs when the two are taken at the same time {112,113}.

Thiazide, and diuretics similar to thiazide, can interact with calcium carbonate and vitamin D supplements to increase the chances of developing hypercalcemia and hypercalciuria (elevated levels of calcium in urine) {113}. Aluminum and magnesium antacids can both increase urinary calcium excretion. Mineral oil and stimulant laxatives can both decrease dietary calcium absorption. Furthermore, glucocorticoids (for example: prednisone) can cause calcium depletion and eventually osteoporosis, when used for more than a few weeks {113}.

Supplemental sources of calcium:

The two main forms of calcium found in supplements are carbonate and citrate. Calcium carbonate is the most common because it is inexpensive and convenient. The absorption of calcium citrate is similar to calcium carbonate. For instance, a calcium carbonate supplement contains 40% calcium while a calcium citrate supplement only contains 21% calcium. However, you have to take more pills of calcium citrate to get the same amount of calcium as you would get from a calcium carbonate pill since citrate is a larger molecule than carbonate. One advantage of calcium citrate over calcium carbonate is better absorption in those individuals who have decreased stomach acid.  {116}. Other forms of calcium in supplements or fortified foods include calcium gluconate, lactate, and phosphate.

The amount of calcium your body obtains from various supplements depends on the amount of elemental calcium in the tablet. The amount of elemental calcium is the amount of calcium that actually is in the supplement. Calcium absorption also depends on the total amount of calcium consumed at one time and whether the calcium is taken with food or on an empty stomach.

Absorption from supplements is best in doses 500 mg or less because the percent of calcium absorbed decreases as the amount of calcium in the supplement increases {117,118}. Therefore, someone taking 1000 mg of calcium in a supplement should take 500 mg twice a day instead of 1000 mg calcium at one time.

Some common complaints of calcium supplement use are gas, bloating and constipation. If you have such symptoms, you may want to spread the calcium dose out throughout the day, change supplement brands, take the supplement with meals and/or check with your pharmacist or health care provider.



WARNING: Discrepancies in labeling can be deceptive and make people believe they are getting more calcium than they think they are. Unless the ingredients are in brackets ( ) you are only getting a fraction of the ingredient,

e.g. Calcium Citrate 1000 mg is the same as Calcium (Citrate) 210 mg.

Without the brackets, it means that 1000 mg of calcium citrate is only 210 mg of calcium [21%]. The remaining 790 mg is citrate.

You are only getting 210 mg instead of 1000 mg of calcium.


Alpha Calcium Health Supprt choose the most NATURAL ingredients so you get the best and most ABSORBABLE liquid calcium supplement available without paying a ridiculous price. Remember... a small amount of 'Natural' ingredients in a liquid form form are more effective than large amounts of 'Synthetic' ingredients in tablet form.


Did you know that too much calcium depletes copper and that it also reduces zinc absorbtion in bone. There is a finite range between the extremes of deficiency and toxicity. Alpha Health Support uses a balanced approach by using the essential nutrients recommended by research and the recommendations of Dr Betty Kamen Ph.D.


Alpha Calcium Health Supprt uses the RDA (Recommended Daily Allowance) for moderation.

ACTIVE LIQUID CALCIUM uses all the cofactors recommended by Dr Betty Kamen Ph.D. and the calcium/magnesium ratio from the Dr Guy Abraham Ph.D. study of 1.2 to 1 of magnesium over calcium.

A Must Read book regarding Calcium and Bone Health.

"Americans drink more milk than the people of any other nation. Yet we have the higest incidence of bone problems."

Dr Betty Kamen Ph.D