Calcium

Calcium, also spelled "calcium," is a silvery-white soft alkaline earth metal that is not stable in air. It has the atomic number 20 and the chemical symbol Ca. It was discovered and described in 1808 by the English chemist Sir Humphry Davy (1778- 1829) in London. It does not occur in nature in pure form, but only in numerous compounds. For example, as calcium carbonate or in limestone, gypsum and dolomite. In total, more than 200 minerals are known to contain calcium. In the earth's crust it is the 5th most common element before sodium.

The number of Ca ions is also a measure of the hardness of (drinking) water. Calcium is stored in the teeth, bones, shells and eggshells of living organisms and is contained in a number of plants. In the human organism and in most animals, calcium is the mineral with the highest content. Thus, an adult male has more than one kilogram of calcium in his body; in women, the proportion is somewhat lower due to their lower skeletal mass. By far the largest proportion of calcium is stored in teeth and bones; only about 1% is found in the blood and other tissues. Of the calcium in the blood, about 55% is present as free Ca2, about 40% is bound to proteins and about 5% to organic acids.

Occurrence

The most important dietary sources of calcium are milk and dairy products. Calcium-rich dairy products include buttermilk and cheese, for example. With cheese, however, the production process plays a decisive role in how high the calcium content is. Hard cheese is usually richer in calcium than soft cheese or even processed cheese. In plant foods, the calcium content is usually only moderately high. Some plant foods, however, such as coconut flakes or sesame seeds, are characterized by a very high calcium content.

Food (per 100 g of edible portion) Calcium (mg):

• Appenzeller, 50 % fat in dry matter 800
• Bavariablu, 70 % fat in dry matter 360
• Mountain cheese, 45 % fat in dry matter 1100
• Celery 80
• Nettle 357
• Brie, 50 % fat in dry matter 400
• Broccoli 105
• Watercress 18
• Butter cheese, 30 % fat in dry matter 800
• Butter cheese, 60 % fat in dry matter 600
• Buttermilk 109
• Soured milk, 3.5 % fat 120
• Edam, 30 % fat in dry matter 800
• Emmental, 45 % fat in dry matter 1100
• Gouda, 40 % fat in dry matter 800
• Gouda, 48 % fat in dry matter 751
• Gruyère, 45 % fat in dry matter 1000
• Kale 212
• Hazelnuts 22
• UHT milk, low-fat, 1.5 % fat 123
• Yogurt, low fat, 1.5 % fat 123
• Yogurt, 3.5% fat 120
• Kefir, 3.5% fat 120
• Leerdamer, 45 % fat in dry matter 751
• Limburger, 20 % fat in dry matter 510
• Limburger, 40 % fat in dry matter 534
• Dandelion 158
• Poppy seed 2475
• Mozzarella 450
• Parmesan, 32 % fat in dry matter 1180
• Romadur, 20 % fat in dry matter 448
• Processed cheese, 45 % fat in dry matter 547
• Sesame 783
• Spinach 126
• Tilsiter, 30 % fat in dry matter 851
• Tilsiter, 45 % fat in dry matter 858
• Soft goat cheese, 45 % fat in dry matter 430

Bioavailability

However, the level of calcium in food is not decisive for the usability of the mineral. In calcium absorption, it plays an important role with which foods it is absorbed. Foods containing oxalic acid, phytic acid and galacturonic acid significantly reduce absorption. In addition, the composition of fatty acids in the foods consumed is an important factor in calcium absorption. Together with calcium, saturated fatty acids form poorly soluble calcium strips that cannot be absorbed. They are excreted again.

The amount of protein consumed in the diet does not affect the absorption of calcium but increases the excretion of the mineral. The availability of the mineral can be increased by substances that form water-soluble calcium salts with calcium. These substances include lactose (in milk and dairy products), citrate (in citrus fruits), hydrogen ions, and certain amino acids and glucose. In addition, strong gastric acid secretion enhances the availability of the calcium consumed. In addition to dietary factors in the absorption of calcium, gender also plays a critical role. Women have a physiologically lower absorption rate than men. The exception is pregnant women.

Tasks

Calcium mainly forms hard tissues of the body. Bones and teeth contain about 99 percent of the calcium in the body. The rest is found in the plasma. Calcium present in plasma is divided into three fractions, each with a different function. These fractions are ionized calcium, calcium bound to blood proteins and complexed calcium. The concentration of calcium in the blood is kept at a constant level by various hormonal systems. Bone tissue is used as a calcium depot that compensates for fluctuations. Calcium is the main mineral responsible for muscle contraction. It is a component of many enzymes and also their activator. In addition, the activation of numerous cells by hormones is controlled by a brief influx of calcium into the cell. Calcium also plays an important role in wound healing and blood clotting.

Metabolism

The absorption rate is on average between 30 and 40 %. The decisive factor for how much calcium can be absorbed is the composition of the ingested food. In other words, the other ingredients that affect calcium absorption. Vitamin D plays a central, but not yet fully elucidated, role in resorption and transport through the cells. Calcium metabolism is regulated by various hormone systems. For example, the hormones of the thyroid gland as well as the hormones estrogen, insulin or glucagon are involved in the calcium concentration of the blood, each with different functions. The hormone parathyroid hormone plays the most important role in raising the calcium level in the blood. It is produced in the parathyroid gland. When blood calcium levels are low, it promotes mobilization of the mineral, increases absorption in the intestine and reduces excretion via the kidneys.

Up to around the age of 30, more calcium is usually deposited in the bones than is broken down. At this time, we also speak of "peak bone mass," the highest bone mass built up in a lifetime. From this point on, bone mass is reduced. This means that bone density decreases. This process cannot be stopped, but it can be slowed down. The decisive factor in the removal of calcium from the bones is an appropriate diet and sufficient physical exercise.

Deficiency symptoms

Decalcification of bones and teeth is the result of calcium deficiency. This increases the risk of bone fractures, among other things, even at low levels of stress. The loss of stability also causes deformities that can lead to back problems and severe pain. Even a slight calcium deficiency can lead to muscular problems such as tremors and cramps, especially in athletes. Calcium is also lost through sweat.

In the working-class neighborhoods of the 19th century, many children suffered from calcium deficiency, which arose because the children had too little vitamin D3 due to the lack of light. The consequence was the so-called vitamin D deficiency rickets. The body produces vitamin D3 itself in the skin under the influence of sunlight. Vitamin D3, in turn, is necessary for the absorption of calcium from the intestine and for the reabsorption of calcium in the kidney. Thus, vitamin D3 increases the concentration of calcium in the blood, which is an essential requirement for bone formation. The symptoms of rickets are severe bone deformities and growth disorders. In industrialized nations, rickets has become a rare disease due to consistent vitamin D3 prophylaxis, especially in infants and young children, as well as health and nutrition education.

Possible health benefits of calcium

Calcium can relieve heartburn

Calcium carbonate is a very effective gastric acid blocker that is also used in the medical field (1, 2).

Calcium can be used to treat low calcium levels

Oral calcium supplements are very effective in treating and preventing low blood calcium levels. However, for serious calcium deficiency symptoms with muscle spasms, intravenous calcium salts are needed (4).

Calcium can reduce high phosphate levels in patients with renal failure

Accumulation of phosphate is a primary problem in patients suffering from renal failure. Oral calcium carbonate or calcium acetate is an effective phosphate binder, although calcium acetate may be the better option and is also used in the medical field for this application (5).

Calcium can be used in osteoporosis for treatment and prevention

Calcium and vitamin D are two crucial nutrients for the prevention and treatment of osteoporosis. The U.S. National Osteoporosis Foundation (NOF) recommends a daily calcium intake of 1200 mg for men between the ages of 50 and 70 and women 51 and older. Calcium supplementation is recommended for individuals who are unable to meet their dietary calcium requirements (6).

Adequate calcium intake in the form of food and supplements may help prevent osteoporosis in young people and specific types (such as glucocorticoid-induced osteoporosis). It should be mentioned here that the scientific evidence for benefits of calcium in this regard is much weaker in men and therefore requires further investigation (7, 8, 9). Although calcium supplements are effective on their own, most experts recommend combining them with vitamin D, which increases calcium absorption and instructs the body to use this calcium to build bone (6, 10).

Calcium could relieve PMS symptoms

Premenstrual syndrome (PMS) is very common and the exact causes are varied. Low vitamin D levels may trigger PMS or contribute to symptoms, according to a review of 28 studies (11). According to numerous studies conducted with women who suffered from PMS, calcium was found to alleviate many of the symptoms such as anxiety, depression, fatigue, and water retention (12, 13, 14, 15).

Calcium could promote bone stability

Sportsman

Some research suggests that calcium may improve bone health in physically active people, such as athletes and people with physically demanding jobs. During intense exercise, blood pH levels drop while lactate levels rise. To compensate, the body releases calcium from the bones, which increases bone loss if calcium needs are not met. Calcium supplements could therefore be helpful during such periods of intense stress on the body and skeletal system (16, 17, 18). In a study of 243 military personnel, a calcium and vitamin D supplement improved bone density and strength (19).

In another study, 32 well-trained female athletes were given a meal containing approximately 1350 mg of calcium 90 minutes before a strenuous exercise session. The calcium reduced the typical bone loss normally observed during prolonged high-intensity exercise (16).

Healthy non-athletes

In a study of 867 healthy men, calcium with vitamin D improved bone mineral density - particularly in the neck, hip and spine. However, a large study review concluded that more studies are needed before a conclusion can be made about whether supplementation is beneficial for all healthy, older men who are not calcium deficient (20). In summary, calcium supplements may strengthen bones in people who are at increased risk for calcium deficiency. These supplements could also protect the bones of very active healthy people and athletes.

Calcium could counteract colon cancer

According to several study reviews, use of calcium supplements may be associated with lower rates of colorectal cancer and fewer recurrences of this condition. Most of the studies found that calcium supplements were more effective when combined with vitamin D (21, 22, 23, 24). Calcium supplements could help prevent colorectal cancer by protecting the cells of the intestine from the damaging effects of free bile acid. Another pathway through which calcium might act is by activating the APC/beta-catenin pathway, which becomes underactive in the early stages of colorectal cancer. In turn, vitamin D helps to break down bile acid and enhances DNA repair (25, 26). In this context, however, it should be strongly cautioned that these studies are not definitive proof of actual anti-cancer effects, so calcium supplements are by no means used as a substitute for traditional cancer therapy.

Calcium could prevent high blood pressure

Adequate calcium intake could prevent the onset of high blood pressure, according to a large study review of over 3000 people. Calcium intake (dietary or in the form of supplements) slightly reduced blood pressure, which was particularly true in people younger than 35, people sensitive to salt, and people with generally low calcium intakes (27). However, a meta-analysis of 8 low-quality clinical trials and 36,800 subjects found no significant effects of a calcium-vitamin D combination on blood pressure. Therefore, further studies are needed to confirm the efficacy of calcium supplements in lowering blood pressure (28).

Calcium could reduce the risk of pregnancy complications

Preeclampsia is a sudden onset of high blood pressure during pregnancy, usually beginning at 20 weeks gestation. This condition affects about 5% of all pregnant women and can lead to organ damage, pregnancy complications and even death if not treated. Adequate calcium intake is an important part of preventing this condition (29). According to a large study review, calcium supplements (over 1 gram per day) could cut the risk of preeclampsia in half (39). Supplementation is especially important if you do not get enough calcium from your diet. The World Health Organization (WHO) recommends calcium supplementation in the range of 1.5 to 2 grams per day for pregnant women with low calcium intakes (31).

Calcium could help with fatty liver disease

Vitamin D deficiency is common in people with fatty liver disease, and ultimately leads to reduced calcium absorption as well (34). In two studies of 120 people with nonalcoholic fatty liver, vitamin D and calcium improved several markers of liver damage and heart health (ALT, AST, triglycerides, and LDL cholesterol). Vitamin D alone did not improve liver health (35, 36). These results highlight the close association and synergy between calcium and vitamin D, and their important role in liver, bone, and heart health. However, further research is needed before definitive conclusions can be drawn.

Daily demand

Most adults need at least 1000mg of calcium per day. Women over 50 need slightly more - about 1200 mg. Teenagers and pregnant or lactating women should consume at least 1300 mg of calcium per day (37). The amount of supplemented calcium needed depends on diet. If dietary calcium intake is low, supplementation with up to 1000 mg per day may be appropriate. Single doses of no more than 500 mg at a time work best (78).

One should avoid excessive calcium intake. The upper tolerable amount per day was set based on age as follows:

• 0 - 6 months: 1000 mg
• 6 -12 months: 1500 mg
• 1 - 3 years: 2500 mg
• 4 - 18 years: 3000 mg
• 19 - 50 years: 2500 mg
• 51 + years: 2000 mg

Higher dosages may increase the risk of serious side effects. Some recent research suggests that dosages above the recommended amount of 1000 to 1300 mg for adults may increase the risk for heart attacks. These studies are troubling, but it is too early to be sure that calcium is actually the cause of heart attacks. Until more is known, one should consume adequate amounts of calcium to meet daily needs, but avoid excessive amounts. In doing so, one should make sure to consider the total intake of calcium from food and supplements and try not to exceed 1000 to 1300 mg of calcium per day.

Safety and side effects

Calcium is probably safe and harmless for most people when taken in the recommended amounts. Calcium can cause side effects such as bloating and belching. With calcium, more is not better. The table below lists the maximum daily intake (food and supplements) that should not be exceeded. About 5% of all women over 50 exceed these levels by almost 400 mg per day (37). Exceeding these maximum safe levels in the short term is unlikely to cause problems, but exceeding them in the longer term is not safe (37). Higher doses may increase the risk for serious side effects.

Some recent research suggests that dosages above the recommended amount of 1000 to 1300 mg for adults may increase the risk of heart attacks. These studies are troubling, but it is too early to be certain that calcium is actually the cause of heart attacks. Until more is known, one should consume adequate amounts of calcium to meet daily needs, but avoid excessive amounts. In doing so, one should make sure to consider the total intake of calcium from food and supplements and try not to exceed 1000 to 1300 mg of calcium per day.

In addition, known potential side effects of calcium supplementation include the following:

Increase in the risk of kidney stones: The best-known side effect of calcium supplements is a slightly increased risk of kidney stones. Data from various studies suggest a 17% increase in the risk of developing kidney stones. The risk could be reduced by using the citrate form of calcium. Calcium citrate reduces formation and growth of the most common type of kidney stone (oxalic acid) (39, 40).

Digestive discomfort: Another common side effect of calcium supplements is digestive discomfort. Symptoms may include constipation, stomach cramps and bloating. Heartburn and nausea are also possible. In most cases, calcium carbonate is the cause of these problems because it requires stomach acid for absorption. Again, choosing the citrate form can minimize this side effect. (39, 41).

Reduced nutrient absorption: Calcium supplements may inhibit iron absorption when taken with meals. Women have higher iron requirements than men and should therefore take calcium supplements at least 2 hours before or after meals (42, 43). Over-supplementation with calcium could result in other nutrient deficiencies. If calcium intake is increased, then care should be taken to ensure that adequate amounts of vitamin D, magnesium, and vitamin K (especially K2) are provided. These important nutrients help calcium work optimally in the body.

Precautions and warnings

• Pregnancy and Lactation: Calcium is likely safe and harmless when used at recommended levels during pregnancy and lactation.
• High or low phosphate levels in the blood: Calcium and phosphate must be in balance in the body. Taking too much calcium can upset this balance and cause damage. You should not take extra calcium without consulting your doctor if you suffer from high or low phosphate levels.
• Hypothyroidism: Calcium may interfere with thyroid hormone replacement therapy. One should take calcium and thyroid medication at least 4 hours apart.

Excessive levels of calcium in the blood, as is the case with parathyroid dysfunction and sarcoidosis: one should avoid calcium if suffering from one of these disorders.

Interactions

One should not use calcium in combination with the following medications:

Ceftriaxone

Intravenous administration of ceftriaxone and calcium may result in life-threatening damage to the lungs and kidneys. Calcium should not be administered intravenously within 48 hours before or after intravenous administration of ceftriaxone.

Care should be taken when using calcium in combination with the following medications:

Antibiotics (Quinolone antibiotics)

Calcium could reduce the amount of antibiotics the body absorbs. Taking calcium in combination with quinolone antibiotics could reduce the effectiveness of these antibiotics. To avoid this interaction, calcium should be taken at least one hour after antibiotics.

Antibiotics (Tetracylin antibiotics)

Calcium can bind to tetracyline antibiotics in the stomach. This reduces the amount of tetracyline antibiotics that can be absorbed by the body. Taking calcium in combination with tetracyline antibiotics could reduce the effectiveness of these antibiotics. To avoid this interaction, calcium should be taken two hours before or four hours after taking tetracyline antibiotics.

Bisphosphonate

Calcium could reduce the amount of bisphosphonate that the body absorbs. Taking calcium in combination with bisphosphonate could reduce the effectiveness of bisphosphate. To avoid this interaction, bisphosphonate should be taken at least 30 minutes before calcium or later in the day.

Calcipotriene

Calcipotriene is a drug that resembles vitamin D. Vitamin D helps the body absorb calcium. Taking calcium supplements in combination with calcipotriene could result in calcium levels in the body that are too high.

Levothyroxine

Levothyroxine is used to treat hypothyroidism. Calcium could reduce the amount of levothyroxine that the body absorbs. Taking calcium in combination with levothyroxine could reduce the effectiveness of levothyroxine. Calcium and levothyroxine should therefore be taken at least 4 hours apart.

Diuretics

Some diuretics can increase the amount of calcium in the body. Taking large amounts of calcium in combination with certain diuretics could result in excessive levels of calcium in the body. This could lead to serious side effects including kidney problems.

Care should be taken when using calcium in combination with the following medications:

Estrogens

Estrogen helps the body absorb calcium. Taking estrogen supplements in combination with large amounts of calcium could increase calcium levels in the body too much.

Medication for high blood pressure

Some medications for high blood pressure can affect calcium levels in the body. These medications are called calcium channel blockers. Calcium injections could reduce the effectiveness of these high blood pressure medications.

References

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