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 its pure form, but only in numerous compounds. For example, as calcium carbonate or in limestone, gypsum and dolomite. In total, over 200 minerals are known to contain calcium. It is the 5th most common element in the earth's crust, ahead of 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 found in a number of plants. In the human organism and in most animals, calcium is the mineral with the highest content. An adult man has over a kilo of calcium in his body, while the proportion is somewhat lower in women due to their lower skeletal mass. The vast majority of calcium is stored in teeth and bones, only about 1% is found in the blood and other tissues. About 55% of the calcium in the blood is present as free Ca2, about 40% is bound to proteins and about 5% to organic acids.

Occurrence

The most important food sources of calcium are milk and dairy products. Calcium-rich dairy products include buttermilk and cheese, for example. In the case of 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. The calcium content of plant-based foods is usually only moderately high. However, some plant-based foods, such as coconut flakes or sesame seeds, are characterized by a very high calcium content.

Food (per 100 g 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 cheese, 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
• Yoghurt, low-fat, 1.5% fat 123
• Yoghurt, 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's cheese, 45 % fat in dry matter 430

Bioavailability

However, the level of calcium in food is not decisive for the usability of the mineral. The foods with which it is absorbed play an important role in calcium absorption. Foods containing oxalic acid, phytic acid and galacturonic acid significantly reduce absorption. The composition of the fatty acids in the food consumed is also 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.

Although the protein content of food does not influence the absorption of calcium, it does increase 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 as well as certain amino acids and glucose. In addition, strong gastric acid secretion improves the availability of the calcium consumed. In addition to the factors that food has on the absorption of calcium, gender also plays a decisive role. Women have a physiologically lower absorption rate than men. Pregnant women are an exception.

Tasks

Calcium mainly forms hard tissue in the body. About 99 percent of the calcium contained in the body is found in bones and teeth. The rest is found in the plasma. The calcium present in the plasma is divided into three fractions, each with different functions. 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. The 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 average absorption rate is between 30 and 40 %. How much calcium can be absorbed depends on the composition of the food consumed. In other words, the other ingredients that have an effect on calcium absorption. Vitamin D plays a central, but not yet fully understood, role in the absorption 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 oestrogen, insulin and 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 the mobilization of the mineral, increases absorption in the intestine and reduces excretion via the kidneys.

Until around the age of 30, more calcium is usually stored 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 onwards, bone mass is reduced. This means that bone density decreases. This process cannot be stopped, but it can be slowed down. An appropriate diet and sufficient physical activity are crucial for calcium leaching from the bones.

Deficiency symptoms

The decalcification of bones and teeth is the result of calcium deficiency. As a result, there is an increased risk of bone fractures, even under low loads. The loss of stability also causes deformation, which 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 result was 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 kidneys. Vitamin D3 thus increases the concentration of calcium in the blood, which is an essential prerequisite for bone formation. The symptoms of rickets are severe bone deformities and growth disorders. In industrialized nations, rickets has become a rare disease thanks 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 stomach 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 when it comes to treating and preventing low calcium blood levels. However, for serious calcium deficiency symptoms with muscle cramps, intravenous calcium salts are needed (4).

Calcium can reduce high phosphate levels in patients with kidney failure

Phosphate accumulation is a primary problem in patients suffering from kidney 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 for the treatment and prevention of osteoporosis

Calcium and vitamin D are two essential nutrients for the prevention and treatment of osteoporosis. The US National Osteoporosis Foundation (NOF) recommends a daily calcium intake of 1200 mg for men aged 50 to 70 and women aged 51 and over. Calcium supplementation is recommended for people who are unable to meet their calcium requirements through their diet (6).

Adequate calcium intake in the form of food and supplements can help prevent osteoporosis in young people and specific types (such as glucocorticoid-induced osteoporosis). It should be noted that the scientific evidence for the 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 alleviate PMS symptoms

Premenstrual syndrome (PMS) is very common and the exact causes are varied. According to a review of 28 studies, low vitamin D levels can trigger PMS or contribute to the symptoms (11). Numerous studies conducted on women suffering from PMS have concluded that calcium can alleviate many of the symptoms such as anxiety, depression, fatigue and water retention (12, 13, 14, 15).

Calcium could promote bone stability

Athletes

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 for this, the body releases calcium from the bones, which increases bone loss if calcium requirements 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 around 1350 mg of calcium 90 minutes before a strenuous training session. The calcium reduced the typical bone loss normally seen with 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 further studies are needed before it can be concluded whether supplementation is beneficial for all healthy, older men who are not calcium deficient (20). In summary, calcium supplements can strengthen bones in people who are at increased risk of calcium deficiency. These supplements may also protect the bones of very active healthy people and athletes.

Calcium could counteract bowel cancer

According to several study reviews, the use of calcium supplements may be associated with lower rates of colorectal cancer and fewer recurrences of the condition. Most of the studies found that calcium supplements were more effective when combined with vitamin D (21, 22, 23, 24). Calcium supplements may help prevent colorectal cancer by protecting the cells of the intestine from the damaging effects of free bile acid. Another way calcium could work is by activating the APC/beta-catenin pathway, which becomes underactive in the early stages of colorectal cancer. Vitamin D, in turn, helps to break down bile acid and enhances DNA repair (25, 26). In this context, however, it should be emphasized that these studies are not definitive proof of actual anti-cancer effects, which is why calcium supplements should never be 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, particularly in people under 35, people sensitive to salt and people with a generally low calcium intake (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. Further studies are therefore needed to confirm the efficacy of calcium supplements in lowering blood pressure (28).

Calcium could reduce the risk of pregnancy complications

Pre-eclampsia is a sudden onset of high blood pressure during pregnancy, which usually occurs from the 20th week of pregnancy. This condition affects about 5% of all pregnant women and can lead to organ damage, pregnancy complications and even death if left untreated. 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 halve the risk of pre-eclampsia (39). Supplementation is particularly 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 intake (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 (34). In two studies of 120 people with non-alcoholic fatty liver disease, 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 requirement

Most adults need at least 1000mg of calcium per day. Women over 50 need slightly more - around 1200mg. Teenagers and pregnant or breastfeeding women should consume at least 1300mg of calcium per day (37). The amount of supplemented calcium needed depends on the 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).

Excessive calcium intake should be avoided. The upper tolerable amount per day was set as follows based on age:

• 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 doses may increase the risk of serious side effects. Some recent research suggests that doses above the recommended 1000 to 1300 mg for adults may increase the risk of heart attacks. These studies are disturbing, but it is too early to be sure that calcium is actually the cause of heart attacks. Until more is known, adequate amounts of calcium should be consumed to meet daily needs, but excessive amounts should be avoided. You should ensure that you take into account your total calcium intake 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 values by almost 400 mg per day (37). Exceeding these maximum safe amounts in the short term is unlikely to cause problems, but exceeding them for longer periods is not safe (37). Higher doses may increase the risk of serious side effects.

Some recent research suggests that doses above the recommended amount of 1000 to 1300 mg for adults may increase the risk of heart attacks. These studies are disturbing, but it is too early to be sure that calcium is actually the cause of heart attacks. Until more is known, adequate amounts of calcium should be consumed to meet daily needs, but excessive amounts should be avoided. You should ensure that you take into account the total intake of calcium from food and supplements and try not to exceed 1000 to 1300 mg of calcium per day.

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

Increased risk of kidney stones: The most well-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 the formation and growth of the most common type of kidney stone (oxalic acid) (39, 40).

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

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

Precautions and warnings

• Pregnancy and lactation: Calcium is probably safe and harmless when used in the recommended amounts during pregnancy and lactation.
• High or low blood phosphate levels: 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 can interfere with thyroid hormone replacement therapy. Calcium and thyroid medication should be taken at least 4 hours apart.

Excessively high calcium levels in the blood, as is the case with parathyroid disorders and sarcoidosis: Calcium should be avoided if you suffer from one of these disorders.

Interactions

Calcium should not be used in combination with the following medications:

Ceftriaxone

Intravenous administration of ceftriaxone and calcium can 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 drugs:

Antibiotics (quinolone antibiotics)

Calcium could reduce the amount of antibiotics absorbed by the body. 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 (tetracyline 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 may reduce the amount of bisphosphonate absorbed by the body. 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 medication similar to vitamin D. Vitamin D helps the body absorb calcium. Taking calcium supplements in combination with calcipotriene could result in high calcium levels in the body.

Levothyroxine

Levothyroxine is used to treat hypothyroidism. Calcium could reduce the amount of levothyroxine absorbed by the body. 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 calcium levels 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 drugs are called calcium channel blockers. Calcium injections may reduce the effectiveness of these high blood pressure medications.

References

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